tcg/loongarch64: Conditionalize tcg_out_exts_i32_i64

Since TCG_TYPE_I32 values are kept sign-extended in registers,
via ".w" instructions, we need not extend if the register matches.
This is already relied upon by comparisons.

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

tcg/loongarch64/tcg-target.c.inc

@@ -463,7 +463,9 @@ static void tcg_out_ext32s(TCGContext *s, TCGReg ret, TCGReg arg)
 
 static void tcg_out_exts_i32_i64(TCGContext *s, TCGReg ret, TCGReg arg)
 {
-    tcg_out_ext32s(s, ret, arg);
+    if (ret != arg) {
+        tcg_out_ext32s(s, ret, arg);
+    }
 }
 
 static void tcg_out_extu_i32_i64(TCGContext *s, TCGReg ret, TCGReg arg)