>
> The following is what I profile-bootstrapped and tested on
> x86_64-unknown-linux-gnu.
>
> Richard.
>
> From d438a0d84cafced85c90204cba81de0f60ad0073 Mon Sep 17 00:00:00 2001
> From: Richard Biener <rguent...@suse.de>
> Date: Thu, 16 Mar 2023 13:51:19 +0100
> Subject: [PATCH] tree-optimization/106912 - clear const attribute from fntype
> To: gcc-patches@gcc.gnu.org
>
> The following makes sure that after clearing pure/const from
> instrumented function declarations we are adjusting call statements
> fntype as well to handle indirect calls and because gimple_call_flags
> looks at both decl and fntype.
>
> Like the pure/const flag clearing on decls we refrain from touching
> calls to known functions that do not have a body in the current TU.
>
> PR tree-optimization/106912
> * tree-profile.cc (tree_profiling): Update stmts only when
> profiling or testing coverage. Make sure to update calls
> fntype, stripping 'const' there.
>
> * gcc.dg/profile-generate-4.c: New testcase.
> ---
> gcc/testsuite/gcc.dg/profile-generate-4.c | 19 ++++++++++++
> gcc/tree-profile.cc | 38 +++++++++++++++++------
> 2 files changed, 47 insertions(+), 10 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/profile-generate-4.c
>
> diff --git a/gcc/testsuite/gcc.dg/profile-generate-4.c
> b/gcc/testsuite/gcc.dg/profile-generate-4.c
> new file mode 100644
> index 00000000000..c2b999fe4cb
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/profile-generate-4.c
> @@ -0,0 +1,19 @@
> +/* PR106912 */
> +/* { dg-require-profiling "-fprofile-generate" } */
> +/* { dg-options "-O2 -fprofile-generate -ftree-vectorize" } */
> +
> +__attribute__ ((__simd__))
> +__attribute__ ((__nothrow__ , __leaf__ , __const__, __noinline__))
> +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 ea9d7a23443..7854cd4bc31 100644
> --- a/gcc/tree-profile.cc
> +++ b/gcc/tree-profile.cc
> @@ -835,16 +835,34 @@ tree_profiling (void)
>
> push_cfun (DECL_STRUCT_FUNCTION (node->decl));
>
> - FOR_EACH_BB_FN (bb, cfun)
> - {
> - gimple_stmt_iterator gsi;
> - for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
> - {
> - gimple *stmt = gsi_stmt (gsi);
> - if (is_gimple_call (stmt))
> - update_stmt (stmt);
> - }
> - }
> + if (profile_arc_flag || flag_test_coverage)
> + FOR_EACH_BB_FN (bb, cfun)
> + {
> + gimple_stmt_iterator gsi;
> + for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
> + {
> + gcall *call = dyn_cast <gcall *> (gsi_stmt (gsi));
> + if (!call)
> + continue;
> +
> + /* We do not clear pure/const on decls without body. */
> + tree fndecl = gimple_call_fndecl (call);
> + if (fndecl && !gimple_has_body_p (fndecl))
> + continue;
> +
> + /* Drop the const attribute from the call type (the pure
> + attribute is not available on types). */
> + tree fntype = gimple_call_fntype (call);
> + if (fntype && TYPE_READONLY (fntype))
> + gimple_call_set_fntype
> + (call, build_qualified_type (fntype, (TYPE_QUALS (fntype)
> + & ~TYPE_QUAL_CONST)));
Sorry, now I am bit confused on why Jakub's fix did not need similar
fixup. The flag is only set during the profiling stage and thus I would
expect it to still run into the problem that VOPs are missing.
Is it only becuase we do not sanity check?
Here is a testcase that shows the problem:
include <math.h>
float c;
__attribute__ ((const))
float
instrument(float v)
{
return sin (v);
}
__attribute__ ((no_profile_instrument_function,const,noinline))
float noinstrument (float v)
{
return instrument (v);
}
m()
{
c+=instrument(c);
if (!__builtin_expect (c,1))
{
c+=noinstrument (c);
}
c+=instrument(c);
}
main()
{
m();
}
Compiling
gcc -O0 t.c -fprofile-arcs -fno-early-inlining --coverage -lm -ftest-coverage
-S ; gcc t.s -ftest-coverage -lm -fprofile-arcs
makes gcov to report 3 executions on instrument while with -O3 it is 2.
This is because the noinstrument has const flag that is not cleared and
it becoames essentially non-const because it calls instrument that gets
intrumented and partially inlined.
Honza
> +
> + /* Update virtual operands of calls to no longer const/pure
> + functions. */
> + update_stmt (call);
> + }
> + }
>
> /* re-merge split blocks. */
> cleanup_tree_cfg ();
> --
> 2.35.3
>
