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* [pushed] c++: #pragma target and deferred instantiation [PR115403]
@ 2024-07-25 23:54 Jason Merrill
  2024-07-26 17:56 ` Patrick Palka
  0 siblings, 1 reply; 2+ messages in thread
From: Jason Merrill @ 2024-07-25 23:54 UTC (permalink / raw)
  To: gcc-patches

Tested x86_64-pc-linux-gnu, applying to trunk.

Also built highway to check.

-- 8< --

My patch for 109753 applies the current #pragma target/optimize to a
function when we compile it, which was a problem for a template
instantiation deferred until EOF, where different #pragmas are active.  So
let's only do this for artificial functions.

	PR c++/115403
	PR c++/109753

gcc/cp/ChangeLog:

	* decl.cc (start_preparsed_function): Only call decl_attributes for
	artificial functions.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/pragma-target1.C: New test.
---
 gcc/cp/decl.cc                            | 7 +++++--
 gcc/testsuite/g++.dg/ext/pragma-target1.C | 6 ++++++
 2 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/ext/pragma-target1.C

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 6b686d75a49..279af21eed0 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -17882,8 +17882,11 @@ start_preparsed_function (tree decl1, tree attrs, int flags)
 	doing_friend = true;
     }
 
-  /* Adjust for #pragma target/optimize.  */
-  decl_attributes (&decl1, NULL_TREE, 0);
+  /* Adjust for #pragma target/optimize if this is an artificial function that
+     (probably) didn't go through grokfndecl.  We particularly don't want this
+     for deferred instantiations, which should match their template.  */
+  if (DECL_ARTIFICIAL (decl1))
+    decl_attributes (&decl1, NULL_TREE, 0);
 
   if (DECL_DECLARED_INLINE_P (decl1)
       && lookup_attribute ("noinline", attrs))
diff --git a/gcc/testsuite/g++.dg/ext/pragma-target1.C b/gcc/testsuite/g++.dg/ext/pragma-target1.C
new file mode 100644
index 00000000000..0ce2438da2f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/pragma-target1.C
@@ -0,0 +1,6 @@
+// PR c++/115403
+// { dg-do compile { target x86_64-*-* } }
+
+template <typename> __attribute__((always_inline)) inline void AssertEqual() {}
+void TestAllF16FromF32() { AssertEqual<float>(); }
+#pragma GCC target "sse4.1"

base-commit: 29341f21ce1eb7cdb8cd468e4ceb0d07cf2775e0
-- 
2.45.2


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [pushed] c++: #pragma target and deferred instantiation [PR115403]
  2024-07-25 23:54 [pushed] c++: #pragma target and deferred instantiation [PR115403] Jason Merrill
@ 2024-07-26 17:56 ` Patrick Palka
  0 siblings, 0 replies; 2+ messages in thread
From: Patrick Palka @ 2024-07-26 17:56 UTC (permalink / raw)
  To: Jason Merrill; +Cc: gcc-patches

On Thu, 25 Jul 2024, Jason Merrill wrote:

> Tested x86_64-pc-linux-gnu, applying to trunk.
> 
> Also built highway to check.
> 
> -- 8< --
> 
> My patch for 109753 applies the current #pragma target/optimize to a
> function when we compile it, which was a problem for a template
> instantiation deferred until EOF, where different #pragmas are active.  So
> let's only do this for artificial functions.
> 
> 	PR c++/115403
> 	PR c++/109753
> 
> gcc/cp/ChangeLog:
> 
> 	* decl.cc (start_preparsed_function): Only call decl_attributes for
> 	artificial functions.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/ext/pragma-target1.C: New test.
> ---
>  gcc/cp/decl.cc                            | 7 +++++--
>  gcc/testsuite/g++.dg/ext/pragma-target1.C | 6 ++++++
>  2 files changed, 11 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/ext/pragma-target1.C
> 
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 6b686d75a49..279af21eed0 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -17882,8 +17882,11 @@ start_preparsed_function (tree decl1, tree attrs, int flags)
>  	doing_friend = true;
>      }
>  
> -  /* Adjust for #pragma target/optimize.  */
> -  decl_attributes (&decl1, NULL_TREE, 0);
> +  /* Adjust for #pragma target/optimize if this is an artificial function that
> +     (probably) didn't go through grokfndecl.  We particularly don't want this
> +     for deferred instantiations, which should match their template.  */
> +  if (DECL_ARTIFICIAL (decl1))
> +    decl_attributes (&decl1, NULL_TREE, 0);

Couldn't an artificial function get synthesized at EOF if e.g. it's
needed by a deferred instantiation?  In that case we'll still call
decl_attributes on it which will inherit the last active #pragma,
which seems unintended.  Maybe we should clear #pragma before
processing deferred instantiations?

>  
>    if (DECL_DECLARED_INLINE_P (decl1)
>        && lookup_attribute ("noinline", attrs))
> diff --git a/gcc/testsuite/g++.dg/ext/pragma-target1.C b/gcc/testsuite/g++.dg/ext/pragma-target1.C
> new file mode 100644
> index 00000000000..0ce2438da2f
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/pragma-target1.C
> @@ -0,0 +1,6 @@
> +// PR c++/115403
> +// { dg-do compile { target x86_64-*-* } }
> +
> +template <typename> __attribute__((always_inline)) inline void AssertEqual() {}
> +void TestAllF16FromF32() { AssertEqual<float>(); }
> +#pragma GCC target "sse4.1"
> 
> base-commit: 29341f21ce1eb7cdb8cd468e4ceb0d07cf2775e0
> -- 
> 2.45.2
> 
> 


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