[PATCH v4 080/101] tcg: Use umax in ussub if available

[Richard Henderson]

Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
 tcg/tcg-op.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index 31c82cfe2fb..a97c0b2f765 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -1192,9 +1192,18 @@ static void gen_ussub(TCGType type, TCGTemp *dst, 
TCGTemp *src1, TCGTemp *src2)
 {
     g_autoptr(TCGTemp) tmp = tcg_temp_new_ebb(type);
 
-    gen_sub(type, tmp, src1, src2);
-    gen_movcond(type, TCG_COND_LTU, dst, src1, src2,
-                tcg_constant_internal(type, 0), tmp);
+    if (tcg_op_supported(INDEX_op_umax, type, 0)) {
+        gen_umax(type, tmp, src1, src2);
+        gen_sub(type, dst, tmp, src2);
+    } else {
+        /*
+         * While umax can be expanded with movcond, some hosts can
+         * perform movcond with a zero source in fewer insns.
+         */
+        gen_sub(type, tmp, src1, src2);
+        gen_movcond(type, TCG_COND_LTU, dst, src1, src2,
+                    tcg_constant_internal(type, 0), tmp);
+    }
 }
 
 static void gen_xor(TCGType type, TCGTemp *dst, TCGTemp *src1, TCGTemp *src2)
-- 
2.53.0