tcg: Expand fallback sub2 with 32-bit operations

No need to expand to i64 to perform the subtract.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index 8b1356c526..127338b994 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -1123,14 +1123,15 @@ void tcg_gen_sub2_i32(TCGv_i32 rl, TCGv_i32 rh, TCGv_i32 al,
     if (TCG_TARGET_HAS_sub2_i32) {
         tcg_gen_op6_i32(INDEX_op_sub2_i32, rl, rh, al, ah, bl, bh);
     } else {
-        TCGv_i64 t0 = tcg_temp_ebb_new_i64();
-        TCGv_i64 t1 = tcg_temp_ebb_new_i64();
-        tcg_gen_concat_i32_i64(t0, al, ah);
-        tcg_gen_concat_i32_i64(t1, bl, bh);
-        tcg_gen_sub_i64(t0, t0, t1);
-        tcg_gen_extr_i64_i32(rl, rh, t0);
-        tcg_temp_free_i64(t0);
-        tcg_temp_free_i64(t1);
+        TCGv_i32 t0 = tcg_temp_ebb_new_i32();
+        TCGv_i32 t1 = tcg_temp_ebb_new_i32();
+        tcg_gen_sub_i32(t0, al, bl);
+        tcg_gen_setcond_i32(TCG_COND_LTU, t1, al, bl);
+        tcg_gen_sub_i32(rh, ah, bh);
+        tcg_gen_sub_i32(rh, rh, t1);
+        tcg_gen_mov_i32(rl, t0);
+        tcg_temp_free_i32(t0);
+        tcg_temp_free_i32(t1);
     }
 }