https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98221
Bug ID: 98221
Summary: [11 regression] Wrong unpack operation emitted in
tree-ssa-forwprop.c
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: krebbel at gcc dot gnu.org
Target Milestone: ---
Created attachment 49728
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49728&action=edit
Fix
The vec-abi-varargs-1.c testcase on IBM Z currently fails.
While adding an SI mode vector to a DI mode vector the first is unpacked using:
_28 = BIT_INSERT_EXPR <{ 0, 0, 0, 0 }, _2, 0>;
_34 = [vec_unpack_lo_expr] _28;
However, on big endian targets lo refers to the right hand side of the vector -
in this case the zeroes.
This appears to be triggered with that patch:
commit 78307657cf9675bc4aa2e77561c823834714b4c8
Author: Richard Biener <rguent...@suse.de>
Date: Thu Nov 28 12:22:04 2019 +0000
re PR tree-optimization/92645 (Hand written vector code is 450 times slower
when compiled with GCC compared to Clang)
2019-11-28 Richard Biener <rguent...@suse.de>
PR tree-optimization/92645
* tree-ssa-forwprop.c (get_bit_field_ref_def): Also handle
conversions inside a mode class. Remove restriction on
preserving the element size.
(simplify_vector_constructor): Deal with the above and for
identity permutes also try using VEC_UNPACK_[FLOAT_]LO_EXPR
and VEC_PACK_TRUNC_EXPR.
* gcc.target/i386/pr92645-4.c: New testcase.
