[vrp] Allow VRP type conversion folding only for widenings upto word mode

Submitted by Senthil Kumar Selvaraj on Nov. 14, 2015, 7:11 a.m.

Details

Message ID 20151114071148.GA16647@jaguar.atmel.com
State New
Headers show

Commit Message

Senthil Kumar Selvaraj Nov. 14, 2015, 7:11 a.m.
This patch came out of a discussion held in the gcc mailing list
(https://gcc.gnu.org/ml/gcc/2015-11/msg00067.html).

The patch restricts folding of conditional exprs with lhs previously
set by a type conversion to occur only if the source of the type 
conversion's mode is word mode or smaller.

Bootstrapped and reg tested on x86_64 (with --enable-languages=c,c++).

If ok, could you commit please? I don't have commit access.

Regards
Senthil

gcc/ChangeLog

2015-11-11  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	* tree-vrp.c (simplify_cond_using_ranges): Fold only
	if innerop's mode is word_mode or smaller.

Comments

Marc Glisse Nov. 14, 2015, 8:13 a.m.
On Sat, 14 Nov 2015, Senthil Kumar Selvaraj wrote:

> This patch came out of a discussion held in the gcc mailing list
> (https://gcc.gnu.org/ml/gcc/2015-11/msg00067.html).
>
> The patch restricts folding of conditional exprs with lhs previously
> set by a type conversion to occur only if the source of the type
> conversion's mode is word mode or smaller.
>
> Bootstrapped and reg tested on x86_64 (with --enable-languages=c,c++).
>
> If ok, could you commit please? I don't have commit access.
>
> Regards
> Senthil
>
> gcc/ChangeLog
>
> 2015-11-11  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
>
> 	* tree-vrp.c (simplify_cond_using_ranges): Fold only
> 	if innerop's mode is word_mode or smaller.
>
>
> diff --git gcc/tree-vrp.c gcc/tree-vrp.c
> index e2393e4..c139bc6 100644
> --- gcc/tree-vrp.c
> +++ gcc/tree-vrp.c
> @@ -9467,6 +9467,8 @@ simplify_cond_using_ranges (gcond *stmt)
>       innerop = gimple_assign_rhs1 (def_stmt);
>
>       if (TREE_CODE (innerop) == SSA_NAME
> +         && (GET_MODE_SIZE(TYPE_MODE(TREE_TYPE(innerop)))
> +           <= GET_MODE_SIZE(word_mode))
> 	  && !POINTER_TYPE_P (TREE_TYPE (innerop)))
> 	{
> 	  value_range *vr = get_value_range (innerop);

I thought the result of the discussion was that the transformation is ok 
if either it is narrowing or it widens but to something no bigger than 
word_mode. So you should have 2 comparisons, or 1 with a max.
Senthil Kumar Selvaraj Nov. 14, 2015, 8:49 a.m.
On Sat, Nov 14, 2015 at 09:13:41AM +0100, Marc Glisse wrote:
> On Sat, 14 Nov 2015, Senthil Kumar Selvaraj wrote:
> 
> >This patch came out of a discussion held in the gcc mailing list
> >(https://gcc.gnu.org/ml/gcc/2015-11/msg00067.html).
> >
> >The patch restricts folding of conditional exprs with lhs previously
> >set by a type conversion to occur only if the source of the type
> >conversion's mode is word mode or smaller.
> >
> >Bootstrapped and reg tested on x86_64 (with --enable-languages=c,c++).
> >
> >If ok, could you commit please? I don't have commit access.
> >
> >Regards
> >Senthil
> >
> >gcc/ChangeLog
> >
> >2015-11-11  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
> >
> >	* tree-vrp.c (simplify_cond_using_ranges): Fold only
> >	if innerop's mode is word_mode or smaller.
> >
> >
> >diff --git gcc/tree-vrp.c gcc/tree-vrp.c
> >index e2393e4..c139bc6 100644
> >--- gcc/tree-vrp.c
> >+++ gcc/tree-vrp.c
> >@@ -9467,6 +9467,8 @@ simplify_cond_using_ranges (gcond *stmt)
> >      innerop = gimple_assign_rhs1 (def_stmt);
> >
> >      if (TREE_CODE (innerop) == SSA_NAME
> >+         && (GET_MODE_SIZE(TYPE_MODE(TREE_TYPE(innerop)))
> >+           <= GET_MODE_SIZE(word_mode))
> >	  && !POINTER_TYPE_P (TREE_TYPE (innerop)))
> >	{
> >	  value_range *vr = get_value_range (innerop);
> 
> I thought the result of the discussion was that the transformation is ok if
> either it is narrowing or it widens but to something no bigger than
> word_mode. So you should have 2 comparisons, or 1 with a max.

Hmm, I came to the opposite conclusion - I thought Richard only okayed
"widening upto word-mode", not the narrowing. 

Richard?

Regards
Senthil
> 
> -- 
> Marc Glisse
Richard Guenther Nov. 14, 2015, 8:57 a.m.
On November 14, 2015 9:49:28 AM GMT+01:00, Senthil Kumar Selvaraj <senthil_kumar.selvaraj@atmel.com> wrote:
>On Sat, Nov 14, 2015 at 09:13:41AM +0100, Marc Glisse wrote:
>> On Sat, 14 Nov 2015, Senthil Kumar Selvaraj wrote:
>> 
>> >This patch came out of a discussion held in the gcc mailing list
>> >(https://gcc.gnu.org/ml/gcc/2015-11/msg00067.html).
>> >
>> >The patch restricts folding of conditional exprs with lhs previously
>> >set by a type conversion to occur only if the source of the type
>> >conversion's mode is word mode or smaller.
>> >
>> >Bootstrapped and reg tested on x86_64 (with
>--enable-languages=c,c++).
>> >
>> >If ok, could you commit please? I don't have commit access.
>> >
>> >Regards
>> >Senthil
>> >
>> >gcc/ChangeLog
>> >
>> >2015-11-11  Senthil Kumar Selvaraj 
><senthil_kumar.selvaraj@atmel.com>
>> >
>> >	* tree-vrp.c (simplify_cond_using_ranges): Fold only
>> >	if innerop's mode is word_mode or smaller.
>> >
>> >
>> >diff --git gcc/tree-vrp.c gcc/tree-vrp.c
>> >index e2393e4..c139bc6 100644
>> >--- gcc/tree-vrp.c
>> >+++ gcc/tree-vrp.c
>> >@@ -9467,6 +9467,8 @@ simplify_cond_using_ranges (gcond *stmt)
>> >      innerop = gimple_assign_rhs1 (def_stmt);
>> >
>> >      if (TREE_CODE (innerop) == SSA_NAME
>> >+         && (GET_MODE_SIZE(TYPE_MODE(TREE_TYPE(innerop)))
>> >+           <= GET_MODE_SIZE(word_mode))
>> >	  && !POINTER_TYPE_P (TREE_TYPE (innerop)))
>> >	{
>> >	  value_range *vr = get_value_range (innerop);
>> 
>> I thought the result of the discussion was that the transformation is
>ok if
>> either it is narrowing or it widens but to something no bigger than
>> word_mode. So you should have 2 comparisons, or 1 with a max.
>
>Hmm, I came to the opposite conclusion - I thought Richard only okayed
>"widening upto word-mode", not the narrowing. 

I didn't mean to suggest narrowing is not OK.  In fact narrowing is always OK.

Richard.

>Richard?
>
>Regards
>Senthil
>> 
>> -- 
>> Marc Glisse

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diff --git gcc/tree-vrp.c gcc/tree-vrp.c
index e2393e4..c139bc6 100644
--- gcc/tree-vrp.c
+++ gcc/tree-vrp.c
@@ -9467,6 +9467,8 @@  simplify_cond_using_ranges (gcond *stmt)
       innerop = gimple_assign_rhs1 (def_stmt);
 
       if (TREE_CODE (innerop) == SSA_NAME
+         && (GET_MODE_SIZE(TYPE_MODE(TREE_TYPE(innerop))) 
+           <= GET_MODE_SIZE(word_mode))
 	  && !POINTER_TYPE_P (TREE_TYPE (innerop)))
 	{
 	  value_range *vr = get_value_range (innerop);