diff mbox series

tree-optimization/109434 - bogus DSE of throwing call LHS

Message ID 20230412064946.231153856940@sourceware.org
State Repeat Merge
Headers
Series tree-optimization/109434 - bogus DSE of throwing call LHS |

Checks

Context Check Description
snail/gcc-patch-check warning Git am fail log

Commit Message

Richard Biener April 12, 2023, 6:49 a.m. UTC 
  The byte tracking of call LHS didn't properly handle possibly
throwing calls correctly which cases bogus DSE and in turn, for the
testcase a bogus uninit diagnostic and (unreliable) wrong-code.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

	PR tree-optimization/109434
	* tree-ssa-dse.cc (initialize_ao_ref_for_dse): Properly
	handle possibly throwing calls when processing the LHS
	and may-defs are not OK.

	* g++.dg/opt/pr109434.C: New testcase.
---
 gcc/testsuite/g++.dg/opt/pr109434.C | 28 ++++++++++++++++++++++++++++
 gcc/tree-ssa-dse.cc                 |  3 ++-
 2 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/opt/pr109434.C
diff mbox series

Patch

diff --git a/gcc/testsuite/g++.dg/opt/pr109434.C b/gcc/testsuite/g++.dg/opt/pr109434.C
new file mode 100644
index 00000000000..cffa327fd9b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr109434.C
@@ -0,0 +1,28 @@ 
+// { dg-do compile }
+// { dg-require-effective-target c++17 }
+// { dg-options "-O2 -Wall" }
+
+#include <optional>
+#include <stdexcept>
+
+std::optional<int> foo()
+{
+  volatile int x = 1;
+  if (x)
+    throw std::runtime_error("haha");
+  return 42;
+}
+
+int main()
+{
+  std::optional<int> optInt;
+  try {
+      // We falsely DSEd the LHS of the call even though foo throws
+      // which results in an uninitialized diagnostic
+      optInt = foo();
+  } catch (...) {
+      return optInt.has_value();
+  }
+  std::optional<double> optDbl{optInt};
+  return optDbl ? optDbl.value () : 2.0;
+}
diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
index 4f8a44fbba0..eabe8ba4522 100644
--- a/gcc/tree-ssa-dse.cc
+++ b/gcc/tree-ssa-dse.cc
@@ -179,7 +179,8 @@  initialize_ao_ref_for_dse (gimple *stmt, ao_ref *write, bool may_def_ok = false)
     }
   if (tree lhs = gimple_get_lhs (stmt))
     {
-      if (TREE_CODE (lhs) != SSA_NAME)
+      if (TREE_CODE (lhs) != SSA_NAME
+	  && (may_def_ok || !stmt_could_throw_p (cfun, stmt)))
 	{
 	  ao_ref_init (write, lhs);
 	  return true;