[x86_64 PATCH] PR target/106481: Handle CONST_WIDE_INT in REG_EQUAL during STV.

[Roger Sayle]

This patch resolves PR target/106481, and is an oversight in my recent
battles with REG_EQUAL notes during TImode STV (see PR target/106278
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598416.html).

The patch above's/current behaviour is that we check that the mode of
the REG_EQUAL note is TImode before using PUT_MODE to set it to V1TImode.
However, the new test case reveals that this doesn't consider REG_EQUAL
notes that are CONST_INT or CONST_WIDE_INT, i.e. that are VOIDmode,
and so STV produces:

(insn 85 84 86 2 (set (reg:V1TI 113)
        (reg:V1TI 84)) "pr106481.c":13:3 1766 {movv1ti_internal}
     (expr_list:REG_EQUAL (const_wide_int 0x0ffffffff00000004)
        (nil)))

which causes problems as the const_wide_int isn't a valid immediate
constant for V1TImode.  With this patch, we now generate the correct:

(insn 85 84 86 2 (set (reg:V1TI 113)
        (reg:V1TI 84)) "pr106481.c":13:3 1766 {movv1ti_internal}
     (expr_list:REG_EQUAL (const_vector:V1TI [
                (const_wide_int 0x0ffffffff00000004)
            ])
        (nil)))


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?


2022-08-01  Roger Sayle  <ro...@nextmovesoftware.com>

gcc/ChangeLog
        PR target/106481
        * config/i386/i386-features.cc (timode_scalar_chain::convert_insn):
        Convert a CONST_SCALAR_INT_P in a REG_EQUAL note into a V1TImode
        CONST_VECTOR.

gcc/testsuite/ChangeLog
        PR target/106481
        * gcc.target/i386/pr106481.c: New test case.


Thanks again,
Roger
--


diff --git a/gcc/config/i386/i386-features.cc b/gcc/config/i386/i386-features.cc
index aa5de71..c1564c4 100644
--- a/gcc/config/i386/i386-features.cc
+++ b/gcc/config/i386/i386-features.cc
@@ -1355,6 +1355,10 @@ timode_scalar_chain::convert_insn (rtx_insn *insn)
          tmp = find_reg_equal_equiv_note (insn);
          if (tmp && GET_MODE (XEXP (tmp, 0)) == TImode)
            PUT_MODE (XEXP (tmp, 0), V1TImode);
+         else if (tmp && CONST_SCALAR_INT_P (XEXP (tmp, 0)))
+           XEXP (tmp, 0) = gen_rtx_CONST_VECTOR (V1TImode,
+                                                 gen_rtvec (1,
+                                                            XEXP (tmp, 0)));
        }
       break;
     case MEM:
diff --git a/gcc/testsuite/gcc.target/i386/pr106481.c 
b/gcc/testsuite/gcc.target/i386/pr106481.c
new file mode 100644
index 0000000..8cc7048
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr106481.c
@@ -0,0 +1,17 @@
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2 -fno-dce -fno-forward-propagate -fno-rerun-cse-after-loop 
-Wno-psabi" } */
+
+typedef int V __attribute__((vector_size (64)));
+typedef __int128 W __attribute__((vector_size (64)));
+
+W w;
+V bar (void);
+
+void
+foo (V v, W)
+{
+  foo ((V){4, ~0}, (W) v);
+  foo (v, w);
+  bar ();
+}
+