[InstCombine] add tests for icmp with mul operand; NFC

Author: rotateright

llvm/test/Transforms/InstCombine/icmp-mul.ll

@@ -857,3 +857,31 @@ define i1 @mul_of_pow2_no_lz_other_op(i32 %x, i8 %y) {
   %r = icmp sgt i32 %m, 254
   ret i1 %r
 }
+
+define i1 @splat_mul_known_lz(i32 %x) {
+; CHECK-LABEL: @splat_mul_known_lz(
+; CHECK-NEXT:    [[Z:%.*]] = zext i32 [[X:%.*]] to i128
+; CHECK-NEXT:    [[M:%.*]] = mul nuw nsw i128 [[Z]], 18446744078004518913
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i128 [[M]], 79228162514264337593543950336
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %z = zext i32 %x to i128
+  %m = mul i128 %z, 18446744078004518913 ; 0x00000000_00000001_00000001_00000001
+  %s = lshr i128 %m, 96
+  %r = icmp eq i128 %s, 0
+  ret i1 %r
+}
+
+define i1 @splat_mul_unknown_lz(i32 %x) {
+; CHECK-LABEL: @splat_mul_unknown_lz(
+; CHECK-NEXT:    [[Z:%.*]] = zext i32 [[X:%.*]] to i128
+; CHECK-NEXT:    [[M:%.*]] = mul nuw nsw i128 [[Z]], 18446744078004518913
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i128 [[M]], 39614081257132168796771975168
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %z = zext i32 %x to i128
+  %m = mul i128 %z, 18446744078004518913 ; 0x00000000_00000001_00000001_00000001
+  %s = lshr i128 %m, 95
+  %r = icmp eq i128 %s, 0
+  ret i1 %r
+}