https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97043
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Ever confirmed|0 |1
Blocks| |96522
Status|UNCONFIRMED |NEW
Last reconfirmed| |2020-09-14
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
This blocks backporting the fix for PR96522, causing the gcc.dg/vect/pr81410.c
testcase to FAIL execution with an unaligned access using an aligned load.
The trunk rev. that fixed this is gbc484e250990393e887f7239157cc85ce6fadcce
A pragmatic fix might be
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index f6331eeea86..3fdf56f9335 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -2309,9 +2309,8 @@ vect_analyze_slp_instance (vec_info *vinfo,
/* The load requires permutation when unrolling exposes
a gap either because the group is larger than the SLP
group-size or because there is a gap between the groups.
*/
- && (known_eq (unrolling_factor, 1U)
- || (group_size == DR_GROUP_SIZE (first_stmt_info)
- && DR_GROUP_GAP (first_stmt_info) == 0)))
+ && group_size == DR_GROUP_SIZE (first_stmt_info)
+ && DR_GROUP_GAP (first_stmt_info) == 0)
{
SLP_TREE_LOAD_PERMUTATION (load_node).release ();
continue;
with biggest effects eventually on load-lane targets (arm/aarch64) where
we then eventually prefer more of those. For the testcase in question
we then generate the following, matching trunk
movdqa (%rdx), %xmm2
movdqa 16(%rdx), %xmm0
shufpd $1, 32(%rdx), %xmm0
instead of
movdqa (%rdx), %xmm1
addq $48, %rdx
movdqu -24(%rdx), %xmm2
(or with the backport of PR96522 a wrong movdqa in place of the movdqu).
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96522
[Bug 96522] [9/10 Regression] Incorrect with with -O -fno-tree-pta
