From: Stefan Schulze Frielinghaus <stefansf@linux.ibm.com>
Date: Wed, 22 Jul 2020 07:27:49 +0000 (+0200)
Subject: vect: Fix infinite loop while determining peeling amount
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=f1660ceb0d3b0076555058087307f88b80619a6f;p=gcc.git

vect: Fix infinite loop while determining peeling amount

This is a follow up to commit 5c9669a0e6c respectively discussion
https://gcc.gnu.org/pipermail/gcc-patches/2020-June/549132.html

In case a type has a lower alignment than its size, ensure that we
advance.  For example, on s390x we have for a long double an alignment
constraint of 8 bytes whereas the size is 16 bytes.  Increasing the loop
variable only by TARGET_ALIGN / DR_SIZE which equals zero in case of a
long double results in an infinite loop.  This is fixed by ensuring that
we advance at least by one.

gcc/ChangeLog:

	* tree-vect-data-refs.c (vect_enhance_data_refs_alignment):
	Ensure that loop variable npeel_tmp advances in each iteration.
---

diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index e35a215e042..a78ae61d1b0 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -1779,7 +1779,7 @@ vect_enhance_data_refs_alignment (loop_vec_info loop_vinfo)
                 {
                   vect_peeling_hash_insert (&peeling_htab, loop_vinfo,
 					    dr_info, npeel_tmp);
-		  npeel_tmp += target_align / dr_size;
+		  npeel_tmp += MAX (1, target_align / dr_size);
                 }
 
 	      one_misalignment_known = true;