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Re: [Patch, vrp] Allow VRP type conversion folding only for widenings upto word mode
- From: Senthil Kumar Selvaraj <senthil_kumar dot selvaraj at atmel dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: <gcc-patches at gcc dot gnu dot org>, <law at redhat dot com>
- Date: Sat, 14 Nov 2015 23:40:44 +0530
- Subject: Re: [Patch, vrp] Allow VRP type conversion folding only for widenings upto word mode
- Authentication-results: sourceware.org; auth=none
- References: <20151114071148 dot GA16647 at jaguar dot atmel dot com> <alpine dot DEB dot 2 dot 20 dot 1511140907420 dot 1923 at laptop-mg dot saclay dot inria dot fr> <20151114084928 dot GA749 at jaguar dot atmel dot com> <595F0CF8-27C1-4A63-8339-F70CB5E76CAB at suse dot de>
On Sat, Nov 14, 2015 at 09:57:40AM +0100, Richard Biener wrote:
> 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.
My bad. Here's a revised patch that checks for both conditions, using
max as Marc suggested to limit to word_mode or narrowing conversions.
Bootstrapped and regtested for x86_64 with c and c++.
Is this ok? If yes, would you commit it
for me please? I don't have commit access.
gcc/ChangeLog
2015-11-14 Senthil Kumar Selvaraj <senthil_kumar.selvaraj@atmel.com>
* tree-vrp.c (simplify_cond_using_ranges): Fold only
if innerop's mode smaller or equal to word_mode or op0's mode.
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index e2393e4..cfd90e7 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -9467,7 +9467,10 @@ simplify_cond_using_ranges (gcond *stmt)
innerop = gimple_assign_rhs1 (def_stmt);
if (TREE_CODE (innerop) == SSA_NAME
- && !POINTER_TYPE_P (TREE_TYPE (innerop)))
+ && !POINTER_TYPE_P (TREE_TYPE (innerop))
+ && (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (innerop)))
+ <= std::max (GET_MODE_SIZE (word_mode),
+ GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (op0))))))
{
value_range *vr = get_value_range (innerop);
Regards
Senthil
>
> Richard.
>
> >Richard?
> >
> >Regards
> >Senthil
> >>
> >> --
> >> Marc Glisse
>
>