https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115659
Bug ID: 115659
Summary: powerpc fallout from removing vcond{,u,eq} patterns
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: linkw at gcc dot gnu.org
Target Milestone: ---
Applying the patch dropping vcond{,u,eq}_optab support
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114189#c2), there is only one
failure on both BE and LE:
FAIL: gcc.target/powerpc/pr66144-3.c scan-assembler-not \\\\mvspltisw\\\\M
Previously I blindly took it as false alarm, but after further checking, I
realized it exposed a miss-opt.
In function rs6000_emit_vector_cond_expr, there is one optimization
/* Optimize vec1 == vec2, to know the mask generates -1/0. */
if (GET_MODE_CLASS (dest_mode) == MODE_VECTOR_INT
&& (GET_CODE (op_true) == CONST_VECTOR
|| GET_CODE (op_false) == CONST_VECTOR))
...
, it's some special handling for
1) op_true -1 and op_false 0
2) op_false 0 and op_true -1
3) op_true -1
4) op_false 0
by reusing the result of vector comparison as it returns -1 or 0.
