[InstCombine] Add test for missed opportunity to fold 'or' into 'mul' operand. NFC

We are able to fold

or (mul X, Y), X --> mul X, (add Y, 1) (when the multiply has no common bits with X)

but we miss it if the mul operands are commuted.

Author: topperc

llvm/test/Transforms/InstCombine/or.ll

@@ -1511,6 +1511,21 @@ define <2 x i12> @mul_no_common_bits_commute(<2 x i12> %p) {
   ret <2 x i12> %r
 }
 
+define i32 @mul_no_common_bits_commute2(i32 %p1, i32 %p2) {
+; CHECK-LABEL: @mul_no_common_bits_commute2(
+; CHECK-NEXT:    [[X:%.*]] = and i32 [[P1:%.*]], 7
+; CHECK-NEXT:    [[Y:%.*]] = shl i32 [[P2:%.*]], 3
+; CHECK-NEXT:    [[M:%.*]] = mul i32 [[Y]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = or disjoint i32 [[M]], [[X]]
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %x = and i32 %p1, 7
+  %y = shl i32 %p2, 3
+  %m = mul i32 %y, %x
+  %r = or i32 %m, %x
+  ret i32 %r
+}
+
 define i32 @mul_no_common_bits_disjoint(i32 %x, i32 %y) {
 ; CHECK-LABEL: @mul_no_common_bits_disjoint(
 ; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[Y:%.*]], 1