From b9d7140c80bd3c7355b8291bb46f0895dcd8c3cb Mon Sep 17 00:00:00 2001
From: Jan Hubicka <jh@suse.cz>
Date: Fri, 28 Jul 2023 09:16:09 +0200
Subject: [PATCH] loop-split improvements, part 1
while looking on profile misupdate on hmmer I noticed that loop splitting pass is not
able to handle the loop it has as an example it should apply on:
One transformation of loops like:
for (i = 0; i < 100; i++)
{
if (i < 50)
A;
else
B;
}
into:
for (i = 0; i < 50; i++)
{
A;
}
for (; i < 100; i++)
{
B;
}
The problem is that ivcanon turns the test into i != 100 and the pass
explicitly gives up on any loops ending with != test. It needs to know
the directoin of the induction variable in order to derive right conditions,
but that can be done also from step.
It turns out that there are no testcases for basic loop splitting. I will add
some with the profile update fix.
gcc/ChangeLog:
* tree-ssa-loop-split.cc (split_loop): Also support NE driven
loops when IV test is not overflowing.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/ifc-12.c: Disable loop splitting.
* gcc.target/i386/avx2-gather-6.c: Likewise.
* gcc.target/i386/avx2-vect-aggressive.c: Likewise.
---
gcc/testsuite/gcc.dg/tree-ssa/ifc-12.c | 2 +-
gcc/testsuite/gcc.target/i386/avx2-gather-6.c | 2 +-
.../gcc.target/i386/avx2-vect-aggressive.c | 2 +-
gcc/tree-ssa-loop-split.cc | 13 ++++++++++---
4 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ifc-12.c b/gcc/testsuite/gcc.dg/tree-ssa/ifc-12.c
index 9468c070489b..7f09c381d9f4 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/ifc-12.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ifc-12.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-Ofast -fdump-tree-ifcvt-stats-blocks-details" } */
+/* { dg-options "-Ofast -fdump-tree-ifcvt-stats-blocks-details -fno-split-loops" } */
/* { dg-require-visibility "" } */
struct st
diff --git a/gcc/testsuite/gcc.target/i386/avx2-gather-6.c b/gcc/testsuite/gcc.target/i386/avx2-gather-6.c
index b9119581ae2c..47a95dbe9891 100644
--- a/gcc/testsuite/gcc.target/i386/avx2-gather-6.c
+++ b/gcc/testsuite/gcc.target/i386/avx2-gather-6.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O3 -mavx2 -fno-common -fdump-tree-vect-details -mtune=skylake" } */
+/* { dg-options "-O3 -mavx2 -fno-common -fdump-tree-vect-details -mtune=skylake -fno-split-loops" } */
#include "avx2-gather-5.c"
diff --git a/gcc/testsuite/gcc.target/i386/avx2-vect-aggressive.c b/gcc/testsuite/gcc.target/i386/avx2-vect-aggressive.c
index 571927918572..fa336e70e84c 100644
--- a/gcc/testsuite/gcc.target/i386/avx2-vect-aggressive.c
+++ b/gcc/testsuite/gcc.target/i386/avx2-vect-aggressive.c
@@ -1,6 +1,6 @@
/* { dg-do run } */
/* { dg-require-effective-target avx2 } */
-/* { dg-options "-mavx2 -O3 -fopenmp-simd -fdump-tree-vect-details -fdisable-tree-thread1" } */
+/* { dg-options "-mavx2 -O3 -fopenmp-simd -fdump-tree-vect-details -fdisable-tree-thread1 -fno-split-loops" } */
#include "avx2-check.h"
#define N 64
diff --git a/gcc/tree-ssa-loop-split.cc b/gcc/tree-ssa-loop-split.cc
index b41b5e614c21..f441f3fe1b51 100644
--- a/gcc/tree-ssa-loop-split.cc
+++ b/gcc/tree-ssa-loop-split.cc
@@ -540,10 +540,17 @@ split_loop (class loop *loop1)
|| !empty_block_p (loop1->latch)
|| !easy_exit_values (loop1)
|| !number_of_iterations_exit (loop1, exit1, &niter, false, true)
- || niter.cmp == ERROR_MARK
- /* We can't yet handle loops controlled by a != predicate. */
- || niter.cmp == NE_EXPR)
+ || niter.cmp == ERROR_MARK)
return false;
+ if (niter.cmp == NE_EXPR)
+ {
+ if (!niter.control.no_overflow)
+ return false;
+ if (tree_int_cst_sign_bit (niter.control.step) > 0)
+ niter.cmp = GT_EXPR;
+ else
+ niter.cmp = LT_EXPR;
+ }
bbs = get_loop_body (loop1);
--
GitLab