From: "Bin.Cheng" <amker.cheng@gmail.com>
To: Zdenek Dvorak <ook@ucw.cz>
Cc: gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Fwd: [PATCH 1/3]Improve induction variable elimination
Date: Mon, 21 Jul 2014 09:47:00 -0000 [thread overview]
Message-ID: <CAHFci2_+jmo4q6Hah-ZX-uJgm0sjdKiqfoKAR5We+=g1mCBvtw@mail.gmail.com> (raw)
In-Reply-To: <002a01cfa19e$8752d0d0$95f87270$@arm.com>
[-- Attachment #1: Type: text/plain, Size: 1525 bytes --]
Hi, forward to Zdenek for the review.
Thanks,
bin
---------- Forwarded message ----------
From: Bin Cheng <bin.cheng@arm.com>
Date: Thu, Jul 17, 2014 at 10:07 AM
Subject: [PATCH 1/3]Improve induction variable elimination
To: gcc-patches@gcc.gnu.org
Hi,
This is a series of three patches improving induction variable elimination.
Currently GCC only eliminates iv for very specific case when the loop's
latch could run zero times, i.e., when may_be_zero field of loop niter
information evaluates to true. In fact, it's so specific that
iv_elimination_compare_lt rarely succeeds during either GCC bootstrap or
spec2000/spec2006 compilation. Though intrusive data shows these patches
don't help iv elimination that much for GCC bootstrap, they do capture
5%~15% more eliminations for compiling spec2000/2006. Detailed numbers are
like:
2k/int 2k/fp 2k6/int 2k6/fp
improve ~9.6% ~4.8% ~5.5% ~14.4%
All patches pass bootstrap and regression test on x86_64/x86. I will
bootstrap and test them on aarch64/arm platforms too.
The first patch turns to tree operand_equal_p to check the number of
iterations in iv_elimination_lt. Though I think this change isn't necessary
for current code, it's needed if we further relax iv elimination for cases
in which sign/unsigned conversion is involved.
Thanks,
bin
2014-07-17 Bin Cheng <bin.cheng@arm.com>
* tree-ssa-loop-ivopts.c (iv_elimination_compare_lt): Check number
of iteration using tree comparison.
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Index: gcc/tree-ssa-loop-ivopts.c
===================================================================
--- gcc/tree-ssa-loop-ivopts.c (revision 212387)
+++ gcc/tree-ssa-loop-ivopts.c (working copy)
@@ -4605,7 +4605,7 @@ iv_elimination_compare_lt (struct ivopts_data *dat
struct tree_niter_desc *niter)
{
tree cand_type, a, b, mbz, nit_type = TREE_TYPE (niter->niter), offset;
- struct aff_tree nit, tmpa, tmpb;
+ struct aff_tree nit, tmp1, tmpa, tmpb;
enum tree_code comp;
HOST_WIDE_INT step;
@@ -4661,15 +4661,19 @@ iv_elimination_compare_lt (struct ivopts_data *dat
return false;
/* Expected number of iterations is B - A - 1. Check that it matches
- the actual number, i.e., that B - A - NITER = 1. */
+ the actual number, i.e., that B - A = NITER + 1. */
tree_to_aff_combination (niter->niter, nit_type, &nit);
- tree_to_aff_combination (fold_convert (nit_type, a), nit_type, &tmpa);
- tree_to_aff_combination (fold_convert (nit_type, b), nit_type, &tmpb);
- aff_combination_scale (&nit, -1);
- aff_combination_scale (&tmpa, -1);
- aff_combination_add (&tmpb, &tmpa);
- aff_combination_add (&tmpb, &nit);
- if (tmpb.n != 0 || tmpb.offset != 1)
+ aff_combination_const (&tmp1, nit_type, 1);
+ tree_to_aff_combination (b, TREE_TYPE (b), &tmpb);
+ aff_combination_add (&nit, &tmp1);
+ if (a != integer_zero_node)
+ {
+ tree_to_aff_combination (a, TREE_TYPE (b), &tmpa);
+ aff_combination_scale (&tmpa, -1);
+ aff_combination_add (&tmpb, &tmpa);
+ }
+ if (!operand_equal_p (aff_combination_to_tree (&nit),
+ aff_combination_to_tree (&tmpb), 0))
return false;
/* Finally, check that CAND->IV->BASE - CAND->IV->STEP * A does not
next prev parent reply other threads:[~2014-07-21 9:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-17 9:08 Bin Cheng
2014-07-21 9:47 ` Bin.Cheng [this message]
2014-07-25 12:27 ` Richard Biener
2014-07-25 14:04 ` Bin.Cheng
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