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From: Jan Hubicka <hubicka@kam.mff.cuni.cz>
To: "Kewen.Lin" <linkw@linux.ibm.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>,
	Richard Sandiford <richard.sandiford@arm.com>,
	Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH] predict: Adjust optimize_function_for_size_p [PR105818]
Date: Tue, 14 Jun 2022 13:37:57 +0200	[thread overview]
Message-ID: <YqhzFZWOPZFKZ/9C@kam.mff.cuni.cz> (raw)
In-Reply-To: <23b4998b-bbe6-b052-d7f5-5304ee0f46a3@linux.ibm.com>

> Hi,
> 
> Function optimize_function_for_size_p returns OPTIMIZE_SIZE_NO
> if func->decl is not null but no cgraph node is available for it.
> As PR105818 shows, this could give unexpected result.  For the
> case in PR105818, when parsing bar decl in function foo, the cfun
> is a function structure for foo, for which there is none cgraph
> node, so it returns OPTIMIZE_SIZE_NO.  But it's incorrect since
> the context is to optimize for size, the flag optimize_size is
> true.
> 
> The patch is to make optimize_function_for_size_p to check
> optimize_size as what it does when func->decl is unavailable.
> 
> One regression failure got exposed on aarch64-linux-gnu:
> 
> PASS->FAIL: gcc.dg/guality/pr54693-2.c   -Os \
> 	    -DPREVENT_OPTIMIZATION  line 21 x == 10 - i
> 
> The difference comes from the macro LOGICAL_OP_NON_SHORT_CIRCUIT
> used in function fold_range_test during c parsing, it uses
> optimize_function_for_speed_p which is equal to the invertion
> of optimize_function_for_size_p.  At that time cfun->decl is valid
> but no cgraph node for it, w/o this patch function
> optimize_function_for_speed_p returns true eventually, while it
> returns false with this patch.  Since the command line option -Os
> is specified, there is no reason to interpret it as "for speed".
> I think this failure is expected and adjust the test case
> accordingly.
> 
> Is it ok for trunk?
> 
> BR,
> Kewen
> -----
> 
> 	PR target/105818
> 
> gcc/ChangeLog:
> 
> 	* predict.cc (optimize_function_for_size_p): Check optimize_size when
> 	func->decl is valid but its cgraph node is unavailable.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.target/powerpc/pr105818.c: New test.
> 	* gcc.dg/guality/pr54693-2.c: Adjust for aarch64.
> ---
>  gcc/predict.cc                              | 2 +-
>  gcc/testsuite/gcc.dg/guality/pr54693-2.c    | 2 +-
>  gcc/testsuite/gcc.target/powerpc/pr105818.c | 9 +++++++++
>  3 files changed, 11 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr105818.c
> 
> diff --git a/gcc/predict.cc b/gcc/predict.cc
> index 5734e4c8516..6c60a973236 100644
> --- a/gcc/predict.cc
> +++ b/gcc/predict.cc
> @@ -268,7 +268,7 @@ optimize_function_for_size_p (struct function *fun)
>    cgraph_node *n = cgraph_node::get (fun->decl);
>    if (n)
>      return n->optimize_for_size_p ();
> -  return OPTIMIZE_SIZE_NO;
> +  return optimize_size ? OPTIMIZE_SIZE_MAX : OPTIMIZE_SIZE_NO;

We could also do (opt_for_fn (cfun->decl, optimize_size) that is
probably better since one can change optimize_size with optimization
attribute.
However I think in most cases we check for optimize_size early I think
we are doing something wrong, since at that time htere is no profile
available.  Why exactly PR105818 hits the flag change issue?

Honza
>  }
> 
>  /* Return true if function FUN should always be optimized for speed.  */
> diff --git a/gcc/testsuite/gcc.dg/guality/pr54693-2.c b/gcc/testsuite/gcc.dg/guality/pr54693-2.c
> index 68aa6c63d71..14ca94ad37d 100644
> --- a/gcc/testsuite/gcc.dg/guality/pr54693-2.c
> +++ b/gcc/testsuite/gcc.dg/guality/pr54693-2.c
> @@ -17,7 +17,7 @@ foo (int x, int y, int z)
>    int i = 0;
>    while (x > 3 && y > 3 && z > 3)
>      {		/* { dg-final { gdb-test .+2 "i" "v + 1" } } */
> -		/* { dg-final { gdb-test .+1 "x" "10 - i" } } */
> +		/* { dg-final { gdb-test .+1 "x" "10 - i" { xfail { aarch64*-*-* && { any-opts "-Os" } } } } } */
>        bar (i);	/* { dg-final { gdb-test . "y" "20 - 2 * i" } } */
>  		/* { dg-final { gdb-test .-1 "z" "30 - 3 * i" { xfail { aarch64*-*-* && { any-opts "-fno-fat-lto-objects" "-Os" } } } } } */
>        i++, x--, y -= 2, z -= 3;
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr105818.c b/gcc/testsuite/gcc.target/powerpc/pr105818.c
> new file mode 100644
> index 00000000000..18781edbf9e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr105818.c
> @@ -0,0 +1,9 @@
> +/* { dg-options "-Os -fno-tree-vectorize" } */
> +
> +#pragma GCC optimize "-fno-tree-vectorize"
> +
> +void
> +foo (void)
> +{
> +  void bar (void);
> +}
> --
> 2.27.0

  reply	other threads:[~2022-06-14 11:37 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-14  7:57 Kewen.Lin
2022-06-14 11:37 ` Jan Hubicka [this message]
2022-06-15  6:20   ` Kewen.Lin
2022-07-11  3:42     ` Kewen.Lin
2022-08-15  8:33       ` Kewen.Lin
2022-08-29  6:35         ` Kewen.Lin
2022-09-28  5:46           ` Kewen.Lin
2022-06-14 12:53 ` Segher Boessenkool
2022-06-15  6:21   ` Kewen.Lin

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