JIT: micro-optimize cmpXX a bit more for lower latency/code size

Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp

@@ -544,7 +544,16 @@ void Jit64::cmpXX(UGeckoInstruction inst)
 			MOV(64, PPCSTATE(cr_val[crf]), R(input));
 			// Place the comparison next to the branch for macro-op fusion
 			if (merge_branch)
-				TEST(64, R(input), R(input));
+			{
+				// We only need to do a 32-bit compare, since the flags set will be the same as a sign-extended
+				// result.
+				// We should also test against gpr.R(a) if it's bound, since that's one less cycle of latency
+				// (the CPU doesn't have to wait for the movsxd to finish to resolve the branch).
+				if (gpr.R(a).IsSimpleReg())
+					TEST(32, gpr.R(a), gpr.R(a));
+				else
+					TEST(32, R(input), R(input));
+			}
 		}
 		else
 		{