i386: Fix up ix86_expand_int_compare with TImode comparisons of SUBREGs from...

i386: Fix up ix86_expand_int_compare with TImode comparisons of SUBREGs from V8{H,B}Fmode against zero [PR116921]

The following testcase ICEs, because the ix86_expand_int_compare
optimization to use {,v}ptest assumes there are instructions for all
16-byte vector modes.  That isn't the case, we only have one for
V16QI, V8HI, V4SI, V2DI, V1TI, V4SF and V2DF, not for
V8HF nor V8BF.

The following patch fixes that by using the V8HI instruction instead
for those 2 modes.  tmp can't be a SUBREG, because it is SUBREG_REG
of another SUBREG, so we don't need to worry about gen_lowpart
failing.

2024-10-04  Jakub Jelinek  <jakub@redhat.com>

	PR target/116921
	* config/i386/i386-expand.cc (ix86_expand_int_compare): Add a SUBREG
	to V8HImode from V8HFmode or V8BFmode before generating a ptest.

	* gcc.target/i386/pr116921.c: New test.

gcc/config/i386/i386-expand.cc

@@ -3095,6 +3095,8 @@ ix86_expand_int_compare (enum rtx_code code, rtx op0, rtx op1)
       && GET_MODE_SIZE (GET_MODE (SUBREG_REG (op0))) == 16)
     {
       tmp = SUBREG_REG (op0);
+      if (GET_MODE (tmp) == V8HFmode || GET_MODE (tmp) == V8BFmode)
+	tmp = gen_lowpart (V8HImode, tmp);
       tmp = gen_rtx_UNSPEC (CCZmode, gen_rtvec (2, tmp, tmp), UNSPEC_PTEST);
     }
   else

gcc/testsuite/gcc.target/i386/pr116921.c

+/* PR target/116921 */
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2 -msse4" } */
+
+long x;
+_Float16 __attribute__((__vector_size__ (16))) f;
+
+void
+foo (void)
+{
+  x -= !(__int128) (f / 2);
+}