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[PULL,10/31] tcg/optimize: Fold movcond with true and false values identical

Message ID 20240922120112.5067-11-richard.henderson@linaro.org
State Accepted
Commit 141125e08cf422e22d40b0114a265c83d888767a
Headers show
Series [PULL,01/31] tcg: Return TCGOp from tcg_gen_op[1-6] | expand

Commit Message

Richard Henderson Sept. 22, 2024, noon UTC 
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>
---
 tcg/optimize.c | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/tcg/optimize.c b/tcg/optimize.c
index ba16ec27e2..cf311790e0 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.