From: Richard Henderson <richard.henderson@linaro.org>
Date: Sat, 7 Sep 2024 04:00:10 +0000 (-0700)
Subject: tcg/optimize: Fold movcond with true and false values identical
X-Git-Tag: v9.2.0-rc0~73^2~21
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=141125e08cf422e22d40b0114a265c83d888767a;p=thirdparty%2Fqemu.git

tcg/optimize: Fold movcond with true and false values identical

Fold "x = cond ? y : y" to "x = y".

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---

diff --git a/tcg/optimize.c b/tcg/optimize.c
index ba16ec27e24..cf311790e05 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -1851,6 +1851,11 @@ static bool fold_movcond(OptContext *ctx, TCGOp *op)
 {
     int i;
 
+    /* If true and false values are the same, eliminate the cmp. */
+    if (args_are_copies(op->args[3], op->args[4])) {
+        return tcg_opt_gen_mov(ctx, op, op->args[0], op->args[3]);
+    }
+
     /*
      * Canonicalize the "false" input reg to match the destination reg so
      * that the tcg backend can implement a "move if true" operation.