From: Richard Henderson <richard.henderson@linaro.org>
Date: Thu, 26 Oct 2023 01:39:43 +0000 (-0700)
Subject: tcg/optimize: Canonicalize subi to addi during optimization
X-Git-Tag: v8.2.0-rc0~26^2~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6334a968eec3f2498a992a7b96c1bfcaf100066f;p=thirdparty%2Fqemu.git

tcg/optimize: Canonicalize subi to addi during optimization

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20231026013945.1152174-3-richard.henderson@linaro.org>
---

diff --git a/tcg/optimize.c b/tcg/optimize.c
index d8e437c8262..468f8273994 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -2166,7 +2166,19 @@ static bool fold_sub_vec(OptContext *ctx, TCGOp *op)
 
 static bool fold_sub(OptContext *ctx, TCGOp *op)
 {
-    return fold_const2(ctx, op) || fold_sub_vec(ctx, op);
+    if (fold_const2(ctx, op) || fold_sub_vec(ctx, op)) {
+        return true;
+    }
+
+    /* Fold sub r,x,i to add r,x,-i */
+    if (arg_is_const(op->args[2])) {
+        uint64_t val = arg_info(op->args[2])->val;
+
+        op->opc = (ctx->type == TCG_TYPE_I32
+                   ? INDEX_op_add_i32 : INDEX_op_add_i64);
+        op->args[2] = arg_new_constant(ctx, -val);
+    }
+    return false;
 }
 
 static bool fold_sub2(OptContext *ctx, TCGOp *op)