diff --git a/gcc/builtins.cc b/gcc/builtins.cc
index 35b9197945f..0cf32a9c443 100644
--- a/gcc/builtins.cc
+++ b/gcc/builtins.cc
@@ -5584,7 +5584,7 @@ expand_builtin_fork_or_exec (tree fn, tree exp, rtx target, int ignore)
   tree call;
 
   /* If we are not profiling, just call the function.  */
-  if (!profile_arc_flag)
+  if (!profile_arc_flag && !profile_condition_flag)
     return NULL_RTX;
 
   /* Otherwise call the wrapper.  This should be equivalent for the rest of
diff --git a/gcc/collect2.cc b/gcc/collect2.cc
index d81c7f28f16..7b0968d535d 100644
--- a/gcc/collect2.cc
+++ b/gcc/collect2.cc
@@ -1032,9 +1032,9 @@ main (int argc, char **argv)
       lto_mode = LTO_MODE_LTO;
   }
 
-  /* -fno-profile-arcs -fno-test-coverage -fno-branch-probabilities
+  /* -fno-profile-arcs -fno-profile-conditions -fno-test-coverage -fno-branch-probabilities
      -fno-exceptions -w -fno-whole-program */
-  num_c_args += 6;
+  num_c_args += 7;
 
   c_argv = XCNEWVEC (char *, num_c_args);
   c_ptr = CONST_CAST2 (const char **, char **, c_argv);
@@ -1230,6 +1230,7 @@ main (int argc, char **argv)
     }
   obstack_free (&temporary_obstack, temporary_firstobj);
   *c_ptr++ = "-fno-profile-arcs";
+  *c_ptr++ = "-fno-profile-conditions";
   *c_ptr++ = "-fno-test-coverage";
   *c_ptr++ = "-fno-branch-probabilities";
   *c_ptr++ = "-fno-exceptions";
diff --git a/gcc/common.opt b/gcc/common.opt
index e7a51e882ba..4da06767bc3 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -865,6 +865,10 @@ Wcoverage-invalid-line-number
 Common Var(warn_coverage_invalid_linenum) Init(1) Warning
 Warn in case a function ends earlier than it begins due to an invalid linenum macros.
 
+Wcoverage-too-many-conditions
+Common Var(warn_too_many_conditions) Init(1) Warning
+Warn when a conditional has too many terms and coverage gives up.
+
 Wmissing-profile
 Common Var(warn_missing_profile) Init(1) Warning
 Warn in case profiles in -fprofile-use do not exist.
@@ -2321,6 +2325,10 @@ fprofile-arcs
 Common Var(profile_arc_flag)
 Insert arc-based program profiling code.
 
+fprofile-conditions
+Common Var(profile_condition_flag)
+Insert condition coverage profiling code.
+
 fprofile-dir=
 Common Joined RejectNegative Var(profile_data_prefix)
 Set the top-level directory for storing the profile data.
diff --git a/gcc/doc/gcov.texi b/gcc/doc/gcov.texi
index a1f7d26e610..7f2c0d00d94 100644
--- a/gcc/doc/gcov.texi
+++ b/gcc/doc/gcov.texi
@@ -124,6 +124,7 @@ gcov [@option{-v}|@option{--version}] [@option{-h}|@option{--help}]
      [@option{-a}|@option{--all-blocks}]
      [@option{-b}|@option{--branch-probabilities}]
      [@option{-c}|@option{--branch-counts}]
+     [@option{-g}|@option{--conditions}]
      [@option{-d}|@option{--display-progress}]
      [@option{-f}|@option{--function-summaries}]
      [@option{-j}|@option{--json-format}]
@@ -169,6 +170,13 @@ be shown, unless the @option{-u} option is given.
 Write branch frequencies as the number of branches taken, rather than
 the percentage of branches taken.
 
+@item -g
+@itemx --conditions
+Write condition coverage to the output file, and write condition summary info
+to the standard output.  This option allows you to see if the conditions in
+your program at least once had an independent effect on the outcome of the
+boolean expression (modified condition/decision coverage).
+
 @item -d
 @itemx --display-progress
 Display the progress on the standard output.
@@ -293,6 +301,7 @@ Each @var{line} has the following form:
 @{
   "branches": ["$branch"],
   "count": 2,
+  "conditions": ["$condition"],
   "line_number": 15,
   "unexecuted_block": false,
   "function_name": "foo",
@@ -341,6 +350,33 @@ Fields of the @var{branch} element have following semantics:
 @var{throw}: true when the branch is an exceptional branch
 @end itemize
 
+Each @var{condition} element have the following semantics:
+
+@smallexample
+@{
+  "count": 4,
+  "covered": 2,
+  "not_covered_false": [],
+  "not_covered_true": [0, 1],
+@}
+@end smallexample
+
+Fields of the @var{condition} element have following semantics:
+
+@itemize @bullet
+@item
+@var{count}: number of conditions in this expression
+
+@item
+@var{covered}: number of covered conditions in this expression
+
+@item
+@var{not_covered_true}: terms, by index, not seen as true in this expression
+
+@item
+@var{not_covered_false}: terms, by index, not seen as false in this expression
+@end itemize
+
 @item -H
 @itemx --human-readable
 Write counts in human readable format (like 24.6k).
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index d5ff1018372..28cc9fa2316 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -602,6 +602,7 @@ Objective-C and Objective-C++ Dialects}.
 @item Program Instrumentation Options
 @xref{Instrumentation Options,,Program Instrumentation Options}.
 @gccoptlist{-p  -pg  -fprofile-arcs  --coverage  -ftest-coverage @gol
+-fprofile-conditions @gol
 -fprofile-abs-path @gol
 -fprofile-dir=@var{path}  -fprofile-generate  -fprofile-generate=@var{path} @gol
 -fprofile-info-section  -fprofile-info-section=@var{name} @gol
@@ -6088,6 +6089,13 @@ error.  @option{-Wno-coverage-invalid-line-number} can be used to disable the
 warning or @option{-Wno-error=coverage-invalid-line-number} can be used to
 disable the error.
 
+@item -Wno-coverage-too-many-conditions
+@opindex Wno-coverage-too-many-conditions
+@opindex Wcoverage-too-many-conditions
+Warn in case a condition have too many terms and GCC gives up coverage.
+Coverage is given up when there are more terms in the conditional than there
+are bits in a @code{gcov_type_unsigned}.  This warning is enabled by default.
+
 @item -Wno-cpp @r{(C, Objective-C, C++, Objective-C++ and Fortran only)}
 @opindex Wno-cpp
 @opindex Wcpp
@@ -15549,6 +15557,13 @@ E.g. @code{gcc a.c b.c -o binary} would generate @file{binary-a.gcda} and
 
 @xref{Cross-profiling}.
 
+@item -fprofile-conditions
+@opindex fprofile-conditions
+Add code so that program conditions are instrumented.  During execution the
+program records what terms in a conditional contributes to a decision.  The
+data may be used to verify that all terms in a booleans are tested and have an
+effect on the outcome of a condition.
+
 @cindex @command{gcov}
 @item --coverage
 @opindex coverage
@@ -15609,6 +15624,10 @@ executed.  When an arc is the only exit or only entrance to a block, the
 instrumentation code can be added to the block; otherwise, a new basic
 block must be created to hold the instrumentation code.
 
+With @option{-fprofile-conditions}, for each conditional in your program GCC
+creates a bitset and records the boolean values that have an independent effect
+on the outcome of that expression.
+
 @need 2000
 @item -ftest-coverage
 @opindex ftest-coverage
diff --git a/gcc/gcc.cc b/gcc/gcc.cc
index 5cbb38560b2..3c0c40bf388 100644
--- a/gcc/gcc.cc
+++ b/gcc/gcc.cc
@@ -1165,7 +1165,7 @@ proper position among the other output files.  */
 	%:include(libgomp.spec)%(link_gomp)}\
     %{fgnu-tm:%:include(libitm.spec)%(link_itm)}\
     %(mflib) " STACK_SPLIT_SPEC "\
-    %{fprofile-arcs|fprofile-generate*|coverage:-lgcov} " SANITIZER_SPEC " \
+    %{fprofile-arcs|fprofile-conditions|fprofile-generate*|coverage:-lgcov} " SANITIZER_SPEC " \
     %{!nostdlib:%{!r:%{!nodefaultlibs:%(link_ssp) %(link_gcc_c_sequence)}}}\
     %{!nostdlib:%{!r:%{!nostartfiles:%E}}} %{T*}  \n%(post_link) }}}}}}"
 #endif
@@ -1282,7 +1282,7 @@ static const char *cc1_options =
  %{!fsyntax-only:%{S:%W{o*}%{!o*:-o %w%b.s}}}\
  %{fsyntax-only:-o %j} %{-param*}\
  %{coverage:-fprofile-arcs -ftest-coverage}\
- %{fprofile-arcs|fprofile-generate*|coverage:\
+ %{fprofile-arcs|fprofile-conditions|fprofile-generate*|coverage:\
    %{!fprofile-update=single:\
      %{pthread:-fprofile-update=prefer-atomic}}}";
 
diff --git a/gcc/gcov-counter.def b/gcc/gcov-counter.def
index 6d2182bd3db..96563a59a45 100644
--- a/gcc/gcov-counter.def
+++ b/gcc/gcov-counter.def
@@ -49,3 +49,6 @@ DEF_GCOV_COUNTER(GCOV_COUNTER_IOR, "ior", _ior)
 
 /* Time profile collecting first run of a function */
 DEF_GCOV_COUNTER(GCOV_TIME_PROFILER, "time_profiler", _time_profile)
+
+/* Conditions.  The counter is interpreted as a bit-set.  */
+DEF_GCOV_COUNTER(GCOV_COUNTER_CONDS, "conditions", _ior)
diff --git a/gcc/gcov-dump.cc b/gcc/gcov-dump.cc
index 0804c794e9e..12830e5984e 100644
--- a/gcc/gcov-dump.cc
+++ b/gcc/gcov-dump.cc
@@ -35,6 +35,7 @@ static void print_version (void);
 static void tag_function (const char *, unsigned, int, unsigned);
 static void tag_blocks (const char *, unsigned, int, unsigned);
 static void tag_arcs (const char *, unsigned, int, unsigned);
+static void tag_conditions (const char *, unsigned, int, unsigned);
 static void tag_lines (const char *, unsigned, int, unsigned);
 static void tag_counters (const char *, unsigned, int, unsigned);
 static void tag_summary (const char *, unsigned, int, unsigned);
@@ -71,6 +72,7 @@ static const tag_format_t tag_table[] =
   {GCOV_TAG_FUNCTION, "FUNCTION", tag_function},
   {GCOV_TAG_BLOCKS, "BLOCKS", tag_blocks},
   {GCOV_TAG_ARCS, "ARCS", tag_arcs},
+  {GCOV_TAG_CONDS, "CONDITIONS", tag_conditions},
   {GCOV_TAG_LINES, "LINES", tag_lines},
   {GCOV_TAG_OBJECT_SUMMARY, "OBJECT_SUMMARY", tag_summary},
   {0, NULL, NULL}
@@ -381,6 +383,28 @@ tag_arcs (const char *filename ATTRIBUTE_UNUSED,
     }
 }
 
+static void
+tag_conditions (const char *filename ATTRIBUTE_UNUSED,
+		unsigned tag ATTRIBUTE_UNUSED, int length ATTRIBUTE_UNUSED,
+		unsigned depth)
+{
+  unsigned n_conditions = GCOV_TAG_CONDS_NUM (length);
+
+  printf (" %u conditionals", n_conditions);
+  if (flag_dump_contents)
+    {
+      for (unsigned ix = 0; ix != n_conditions; ix++)
+	{
+	  const unsigned blockno = gcov_read_unsigned ();
+	  const unsigned nterms = gcov_read_unsigned ();
+
+	  printf ("\n");
+	  print_prefix (filename, depth, gcov_position ());
+	  printf (VALUE_PADDING_PREFIX "block %u:", blockno);
+	  printf (" %u", nterms);
+	}
+    }
+}
 static void
 tag_lines (const char *filename ATTRIBUTE_UNUSED,
 	   unsigned tag ATTRIBUTE_UNUSED, int length ATTRIBUTE_UNUSED,
diff --git a/gcc/gcov-io.h b/gcc/gcov-io.h
index 30947634d73..eaf3f366f5d 100644
--- a/gcc/gcov-io.h
+++ b/gcc/gcov-io.h
@@ -261,6 +261,9 @@ typedef uint64_t gcov_type_unsigned;
 #define GCOV_TAG_ARCS		 ((gcov_unsigned_t)0x01430000)
 #define GCOV_TAG_ARCS_LENGTH(NUM)  (1 + (NUM) * 2 * GCOV_WORD_SIZE)
 #define GCOV_TAG_ARCS_NUM(LENGTH)  (((LENGTH / GCOV_WORD_SIZE) - 1) / 2)
+#define GCOV_TAG_CONDS             ((gcov_unsigned_t)0x01470000)
+#define GCOV_TAG_CONDS_LENGTH(NUM) ((NUM) * 2 * GCOV_WORD_SIZE)
+#define GCOV_TAG_CONDS_NUM(LENGTH) (((LENGTH) / GCOV_WORD_SIZE) / 2)
 #define GCOV_TAG_LINES		 ((gcov_unsigned_t)0x01450000)
 #define GCOV_TAG_COUNTER_BASE 	 ((gcov_unsigned_t)0x01a10000)
 #define GCOV_TAG_COUNTER_LENGTH(NUM) ((NUM) * 2 * GCOV_WORD_SIZE)
diff --git a/gcc/gcov.cc b/gcc/gcov.cc
index 27be5ff0911..9fa26db814c 100644
--- a/gcc/gcov.cc
+++ b/gcc/gcov.cc
@@ -79,6 +79,7 @@ using namespace std;
 class function_info;
 class block_info;
 class source_info;
+class condition_info;
 
 /* Describes an arc between two basic blocks.  */
 
@@ -132,6 +133,28 @@ public:
   vector<unsigned> lines;
 };
 
+class condition_info
+{
+public:
+  condition_info ();
+
+  int popcount () const;
+
+  gcov_type_unsigned truev;
+  gcov_type_unsigned falsev;
+
+  unsigned n_terms;
+};
+
+condition_info::condition_info (): truev (0), falsev (0), n_terms (0)
+{
+}
+
+int condition_info::popcount () const
+{
+    return __builtin_popcountll (truev) + __builtin_popcountll (falsev);
+}
+
 /* Describes a basic block. Contains lists of arcs to successor and
    predecessor blocks.  */
 
@@ -165,6 +188,8 @@ public:
   /* Block is a landing pad for longjmp or throw.  */
   unsigned is_nonlocal_return : 1;
 
+  condition_info conditions;
+
   vector<block_location_info> locations;
 
   struct
@@ -275,6 +300,8 @@ public:
   vector<block_info> blocks;
   unsigned blocks_executed;
 
+  vector<condition_info*> conditions;
+
   /* Raw arc coverage counts.  */
   vector<gcov_type> counts;
 
@@ -351,6 +378,9 @@ struct coverage_info
   int branches_executed;
   int branches_taken;
 
+  int conditions;
+  int conditions_covered;
+
   int calls;
   int calls_executed;
 
@@ -550,6 +580,10 @@ static int multiple_files = 0;
 
 static int flag_branches = 0;
 
+/* Output conditions (modified condition/decision coverage) */
+
+static int flag_conditions = 0;
+
 /* Show unconditional branches too.  */
 static int flag_unconditional = 0;
 
@@ -656,6 +690,7 @@ static int read_count_file (void);
 static void solve_flow_graph (function_info *);
 static void find_exception_blocks (function_info *);
 static void add_branch_counts (coverage_info *, const arc_info *);
+static void add_condition_counts (coverage_info *, const block_info *);
 static void add_line_counts (coverage_info *, function_info *);
 static void executed_summary (unsigned, unsigned);
 static void function_summary (const coverage_info *);
@@ -664,6 +699,7 @@ static const char *format_gcov (gcov_type, gcov_type, int);
 static void accumulate_line_counts (source_info *);
 static void output_gcov_file (const char *, source_info *);
 static int output_branch_count (FILE *, int, const arc_info *);
+static void output_conditions (FILE *, const block_info *);
 static void output_lines (FILE *, const source_info *);
 static string make_gcov_file_name (const char *, const char *);
 static char *mangle_name (const char *);
@@ -928,6 +964,7 @@ print_usage (int error_p)
   fnotice (file, "  -b, --branch-probabilities      Include branch probabilities in output\n");
   fnotice (file, "  -c, --branch-counts             Output counts of branches taken\n\
                                     rather than percentages\n");
+  fnotice (file, "  -g, --conditions                Include condition/decision coverage in output\n");
   fnotice (file, "  -d, --display-progress          Display progress information\n");
   fnotice (file, "  -D, --debug			    Display debugging dumps\n");
   fnotice (file, "  -f, --function-summaries        Output summaries for each function\n");
@@ -980,6 +1017,7 @@ static const struct option options[] =
   { "all-blocks",           no_argument,       NULL, 'a' },
   { "branch-probabilities", no_argument,       NULL, 'b' },
   { "branch-counts",        no_argument,       NULL, 'c' },
+  { "conditions",           no_argument,       NULL, 'g' },
   { "json-format",	    no_argument,       NULL, 'j' },
   { "human-readable",	    no_argument,       NULL, 'H' },
   { "no-output",            no_argument,       NULL, 'n' },
@@ -1008,7 +1046,7 @@ process_args (int argc, char **argv)
 {
   int opt;
 
-  const char *opts = "abcdDfhHijklmno:pqrs:tuvwx";
+  const char *opts = "abcdDfghHijklmno:pqrs:tuvwx";
   while ((opt = getopt_long (argc, argv, opts, options, NULL)) != -1)
     {
       switch (opt)
@@ -1025,6 +1063,9 @@ process_args (int argc, char **argv)
 	case 'f':
 	  flag_function_summary = 1;
 	  break;
+	case 'g':
+	  flag_conditions = 1;
+	  break;
 	case 'h':
 	  print_usage (false);
 	  /* print_usage will exit.  */
@@ -1132,6 +1173,45 @@ output_intermediate_json_line (json::array *object,
 	  }
       }
 
+  json::array *conditions = new json::array ();
+  lineo->set ("conditions", conditions);
+  if (flag_conditions)
+  {
+    vector<block_info *>::const_iterator it;
+    for (it = line->blocks.begin (); it != line->blocks.end (); it++)
+      {
+	const condition_info& info = (*it)->conditions;
+	if (info.n_terms == 0)
+	    continue;
+
+	const int count = 2 * info.n_terms;
+	const int covered = info.popcount ();
+
+	json::object *cond = new json::object ();
+	cond->set ("count", new json::integer_number (count));
+	cond->set ("covered", new json::integer_number (covered));
+
+	json::array *mtrue = new json::array ();
+	json::array *mfalse = new json::array ();
+	cond->set ("not_covered_true", mtrue);
+	cond->set ("not_covered_false", mfalse);
+
+	if (count != covered)
+	  {
+	    for (unsigned i = 0; i < info.n_terms; i++)
+	      {
+		gcov_type_unsigned index = 1;
+		index <<= i;
+		if (!(index & info.truev))
+		    mtrue->append (new json::integer_number (i));
+		if (!(index & info.falsev))
+		    mfalse->append (new json::integer_number (i));
+	      }
+	  }
+	conditions->append (cond);
+      }
+  }
+
   object->append (lineo);
 }
 
@@ -1956,6 +2036,28 @@ read_graph_file (void)
 		  }
 	    }
 	}
+      else if (fn && tag == GCOV_TAG_CONDS)
+	{
+	  unsigned num_dests = GCOV_TAG_CONDS_NUM (length);
+
+	  if (!fn->conditions.empty ())
+	    fnotice (stderr, "%s:already seen conditions for '%s'\n",
+		     bbg_file_name, fn->get_name ());
+	  else
+	    fn->conditions.resize (num_dests);
+
+	  for (unsigned i = 0; i < num_dests; ++i)
+	    {
+	      unsigned idx = gcov_read_unsigned ();
+
+	      if (idx >= fn->blocks.size ())
+		goto corrupt;
+
+	      condition_info *info = &fn->blocks[idx].conditions;
+	      info->n_terms = gcov_read_unsigned ();
+	      fn->conditions[i] = info;
+	    }
+	}
       else if (fn && tag == GCOV_TAG_LINES)
 	{
 	  unsigned blockno = gcov_read_unsigned ();
@@ -2086,11 +2188,26 @@ read_count_file (void)
 	      goto cleanup;
 	    }
 	}
-      else if (tag == GCOV_TAG_FOR_COUNTER (GCOV_COUNTER_ARCS) && fn)
+      else if (tag == GCOV_TAG_FOR_COUNTER (GCOV_COUNTER_CONDS) && fn)
 	{
+	  length = abs (read_length);
+	    if (length != GCOV_TAG_COUNTER_LENGTH (2 * fn->conditions.size ()))
+		goto mismatch;
+
+	    if (read_length > 0)
+	      {
+		for (ix = 0; ix != fn->conditions.size (); ix++)
+		{
+		    fn->conditions[ix]->truev  |= gcov_read_counter ();
+		    fn->conditions[ix]->falsev |= gcov_read_counter ();
+		}
+	      }
+	}
+      else if (tag == GCOV_TAG_FOR_COUNTER (GCOV_COUNTER_ARCS) && fn)
+      {
 	  length = abs (read_length);
 	  if (length != GCOV_TAG_COUNTER_LENGTH (fn->counts.size ()))
-	    goto mismatch;
+	      goto mismatch;
 
 	  if (read_length > 0)
 	    for (ix = 0; ix != fn->counts.size (); ix++)
@@ -2430,6 +2547,13 @@ add_branch_counts (coverage_info *coverage, const arc_info *arc)
     }
 }
 
+static void
+add_condition_counts (coverage_info *coverage, const block_info *block)
+{
+  coverage->conditions += 2 * block->conditions.n_terms;
+  coverage->conditions_covered += block->conditions.popcount ();
+}
+
 /* Format COUNT, if flag_human_readable_numbers is set, return it human
    readable format.  */
 
@@ -2533,6 +2657,18 @@ file_summary (const coverage_info *coverage)
 		 coverage->calls);
       else
 	fnotice (stdout, "No calls\n");
+
+    }
+
+  if (flag_conditions)
+    {
+      if (coverage->conditions)
+	fnotice (stdout, "Decisions covered:%s of %d\n",
+		 format_gcov (coverage->conditions_covered,
+			      coverage->conditions, 2),
+		 coverage->conditions);
+      else
+	fnotice (stdout, "No decisions\n");
     }
 }
 
@@ -2760,6 +2896,12 @@ static void accumulate_line_info (line_info *line, source_info *src,
 	 it != line->branches.end (); it++)
       add_branch_counts (&src->coverage, *it);
 
+  if (add_coverage)
+    for (vector<block_info *>::iterator it = line->blocks.begin ();
+	 it != line->blocks.end (); it++)
+      add_condition_counts (&src->coverage, *it);
+
+
   if (!line->blocks.empty ())
     {
       /* The user expects the line count to be the number of times
@@ -2861,6 +3003,33 @@ accumulate_line_counts (source_info *src)
       }
 }
 
+static void
+output_conditions (FILE *gcov_file, const block_info *binfo)
+{
+    const condition_info& info = binfo->conditions;
+    if (info.n_terms == 0)
+	return;
+
+    const int expected = 2 * info.n_terms;
+    const int got = info.popcount ();
+
+    fnotice (gcov_file, "decisions covered %d/%d\n", got, expected);
+    if (expected == got)
+	return;
+
+    for (unsigned i = 0; i < info.n_terms; i++)
+    {
+	gcov_type_unsigned index = 1;
+	index <<= i;
+	if ((index & info.truev & info.falsev))
+	    continue;
+
+	const char *t = (index & info.truev) ? "" : "true";
+	const char *f = (index & info.falsev) ? "" : " false";
+	fnotice (gcov_file, "condition %2u not covered (%s%s)\n", i, t, f + !t[0]);
+    }
+}
+
 /* Output information about ARC number IX.  Returns nonzero if
    anything is output.  */
 
@@ -3071,16 +3240,29 @@ output_line_details (FILE *f, const line_info *line, unsigned line_num)
 	  if (flag_branches)
 	    for (arc = (*it)->succ; arc; arc = arc->succ_next)
 	      jx += output_branch_count (f, jx, arc);
+
+	  if (flag_conditions)
+	      output_conditions (f, *it);
 	}
     }
-  else if (flag_branches)
+  else
     {
-      int ix;
+      if (flag_branches)
+	{
+	  int ix;
+
+	  ix = 0;
+	  for (vector<arc_info *>::const_iterator it = line->branches.begin ();
+		  it != line->branches.end (); it++)
+	      ix += output_branch_count (f, ix, (*it));
+	}
 
-      ix = 0;
-      for (vector<arc_info *>::const_iterator it = line->branches.begin ();
-	   it != line->branches.end (); it++)
-	ix += output_branch_count (f, ix, (*it));
+      if (flag_conditions)
+	{
+	  for (vector<block_info *>::const_iterator it = line->blocks.begin ();
+	       it != line->blocks.end (); it++)
+	      output_conditions (f, *it);
+	}
     }
 }
 
diff --git a/gcc/ipa-inline.cc b/gcc/ipa-inline.cc
index 14969198cde..3e37305843e 100644
--- a/gcc/ipa-inline.cc
+++ b/gcc/ipa-inline.cc
@@ -646,7 +646,7 @@ can_early_inline_edge_p (struct cgraph_edge *e)
 			 "  edge not inlinable: not in SSA form\n");
       return false;
     }
-  else if (profile_arc_flag
+  else if ((profile_arc_flag || profile_condition_flag)
 	   && ((lookup_attribute ("no_profile_instrument_function",
 				 DECL_ATTRIBUTES (caller->decl)) == NULL_TREE)
 	       != (lookup_attribute ("no_profile_instrument_function",
diff --git a/gcc/ipa-split.cc b/gcc/ipa-split.cc
index 16734617d03..07d2b17ab12 100644
--- a/gcc/ipa-split.cc
+++ b/gcc/ipa-split.cc
@@ -1929,7 +1929,8 @@ pass_split_functions::gate (function *)
   /* When doing profile feedback, we want to execute the pass after profiling
      is read.  So disable one in early optimization.  */
   return (flag_partial_inlining
-	  && !profile_arc_flag && !flag_branch_probabilities);
+      && !profile_arc_flag && !flag_branch_probabilities
+      && !profile_condition_flag);
 }
 
 } // anon namespace
diff --git a/gcc/passes.cc b/gcc/passes.cc
index 78a07f8691a..3457ad1c5b3 100644
--- a/gcc/passes.cc
+++ b/gcc/passes.cc
@@ -352,7 +352,8 @@ finish_optimization_passes (void)
   gcc::dump_manager *dumps = m_ctxt->get_dumps ();
 
   timevar_push (TV_DUMP);
-  if (profile_arc_flag || flag_test_coverage || flag_branch_probabilities)
+  if (profile_arc_flag || profile_condition_flag || flag_test_coverage
+      || flag_branch_probabilities)
     {
       dumps->dump_start (pass_profile_1->static_pass_number, NULL);
       end_branch_prob ();
diff --git a/gcc/profile.cc b/gcc/profile.cc
index 08af512cbca..a4751279571 100644
--- a/gcc/profile.cc
+++ b/gcc/profile.cc
@@ -66,9 +66,19 @@ along with GCC; see the file COPYING3.  If not see
 #include "cfgloop.h"
 #include "sreal.h"
 #include "file-prefix-map.h"
+#include "stringpool.h"
 
 #include "profile.h"
 
+struct condcov;
+struct condcov *find_conditions (struct function*);
+unsigned cov_length (const struct condcov*);
+array_slice<basic_block> cov_blocks (struct condcov*, unsigned);
+array_slice<gcov_type_unsigned > cov_masks (struct condcov*, unsigned);
+void cov_free (struct condcov*);
+int instrument_decisions (array_slice<basic_block>, unsigned, tree*,
+			  gcov_type_unsigned*);
+
 /* Map from BBs/edges to gcov counters.  */
 vec<gcov_type> bb_gcov_counts;
 hash_map<edge,gcov_type> *edge_gcov_counts;
@@ -100,6 +110,7 @@ static int total_num_passes;
 static int total_num_times_called;
 static int total_hist_br_prob[20];
 static int total_num_branches;
+static int total_num_conds;
 
 /* Forward declarations.  */
 static void find_spanning_tree (struct edge_list *);
@@ -1154,6 +1165,12 @@ read_thunk_profile (struct cgraph_node *node)
    the flow graph that are needed to reconstruct the dynamic behavior of the
    flow graph.  This data is written to the gcno file for gcov.
 
+   When FLAG_PROFILE_CONDITIONS is nonzero, this functions instruments the
+   edges in the control flow graph to track what conditions are evaluated to in
+   order to determine what conditions are covered and have an independent
+   effect on the outcome (modified condition/decision coverage).  This data is
+   written to the gcno file for gcov.
+
    When FLAG_BRANCH_PROBABILITIES is nonzero, this function reads auxiliary
    information from the gcda file containing edge count information from
    previous executions of the function being compiled.  In this case, the
@@ -1172,6 +1189,7 @@ branch_prob (bool thunk)
   struct edge_list *el;
   histogram_values values = histogram_values ();
   unsigned cfg_checksum, lineno_checksum;
+  bool output_to_file;
 
   total_num_times_called++;
 
@@ -1396,10 +1414,18 @@ branch_prob (bool thunk)
 
   /* Write the data from which gcov can reconstruct the basic block
      graph and function line numbers (the gcno file).  */
+  output_to_file = false;
   if (coverage_begin_function (lineno_checksum, cfg_checksum))
     {
       gcov_position_t offset;
 
+      /* The condition coverage needs a deeper analysis to identify expressions
+       * of conditions, which means it is not yet ready to write to the gcno
+       * file.  It will write its entries later, but needs to know if it do it
+       * in the first place, which is controlled by the return value of
+       * coverage_begin_function. */
+      output_to_file = true;
+
       /* Basic block flags */
       offset = gcov_write_tag (GCOV_TAG_BLOCKS);
       gcov_write_unsigned (n_basic_blocks_for_fn (cfun));
@@ -1511,29 +1537,74 @@ branch_prob (bool thunk)
 
   remove_fake_edges ();
 
+  if (profile_condition_flag || profile_arc_flag)
+      gimple_init_gcov_profiler ();
+
+  if (profile_condition_flag)
+    {
+      struct condcov *cov = find_conditions (cfun);
+      gcc_assert (cov);
+      const unsigned nconds = cov_length (cov);
+      total_num_conds += nconds;
+
+      if (coverage_counter_alloc (GCOV_COUNTER_CONDS, 2 * nconds))
+	{
+	  /* Add two extra variables to the function for the local
+	     accumulators, which are zero'd on the entry of a new conditional.
+	     The local accumulators are shared between decisions in order to
+	     use less stack space. */
+	  tree accu[2] = {
+	    build_decl (UNKNOWN_LOCATION, VAR_DECL,
+			get_identifier ("__accu_t"), get_gcov_type ()),
+	    build_decl (UNKNOWN_LOCATION, VAR_DECL,
+			get_identifier ("__accu_f"), get_gcov_type ()),
+	  };
+
+	  gcov_position_t offset {};
+	  if (output_to_file)
+	      offset = gcov_write_tag (GCOV_TAG_CONDS);
+
+	  for (unsigned i = 0; i < nconds; ++i)
+	    {
+	      array_slice<basic_block> expr = cov_blocks (cov, i);
+	      array_slice<gcov_type_unsigned> masks = cov_masks (cov, i);
+	      gcc_assert (expr.is_valid ());
+	      gcc_assert (masks.is_valid ());
+
+	      int terms = instrument_decisions (expr, i, accu, masks.begin ());
+	      if (output_to_file)
+		{
+		  gcov_write_unsigned (expr.front ()->index);
+		  gcov_write_unsigned (terms);
+		}
+	    }
+	  if (output_to_file)
+	      gcov_write_length (offset);
+	}
+      cov_free (cov);
+    }
+
   /* For each edge not on the spanning tree, add counting code.  */
   if (profile_arc_flag
       && coverage_counter_alloc (GCOV_COUNTER_ARCS, num_instrumented))
     {
       unsigned n_instrumented;
 
-      gimple_init_gcov_profiler ();
-
       n_instrumented = instrument_edges (el);
 
       gcc_assert (n_instrumented == num_instrumented);
 
       if (flag_profile_values)
 	instrument_values (values);
-
-      /* Commit changes done by instrumentation.  */
-      gsi_commit_edge_inserts ();
     }
 
   free_aux_for_edges ();
 
   values.release ();
   free_edge_list (el);
+  /* Commit changes done by instrumentation.  */
+  gsi_commit_edge_inserts ();
+
   coverage_end_function (lineno_checksum, cfg_checksum);
   if (flag_branch_probabilities
       && (profile_status_for_fn (cfun) == PROFILE_READ))
@@ -1663,6 +1734,7 @@ init_branch_prob (void)
   total_num_passes = 0;
   total_num_times_called = 0;
   total_num_branches = 0;
+  total_num_conds = 0;
   for (i = 0; i < 20; i++)
     total_hist_br_prob[i] = 0;
 }
@@ -1702,5 +1774,7 @@ end_branch_prob (void)
 		     (total_hist_br_prob[i] + total_hist_br_prob[19-i]) * 100
 		     / total_num_branches, 5*i, 5*i+5);
 	}
+      fprintf (dump_file, "Total number of conditions: %d\n",
+	       total_num_conds);
     }
 }
diff --git a/gcc/testsuite/g++.dg/gcov/gcov-18.C b/gcc/testsuite/g++.dg/gcov/gcov-18.C
new file mode 100644
index 00000000000..310ed5297c0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/gcov/gcov-18.C
@@ -0,0 +1,234 @@
+/* { dg-options "--coverage -fprofile-conditions -std=c++11" } */
+/* { dg-do run { target native } } */
+
+#include <vector>
+#include <stdexcept>
+
+class nontrivial_destructor
+{
+public:
+    explicit nontrivial_destructor (int v) : val (v) {}
+    ~nontrivial_destructor () {}
+
+    explicit operator bool() const { return bool(val); }
+
+    int val;
+};
+
+int identity (int x) { return x; }
+int throws (int) { throw std::runtime_error("exception"); }
+
+int throw_if (int x)
+{
+    if (x) /* conditions(1/2) true(0) */
+	   /* conditions(end) */
+	throw std::runtime_error("exception");
+    return x;
+}
+
+/* used for side effects to insert nodes in conditional bodies etc. */
+int x = 0;
+
+/* conditionals work in the presence of non-trivial destructors */
+void mcdc001a (int a)
+{
+    nontrivial_destructor v (a);
+
+    if (v.val > 0) /* conditions(2/2) */
+	x = v.val;
+    else
+	x = -v.val;
+}
+
+/* non-trivial destructor in-loop temporary */
+nontrivial_destructor
+mcdc002a (int a, int b)
+{
+    for (int i = 0; i < a; i++) /* conditions(2/2) */
+    {
+	nontrivial_destructor tmp (a);
+	if (tmp.val % b) /* conditions(2/2) */
+	    return nontrivial_destructor (0);
+	x += i;
+    } /* conditions(suppress) */
+      /* conditions(end) */
+
+    return nontrivial_destructor (a * b);
+}
+
+/* conditional in constructor */
+void mcdc003a (int a)
+{
+    class C
+    {
+    public:
+	explicit C (int e) : v (e)
+	{
+	    if (e) /* conditions(1/2) false(0) */
+		v = x - e;
+	}
+	int v;
+    };
+
+    C c (a);
+    if (c.v > 2) /* conditions(1/2) true(0) */
+		 /* conditions(end) */
+	x = c.v + a;
+}
+
+/* conditional in destructor */
+void mcdc004a (int a)
+{
+    class C
+    {
+    public:
+	explicit C (int e) : v (e) {}
+	~C ()
+	{
+	    if (v) /* conditions(2/2) */
+		x = 2 * v;
+	}
+	int v;
+    };
+
+    C c (a);
+    x = 1; // arbitrary action between ctor+dtor
+}
+
+/* conditional in try */
+void mcdc005a (int a)
+{
+    try
+    {
+	if (a) /* conditions(1/2) true(0) */
+	       /* conditions(end) */
+	    x = 2 * identity (a);
+	else
+	    x = 1;
+    }
+    catch (...)
+    {
+	x = 0;
+    }
+}
+
+/* conditional in catch */
+void mcdc006a (int a) {
+    try
+    {
+	throws (a);
+    }
+    catch (std::exception&)
+    {
+	if (a) /* conditions(1/2) false(0) */
+	       /* conditions(end) */
+	    x = identity (a);
+	else
+	    x = 0;
+    }
+}
+
+void mcdc006b (int a)
+{
+    if (a) /* conditions(1/2) true(0) */
+	   /* conditions(end) */
+	throws (a);
+    else
+	x = 1;
+}
+
+void mcdc006c (int a) try
+{
+    throws (a);
+}
+catch (...) {
+    if (a) /* conditions(2/2) */
+	x = 5;
+}
+
+/* temporary with destructor as term */
+void mcdc007a (int a, int b)
+{
+    x = a && nontrivial_destructor (b); /* conditions(3/4) false(1) destructor() */
+}
+
+void mcdc007b (int a, int b)
+{
+    if (a || throw_if (b)) /* conditions(3/4) true(1) destructor() */
+	x = -1;
+    else
+	x = 1;
+}
+
+void mcdc007c (int a, int b)
+{
+    if (throw_if (a) || throw_if (b)) /* conditions(2/4) true(0 1) destructor() */
+	x = -1;
+    else
+	x = 1;
+}
+
+/* destructor with delete */
+void mcdc008a (int a)
+{
+    class C
+    {
+    public:
+        int size = 5;
+        int* ptr = nullptr;
+
+        explicit C (int v) : size (v + 5), ptr (new int[size]) /* conditions(suppress) */
+							       /* conditions(end) */
+        {
+	    for (int i = 0; i < size; i++) /* conditions(2/2) */
+		ptr[i] = i + 1;
+        }
+        ~C()
+        {
+	    // delete with implicit nullptr check
+	    delete ptr; /* conditions(1/2) false(0) */
+			/* conditions(end) */
+	}
+    };
+
+    C c (a);
+    if (c.ptr[a + 1]) /* conditions(1/2) false(0) */
+	x = a;
+}
+
+int
+main (void)
+{
+    mcdc001a (0);
+    mcdc001a (1);
+
+    mcdc002a (1, 1);
+    mcdc002a (1, 2);
+
+    mcdc003a (1);
+
+    mcdc004a (0);
+    mcdc004a (1);
+
+    mcdc005a (0);
+
+    mcdc006a (1);
+
+    mcdc006b (0);
+
+    mcdc006c (0);
+    mcdc006c (1);
+
+    mcdc007a (0, 0);
+    mcdc007a (1, 1);
+
+    mcdc007b (0, 0);
+    mcdc007b (1, 0);
+
+    mcdc007c (0, 0);
+
+    mcdc008a (1);
+
+}
+
+/* { dg-final { run-gcov conditions { --conditions gcov-18.C } } } */
diff --git a/gcc/testsuite/gcc.misc-tests/gcov-19.c b/gcc/testsuite/gcc.misc-tests/gcov-19.c
new file mode 100644
index 00000000000..fb3be7dac76
--- /dev/null
+++ b/gcc/testsuite/gcc.misc-tests/gcov-19.c
@@ -0,0 +1,1137 @@
+/* { dg-options "-fprofile-conditions -ftest-coverage" } */
+/* { dg-do run { target native } } */
+
+/* some side effect to stop branches from being pruned */
+int x = 0;
+
+/* || works */
+void
+mcdc001a (int a, int b)
+{
+    if (a || b) /* conditions(1/4) true(0) false(0 1) */
+		/* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc001b (int a, int b)
+{
+    if (a || b) /* conditions(3/4) true(0) */
+		/* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc001c (int a, int b)
+{
+    if (a || b) /* conditions(4/4) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc001d (int a, int b, int c)
+{
+    if (a || b || c) /* conditions(2/6) false(0 1 2) true(2) */
+		     /* conditions(end) */
+	x = 1;
+}
+
+/* && works */
+void
+mcdc002a (int a, int b)
+{
+    if (a && b) /* conditions(1/4) true(0 1) false(0) */
+		/* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc002b (int a, int b)
+{
+    if (a && b) /* conditions(3/4) false(0) */
+		/* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc002c (int a, int b)
+{
+    if (a && b) /* conditions(4/4) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc002d (int a, int b, int c)
+{
+    if (a && b && c) /* conditions(4/6) false(0 2) */
+		     /* conditions(end) */
+	x = 1;
+}
+
+/* negation works */
+void
+mcdc003a (int a, int b)
+{
+    if (!a || !b) /* conditions(2/4) false(0 1) */
+		  /* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+/* single conditionals with and without else */
+void
+mcdc004a (int a)
+{
+    if (a) /* conditions(1/2) true(0) */
+	   /* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc004b (int a)
+{
+    if (a) /* conditions(2/2) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc004c (int a)
+{
+    if (a) /* conditions(1/2) false(0) */
+	   /* conditions(end) */
+	x = 1;
+}
+
+void
+mcdc004d (int a, int b, int c)
+{
+    /* With no else this is interpreted as (a && (b || c)) */
+    if (a)  /* conditions(3/6) true(2) false(1 2)*/
+    {
+	if (b || c)
+	    x = a + b + c;
+    }
+}
+
+void
+mcdc004e (int a, int b, int c)
+{
+    /* With the else, this is interpreted as 2 expressions */
+    if (a)  /* conditions(2/2) */
+    {
+	if (b || c) /* conditions(1/4) true(1) false(0 1) */
+	    x = a + b + c;
+    }
+    else
+    {
+	x = c;
+    }
+}
+
+/* mixing && and || works */
+void
+mcdc005a (int a, int b, int c)
+{
+    if ((a && b) || c) /* conditions(1/6) true(0 1) false(0 1 2) */
+		       /* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc005b (int a, int b, int c, int d)
+{
+    /* This is where masking MC/DC gets unintuitive:
+
+       1 1 0 0 => covers 1 (d = 0) as && 0 masks everything to the left
+       1 0 0 0 => covers 2 (b = 0, c = 0) as (a && 0) masks a and d is never
+       evaluated. */
+    if ((a && (b || c)) && d) /* conditions(3/8) true(0 1 2 3) false(0) */
+			      /* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc005c (int a, int b, int c, int d)
+{
+    if (a || (b && c) || d) /* conditions(2/8) true(0 3) false(0 1 2 3) */
+			    /* conditions(end) */
+        x = a + b + c + d;
+}
+
+void
+mcdc005d (int a, int b, int c, int d)
+{
+    /* This test is quite significant - it has a single input
+       (1, 0, 0, 0) and tests specifically for when a multi-term left operand
+       is masked. d = 0 should mask a || b and for the input there are no other
+       sources for masking a (since b = 0). */
+    if ((a || b) && (c || d)) /* conditions(2/8) true(0 1 2 3) false(0 1) */
+			      /* conditions(end) */
+	x = a + b;
+    else
+	x = c + d;
+}
+
+/* nested conditionals */
+void
+mcdc006a (int a, int b, int c, int d, int e)
+{
+    if (a) /* conditions(2/2) */
+    {
+	if (b && c) /* conditions(3/4) false(1) */
+		    /* conditions(end) */
+	    x = 1;
+	else
+	    x = 2;
+    }
+    else
+    {
+	if (c || d) /* conditions(2/4) true(0 1) */
+		    /* conditions(end) */
+	    x = 3;
+	else
+	    x = 4;
+    }
+}
+
+void
+mcdc006b (int a, int b, int c)
+{
+    if (a) /* conditions(6/6) */
+	if (b)
+	    if (c)
+		x = a + b + c;
+}
+
+void
+mcdc006c (int a, int b, int c)
+{
+    if (a) /* conditions(2/2) */
+    {
+	if (b) /*conditions(2/2) */
+	{
+	    if (c) /* conditions(2/2) */
+	    {
+		x = a + b + c;
+	    }
+	}
+	else
+	{
+	    x = b;
+	}
+    }
+    else
+    {
+	x = a;
+    }
+}
+
+/* else/if */
+void
+mcdc007a (int a, int b, int c, int d)
+{
+    if (a) /* conditions(2/2) */
+    {
+	if (b) /* conditions(1/2) true(0) */
+	       /* conditions(end) */
+	    x = 1;
+	else
+	    x = 2;
+    }
+    else if (c) /* conditions(2/2) */
+    {
+	if (d) /* conditions(1/2) true(0) */
+	       /* conditions(end) */
+	    x = 3;
+	else
+	    x = 4;
+    }
+}
+
+void
+mcdc007b (int a, int b, int c)
+{
+    goto begin;
+then:
+    x = 1;
+    return;
+begin:
+    /* similar to if (a || b || c) x = 1 */
+    if (a) /* conditions(2/2) */
+	goto then;
+    else if (b) /* conditions(2/2) */
+	goto then;
+    else if (c) /* conditions(1/2) true(0) */
+		/* conditions(end) */
+	goto then;
+}
+
+/* while loop */
+void
+mcdc008a (int a)
+{
+    while (a < 10) /* conditions(2/2) */
+	x = a++;
+}
+
+void
+mcdc008b (int a)
+{
+    while (a > 10) /* conditions(1/2) true(0) */
+		   /* conditions(end) */
+	x = a--;
+}
+
+void
+mcdc008c (int a)
+{
+    // should work, even with no body
+    while (a) /* conditions(2/2) */
+	break;
+}
+
+void
+mcdc008d (int a, int b, int c, int d)
+{
+    /* multi-term loop conditional */
+    while ((a && (b || c)) && d) /* conditions(8/8) */
+	a = b = c = d = 0;
+}
+
+void
+mcdc009a (int a, int b)
+{
+    while (a > 0 && b > 0) /* conditions(3/4) false(1) */
+			   /* conditions(end) */
+	x = a--;
+}
+
+/* for loop */
+void
+mcdc010a(int a, int b)
+{
+    for (int i = 0; i < b; i++) /* conditions(2/2) */
+    {
+	if (a < b) /* conditions(2/2) */
+	    x = 1;
+	else
+	    x = a += 2;
+    }
+}
+
+void
+mcdc010b ()
+{
+    for (int a = 0; a <= 1; ++a) /* conditions(2/2) */
+    {
+	x = a;
+    }
+}
+
+int always (int x) { (void) x; return 1; }
+
+/* no-condition infinite loops */
+void
+mcdc010c (int a)
+{
+    for (;;)
+    {
+	if (always(a)) /* conditions(1/2) false(0) */
+		       /* conditions(end) */
+	{
+	    x = a;
+	    break;
+	}
+	x += a + 1;
+    }
+}
+
+/* conditionals without control flow constructs work */
+void
+mcdc011a (int a, int b, int c)
+{
+    x = (a && b) || c; /* conditions(5/6) false(1) */
+		       /* conditions(end) */
+}
+
+/* sequential expressions are handled independently */
+void
+mcdc012a (int a, int b, int c)
+{
+    if (a || b) /* conditions(3/4) true(0) */
+		/* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+
+    if (c) /* conditions(2/2) */
+	x = 1;
+}
+
+/*
+ * cannot ever satisfy MC/DC, even with all input combinations, because not all
+ * variables independently affect the decision
+ */
+void
+mcdc013a (int a, int b, int c)
+{
+    (void)b;
+    /*
+     * Specification: (a && b) || c
+     *
+     * But the expression was implemented wrong. This has branch coverage, but
+     * not MC/DC
+     */
+    if ((a && !c) || c) /* conditions(5/6) false(1) */
+	/* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+void
+mcdc014a ()
+{
+    int conds[64] = { 0 };
+    /* conditions(64/128) true(0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63) */
+    x = conds[ 0] || conds[ 1] || conds[ 2] || conds[ 3] || conds[ 4] ||
+	conds[ 5] || conds[ 6] || conds[ 7] || conds[ 8] || conds[ 9] ||
+	conds[10] || conds[11] || conds[12] || conds[13] || conds[14] ||
+	conds[15] || conds[16] || conds[17] || conds[18] || conds[19] ||
+	conds[20] || conds[21] || conds[22] || conds[23] || conds[24] ||
+	conds[25] || conds[26] || conds[27] || conds[28] || conds[29] ||
+	conds[30] || conds[31] || conds[32] || conds[33] || conds[34] ||
+	conds[35] || conds[36] || conds[37] || conds[38] || conds[39] ||
+	conds[40] || conds[41] || conds[42] || conds[43] || conds[44] ||
+	conds[45] || conds[46] || conds[47] || conds[48] || conds[49] ||
+	conds[50] || conds[51] || conds[52] || conds[53] || conds[54] ||
+	conds[55] || conds[56] || conds[57] || conds[58] || conds[59] ||
+	conds[60] || conds[61] || conds[62] || conds[63]
+	;  /* conditions(end) */
+}
+
+/* early returns */
+void
+mcdc015a (int a, int b)
+{
+    if (a) /* conditions(2/2) */
+	return;
+
+    if (b) /* conditions(1/2) true(0) */
+	   /* conditions(end) */
+	x = 1;
+}
+
+void
+mcdc015b (int a, int b)
+{
+    for (int i = 5; i > a; i--) /* conditions(2/2) */
+    {
+	if (i == b) /* conditions(2/2) */
+	    return;
+	x = i;
+    }
+}
+
+void
+mcdc015c (int a, int b)
+{
+    for (int i = 5; i > a; i--) /* conditions(2/2) */
+    {
+	if (i == b) /* conditions(2/2) */
+	{
+	    x = 0;
+	    return;
+	}
+	else
+	{
+	    x = 1;
+	    return;
+	}
+
+	x = i;
+    }
+}
+
+
+/* check nested loops */
+void
+mcdc016a (int a, int b)
+{
+    for (int i = 0; i < a; i++) /* conditions(2/2) */
+	for (int k = 0; k < b; k++) /* conditions(2/2) */
+	    x = i + k;
+}
+
+void
+mcdc016b (int a, int b)
+{
+    for (int i = 0; i < a; i++) /* conditions(2/2) */
+    {
+	if (a > 5) /* conditions(2/2) */
+	    break;
+
+	for (int k = 0; k < b; k++) /* conditions(2/2) */
+	    x = i + k;
+    }
+}
+
+void
+mcdc016c (int a, int b)
+{
+    for (int i = 0; i < a; i++) /* conditions(2/2) */
+    {
+	if (a > 5) /* conditions(1/2) true(0) */
+		   /* conditions(end) */
+	    return;
+
+	for (int k = 0; k < b; k++) /* conditions(2/2) */
+	    x = i + k;
+    }
+}
+
+void
+mcdc016d (int a, int b)
+{
+    for (int i = 0; i < a; i++) /* conditions(2/2) */
+    {
+	for (int k = 0; k < 5; k++) /* conditions(2/2) */
+	{
+	    if (b > 5) /* conditions(1/2) true(0) */
+		       /* conditions(end) */
+		return;
+	    x = i + k;
+	}
+
+    }
+}
+
+/* do-while loops */
+void
+mcdc017a (int a)
+{
+    do
+    {
+	a--;
+    } while (a > 0); /* conditions(2/2) */
+}
+
+void
+noop () {}
+
+void
+mcdc017b (int a, int b)
+{
+    do
+    {
+	/*
+	 * This call is important; it can add more nodes to the body in the
+	 * CFG, which has changes how close exits and breaks are to the loop
+	 * conditional.
+	 */
+	noop ();
+	a--;
+	if (b) /* conditions(2/2) */
+	    break;
+
+    } while (a > 0); /* conditions(2/2) */
+}
+
+void
+mcdc017c (int a, int b)
+{
+    int left = 0;
+    int right = 0;
+    int n = a + b;
+    do
+    {
+	if (a) /* conditions(1/2) false(0) */
+	       /* conditions(end) */
+	{
+	    left = a > left ? b : left; /* conditions(2/2) */
+	}
+	if (b) /* conditions(1/2) false(0) */
+	{
+	    right = b > right ? a : right; /* conditions(2/2) */
+	}
+    } while (n-- > 0); /* conditions(2/2) */
+}
+
+int id  (int x) { return  x; }
+int inv (int x) { return !x; }
+
+/* collection of odd cases lifted-and-adapted from real-world code */
+int mcdc018a (int a, int b, int c, int d, int e, int f, int g, int len)
+{
+    int n;
+    /* adapted from zlib/gz_read */
+    do
+    {
+	n = -1;
+	if (n > len) /* conditions(2/2) */
+	    n = len;
+
+	if (b) /* conditions(2/2) */
+	{
+	    if (b < 5) /* conditions(2/2) */
+		x = 1;
+	    noop();
+	}
+	else if (c && d) /* conditions(3/4) false(1) */
+	{
+	    x = 2;
+	    break;
+	}
+	else if (e || f) /* conditions(2/4) false(0 1) */
+			 /* conditions(end) */
+	{
+	    if (id(g)) /* conditions(2/2) */
+		return 0;
+	    continue;
+	}
+    } while (a-- > 0); /* conditions(2/2) */
+
+    return 1;
+}
+
+void
+mcdc018b (int a, int b, int c)
+{
+    int n;
+    while (a) /* conditions(2/2) */
+    {
+	/* else block does not make a difference for the problem, but ensures
+	   loop termination. */
+	if (b) /* conditions(2/2) */
+	    n = c ? 0 : 0; // does not show up in CFG (embedded in the block)
+	else
+	    n = 0;
+	a = n;
+    }
+}
+
+/* Adapted from zlib/compress2 */
+void
+mcdc018c (int a, int b)
+{
+    int err;
+    do
+    {
+	a = inv (a);
+	err = a;
+    } while (err); /* conditions(1/2) true(0) */
+		   /* conditions(end) */
+
+    a = id (a);
+    if (a) /* conditions(1/2) true(0) */
+	x *= a + 1;
+}
+
+/* too many conditions, coverage gives up */
+void
+mcdc019a ()
+{
+    int conds[65] = { 0 };
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wcoverage-too-many-conditions"
+    x = conds[ 0] || conds[ 1] || conds[ 2] || conds[ 3] || conds[ 4] ||
+	conds[ 5] || conds[ 6] || conds[ 7] || conds[ 8] || conds[ 9] ||
+	conds[10] || conds[11] || conds[12] || conds[13] || conds[14] ||
+	conds[15] || conds[16] || conds[17] || conds[18] || conds[19] ||
+	conds[20] || conds[21] || conds[22] || conds[23] || conds[24] ||
+	conds[25] || conds[26] || conds[27] || conds[28] || conds[29] ||
+	conds[30] || conds[31] || conds[32] || conds[33] || conds[34] ||
+	conds[35] || conds[36] || conds[37] || conds[38] || conds[39] ||
+	conds[40] || conds[41] || conds[42] || conds[43] || conds[44] ||
+	conds[45] || conds[46] || conds[47] || conds[48] || conds[49] ||
+	conds[50] || conds[51] || conds[52] || conds[53] || conds[54] ||
+	conds[55] || conds[56] || conds[57] || conds[58] || conds[59] ||
+	conds[60] || conds[61] || conds[62] || conds[63] || conds[64]
+	;
+    #pragma GCC diagnostic pop
+}
+
+/* ternary */
+void
+mcdc020a (int a)
+{
+    // special case, this can be reduced to:
+    // _1 = argc != 0;
+    // e = (int) _1;
+    x = a ? 1 : 0;
+
+    // changing to different int makes branch
+    x = a ? 2 : 1; /* conditions(2/2) */
+}
+
+void
+mcdc020b (int a, int b)
+{
+    x = (a || b) ? 1 : 0; /* conditions(3/4) true(1) */
+}
+
+void
+mcdc020c (int a, int b)
+{
+    x = a ? 0
+	: b ? 1 /* conditions(2/2) */
+	: 2;    /* conditions(1/2) false(0) */
+		/* conditions(end) */
+}
+
+/* Infinite loop (no exit-edge), this should not be called, but it should
+   compile fine */
+void
+mcdc021a ()
+{
+    while (1)
+	;
+}
+
+/* Computed goto can give all sorts of problems, including difficult path
+   contractions. */
+void
+mcdc021b ()
+{
+  void *op = &&dest;
+dest:
+  if (op) /* conditions(0/2) true(0) false(0) */
+	  /* conditions(end) */
+    goto * 0;
+}
+
+int __sigsetjmp ();
+
+/* This should compile, but not called. */
+void
+mcdc021c ()
+{
+  while (x) /* conditions(0/2) true(0) false(0)*/
+	    /* conditions(end) */
+     __sigsetjmp ();
+}
+
+/* If edges are not properly contracted the a && id (b) will be interpreted as
+   two independent expressions. */
+void
+mcdc021d (int a, int b, int c, int d)
+{
+    if (a && id (b)) /* conditions(1/4) true(0 1) false(0) */
+		     /* conditions(end) */
+	x = 1;
+    else if (c && id (d)) /* conditions(1/4) true(0 1) false(0) */
+			  /* conditions(end) */
+	x = 2;
+    else
+	x = 3;
+}
+
+/* Adapted from linux arch/x86/tools/relocs.c
+   With poor edge contracting this became an infinite loop. */
+void
+mcdc022a (int a, int b)
+{
+    for (int i = 0; i < 5; i++) /* conditions(2/2) */
+    {
+	x = i;
+	for (int j = i; j < 5; j++) /* conditions(2/2) */
+	{
+	    if (id (id (a)) || id (b)) /* conditions(3/4) true(0) */
+				       /* conditions(end) */
+		continue;
+	    b = inv(b);
+	}
+    }
+}
+
+int
+mcdc022b (int a)
+{
+    int devt;
+    if (a) /* conditions(2/2) */
+    {
+	x = a * 2;
+	if (x != a / 10 || x != a % 10) /* conditions(1/4) true(1) false(0 1) */
+					/* conditions(end) */
+	    return 0;
+    } else {
+	devt = id (a);
+	if (devt) /* conditions(1/2) true(0) */
+		  /* conditions(end) */
+	    return 0;
+    }
+
+    return devt;
+}
+
+/* Adapted from linux arch/x86/events/intel/ds.c
+
+   It broken sorting so that the entry block was not the first node after
+   sorting. */
+void
+mcdc022c (int a)
+{
+    if (!a) /* conditions(2/2) */
+	return;
+
+    for (int i = 0; i < 5; i++) /* conditions(2/2) */
+    {
+	if (id (a + i) || inv (a - 1)) /* conditions(1/4) false(0 1) true(1) */
+				       /* conditions(end) */
+	    x = a + i;
+	if (inv (a)) /* conditions(1/2) true(0) */
+		     /* conditions(end) */
+	    break;
+    }
+}
+
+void
+mcdc022d (int a)
+{
+    int i;
+    for (i = 0; i < id (a); i++) /* conditions(1/2) false(0) */
+    {
+	if (!inv (a)) /* conditions(1/2) false(0)*/
+		      /* conditions(end) */
+	    break;
+    }
+
+    if (i < a) /* conditions(1/2) false(0) */
+	       /* conditions(end) */
+	x = a + 1;
+}
+
+/* 023 specifically tests that masking works correctly, which gets complicated
+   fast with a mix of operators and deep subexpressions.  These tests violates
+   the style guide slightly to emphasize the nesting.  They all share the same
+   implementation and only one input is given to each function to obtain clean
+   coverage results. */
+void
+mcdc023a (int a, int b, int c, int d, int e, int f, int g, int h, int i, int k,
+	  int l, int m, int n)
+{
+    // [a m n] = 0, [b, ...] = 1
+    // a is masked by b and the remaining terms should be short circuited
+    if (/* conditions(1/24) true(0 2 3 4 5 6 7 8 9 10 11) false(0 1 2 3 4 5 6 7 8 9 10 11) */
+	/* conditions(end) */
+	   (a || b)
+	|| (   ((c && d) || (e && (f || g) && h))
+	    && (k || l)
+	    && (m || n)))
+	x = a + b;
+    else
+	x = b + c;
+}
+
+void
+mcdc023b (int a, int b, int c, int d, int e, int f, int g, int h, int i, int k,
+	  int l, int m, int n)
+{
+    // [a b d h] = 0, [c, ...] = 1
+    // h = 0 => false but does not mask (a || b) or (c && d). d = 0 masks c.
+    if (/* conditions(4/24) true(0 1 2 3 4 5 6 7 8 9 10 11) false(2 4 5 6 8 9 10 11) */
+	/* conditions(end) */
+	   (a || b)
+	|| (   ((c && d) || (e && (f || g) && h))
+	    && (k || l)
+	    && (m || n)))
+	x = a + b;
+    else
+	x = b + c;
+}
+
+void
+mcdc023c (int a, int b, int c, int d, int e, int f, int g, int h, int i, int k,
+	  int l, int m, int n)
+{
+    /* [m n a b] = 0, [...] = 1
+       n,m = 0 should mask all other terms than a, b */
+    if (/* conditions(4/24) true(0 1 2 3 4 5 6 7 8 9 10 11) false(2 3 4 5 6 7 8 9) */
+	/* conditions(end) */
+	   (a || b)
+	|| (   ((c && d) || (e && (f || g) && h))
+	    && (k || l)
+	    && (m || n)))
+	x = a + b;
+    else
+	x = b + c;
+}
+
+void
+mcdc023d (int a, int b, int c, int d, int e, int f, int g, int h, int i, int k,
+	  int l, int m, int n)
+{
+    /* [a b] = 0, [h, ...] = 1
+       n,m = 0 should mask all other terms than a, b */
+    if (/* conditions(4/24) true(0 1 2 3 4 5 6 7 8 9 10 11) false(2 3 4 5 6 7 10 11) */
+	/* conditions(end) */
+	   (a || b)
+	|| (   ((c && d) || (e && (f || g) && h))
+	    && (k || l)
+	    && (m || n)))
+	x = a + b;
+    else
+	x = b + c;
+}
+
+void
+mcdc023e (int a, int b, int c, int d, int e, int f, int g, int h, int i, int k,
+	  int l, int m, int n)
+{
+    /* [a b d] = 0, [c h, ...] = 1
+       h = 1 should mask c, d, leave other terms intact.
+       If [k l m n] were false then h itself would be masked.
+       [a b] are masked as collateral by [m n]. */
+    if (/* conditions(5/24) true(0 1 2 3 6 9 11) false(0 1 2 3 4 5 6 7 8 9 10 11) */
+	/* conditions(end) */
+	   (a || b)
+	|| (   ((c && d) || (e && (f || g) && h))
+	    && (k || l)
+	    && (m || n)))
+	x = a + b;
+    else
+	x = b + c;
+}
+
+void
+mcdc023f (int a, int b, int c, int d, int e, int f, int g, int h, int i, int k,
+	  int l, int m, int n)
+{
+    /* [a b c f g] = 0, [e, ...] = 1
+       [f g] = 0 should mask e, leave [c d] intact. */
+    if (/* conditions(5/24) true(0 1 2 3 4 5 6 7 8 9 10 11) false(3 4 7 8 9 10 11) */
+	/* conditions(end) */
+	   (a || b)
+	|| (   ((c && d) || (e && (f || g) && h))
+	    && (k || l)
+	    && (m || n)))
+	x = a + b;
+    else
+	x = b + c;
+}
+
+void
+mcdc023g (int a, int b, int c, int d, int e, int f, int g, int h, int i, int k,
+	  int l, int m, int n)
+{
+    /* [a b d f g] = 0, [e c, ...] = 1
+       Same as 023f but with [c d] flipped so d masks c rather than c
+       short-circuits.  This should not be lost. */
+    if (/* conditions(5/24) true(0 1 2 3 4 5 6 7 8 9 10 11) false(2 4 7 8 9 10 11) */
+	/* conditions(end) */
+	   (a || b)
+	|| (   ((c && d) || (e && (f || g) && h))
+	    && (k || l)
+	    && (m || n)))
+	x = a + b;
+    else
+	x = b + c;
+}
+
+int main ()
+{
+    mcdc001a (0, 1);
+
+    mcdc001b (0, 1);
+    mcdc001b (0, 0);
+
+    mcdc001c (0, 1);
+    mcdc001c (0, 0);
+    mcdc001c (1, 1);
+
+    mcdc001d (1, 1, 1);
+    mcdc001d (0, 1, 0);
+
+    mcdc002a (1, 0);
+
+    mcdc002b (1, 0);
+    mcdc002b (1, 1);
+
+    mcdc002c (0, 0);
+    mcdc002c (1, 1);
+    mcdc002c (1, 0);
+
+    mcdc002d (1, 1, 1);
+    mcdc002d (1, 0, 0);
+
+    mcdc003a (0, 0);
+    mcdc003a (1, 0);
+
+    mcdc004a (0);
+    mcdc004b (0);
+    mcdc004b (1);
+    mcdc004c (1);
+
+    mcdc004d (0, 0, 0);
+    mcdc004d (1, 1, 1);
+
+    mcdc004e (0, 0, 0);
+    mcdc004e (1, 1, 1);
+
+    mcdc005a (1, 0, 1);
+
+    mcdc005b (1, 1, 0, 0);
+    mcdc005b (1, 0, 0, 0);
+
+    mcdc005c (0, 1, 1, 0);
+
+    mcdc005d (1, 0, 0, 0);
+
+    mcdc006a (0, 0, 0, 0, 0);
+    mcdc006a (1, 0, 0, 0, 0);
+    mcdc006a (1, 1, 1, 0, 0);
+
+    mcdc006b (0, 0, 0);
+    mcdc006b (1, 0, 0);
+    mcdc006b (1, 1, 0);
+    mcdc006b (1, 1, 1);
+
+    mcdc006c (0, 0, 0);
+    mcdc006c (1, 0, 0);
+    mcdc006c (1, 1, 0);
+    mcdc006c (1, 1, 1);
+
+    mcdc007a (0, 0, 0, 0);
+    mcdc007a (1, 0, 0, 0);
+    mcdc007a (0, 0, 1, 0);
+
+    mcdc007b (0, 0, 0);
+    mcdc007b (0, 1, 1);
+    mcdc007b (1, 0, 1);
+
+    mcdc008a (0);
+
+    mcdc008b (0);
+
+    mcdc008c (0);
+    mcdc008c (1);
+
+    mcdc008d (0, 0, 0, 0);
+    mcdc008d (1, 0, 0, 0);
+    mcdc008d (1, 0, 1, 0);
+    mcdc008d (1, 0, 1, 1);
+    mcdc008d (1, 1, 1, 1);
+
+    mcdc009a (0, 0);
+    mcdc009a (1, 1);
+
+    mcdc010a (0, 0);
+    mcdc010a (0, 9);
+    mcdc010a (2, 1);
+
+    mcdc010b ();
+
+    mcdc010c (1);
+
+    mcdc011a (0, 0, 0);
+    mcdc011a (1, 1, 0);
+    mcdc011a (1, 0, 1);
+
+    mcdc012a (0, 0, 0);
+    mcdc012a (0, 1, 1);
+
+    mcdc013a (0, 0, 0);
+    mcdc013a (0, 0, 1);
+    mcdc013a (0, 1, 0);
+    mcdc013a (0, 1, 1);
+    mcdc013a (1, 0, 0);
+    mcdc013a (1, 0, 1);
+    mcdc013a (1, 1, 0);
+    mcdc013a (1, 1, 1);
+
+    mcdc014a ();
+
+    mcdc015a (0, 0);
+    mcdc015a (1, 0);
+
+    mcdc015b (0, 0);
+    mcdc015b (0, 1);
+    mcdc015b (6, 1);
+
+    mcdc015c (0, 0);
+    mcdc015c (0, 5);
+    mcdc015c (6, 1);
+
+    mcdc016a (5, 5);
+
+    mcdc016b (5, 5);
+    mcdc016b (6, 5);
+
+    mcdc016c (5, 5);
+
+    mcdc016d (1, 0);
+
+    mcdc017a (0);
+    mcdc017a (2);
+
+    mcdc017b (2, 0);
+    mcdc017b (0, 1);
+
+    mcdc017c (1, 1);
+
+    mcdc018a (0, 0, 1, 1, 0, 0, 0, 0);
+    mcdc018a (0, 1, 0, 0, 0, 0, 1, -2);
+    mcdc018a (0, 6, 0, 0, 0, 0, 1, -2);
+    mcdc018a (0, 6, 0, 0, 0, 0, 1, -2);
+    mcdc018a (0, 0, 0, 1, 0, 1, 1, 0);
+    mcdc018a (1, 0, 0, 0, 1, 1, 0, 0);
+
+    mcdc018b (1, 0, 0);
+    mcdc018b (1, 1, 0);
+
+    mcdc018c (1, 1);
+
+    mcdc019a ();
+
+    mcdc020a (0);
+    mcdc020a (1);
+
+    mcdc020b (0, 0);
+    mcdc020b (1, 0);
+
+    mcdc020c (0, 1);
+    mcdc020c (1, 1);
+
+    mcdc021d (1, 0, 1, 0);
+
+    mcdc022a (0, 0);
+
+    mcdc022b (0);
+    mcdc022b (1);
+
+    mcdc022c (0);
+    mcdc022c (1);
+
+    mcdc022d (1);
+
+    mcdc023a (0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1);
+    mcdc023b (0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1);
+    mcdc023c (0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0);
+    mcdc023d (0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1);
+    mcdc023e (0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1);
+    mcdc023f (0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1);
+    mcdc023g (0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1);
+}
+
+/* { dg-final { run-gcov conditions { --conditions gcov-19.c } } } */
diff --git a/gcc/testsuite/gcc.misc-tests/gcov-20.c b/gcc/testsuite/gcc.misc-tests/gcov-20.c
new file mode 100644
index 00000000000..847dae495db
--- /dev/null
+++ b/gcc/testsuite/gcc.misc-tests/gcov-20.c
@@ -0,0 +1,22 @@
+/* { dg-options "-fprofile-conditions -ftest-coverage -fprofile-update=atomic" } */
+/* { dg-do run { target native } } */
+
+/* some side effect to stop branches from being pruned */
+int x = 0;
+
+void
+conditions_atomic001 (int a, int b)
+{
+    if (a || b) /* conditions(1/4) true(0) false(0 1) */
+		/* conditions(end) */
+	x = 1;
+    else
+	x = 2;
+}
+
+int main ()
+{
+    conditions_atomic001 (0, 1);
+}
+
+/* { dg-final { run-gcov conditions { --conditions gcov-20.c } } } */
diff --git a/gcc/testsuite/gcc.misc-tests/gcov-21.c b/gcc/testsuite/gcc.misc-tests/gcov-21.c
new file mode 100644
index 00000000000..978be3276a2
--- /dev/null
+++ b/gcc/testsuite/gcc.misc-tests/gcov-21.c
@@ -0,0 +1,16 @@
+/* { dg-options "-fprofile-conditions" } */
+
+/* https://gcc.gnu.org/pipermail/gcc-patches/2022-April/592927.html */
+char trim_filename_name;
+int r;
+
+void trim_filename() {
+    if (trim_filename_name)
+	r = 123;
+    while (trim_filename_name)
+	;
+}
+
+int main ()
+{
+}
diff --git a/gcc/testsuite/lib/gcov.exp b/gcc/testsuite/lib/gcov.exp
index 9d5b2cdb86b..f1c32ed0138 100644
--- a/gcc/testsuite/lib/gcov.exp
+++ b/gcc/testsuite/lib/gcov.exp
@@ -174,6 +174,184 @@ proc verify-branches { testname testcase file } {
     return $failed
 }
 
+#
+# verify-conditions -- check that conditions are checked as expected
+#
+# TESTNAME is the name of the test, including unique flags.
+# TESTCASE is the name of the test file.
+# FILE is the name of the gcov output file.
+#
+# Checks are based on comments in the source file. Condition coverage comes
+# with with two types of output, a summary and a list of the uncovered
+# conditions. Both must be checked to pass the test
+#
+# To check for conditions, add a comment the line of a conditional:
+# /* conditions(n/m) true(0 1) false(1) */
+#
+# where n/m are the covered and total conditions in the expression. The true()
+# and false() take the indices expected *not* covered.
+#
+# This means that all coverage statements should have been seen:
+# /* conditions(end) */
+#
+# If all conditions are covered i.e. n == m, then conditions(end) can be
+# omitted. If either true() or false() are empty they can be omitted too.
+#
+# C++ can insert conditionals in the CFG that are not present in source code.
+# These must be manually suppressed since unexpected and unhandled conditions
+# are an error (to help combat regressions). Output can be suppressed with
+# conditions(suppress) and conditions(end). suppress should usually be on a
+# closing brace.
+#
+# Some expressions, when using unnamed temporaries as operands, will have
+# destructors in expressions. The coverage of the destructor will be reported
+# on the same line as the expression itself, but suppress() would also swallow
+# the expected tested-for messages. To handle these, use the destructor() [1]
+# which will suppress everything from and including the second "conditions
+# covered".
+#
+# [1] it is important that the destructor() is *on the same line* as the
+#     conditions(m/n)
+proc verify-conditions { testname testcase file } {
+    set failed 0
+    set suppress 0
+    set destructor 0
+    set should ""
+    set shouldt ""
+    set shouldf ""
+    set shouldall ""
+    set fd [open $file r]
+    set n 0
+    set keywords {"end" "suppress"}
+    while {[gets $fd line] >= 0} {
+        regexp "^\[^:\]+: *(\[0-9\]+):" "$line" all n
+        set prefix "$testname line $n"
+
+        if {![regexp "condition" $line] && ![regexp "decision" $line]} {
+            continue
+        }
+
+        # Missing coverage for both true and false will cause a failure, but
+        # only count it once for the report.
+        set ok 1
+        if [regexp {conditions *\(([0-9a-z/]+)\)} "$line" all e] {
+            # *Very* coarse sanity check: conditions() should either be a
+            # keyword or n/m, anything else means a buggy test case. end is
+            # optional for cases where all conditions are covered, since it
+            # only expects a single line of output.
+            if {([lsearch -exact $keywords $e] >= 0 || [regexp {\d+/\d+} "$e"]) == 0} {
+                fail "$prefix: expected conditions (n/m), (suppress) or (end); was ($e)"
+                incr failed
+                continue
+            }
+
+            # Any keyword means a new context. Set the error flag if not all
+            # expected output has been seen, and reset the state.
+
+            if {[llength $shouldt] != 0} {
+                fail "$prefix: expected 'not covered (true)' for terms: $shouldt"
+                set ok 0
+            }
+
+            if {[llength $shouldf] != 0} {
+                fail "$prefix: expected 'not covered (false)' for terms: $shouldf"
+                set ok 0
+            }
+
+            if {$shouldall ne ""} {
+                fail "$prefix: coverage summary not found; expected $shouldall"
+                set ok 0
+            }
+
+            set suppress 0
+            set destructor 0
+            set should ""
+            set shouldt ""
+            set shouldf ""
+            set shouldall ""
+            set newt ""
+            set newf ""
+
+            if [regexp {destructor\(\)} "$line"] {
+                set destructor 1
+            }
+
+            if [regexp {(\d+)/(\d+)} "$e" all i k] {
+                regexp {true\(([0-9 ]+)\)}  "$line" all newt
+                regexp {false\(([0-9 ]+)\)} "$line" all newf
+
+                # Sanity check - if the true() and false() vectors should have
+                # m-n elements to cover all uncovered conditions. Because of
+                # masking it can sometimes be surprising what terms are
+                # independent, so this makes for more robust test at the cost
+                # of being slightly more annoying to write.
+                set nterms [expr [llength $newt] + [llength $newf]]
+                set nexpected [expr {$k - $i}]
+                if {$nterms != $nexpected} {
+                    fail "$prefix: expected $nexpected uncovered terms; got $nterms"
+                    set ok 0
+                }
+                set shouldall $e
+                set shouldt $newt
+                set shouldf $newf
+            } elseif {$e == "end"} {
+                # no-op - state has already been reset, and errors flagged
+            } elseif {$e == "suppress"} {
+                set suppress 1
+            } else {
+                # this should be unreachable, 
+                fail "$prefix: unhandled control ($e), should be unreachable"
+                set ok 0
+            }
+        } elseif {$suppress == 1} {
+            # ignore everything in a suppress block. C++ especially can insert
+            # conditionals in exceptions and destructors which would otherwise
+            # be considered unhandled.
+            continue
+        } elseif [regexp {condition +(\d+) not covered \((.*)\)} "$line" all cond condv] {
+            foreach v {true false} {
+                if [regexp $v $condv] {
+                    if {"$v" == "true"} {
+                        set should shouldt
+                    } else {
+                        set should shouldf
+                    }
+
+                    set i [lsearch [set $should] $cond]
+                    if {$i != -1} {
+                        set $should [lreplace [set $should] $i $i]
+                    } else {
+                        fail "$testname line $n: unexpected uncovered term $cond ($v)"
+                        set ok 0
+                    }
+                }
+            }
+        } elseif [regexp {decisions covered (\d+/\d+)} "$line" all cond] {
+            # the destructor-generated "conditions covered" lines will be
+            # written after all expression-related output. Handle these by
+            # turning on suppression if the destructor-suppression is
+            # requested.
+            if {$shouldall == "" && $destructor == 1} {
+                set suppress 1
+                continue
+            }
+
+            if {$cond == $shouldall} {
+                set shouldall ""
+            } else {
+                fail "$testname line $n: unexpected summary $cond"
+                set ok 0
+            }
+        }
+
+        if {$ok != 1} {
+            incr failed
+        }
+    }
+    close $fd
+    return $failed
+}
+
 #
 # verify-calls -- check that call return percentages are as expected
 #
@@ -321,6 +499,7 @@ proc run-gcov { args } {
     set gcov_args ""
     set gcov_verify_calls 0
     set gcov_verify_branches 0
+    set gcov_verify_conditions 0
     set gcov_verify_lines 1
     set gcov_verify_intermediate 0
     set gcov_remove_gcda 0
@@ -331,10 +510,13 @@ proc run-gcov { args } {
 	  set gcov_verify_calls 1
 	} elseif { $a == "branches" } {
 	  set gcov_verify_branches 1
+	} elseif { $a == "conditions" } {
+	  set gcov_verify_conditions 1
 	} elseif { $a == "intermediate" } {
 	  set gcov_verify_intermediate 1
 	  set gcov_verify_calls 0
 	  set gcov_verify_branches 0
+	  set gcov_verify_conditions 0
 	  set gcov_verify_lines 0
 	} elseif { $a == "remove-gcda" } {
 	  set gcov_remove_gcda 1
@@ -404,6 +586,11 @@ proc run-gcov { args } {
     } else {
 	set bfailed 0
     }
+    if { $gcov_verify_conditions } {
+	set cdfailed [verify-conditions $testname $testcase $testcase.gcov]
+    } else {
+	set cdfailed 0
+    }
     if { $gcov_verify_calls } {
 	set cfailed [verify-calls $testname $testcase $testcase.gcov]
     } else {
@@ -418,12 +605,12 @@ proc run-gcov { args } {
 
     # Report whether the gcov test passed or failed.  If there were
     # multiple failures then the message is a summary.
-    set tfailed [expr $lfailed + $bfailed + $cfailed + $ifailed]
+    set tfailed [expr $lfailed + $bfailed + $cdfailed + $cfailed + $ifailed]
     if { $xfailed } {
 	setup_xfail "*-*-*"
     }
     if { $tfailed > 0 } {
-	fail "$testname gcov: $lfailed failures in line counts, $bfailed in branch percentages, $cfailed in return percentages, $ifailed in intermediate format"
+	fail "$testname gcov: $lfailed failures in line counts, $bfailed in branch percentages, $cdfailed in condition/decision, $cfailed in return percentages, $ifailed in intermediate format"
 	if { $xfailed } {
 	    clean-gcov $testcase
 	}
diff --git a/gcc/tree-profile.cc b/gcc/tree-profile.cc
index 2beb49241f2..f2c6617ad44 100644
--- a/gcc/tree-profile.cc
+++ b/gcc/tree-profile.cc
@@ -58,6 +58,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "alloc-pool.h"
 #include "symbol-summary.h"
 #include "symtab-thunks.h"
+#include "cfganal.h"
+#include "cfgloop.h"
 
 static GTY(()) tree gcov_type_node;
 static GTY(()) tree tree_interval_profiler_fn;
@@ -73,6 +75,976 @@ static GTY(()) tree ic_tuple_var;
 static GTY(()) tree ic_tuple_counters_field;
 static GTY(()) tree ic_tuple_callee_field;
 
+namespace
+{
+/* Some context and reused instances between function calls.  Large embedded
+   buffers are used to up-front request enough memory for most programs and
+   merge them into a single allocation at the cost of using more memory in the
+   average case.  Some numbers from linux v5.13 which is assumed to be a
+   reasonably diverse code base: 75% of the functions in linux have less than
+   16 nodes in the CFG and approx 2.5% have more than 64 nodes.  The functions
+   that go beyond a few dozen nodes tend to be very large (>100) and so 64
+   seems like a good balance.
+
+   This is really just a performance balance of the cost of allocation and
+   wasted memory. */
+struct conds_ctx
+{
+    /* Bitmap of the processed blocks.  Bit n set means basic_block->index has
+       been processed either explicitly or as a part of an expression. */
+    auto_sbitmap marks;
+
+    /* This is both a reusable shared allocation which is also used to return
+       single expressions, which means it for most code should only hold a
+       couple of elements. */
+    auto_vec<basic_block, 32> blocks;
+
+    /* Map from basic_block->index to an ordering so that for a single
+       expression (a || b && c) => index_map[a] < index_map[b] < index_map[c].
+       The values do not have to be consecutive and can be interleaved by
+       values from other expressions, so comparisons only make sense for blocks
+       that belong to the same expression. */
+    auto_vec<int, 64> index_map;
+
+    /* Pre-allocate bitmaps and vectors for per-function book keeping.  This is
+       pure instance reuse and the bitmaps carry no data between function
+       calls. */
+    auto_vec<basic_block, 64> B1;
+    auto_vec<basic_block, 64> B2;
+    auto_sbitmap G1;
+    auto_sbitmap G2;
+    auto_sbitmap G3;
+
+    explicit conds_ctx (unsigned size) noexcept (true) : marks (size),
+    G1 (size), G2 (size), G3 (size)
+    {
+	bitmap_clear (marks);
+    }
+
+    /* Mark a node as processed so nodes are not processed twice for example in
+       loops, gotos. */
+    void mark (const basic_block b) noexcept (true)
+    {
+	gcc_assert (!bitmap_bit_p (marks, b->index));
+	bitmap_set_bit (marks, b->index);
+    }
+
+    /* Mark nodes as processed so they are not processed twice. */
+    void mark (const vec<basic_block>& bs) noexcept (true)
+    {
+	for (const basic_block b : bs)
+	    mark (b);
+    }
+
+    /* Check if all nodes are marked.  A successful run should visit & mark
+       every reachable node exactly once. */
+    bool all_marked (const vec<basic_block>& reachable) const noexcept (true)
+    {
+	for (const basic_block b : reachable)
+	    if (!bitmap_bit_p (marks, b->index))
+		return false;
+	return true;
+    }
+};
+
+/* Only instrument terms with fewer than number of bits in a (wide) gcov
+   integer, which is probably 64.  The algorithm itself does not impose this
+   limitation, but it makes for a simpler implementation.
+
+   * Allocating the output data structure (coverage_counter_alloc ()) can
+     assume pairs of gcov_type_unsigned and not use a separate length field.
+   * A pair gcov_type_unsigned can be used as accumulators.
+   * Updating accumulators is can use the bitwise operations |=, &= and not
+     custom operators that work for arbitrary-sized bit-sets.
+
+   Most real-world code should be unaffected by this, but it is possible
+   (especially for generated code) to exceed this limit.
+ */
+#define CONDITIONS_MAX_TERMS (sizeof (gcov_type_unsigned) * BITS_PER_UNIT)
+#define EDGE_CONDITION (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)
+
+/* Compare two basic blocks by their order in the expression i.e. for (a || b)
+   then cmp_index_map (a, b, ...) < 0.  The result is undefined if lhs, rhs
+   belong to different expressions. */
+int
+cmp_index_map (const void *lhs, const void *rhs, void *index_map)
+{
+    const_basic_block l = *(const basic_block*) lhs;
+    const_basic_block r = *(const basic_block*) rhs;
+    const vec<int>* im = (const vec<int>*) index_map;
+    return (*im)[l->index] - (*im)[r->index];
+}
+
+/* Find the index of needle in blocks; return -1 if not found. This has two
+   uses, sometimes for the index and sometimes for set member checks.  Sets are
+   typically very small (number of conditions, >8 is uncommon) so linear search
+   should be very fast. */
+int
+index_of (const basic_block needle, array_slice<basic_block> blocks)
+{
+    const int size = int (blocks.size ());
+    for (int i = 0; i < size; i++)
+	if (blocks[i] == needle)
+	    return i;
+    return -1;
+}
+
+/* Returns true if this is a conditional node, i.e. it has outgoing true and
+   false edges. */
+bool
+block_conditional_p (const basic_block b)
+{
+    unsigned t = 0;
+    unsigned f = 0;
+    for (edge e : b->succs)
+    {
+	t |= (e->flags & EDGE_TRUE_VALUE);
+	f |= (e->flags & EDGE_FALSE_VALUE);
+    }
+    return t && f;
+}
+
+/* Check if the edge is a conditional. */
+bool
+edge_conditional_p (const edge e)
+{
+    return e->flags & EDGE_CONDITION;
+}
+
+/* Special cases of the single_*_p and single_*_edge functions in basic-block.h
+   that don't consider exception handling or other complex edges.  This helps
+   create a view of the CFG with only normal edges - if a basic block has both
+   an outgoing fallthrough and exceptional edge [1], it should be considered a
+   single-successor.
+
+   [1] if this is not possible, these functions can be removed and replaced by
+       their basic-block.h cousins. */
+bool
+single (const vec<edge, va_gc> *edges)
+{
+    int n = EDGE_COUNT (edges);
+    if (n == 0)
+	return false;
+
+    for (edge e : edges)
+	if (e->flags & EDGE_COMPLEX)
+	    n -= 1;
+
+    return n == 1;
+}
+
+/* Get the single, non-complex edge.  Behavior is undefined edges have more
+   than 1 non-complex edges. */
+edge
+single_edge (const vec<edge, va_gc> *edges)
+{
+    for (edge e : edges)
+    {
+	if (e->flags & EDGE_COMPLEX)
+	    continue;
+	return e;
+    }
+    return NULL;
+}
+
+/* Sometimes, for example with function calls and C++ destructors, the CFG gets
+   extra nodes that are essentially single-entry-single-exit in the middle of
+   boolean expressions.  For example:
+
+      x || can_throw (y)
+
+               A
+              /|
+             / |
+            B  |
+            |  |
+            C  |
+           / \ |
+          /   \|
+         F     T
+
+   Without the extra node inserted by the function + exception it becomes a
+   proper 2-term graph, not 2 single-term graphs.
+
+               A
+              /|
+             C |
+            / \|
+           F   T
+
+   contract_edge ignores the series of intermediate nodes and makes a virtual
+   edge A -> C without having to construct a new simplified CFG explicitly.  It
+   gets more complicated as non-conditional edges is how the body of the
+   then/else blocks are separated from the boolean expression, so only edges
+   that are inserted because of function calls in the expression itself must be
+   merged.
+
+   Only chains of single-exit single-entry nodes that end with a condition
+   should be contracted. */
+edge
+contract_edge (edge e)
+{
+    edge source = e;
+    while (true)
+    {
+	basic_block dest = e->dest;
+	if (!single (dest->preds))
+	    return source;
+	if (e->flags & EDGE_DFS_BACK)
+	    return source;
+	if (block_conditional_p (dest))
+	    return e;
+
+	e = single_edge (dest->succs);
+	if (!e)
+	    return source;
+    }
+}
+
+/* This is the predecessor dual of contract_edge; it collapses the predecessor
+   blocks between two operands in a boolean expression. */
+edge
+contract_edge_up (edge e)
+{
+    while (true)
+    {
+	basic_block src = e->src;
+	if (edge_conditional_p (e))
+	    return e;
+	if (!single (src->preds))
+	    return e;
+	e = single_edge (src->preds);
+    }
+}
+
+/* Find the set {ancestors(p) intersect G} where ancestors is the recursive set
+   of predecessors for p.  Limiting to the ancestors that are also in G (see
+   cond_reachable_from) and by q is an optimization as ancestors outside G have
+   no effect when isolating expressions.
+
+   dfs_enumerate_from () does not work as the filter function needs edge
+   information and dfs_enumerate_from () only considers blocks. */
+void
+ancestors_of (basic_block p, basic_block q, const sbitmap G, sbitmap ancestors)
+{
+    if (!bitmap_bit_p (G, p->index))
+	return;
+
+    bitmap_set_bit (ancestors, p->index);
+    bitmap_set_bit (ancestors, q->index);
+    if (p == q)
+	return;
+
+    auto_vec<basic_block, 16> stack;
+    stack.safe_push (p);
+
+    while (!stack.is_empty())
+    {
+	basic_block b = stack.pop ();
+	if (single (b->preds))
+	{
+	    edge e = single_edge (b->preds);
+	    e = contract_edge_up (e);
+	    b = e->dest;
+	}
+
+	for (edge e : b->preds)
+	{
+	    basic_block src = e->src;
+	    if (bitmap_bit_p (ancestors, e->src->index))
+		continue;
+	    if (!bitmap_bit_p (G, e->src->index))
+		continue;
+	    bitmap_set_bit (ancestors, src->index);
+	    stack.safe_push (src);
+	}
+    }
+}
+
+/* A simple struct for storing/returning outcome block pairs.  Either both
+   blocks are set or both are NULL. */
+struct outcomes
+{
+    basic_block t = NULL;
+    basic_block f = NULL;
+
+    operator bool () const noexcept (true)
+    {
+	return t && f;
+    }
+};
+
+/* Get the true/false successors of a basic block. If b is not a conditional
+   block both edges are NULL. */
+outcomes
+conditional_succs (const basic_block b)
+{
+    outcomes c;
+    for (edge e : b->succs)
+    {
+	if (e->flags & EDGE_TRUE_VALUE)
+	    c.t = (e)->dest;
+	if (e->flags & EDGE_FALSE_VALUE)
+	    c.f = (e)->dest;
+    }
+
+    gcc_assert ((c.t && c.f) || (!c.t && !c.f));
+    return c;
+}
+
+/* Get the index or offset of a conditional flag, 0 for true and 1 for false.
+   These indices carry no semantics but must be consistent as they are used to
+   index into data structures in code generation and gcov. */
+unsigned
+condition_index (unsigned flag)
+{
+    return (flag & EDGE_CONDITION) == EDGE_TRUE_VALUE ? 0 : 1;
+}
+
+/* Compute the masking vector.
+
+   Masking and short circuiting are deeply connected - masking occurs when
+   control flow reaches a state that is also reachable with short circuiting.
+   In fact, masking corresponds to short circuiting in the CFG for the reversed
+   expression.  This means we can find the limits, the last term in preceeding
+   subexpressions, by following the edges that short circuit to the same
+   outcome.
+
+   In the simplest case a || b:
+
+   a
+   |\
+   | b
+   |/ \
+   T   F
+
+   T has has multiple incoming edges and is the outcome of a short circuit,
+   with top = a, bot = b.  The top node (a)is masked when the edge (b, T) is
+   taken.
+
+   The names "top" and "bot" refer to a pair of nodes with a shared
+   destination. The top is always the node corresponding to the left-most
+   operand of the two it holds that index_map[top] < index_map[bot].
+
+   Now consider (a && b) || (c && d) and its masking vectors:
+
+   a
+   |\
+   b \
+   |\|
+   | c
+   | |\
+   | d \
+   |/ \|
+   T   F
+
+   a[0] = {}
+   a[1] = {}
+   b[0] = {a}
+   b[1] = {}
+   c[0] = {}
+   c[1] = {}
+   d[0] = {c}
+   d[1] = {a,b}
+
+   Note that 0 and 1 are indices and not boolean values - a[0] is the index in
+   the masking vector when a takes the true edge.
+
+   b[0] and d[0] are identical to the a || b example, and d[1] is the bot in
+   the triangle [d, b] -> T.  b is the top node in the [d, b] relationship and
+   last term in (a && b).  To find the other terms masked we use the fact that
+   all nodes in an expression have outgoing edges to either the outcome or some
+   other node in the expression.  We know one outcome is T and that b is the
+   last term, which means the other outcome is b's other successor (in this
+   case c).  We find the terms by marking the outcomes (in this case c, T) and
+   walk the predecessors starting at top (in this case b) and masking nodes
+   when both successors are marked.
+
+   The masking vector is represented as two bitfields per term in the
+   expression with the index corresponding to the term in the source
+   expression.  a || b && c becomes the term vector [a b c] and the masking
+   vectors [a[0] a[1] b[0] ...].  The kth bit of a masking vector is set if the
+   the kth term is masked by taking the edge. */
+void
+masking_vectors (conds_ctx& ctx, array_slice<basic_block> blocks,
+		 array_slice<gcov_type_unsigned> masks)
+{
+    gcc_assert (blocks.is_valid ());
+    gcc_assert (!blocks.empty ());
+    gcc_assert (masks.is_valid ());
+
+    sbitmap marks = ctx.G1;
+    sbitmap expr = ctx.G2;
+    vec<basic_block>& queue = ctx.B1;
+    vec<basic_block>& body = ctx.B2;
+    const vec<int>& index_map = ctx.index_map;
+    bitmap_clear (expr);
+
+    for (const basic_block b : blocks)
+	bitmap_set_bit (expr, b->index);
+
+    /* Set up for the iteration - include two outcome nodes in the traversal and
+       ignore the leading term since it cannot mask anything.  The algorithm is
+       not sensitive to the traversal order. */
+    body.truncate (0);
+    body.reserve (blocks.size () + 2);
+    for (const basic_block b : blocks)
+	body.quick_push (b);
+
+    outcomes out = conditional_succs (blocks.back ());
+    body.quick_push (out.t);
+    body.quick_push (out.f);
+    body[0] = body.pop ();
+
+    for (const basic_block b : body)
+    {
+	for (edge e1 : b->preds)
+	for (edge e2 : b->preds)
+	{
+	    const basic_block top = e1->src;
+	    const basic_block bot = e2->src;
+	    const unsigned cond = e1->flags & e2->flags & (EDGE_CONDITION);
+
+	    if (!cond)
+		continue;
+	    if (e1 == e2)
+		continue;
+	    if (!bitmap_bit_p (expr, top->index))
+		continue;
+	    if (!bitmap_bit_p (expr, bot->index))
+		continue;
+	    if (index_map[top->index] > index_map[bot->index])
+		continue;
+
+	    outcomes out = conditional_succs (top);
+	    gcc_assert (out);
+	    bitmap_clear (marks);
+	    bitmap_set_bit (marks, out.t->index);
+	    bitmap_set_bit (marks, out.f->index);
+	    queue.truncate (0);
+	    queue.safe_push (top);
+
+	    // The edge bot -> outcome triggers the masking
+	    const int m = 2*index_of (bot, blocks) + condition_index (cond);
+	    while (!queue.is_empty())
+	    {
+		basic_block q = queue.pop ();
+		/* q may have been processed & completed by being added to the
+		   queue multiple times, so check that there is still work to
+		   do before continuing. */
+		if (bitmap_bit_p (marks, q->index))
+		    continue;
+
+		outcomes succs = conditional_succs (q);
+		if (!bitmap_bit_p (marks, succs.t->index))
+		    continue;
+		if (!bitmap_bit_p (marks, succs.f->index))
+		    continue;
+
+		const int index = index_of (q, blocks);
+		gcc_assert (index != -1);
+		masks[m] |= gcov_type_unsigned (1) << index;
+		bitmap_set_bit (marks, q->index);
+
+		for (edge e : q->preds)
+		{
+		    e = contract_edge_up (e);
+		    if (!edge_conditional_p (e))
+			continue;
+		    if (e->flags & EDGE_DFS_BACK)
+			continue;
+		    if (bitmap_bit_p (marks, e->src->index))
+			continue;
+		    if (!bitmap_bit_p (expr, e->src->index))
+			continue;
+		    queue.safe_push (e->src);
+		}
+	    }
+	}
+    }
+}
+
+/* Find the nodes reachable from p by following only (possibly contracted)
+   condition edges dominated by p and ignore DFS back edges.  From a high level
+   this is partitioning the CFG into subgraphs by removing all non-condition
+   edges and selecting a single connected subgraph.  This creates a cut C = (G,
+   G') where G is the returned explicitly by this function.
+
+   It is assumed that all paths from p go through q (q post-dominates p).  p
+   must always be the first term in an expression and a condition node.
+
+   If |G| = 1 then this is a single term expression. If |G| > 1 then either
+   this is a multi-term expression or the first block in the then/else block is
+   a conditional expression as well.
+
+   Only nodes dominated by p is added - under optimization some blocks may be
+   merged and multiple independent conditions may share the same outcome
+   (making successors misidentified as a right operands), but true right-hand
+   operands are always dominated by the first term.
+
+   The function outputs both a bitmap and a vector as both are useful to the
+   caller. */
+void
+cond_reachable_from (basic_block p, basic_block q, sbitmap expr,
+		     vec<basic_block>& out)
+{
+    out.safe_push (p);
+    bitmap_set_bit (expr, p->index);
+    for (unsigned pos = 0; pos < out.length (); pos++)
+    {
+	for (edge e : out[pos]->succs)
+	{
+	    basic_block dest = contract_edge (e)->dest;
+	    if (dest == q)
+		continue;
+	    if (!dominated_by_p (CDI_DOMINATORS, dest, p))
+		continue;
+	    if (!block_conditional_p (dest))
+		continue;
+	    if (bitmap_bit_p (expr, dest->index))
+		continue;
+	    if (e->flags & EDGE_DFS_BACK)
+		continue;
+
+	    bitmap_set_bit (expr, dest->index);
+	    out.safe_push (dest);
+	}
+    }
+}
+
+/* Find the neighborhood of the graph G = [blocks, blocks+n), the
+   successors of nodes in G that are not also in G.  In the cut C = (G, G')
+   these are the nodes in G' with incoming edges that cross the span. */
+void
+neighborhood (const vec<basic_block>& blocks, const sbitmap G,
+	      vec<basic_block>& out)
+{
+    for (const basic_block b : blocks)
+    {
+	for (edge e : b->succs)
+	{
+	    basic_block dest = contract_edge (e)->dest;
+	    if (bitmap_bit_p (G, dest->index))
+		continue;
+	    if (!out.contains (dest))
+		out.safe_push (dest);
+	}
+    }
+}
+
+/* Find and isolate the expression starting at p.
+
+   Make a cut C = (G, G') following only condition edges.  G is a superset of
+   the expression B, but the walk may include expressions from the then/else
+   blocks if they start with conditions.  Only the subgraph B is the ancestor
+   of *both* the then/else outcome, which means B is the intersection of the
+   ancestors of the nodes in the neighborhood N(G). */
+void
+isolate_expression (conds_ctx &ctx, basic_block p, vec<basic_block>& out)
+{
+    sbitmap expr = ctx.G1;
+    sbitmap reachable = ctx.G2;
+    sbitmap ancestors = ctx.G3;
+    bitmap_clear (expr);
+    bitmap_clear (reachable);
+
+    vec<basic_block>& G = ctx.B1;
+    vec<basic_block>& NG = ctx.B2;
+    G.truncate (0);
+    NG.truncate (0);
+
+    basic_block post = get_immediate_dominator (CDI_POST_DOMINATORS, p);
+    cond_reachable_from (p, post, reachable, G);
+    if (G.length () == 1)
+    {
+	out.safe_push (p);
+	return;
+    }
+
+    neighborhood (G, reachable, NG);
+    bitmap_copy (expr, reachable);
+
+    for (const basic_block neighbor : NG)
+    {
+	bitmap_clear (ancestors);
+	for (edge e : neighbor->preds)
+	    ancestors_of (e->src, p, reachable, ancestors);
+	bitmap_and (expr, expr, ancestors);
+    }
+
+    for (const basic_block b : G)
+	if (bitmap_bit_p (expr, b->index))
+	    out.safe_push (b);
+    out.sort (cmp_index_map, &ctx.index_map);
+}
+
+/* Emit lhs = op1 <op> op2 on edges.  This emits non-atomic instructions and
+   should only be used on the local accumulators. */
+void
+emit_bitwise_op (edge e, tree lhs, tree op1, tree_code op, tree op2)
+{
+    tree tmp;
+    gassign *read;
+    gassign *bitw;
+    gimple *write;
+
+    tmp = make_temp_ssa_name (gcov_type_node, NULL, "__conditions_tmp");
+    read = gimple_build_assign (tmp, op1);
+    tmp = make_temp_ssa_name (gcov_type_node, NULL, "__conditions_tmp");
+    bitw = gimple_build_assign (tmp, op, gimple_assign_lhs (read), op2);
+    write = gimple_build_assign (lhs, gimple_assign_lhs (bitw));
+
+    gsi_insert_on_edge (e, read);
+    gsi_insert_on_edge (e, bitw);
+    gsi_insert_on_edge (e, write);
+}
+
+/* Visitor for make_index_map. */
+void
+make_index_map_visit (basic_block b, vec<basic_block>& L, vec<int>& marks)
+{
+    if (marks[b->index])
+	return;
+
+    for (edge e : b->succs)
+	if (!(e->flags & EDGE_DFS_BACK))
+	    make_index_map_visit (e->dest, L, marks);
+
+    marks[b->index] = 1;
+    L.quick_push (b);
+}
+
+/* Find a topological sorting of the blocks in a function so that left operands
+   are before right operands including subexpressions.  Sorting on block index
+   does not guarantee this property and the syntactical order of terms is very
+   important to the condition coverage.  The sorting algorithm is from Cormen
+   et al (2001) but with back-edges ignored and thus there is no need for
+   temporary marks (for cycle detection).
+
+   It is important to select unvisited nodes in DFS order to ensure the
+   roots/leading terms of boolean expressions are visited first (the other
+   terms being covered by the recursive step), but the visiting order of
+   individual boolean expressions carries no significance.
+
+   For the expression (a || (b && c) || d) the blocks should be [a b c d]. */
+void
+make_index_map (const vec<basic_block>& blocks, int max_index,
+		vec<basic_block>& L, vec<int>& index_map)
+{
+    L.truncate (0);
+    L.reserve (max_index);
+
+    /* Use of the output map as a temporary for tracking visited status. */
+    index_map.truncate (0);
+    index_map.safe_grow_cleared (max_index);
+    for (const basic_block b : blocks)
+	make_index_map_visit (b, L, index_map);
+
+    /* Insert canaries - if there are unreachable nodes (for example infinite
+       loops) then the unreachable nodes should never be needed for comparison,
+       and L.length () < max_index.  An index mapping should also never be
+       recorded twice. */
+    for (unsigned i = 0; i < index_map.length (); i++)
+	index_map[i] = -1;
+
+    gcc_assert (blocks.length () == L.length ());
+    L.reverse ();
+    const int nblocks = L.length ();
+    for (int i = 0; i < nblocks; i++)
+    {
+	gcc_assert (L[i]->index != -1);
+	index_map[L[i]->index] = i;
+    }
+}
+
+/* Walk the CFG and collect conditionals.
+
+   1. Collect a candidate set G by walking from the root following all
+      (contracted) condition edges.
+   2. This creates a cut C = (G, G'); find the neighborhood N(G).
+   3. For every node in N(G), follow the edges across the cut and collect all
+      ancestors (that are also in G).
+   4. The intersection of all these ancestor sets is the boolean expression B
+      that starts in root.
+
+   Walking is not guaranteed to find nodes in the order of the expression, it
+   might find (a || b) && c as [a c b], so the result must be sorted by the
+   index map. */
+const vec<basic_block>&
+collect_conditions (conds_ctx& ctx, const basic_block block)
+{
+    vec<basic_block>& blocks = ctx.blocks;
+    blocks.truncate (0);
+
+    if (bitmap_bit_p (ctx.marks, block->index))
+	return blocks;
+
+    if (!block_conditional_p (block))
+    {
+	ctx.mark (block);
+	return blocks;
+    }
+
+    isolate_expression (ctx, block, blocks);
+    ctx.mark (blocks);
+
+    if (blocks.length () > CONDITIONS_MAX_TERMS)
+    {
+	location_t loc = gimple_location (gsi_stmt (gsi_last_bb (block)));
+	warning_at (loc, OPT_Wcoverage_too_many_conditions,
+		    "Too many conditions (found %u); giving up coverage",
+		    blocks.length ());
+	blocks.truncate (0);
+    }
+    return blocks;
+}
+
+/* Used for dfs_enumerate_from () to include all reachable nodes. */
+bool
+yes (const_basic_block, const void *)
+{
+    return true;
+}
+
+}
+
+struct condcov {
+    explicit condcov (unsigned nblocks) noexcept (true) : ctx (nblocks) {}
+    auto_vec<int, 128> m_index;
+    auto_vec<basic_block, 256> m_blocks;
+    auto_vec<gcov_type_unsigned, 512> m_masks;
+    conds_ctx ctx;
+};
+
+unsigned
+cov_length (const struct condcov* cov)
+{
+    if (cov->m_index.is_empty ())
+	return 0;
+    return cov->m_index.length () - 1;
+}
+
+array_slice<basic_block>
+cov_blocks (struct condcov* cov, unsigned n)
+{
+    if (n >= cov->m_index.length ())
+	return array_slice<basic_block>::invalid ();
+
+    basic_block *begin = cov->m_blocks.begin () + cov->m_index[n];
+    basic_block *end = cov->m_blocks.begin () + cov->m_index[n + 1];
+    return array_slice<basic_block> (begin, end - begin);
+}
+
+array_slice<gcov_type_unsigned>
+cov_masks (struct condcov* cov, unsigned n)
+{
+    if (n >= cov->m_index.length ())
+	return array_slice<gcov_type_unsigned>::invalid ();
+
+    gcov_type_unsigned *begin = cov->m_masks.begin () + 2*cov->m_index[n];
+    gcov_type_unsigned *end = cov->m_masks.begin () + 2*cov->m_index[n + 1];
+    return array_slice<gcov_type_unsigned> (begin, end - begin);
+}
+
+void
+cov_free (struct condcov* cov)
+{
+    delete cov;
+}
+
+/* Condition coverage (MC/DC)
+
+   Algorithm
+   ---------
+   Whalen, Heimdahl, De Silva in "Efficient Test Coverage Measurement for
+   MC/DC" describe an algorithm for modified condition/decision coverage based
+   on AST analysis.  This algorithm analyses the control flow graph to analyze
+   expressions and compute masking vectors, but is inspired by their marking
+   functions for recording outcomes.  The individual phases are described in
+   more detail closer to the implementation.
+
+   The CFG is traversed in DFS order.  It is important that the first basic
+   block in an expression is the first one visited, but the order of
+   independent expressions does not matter.  When the function terminates,
+   every node in the dfs should have been processed and marked exactly once.
+   If there are unreachable nodes they are ignored and not instrumented.
+
+   The CFG is broken up into segments between dominators.  This isn't strictly
+   necessary, but since boolean expressions cannot cross dominators it makes
+   for a nice way to introduce limits to searches.
+
+   The coverage only considers the positions, not the symbols, in a
+   conditional, e.g. !A || (!B && A) is a 3-term conditional even though A
+   appears twice.  Subexpressions have no effect on term ordering:
+   (a && (b || (c && d)) || e) comes out as [a b c d e].
+
+   The output for gcov is a vector of pairs of unsigned integers, interpreted
+   as bit-sets, where the bit index corresponds to the index of the condition
+   in the expression.
+ */
+struct condcov*
+find_conditions (struct function *fn)
+{
+    record_loop_exits ();
+    mark_dfs_back_edges (fn);
+
+    const bool have_dom = dom_info_available_p (fn, CDI_DOMINATORS);
+    const bool have_post_dom = dom_info_available_p (fn, CDI_POST_DOMINATORS);
+    if (!have_dom)
+	calculate_dominance_info (CDI_DOMINATORS);
+    if (!have_post_dom)
+	calculate_dominance_info (CDI_POST_DOMINATORS);
+
+    const unsigned nblocks = n_basic_blocks_for_fn (fn);
+    condcov *cov = new condcov (nblocks);
+    conds_ctx& ctx = cov->ctx;
+
+    auto_vec<basic_block, 16> dfs;
+    dfs.safe_grow (nblocks);
+    const basic_block entry = ENTRY_BLOCK_PTR_FOR_FN (fn);
+    const basic_block exit = ENTRY_BLOCK_PTR_FOR_FN (fn);
+    int n = dfs_enumerate_from (entry, 0, yes, dfs.address (), nblocks, exit);
+    dfs.truncate (n);
+    make_index_map (dfs, nblocks, ctx.B1, ctx.index_map);
+
+    /* Visit all reachable nodes and collect conditions.  DFS order is
+       important so the first node of a boolean expression is visited first
+       (it will mark subsequent terms). */
+    cov->m_index.safe_push (0);
+    for (const basic_block b : dfs)
+    {
+	const vec<basic_block>& expr = collect_conditions (ctx, b);
+	if (!expr.is_empty ())
+	{
+	    cov->m_blocks.safe_splice (expr);
+	    cov->m_index.safe_push (cov->m_blocks.length ());
+	}
+    }
+    gcc_assert (ctx.all_marked (dfs));
+
+    if (!have_dom)
+	free_dominance_info (fn, CDI_DOMINATORS);
+    if (!have_post_dom)
+	free_dominance_info (fn, CDI_POST_DOMINATORS);
+
+    cov->m_masks.safe_grow_cleared (2 * cov->m_index.last());
+    const unsigned length = cov_length (cov);
+    for (unsigned i = 0; i < length; i++)
+	masking_vectors (ctx, cov_blocks (cov, i), cov_masks (cov, i));
+
+    return cov;
+}
+
+int
+instrument_decisions (array_slice<basic_block> expr, unsigned condno,
+		      tree *accu, gcov_type_unsigned *masks)
+{
+    /* Zero the local accumulators. */
+    tree zero = build_int_cst (get_gcov_type (), 0);
+    for (edge e : expr[0]->succs)
+    {
+	gsi_insert_on_edge (e, gimple_build_assign (accu[0], zero));
+	gsi_insert_on_edge (e, gimple_build_assign (accu[1], zero));
+    }
+    /* Add instructions for updating the function-local accumulators.  */
+    for (size_t i = 0; i < expr.size (); i++)
+    {
+	for (edge e : expr[i]->succs)
+	{
+	    if (!edge_conditional_p (e))
+		continue;
+
+	    /* accu |= expr[i] */
+	    const int k = condition_index (e->flags);
+	    tree rhs = build_int_cst (gcov_type_node, 1ULL << i);
+	    emit_bitwise_op (e, accu[k], accu[k], BIT_IOR_EXPR, rhs);
+
+	    if (masks[2*i + k] == 0)
+		continue;
+
+	    /* accu &= mask[i] */
+	    tree mask = build_int_cst (gcov_type_node, ~masks[2*i + k]);
+	    for (int j = 0; j < 2; j++)
+		emit_bitwise_op (e, accu[j], accu[j], BIT_AND_EXPR, mask);
+	}
+    }
+
+    const bool atomic = flag_profile_update == PROFILE_UPDATE_ATOMIC;
+    const tree atomic_ior = builtin_decl_explicit
+	(TYPE_PRECISION (gcov_type_node) > 32
+	 ? BUILT_IN_ATOMIC_FETCH_OR_8
+	 : BUILT_IN_ATOMIC_FETCH_OR_4);
+
+    /* Add instructions for flushing the local accumulators.
+
+       It is important that the flushes happen on on the outcome's incoming
+       edges, otherwise flushes could be lost to exception handling.
+
+       void fn (int a)
+       {
+	   if (a)
+	    fclose();
+	   exit();
+       }
+
+       Can yield the CFG:
+       A
+       |\
+       | B
+       |/
+       e
+
+       This typically only happen in optimized builds, but gives linker errors
+       because the counter is left as an undefined symbol. */
+
+    outcomes out = conditional_succs (expr.back ());
+    const basic_block outcome_blocks[] = { out.t, out.t, out.f, out.f, };
+    const int outcome[] = { 0, 1, 0, 1 };
+    for (int i = 0; i < 4; i++)
+    {
+	const int k = outcome[i];
+	for (edge e : outcome_blocks[i]->preds)
+	{
+	    /* Only instrument edges from inside the expression. Sometimes
+	       complicated control flow (like sigsetjmp and gotos) add
+	       predecessors that don't come from the boolean expression. */
+	    if (index_of (e->src, expr) == -1)
+		continue;
+
+	    tree ref = tree_coverage_counter_ref (GCOV_COUNTER_CONDS,
+						  2*condno + k);
+	    tree tmp = make_temp_ssa_name (gcov_type_node, NULL,
+					   "__conditions_tmp");
+	    if (atomic)
+	    {
+		tree relaxed = build_int_cst (integer_type_node,
+					      MEMMODEL_RELAXED);
+		ref = unshare_expr (ref);
+		gassign *read = gimple_build_assign (tmp, accu[k]);
+		gcall *flush = gimple_build_call (atomic_ior, 3,
+						  build_addr (ref),
+						  gimple_assign_lhs (read),
+						  relaxed);
+
+		gsi_insert_on_edge (e, read);
+		gsi_insert_on_edge (e, flush);
+	    }
+	    else
+	    {
+		gassign *read = gimple_build_assign (tmp, ref);
+		tmp = gimple_assign_lhs (read);
+		gsi_insert_on_edge (e, read);
+		ref = unshare_expr (ref);
+		emit_bitwise_op (e, ref, accu[k], BIT_IOR_EXPR, tmp);
+	    }
+	}
+    }
+    return expr.size ();
+}
+
+#undef CONDITIONS_MAX_TERMS
+#undef EDGE_CONDITION
+
 /* Do initialization work for the edge profiler.  */
 
 /* Add code:
@@ -758,7 +1730,7 @@ tree_profiling (void)
 	  thunk = true;
 	  /* When generate profile, expand thunk to gimple so it can be
 	     instrumented same way as other functions.  */
-	  if (profile_arc_flag)
+	  if (profile_arc_flag || profile_condition_flag)
 	    expand_thunk (node, false, true);
 	  /* Read cgraph profile but keep function as thunk at profile-use
 	     time.  */
@@ -803,7 +1775,7 @@ tree_profiling (void)
   release_profile_file_filtering ();
 
   /* Drop pure/const flags from instrumented functions.  */
-  if (profile_arc_flag || flag_test_coverage)
+  if (profile_arc_flag || profile_condition_flag || flag_test_coverage)
     FOR_EACH_DEFINED_FUNCTION (node)
       {
 	if (!gimple_has_body_p (node->decl)
@@ -897,7 +1869,7 @@ pass_ipa_tree_profile::gate (function *)
      disabled.  */
   return (!in_lto_p && !flag_auto_profile
 	  && (flag_branch_probabilities || flag_test_coverage
-	      || profile_arc_flag));
+	      || profile_arc_flag || profile_condition_flag));
 }
 
 } // anon namespace
diff --git a/libgcc/libgcov-merge.c b/libgcc/libgcov-merge.c
index 89741f637e1..9e3e8ee5657 100644
--- a/libgcc/libgcov-merge.c
+++ b/libgcc/libgcov-merge.c
@@ -33,6 +33,11 @@ void __gcov_merge_add (gcov_type *counters  __attribute__ ((unused)),
                        unsigned n_counters __attribute__ ((unused))) {}
 #endif
 
+#ifdef L_gcov_merge_ior
+void __gcov_merge_ior (gcov_type *counters  __attribute__ ((unused)),
+		       unsigned n_counters __attribute__ ((unused))) {}
+#endif
+
 #ifdef L_gcov_merge_topn
 void __gcov_merge_topn (gcov_type *counters  __attribute__ ((unused)),
 			unsigned n_counters __attribute__ ((unused))) {}
