[x86_64 PATCH] PR target/110083: Fix-up REG_EQUAL notes on COMPARE in STV.

["Roger Sayle" <roger@nextmovesoftware.com>]

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This patch fixes PR target/110083, an ICE-on-valid regression exposed by
my recent PTEST improvements (to address PR target/109973).  The latent
bug (admittedly mine) is that the scalar-to-vector (STV) pass doesn't update
or delete REG_EQUAL notes attached to COMPARE instructions.  As a result
the operands of COMPARE would be mismatched, with the register transformed
to V1TImode, but the immediate operand left as const_wide_int, which is
valid for TImode but not V1TImode.  This remained latent when the STV
conversion converted the mode of the COMPARE to CCmode, with later passes
recognizing the REG_EQUAL note is obviously invalid as the modes didn't
match, but now that we (correctly) preserve the CCZmode on COMPARE, the
mismatched operand modes trigger a sanity checking ICE downstream.

Fixed by updating (or deleting) any REG_EQUAL notes in convert_compare.

Before:
    (expr_list:REG_EQUAL (compare:CCZ (reg:V1TI 119 [ ivin.29_38 ])
        (const_wide_int 0x80000000000000000000000000000000))

After:
    (expr_list:REG_EQUAL (compare:CCZ (reg:V1TI 119 [ ivin.29_38 ])
        (const_vector:V1TI [
            (const_wide_int 0x80000000000000000000000000000000)
         ]))

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.  Ok for mainline?


2023-06-03  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
        PR target/110083
        * config/i386/i386-features.cc (scalar_chain::convert_compare):
        Update or delete REG_EQUAL notes, converting CONST_INT and
        CONST_WIDE_INT immediate operands to a suitable CONST_VECTOR.

gcc/testsuite/ChangeLog
        PR target/110083
        * gcc.target/i386/pr110083.c: New test case.


Roger
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diff --git a/gcc/config/i386/i386-features.cc b/gcc/config/i386/i386-features.cc
index 3417f6b..4a3b07a 100644
--- a/gcc/config/i386/i386-features.cc
+++ b/gcc/config/i386/i386-features.cc
@@ -980,6 +980,39 @@ rtx
 scalar_chain::convert_compare (rtx op1, rtx op2, rtx_insn *insn)
 {
   rtx src, tmp;
+
+  /* Handle any REG_EQUAL notes.  */
+  tmp = find_reg_equal_equiv_note (insn);
+  if (tmp)
+    {
+      if (GET_CODE (XEXP (tmp, 0)) == COMPARE
+	  && GET_MODE (XEXP (tmp, 0)) == CCZmode
+	  && REG_P (XEXP (XEXP (tmp, 0), 0)))
+	{
+	  rtx *op = &XEXP (XEXP (tmp, 0), 1);
+	  if (CONST_SCALAR_INT_P (*op))
+	    {
+	      if (constm1_operand (*op, GET_MODE (*op)))
+		*op = CONSTM1_RTX (vmode);
+	      else
+		{
+		  unsigned n = GET_MODE_NUNITS (vmode);
+		  rtx *v = XALLOCAVEC (rtx, n);
+		  v[0] = *op;
+		  for (unsigned i = 1; i < n; ++i)
+		    v[i] = const0_rtx;
+		  *op = gen_rtx_CONST_VECTOR (vmode, gen_rtvec_v (n, v));
+		}
+	      tmp = NULL_RTX;
+	    }
+	  else if (REG_P (*op))
+	    tmp = NULL_RTX;
+	}
+
+      if (tmp)
+	remove_note (insn, tmp);
+    }
+
   /* Comparison against anything other than zero, requires an XOR.  */
   if (op2 != const0_rtx)
     {
diff --git a/gcc/testsuite/gcc.target/i386/pr110083.c b/gcc/testsuite/gcc.target/i386/pr110083.c
new file mode 100644
index 0000000..4b38ca8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr110083.c
@@ -0,0 +1,26 @@
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2 -msse4 -mstv -mno-stackrealign" } */
+typedef int TItype __attribute__ ((mode (TI)));
+typedef unsigned int UTItype __attribute__ ((mode (TI)));
+
+void foo (void)
+{
+  static volatile TItype ivin, ivout;
+  static volatile float fv1, fv2;
+  ivin = ((TItype) (UTItype) ~ (((UTItype) ~ (UTItype) 0) >> 1));
+  fv1 = ((TItype) (UTItype) ~ (((UTItype) ~ (UTItype) 0) >> 1));
+  fv2 = ivin;
+  ivout = fv2;
+  if (ivin != ((TItype) (UTItype) ~ (((UTItype) ~ (UTItype) 0) >> 1))
+      || ((((128) > sizeof (TItype) * 8 - 1)) && ivout != ivin)
+      || ((((128) > sizeof (TItype) * 8 - 1))
+	  && ivout !=
+	  ((TItype) (UTItype) ~ (((UTItype) ~ (UTItype) 0) >> 1)))
+      || fv1 !=
+      (float) ((TItype) (UTItype) ~ (((UTItype) ~ (UTItype) 0) >> 1))
+      || fv2 !=
+      (float) ((TItype) (UTItype) ~ (((UTItype) ~ (UTItype) 0) >> 1))
+      || fv1 != fv2)
+    __builtin_abort ();
+}
+