Re: [PATCH] tree-optimization/106912 - IPA profile and pure/const

[Jan Hubicka <hubicka@ucw.cz>]

> IPA profile instrumentation tries to clear the pure and const
> flags of functions but that's quite hopeless in particular for
> const since that attribute prevails on the type and thus on each
> call to the function leading to inconsistencies in the IL and
> eventual checking ICEs.  There's no good reason to do this and
> it wouldn't fixup any indirect calls so just don't.  No other
> instrumentation GCC does bothers about this.

This was mostly meant to deadl with situation where we auto-detect
function to be const and then partially inline it to a loop.
Then both caller and callee accesses same counters in the memory and if
you move load/stores out of the loop in caller you lose counters and get
inconsistencies at profile read-in time.

Honza
> 
> Bootstrap and regtest pending on x86_64-unknown-linux-gnu, OK?
> 
> Thanks,
> Richard.
> 
> 	PR tree-optimization/106912
> 	* tree-profile.cc (tree_profiling): Do not clear pure/const
> 	flags.
> 
> 	* gcc.dg/pr106912.c: New testcase.
> ---
>  gcc/testsuite/gcc.dg/pr106912.c | 16 ++++++++++++++++
>  gcc/tree-profile.cc             |  3 ---
>  2 files changed, 16 insertions(+), 3 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/pr106912.c
> 
> diff --git a/gcc/testsuite/gcc.dg/pr106912.c b/gcc/testsuite/gcc.dg/pr106912.c
> new file mode 100644
> index 00000000000..8faa877d8b3
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr106912.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fPIC -ftree-vectorize -fprofile-generate" } */
> +
> +__attribute__ ((__simd__))
> +__attribute__ ((__nothrow__ , __leaf__ , __const__))
> +double foo (double x);
> +void bar(double *f, int n)
> +{
> +  int i;
> +  for (i = 0; i < n; i++)
> +    f[i] = foo(f[i]);
> +}
> +double foo(double x)
> +{
> +  return x * x / 3.0;
> +}
> diff --git a/gcc/tree-profile.cc b/gcc/tree-profile.cc
> index 2beb49241f2..5491b398870 100644
> --- a/gcc/tree-profile.cc
> +++ b/gcc/tree-profile.cc
> @@ -814,9 +814,6 @@ tree_profiling (void)
>  	/* Don't profile functions produced for builtin stuff.  */
>  	if (DECL_SOURCE_LOCATION (node->decl) == BUILTINS_LOCATION)
>  	  continue;
> -
> -	node->set_const_flag (false, false);
> -	node->set_pure_flag (false, false);
>        }
>  
>    /* Update call statements and rebuild the cgraph.  */
> -- 
> 2.35.3