From 19517b8397940955c2638700f9cad3dbdb90c4c0 Mon Sep 17 00:00:00 2001
From: Richard Henderson <richard.henderson@linaro.org>
Date: Tue, 26 Mar 2024 14:48:36 -1000
Subject: [PATCH] tcg/i386: Optimize setcond of TST{EQ,NE} with 0xffffffff
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This may be treated as a 32-bit EQ/NE comparison against 0,
which is in turn treated as a LTU/GEU comparison against 1.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 tcg/i386/tcg-target.c.inc | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/tcg/i386/tcg-target.c.inc b/tcg/i386/tcg-target.c.inc
index 6837c519b0..59235b4f38 100644
--- a/tcg/i386/tcg-target.c.inc
+++ b/tcg/i386/tcg-target.c.inc
@@ -1658,6 +1658,7 @@ static void tcg_out_setcond(TCGContext *s, int rexw, TCGCond cond,
                             TCGArg dest, TCGArg arg1, TCGArg arg2,
                             int const_arg2, bool neg)
 {
+    int cmp_rexw = rexw;
     bool inv = false;
     bool cleared;
     int jcc;
@@ -1674,6 +1675,18 @@ static void tcg_out_setcond(TCGContext *s, int rexw, TCGCond cond,
         }
         break;
 
+    case TCG_COND_TSTNE:
+        inv = true;
+        /* fall through */
+    case TCG_COND_TSTEQ:
+        /* If arg2 is -1, convert to LTU/GEU vs 1. */
+        if (const_arg2 && arg2 == 0xffffffffu) {
+            arg2 = 1;
+            cmp_rexw = 0;
+            goto do_ltu;
+        }
+        break;
+
     case TCG_COND_LEU:
         inv = true;
         /* fall through */
@@ -1697,7 +1710,7 @@ static void tcg_out_setcond(TCGContext *s, int rexw, TCGCond cond,
          * We can then use NEG or INC to produce the desired result.
          * This is always smaller than the SETCC expansion.
          */
-        tcg_out_cmp(s, TCG_COND_LTU, arg1, arg2, const_arg2, rexw);
+        tcg_out_cmp(s, TCG_COND_LTU, arg1, arg2, const_arg2, cmp_rexw);
 
         /* X - X - C = -C = (C ? -1 : 0) */
         tgen_arithr(s, ARITH_SBB + (neg ? rexw : 0), dest, dest);
@@ -1744,7 +1757,7 @@ static void tcg_out_setcond(TCGContext *s, int rexw, TCGCond cond,
         cleared = true;
     }
 
-    jcc = tcg_out_cmp(s, cond, arg1, arg2, const_arg2, rexw);
+    jcc = tcg_out_cmp(s, cond, arg1, arg2, const_arg2, cmp_rexw);
     tcg_out_modrm(s, OPC_SETCC | jcc, 0, dest);
 
     if (!cleared) {