tcg-ppc64: Cleanup i32 constants to tcg_out_cmp

Nothing else in the call chain ensures that these
constants don't have garbage in the high bits.

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>

tcg/ppc64/tcg-target.c

@@ -1059,6 +1059,11 @@ static void tcg_out_cmp(TCGContext *s, int cond, TCGArg arg1, TCGArg arg2,
     int imm;
     uint32_t op;
 
+    /* Simplify the comparisons below wrt CMPI.  */
+    if (type == TCG_TYPE_I32) {
+        arg2 = (int32_t)arg2;
+    }
+
     switch (cond) {
     case TCG_COND_EQ:
     case TCG_COND_NE: