target/arm: Use tcg_gen_rotri_i32 for gen_swap_half

Rotate is the more compact and obvious way to swap 16-bit
elements of a 32-bit word.
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190808202616.13782-6-richard.henderson@linaro.org
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/translate.c

@@ -444,11 +444,7 @@ static TCGv_i64 gen_muls_i64_i32(TCGv_i32 a, TCGv_i32 b)
 /* Swap low and high halfwords.  */
 static void gen_swap_half(TCGv_i32 var)
 {
-    TCGv_i32 tmp = tcg_temp_new_i32();
-    tcg_gen_shri_i32(tmp, var, 16);
-    tcg_gen_shli_i32(var, var, 16);
-    tcg_gen_or_i32(var, var, tmp);
-    tcg_temp_free_i32(tmp);
+    tcg_gen_rotri_i32(var, var, 16);
 }
 
 /* Dual 16-bit add.  Result placed in t0 and t1 is marked as dead.