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[v2,22/23] tcg/i386: Use shift in tcg_out_setcond

Message ID 20230818221327.150194-23-richard.henderson@linaro.org
State Superseded
Headers show
Series tcg: Introduce negsetcond opcodes | expand

Commit Message

Richard Henderson Aug. 18, 2023, 10:13 p.m. UTC 
For LT/GE vs zero, shift down the sign bit.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 tcg/i386/tcg-target.c.inc | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
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Patch

diff --git a/tcg/i386/tcg-target.c.inc b/tcg/i386/tcg-target.c.inc
index 3f3c114efd..16e830051d 100644
--- a/tcg/i386/tcg-target.c.inc
+++ b/tcg/i386/tcg-target.c.inc
@@ -1578,6 +1578,21 @@  static void tcg_out_setcond(TCGContext *s, int rexw, TCGCond cond,
         }
         return;
 
+    case TCG_COND_GE:
+        inv = true;
+        /* fall through */
+    case TCG_COND_LT:
+        /* If arg2 is 0, extract the sign bit. */
+        if (const_arg2 && arg2 == 0) {
+            tcg_out_mov(s, rexw ? TCG_TYPE_I64 : TCG_TYPE_I32, dest, arg1);
+            if (inv) {
+                tcg_out_modrm(s, OPC_GRP3_Ev + rexw, EXT3_NOT, dest);
+            }
+            tcg_out_shifti(s, SHIFT_SHR + rexw, dest, rexw ? 63 : 31);
+            return;
+        }
+        break;
+
     default:
         break;
     }