c++, v2: Drop TREE_READONLY on vars (possibly) initialized by tls wrapper [PR109164]

Message ID ZBXUQ06ObKinZSSc@tucnak
State Unresolved
Headers
Series c++, v2: Drop TREE_READONLY on vars (possibly) initialized by tls wrapper [PR109164] |

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Commit Message

Jakub Jelinek March 18, 2023, 3:09 p.m. UTC
  On Sat, Mar 18, 2023 at 01:54:58PM +0100, Jakub Jelinek via Gcc-patches wrote:
> The patch is mostly about DECL_EXTERNAL cases, the others are supposedly
> handled by the var_definition_p code there (or at least I assumed;
> testcases certainly test only DECL_EXTERNAL).
> I guess it could be done in cp_finish_decl, maybe better next to the
>   /* A reference will be modified here, as it is initialized.  */
>   if (! DECL_EXTERNAL (decl)
>       && TREE_READONLY (decl)
>       && TYPE_REF_P (type))
>     {
>       was_readonly = 1;
>       TREE_READONLY (decl) = 0;
>     }
> spot, but we'd need to export the decl2.cc helpers for it,
> because not all DECL_THREAD_LOCAL_P vars need to be treated that way.
>   if (VAR_P (decl)
>       && CP_DECL_THREAD_LOCAL_P (decl)
>       && var_needs_tls_wrapper (decl)
>       && (!DECL_EXTERNAL (decl) || flag_extern_tls_init))
>     TREE_READONLY (decl) = 0;
> where var_needs_tls_wrapper would need to be exported from decl2.cc.
> Though, var_needs_tls_wrapper -> var_defined_without_dynamic_init
> needs
> DECL_NONTRIVIALLY_INITIALIZED_P/DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P,
> so perhaps that is accurate only closer to the end of cp_finish_decl?

Here it is in patch form, tested so far on tls.exp:

2023-03-18  Jakub Jelinek  <jakub@redhat.com>

	PR c++/109164
	* cp-tree.h (var_needs_tls_wrapper): Declare.
	* decl2.cc (var_needs_tls_wrapper): No longer static.
	* decl.cc (cp_finish_decl): Clear TREE_READONLY on TLS variables
	for which a TLS wrapper will be needed.

	* g++.dg/tls/thread_local13.C: New test.
	* g++.dg/tls/thread_local13-aux.cc: New file.
	* g++.dg/tls/thread_local14.C: New test.
	* g++.dg/tls/thread_local14-aux.cc: New file.



	Jakub
  

Comments

Jakub Jelinek March 20, 2023, 3:45 p.m. UTC | #1
On Sat, Mar 18, 2023 at 04:09:55PM +0100, Jakub Jelinek via Gcc-patches wrote:
> On Sat, Mar 18, 2023 at 01:54:58PM +0100, Jakub Jelinek via Gcc-patches wrote:
> > The patch is mostly about DECL_EXTERNAL cases, the others are supposedly
> > handled by the var_definition_p code there (or at least I assumed;
> > testcases certainly test only DECL_EXTERNAL).
> > I guess it could be done in cp_finish_decl, maybe better next to the
> >   /* A reference will be modified here, as it is initialized.  */
> >   if (! DECL_EXTERNAL (decl)
> >       && TREE_READONLY (decl)
> >       && TYPE_REF_P (type))
> >     {
> >       was_readonly = 1;
> >       TREE_READONLY (decl) = 0;
> >     }
> > spot, but we'd need to export the decl2.cc helpers for it,
> > because not all DECL_THREAD_LOCAL_P vars need to be treated that way.
> >   if (VAR_P (decl)
> >       && CP_DECL_THREAD_LOCAL_P (decl)
> >       && var_needs_tls_wrapper (decl)
> >       && (!DECL_EXTERNAL (decl) || flag_extern_tls_init))
> >     TREE_READONLY (decl) = 0;
> > where var_needs_tls_wrapper would need to be exported from decl2.cc.
> > Though, var_needs_tls_wrapper -> var_defined_without_dynamic_init
> > needs
> > DECL_NONTRIVIALLY_INITIALIZED_P/DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P,
> > so perhaps that is accurate only closer to the end of cp_finish_decl?
> 
> Here it is in patch form, tested so far on tls.exp:

And successfully bootstrapped/regtested on x86_64-linux and i686-linux over
the weekend.

> 2023-03-18  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/109164
> 	* cp-tree.h (var_needs_tls_wrapper): Declare.
> 	* decl2.cc (var_needs_tls_wrapper): No longer static.
> 	* decl.cc (cp_finish_decl): Clear TREE_READONLY on TLS variables
> 	for which a TLS wrapper will be needed.
> 
> 	* g++.dg/tls/thread_local13.C: New test.
> 	* g++.dg/tls/thread_local13-aux.cc: New file.
> 	* g++.dg/tls/thread_local14.C: New test.
> 	* g++.dg/tls/thread_local14-aux.cc: New file.

	Jakub
  
Jason Merrill March 20, 2023, 7:15 p.m. UTC | #2
On 3/18/23 11:09, Jakub Jelinek wrote:
> On Sat, Mar 18, 2023 at 01:54:58PM +0100, Jakub Jelinek via Gcc-patches wrote:
>> The patch is mostly about DECL_EXTERNAL cases, the others are supposedly
>> handled by the var_definition_p code there (or at least I assumed;
>> testcases certainly test only DECL_EXTERNAL).
>> I guess it could be done in cp_finish_decl, maybe better next to the
>>    /* A reference will be modified here, as it is initialized.  */
>>    if (! DECL_EXTERNAL (decl)
>>        && TREE_READONLY (decl)
>>        && TYPE_REF_P (type))
>>      {
>>        was_readonly = 1;
>>        TREE_READONLY (decl) = 0;
>>      }
>> spot, but we'd need to export the decl2.cc helpers for it,
>> because not all DECL_THREAD_LOCAL_P vars need to be treated that way.
>>    if (VAR_P (decl)
>>        && CP_DECL_THREAD_LOCAL_P (decl)
>>        && var_needs_tls_wrapper (decl)
>>        && (!DECL_EXTERNAL (decl) || flag_extern_tls_init))
>>      TREE_READONLY (decl) = 0;
>> where var_needs_tls_wrapper would need to be exported from decl2.cc.
>> Though, var_needs_tls_wrapper -> var_defined_without_dynamic_init
>> needs
>> DECL_NONTRIVIALLY_INITIALIZED_P/DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P,
>> so perhaps that is accurate only closer to the end of cp_finish_decl?
> 
> Here it is in patch form, tested so far on tls.exp:
> 
> 2023-03-18  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/109164
> 	* cp-tree.h (var_needs_tls_wrapper): Declare.
> 	* decl2.cc (var_needs_tls_wrapper): No longer static.
> 	* decl.cc (cp_finish_decl): Clear TREE_READONLY on TLS variables
> 	for which a TLS wrapper will be needed.
> 
> 	* g++.dg/tls/thread_local13.C: New test.
> 	* g++.dg/tls/thread_local13-aux.cc: New file.
> 	* g++.dg/tls/thread_local14.C: New test.
> 	* g++.dg/tls/thread_local14-aux.cc: New file.
> 
> --- gcc/cp/cp-tree.h.jj	2023-03-17 08:37:07.542937058 +0100
> +++ gcc/cp/cp-tree.h	2023-03-18 16:02:46.771230806 +0100
> @@ -6989,6 +6989,7 @@ extern void copy_linkage			(tree, tree);
>   extern tree get_guard				(tree);
>   extern tree get_guard_cond			(tree, bool);
>   extern tree set_guard				(tree);
> +extern bool var_needs_tls_wrapper		(tree);
>   extern tree maybe_get_tls_wrapper_call		(tree);
>   extern void mark_needed				(tree);
>   extern bool decl_needed_p			(tree);
> --- gcc/cp/decl2.cc.jj	2023-03-17 16:09:01.749244271 +0100
> +++ gcc/cp/decl2.cc	2023-03-18 15:48:31.340642324 +0100
> @@ -3623,7 +3623,7 @@ var_defined_without_dynamic_init (tree v
>   /* Returns true iff VAR is a variable that needs uses to be
>      wrapped for possible dynamic initialization.  */
>   
> -static bool
> +bool
>   var_needs_tls_wrapper (tree var)
>   {
>     return (!error_operand_p (var)
> --- gcc/cp/decl.cc.jj	2023-03-18 15:47:32.198500421 +0100
> +++ gcc/cp/decl.cc	2023-03-18 16:00:04.565584266 +0100
> @@ -8706,6 +8706,18 @@ cp_finish_decl (tree decl, tree init, bo
>   	  if (!decl_maybe_constant_destruction (decl, type))
>   	    TREE_READONLY (decl) = 0;
>   	}
> +      else if (VAR_P (decl)
> +	       && CP_DECL_THREAD_LOCAL_P (decl)
> +	       && (!DECL_EXTERNAL (decl) || flag_extern_tls_init)

Hmm, I wonder why we don't check the above line in var_needs_tls_wrapper?

But the patch is OK.

> +	       && (was_readonly || TREE_READONLY (decl))
> +	       && var_needs_tls_wrapper (decl))
> +	{
> +	  /* TLS variables need dynamic initialization by the TLS wrapper
> +	     function, we don't want to hoist accesses to it before the
> +	     wrapper.  */
> +	  was_readonly = 0;
> +	  TREE_READONLY (decl) = 0;
> +	}
>   
>         make_rtl_for_nonlocal_decl (decl, init, asmspec);
>   
> --- gcc/testsuite/g++.dg/tls/thread_local13.C.jj	2023-03-18 15:47:50.934228583 +0100
> +++ gcc/testsuite/g++.dg/tls/thread_local13.C	2023-03-18 15:47:50.934228583 +0100
> @@ -0,0 +1,21 @@
> +// PR c++/109164
> +// { dg-do run { target c++11 } }
> +// { dg-options "-O2" }
> +// { dg-add-options tls }
> +// { dg-require-effective-target tls_runtime }
> +// { dg-additional-sources "thread_local13-aux.cc" }
> +
> +struct S { virtual void foo (); int s; };
> +extern thread_local S &t;
> +bool bar ();
> +
> +bool
> +baz ()
> +{
> +  while (1)
> +    {
> +      t.foo ();
> +      if (!bar ())
> +        return false;
> +    }
> +}
> --- gcc/testsuite/g++.dg/tls/thread_local13-aux.cc.jj	2023-03-18 15:47:50.934228583 +0100
> +++ gcc/testsuite/g++.dg/tls/thread_local13-aux.cc	2023-03-18 15:47:50.934228583 +0100
> @@ -0,0 +1,35 @@
> +// PR c++/109164
> +
> +struct S { virtual void foo (); int s; };
> +extern bool baz ();
> +
> +void
> +S::foo ()
> +{
> +  if (s != 42)
> +    __builtin_abort ();
> +}
> +
> +S s;
> +
> +S &
> +qux ()
> +{
> +  s.s = 42;
> +  return s;
> +}
> +
> +thread_local S &t = qux ();
> +
> +bool
> +bar ()
> +{
> +  return false;
> +}
> +
> +int
> +main ()
> +{
> +  if (baz ())
> +    __builtin_abort ();
> +}
> --- gcc/testsuite/g++.dg/tls/thread_local14.C.jj	2023-03-18 15:47:50.934228583 +0100
> +++ gcc/testsuite/g++.dg/tls/thread_local14.C	2023-03-18 15:47:50.934228583 +0100
> @@ -0,0 +1,19 @@
> +// PR c++/109164
> +// { dg-do run { target c++11 } }
> +// { dg-options "-O2" }
> +// { dg-add-options tls }
> +// { dg-require-effective-target tls_runtime }
> +// { dg-additional-sources "thread_local14-aux.cc" }
> +
> +extern thread_local const int t;
> +bool bar (int);
> +
> +bool
> +baz ()
> +{
> +  while (1)
> +    {
> +      if (!bar (t))
> +        return false;
> +    }
> +}
> --- gcc/testsuite/g++.dg/tls/thread_local14-aux.cc.jj	2023-03-18 15:47:50.934228583 +0100
> +++ gcc/testsuite/g++.dg/tls/thread_local14-aux.cc	2023-03-18 15:47:50.934228583 +0100
> @@ -0,0 +1,26 @@
> +// PR c++/109164
> +
> +extern bool baz ();
> +
> +int
> +qux ()
> +{
> +  return 42;
> +}
> +
> +extern thread_local const int t = qux ();
> +
> +bool
> +bar (int x)
> +{
> +  if (x != 42)
> +    __builtin_abort ();
> +  return false;
> +}
> +
> +int
> +main ()
> +{
> +  if (baz ())
> +    __builtin_abort ();
> +}
> 
> 
> 	Jakub
>
  
Jakub Jelinek March 20, 2023, 7:26 p.m. UTC | #3
On Mon, Mar 20, 2023 at 03:15:32PM -0400, Jason Merrill wrote:
> > +      else if (VAR_P (decl)
> > +	       && CP_DECL_THREAD_LOCAL_P (decl)
> > +	       && (!DECL_EXTERNAL (decl) || flag_extern_tls_init)
> 
> Hmm, I wonder why we don't check the above line in var_needs_tls_wrapper?

It is tested in get_tls_init_fn (one of the 2 previous callers of
var_needs_tls_wrapper).  No idea why it isn't in get_tls_wrapper_fn (the
other caller of it).

	Jakub
  
Jason Merrill March 20, 2023, 7:28 p.m. UTC | #4
On 3/20/23 15:26, Jakub Jelinek wrote:
> On Mon, Mar 20, 2023 at 03:15:32PM -0400, Jason Merrill wrote:
>>> +      else if (VAR_P (decl)
>>> +	       && CP_DECL_THREAD_LOCAL_P (decl)
>>> +	       && (!DECL_EXTERNAL (decl) || flag_extern_tls_init)
>>
>> Hmm, I wonder why we don't check the above line in var_needs_tls_wrapper?
> 
> It is tested in get_tls_init_fn (one of the 2 previous callers of
> var_needs_tls_wrapper).  No idea why it isn't in get_tls_wrapper_fn (the
> other caller of it).

I suppose because we might see a definition of the variable later on, 
and we don't want to have previously decided to omit the wrapper because 
we hadn't seen it yet.

Jason
  

Patch

--- gcc/cp/cp-tree.h.jj	2023-03-17 08:37:07.542937058 +0100
+++ gcc/cp/cp-tree.h	2023-03-18 16:02:46.771230806 +0100
@@ -6989,6 +6989,7 @@  extern void copy_linkage			(tree, tree);
 extern tree get_guard				(tree);
 extern tree get_guard_cond			(tree, bool);
 extern tree set_guard				(tree);
+extern bool var_needs_tls_wrapper		(tree);
 extern tree maybe_get_tls_wrapper_call		(tree);
 extern void mark_needed				(tree);
 extern bool decl_needed_p			(tree);
--- gcc/cp/decl2.cc.jj	2023-03-17 16:09:01.749244271 +0100
+++ gcc/cp/decl2.cc	2023-03-18 15:48:31.340642324 +0100
@@ -3623,7 +3623,7 @@  var_defined_without_dynamic_init (tree v
 /* Returns true iff VAR is a variable that needs uses to be
    wrapped for possible dynamic initialization.  */
 
-static bool
+bool
 var_needs_tls_wrapper (tree var)
 {
   return (!error_operand_p (var)
--- gcc/cp/decl.cc.jj	2023-03-18 15:47:32.198500421 +0100
+++ gcc/cp/decl.cc	2023-03-18 16:00:04.565584266 +0100
@@ -8706,6 +8706,18 @@  cp_finish_decl (tree decl, tree init, bo
 	  if (!decl_maybe_constant_destruction (decl, type))
 	    TREE_READONLY (decl) = 0;
 	}
+      else if (VAR_P (decl)
+	       && CP_DECL_THREAD_LOCAL_P (decl)
+	       && (!DECL_EXTERNAL (decl) || flag_extern_tls_init)
+	       && (was_readonly || TREE_READONLY (decl))
+	       && var_needs_tls_wrapper (decl))
+	{
+	  /* TLS variables need dynamic initialization by the TLS wrapper
+	     function, we don't want to hoist accesses to it before the
+	     wrapper.  */
+	  was_readonly = 0;
+	  TREE_READONLY (decl) = 0;
+	}
 
       make_rtl_for_nonlocal_decl (decl, init, asmspec);
 
--- gcc/testsuite/g++.dg/tls/thread_local13.C.jj	2023-03-18 15:47:50.934228583 +0100
+++ gcc/testsuite/g++.dg/tls/thread_local13.C	2023-03-18 15:47:50.934228583 +0100
@@ -0,0 +1,21 @@ 
+// PR c++/109164
+// { dg-do run { target c++11 } }
+// { dg-options "-O2" }
+// { dg-add-options tls }
+// { dg-require-effective-target tls_runtime }
+// { dg-additional-sources "thread_local13-aux.cc" }
+
+struct S { virtual void foo (); int s; };
+extern thread_local S &t;
+bool bar ();
+
+bool
+baz ()
+{
+  while (1)
+    {
+      t.foo ();
+      if (!bar ())
+        return false;
+    }
+}
--- gcc/testsuite/g++.dg/tls/thread_local13-aux.cc.jj	2023-03-18 15:47:50.934228583 +0100
+++ gcc/testsuite/g++.dg/tls/thread_local13-aux.cc	2023-03-18 15:47:50.934228583 +0100
@@ -0,0 +1,35 @@ 
+// PR c++/109164
+
+struct S { virtual void foo (); int s; };
+extern bool baz ();
+
+void
+S::foo ()
+{
+  if (s != 42)
+    __builtin_abort ();
+}
+
+S s;
+
+S &
+qux ()
+{
+  s.s = 42;
+  return s;
+}
+
+thread_local S &t = qux ();
+
+bool
+bar ()
+{
+  return false;
+}
+
+int
+main ()
+{
+  if (baz ())
+    __builtin_abort ();
+}
--- gcc/testsuite/g++.dg/tls/thread_local14.C.jj	2023-03-18 15:47:50.934228583 +0100
+++ gcc/testsuite/g++.dg/tls/thread_local14.C	2023-03-18 15:47:50.934228583 +0100
@@ -0,0 +1,19 @@ 
+// PR c++/109164
+// { dg-do run { target c++11 } }
+// { dg-options "-O2" }
+// { dg-add-options tls }
+// { dg-require-effective-target tls_runtime }
+// { dg-additional-sources "thread_local14-aux.cc" }
+
+extern thread_local const int t;
+bool bar (int);
+
+bool
+baz ()
+{
+  while (1)
+    {
+      if (!bar (t))
+        return false;
+    }
+}
--- gcc/testsuite/g++.dg/tls/thread_local14-aux.cc.jj	2023-03-18 15:47:50.934228583 +0100
+++ gcc/testsuite/g++.dg/tls/thread_local14-aux.cc	2023-03-18 15:47:50.934228583 +0100
@@ -0,0 +1,26 @@ 
+// PR c++/109164
+
+extern bool baz ();
+
+int
+qux ()
+{
+  return 42;
+}
+
+extern thread_local const int t = qux ();
+
+bool
+bar (int x)
+{
+  if (x != 42)
+    __builtin_abort ();
+  return false;
+}
+
+int
+main ()
+{
+  if (baz ())
+    __builtin_abort ();
+}