This patch fixes the wrong code regression PR target/124194 on x86_64.
The target implements a pre-reload splitter that recognizes that
integer vector comparisons can be evaluated at compile-time when the
operands being compared are the same (register). The (admittedly rare)
case when the comparison operator is always-true, was incorrectly
handled and folded to false instead of the correct value true.
This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check, both with and without --target_board=unix{-m32}
with no new failures. Committed as pre-approved by Hongtao in bugzilla
(many thanks).
2025-02-26 Roger Sayle <[email protected]>
gcc/ChangeLog
PR target/124194
* config/i386/sse.md (*<avx512>_cmp<mode>3_dup_op): Also return
CONSTM1_RTX for the case cmp_imm == 7 (predicate TRUE).
gcc/testsuite/ChangeLog
PR target/124194
* gcc.target/i386/pr124194.c: New test case.
Roger
--
diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md
index cfe7a046f42..2e15842b3c7 100644
--- a/gcc/config/i386/sse.md
+++ b/gcc/config/i386/sse.md
@@ -4913,8 +4913,8 @@
{
int cmp_imm = INTVAL (operands[3]);
rtx res = CONST0_RTX (<avx512fmaskmode>mode);
- /* EQ/LE/NLT. */
- if (cmp_imm == 0 || cmp_imm == 2 || cmp_imm == 5)
+ /* EQ/LE/NLT/TRUE. */
+ if (cmp_imm == 0 || cmp_imm == 2 || cmp_imm == 5 || cmp_imm == 7)
{
int nelts = GET_MODE_NUNITS (<MODE>mode);
if (nelts >= 8)
diff --git a/gcc/testsuite/gcc.target/i386/pr124194.c
b/gcc/testsuite/gcc.target/i386/pr124194.c
new file mode 100644
index 00000000000..c295b69b49a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr124194.c
@@ -0,0 +1,15 @@
+/* PR target/124194 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -mavx512vl" } */
+typedef __attribute__((__vector_size__ (8 *sizeof (int)))) int V;
+
+int
+main ()
+{
+ unsigned char x = __builtin_ia32_cmpd256_mask ((V){}, (V){}, 7, 0xff);
+ if (x != 0xff)
+ __builtin_abort();
+ return 0;
+}
+/* { dg-final { scan-assembler-times "xorl" 1 } } */
+/* { dg-final { scan-assembler-not "vpcmpd" } } */
