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> Subject: Re: Patch: Refactor number_of_iterations_exit
> From: richard.guent...@gmail.com
> Date: Thu, 7 May 2015 19:47:37 +0200
> To: hiradi...@msn.com; gcc-patches@gcc.gnu.org
>
> On May 7, 2015 6:27:28 PM GMT+02:00, Aditya K <hiradi...@msn.com> wrote:
>>Hi,
>>I refactored number_of_iterations_exit a little bit. I hope it is
>>helpful.
>>The idea is to move the call to function dominated_by_p after some
>>sanity checks so as to avoid call to it.
>
> The call is very cheap though. Do you have data that shows it often passes
> when the later checks fail?
I don't have any data. I was going through this code and realized that when
last_stmt(exit->src)
would fail or when the last_stmt is not a conditional it would be pointless to
find if exit->src dominates loop->latch
(which would be true for most simple loops, but then most simple loops would
have conditionals as last statements. So I'm not very sure about this.)
-Aditya
>
> Richard.
>
>>
>>Thanks,
>>-Aditya
>>
>>
>>2015-05-07 Aditya Kumar <hiradi...@msn.com>
>>
>> * tree-ssa-loop-niter.c (number_of_iterations_exit): Move call
>>to dominated_by_p later in the function.
>>
>>diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
>>index 042f8df..3d49bb8 100644
>>--- a/gcc/tree-ssa-loop-niter.c
>>+++ b/gcc/tree-ssa-loop-niter.c
>>@@ -1959,11 +1959,6 @@ number_of_iterations_exit (struct loop *loop,
>>edge exit,
>> affine_iv iv0, iv1;
>> bool safe;
>>
>>- safe = dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src);
>>-
>>- if (every_iteration && !safe)
>>- return false;
>>-
>> niter->assumptions = boolean_false_node;
>> last = last_stmt (exit->src);
>> if (!last)
>>@@ -1972,6 +1967,11 @@ number_of_iterations_exit (struct loop *loop,
>>edge exit,
>> if (!stmt)
>> return false;
>>
>>+ safe = dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src);
>>+
>>+ if (every_iteration && !safe)
>>+ return false;
>>+
>> /* We want the condition for staying inside loop. */
>> code = gimple_cond_code (stmt);
>> if (exit->flags & EDGE_TRUE_VALUE)
>>
>>
>
>
