[llvm] [InstSimplify] Simplify select if it combinated `and/or/xor` (PR #73362)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> @dtcxzyw I commented on the comment above, can you see it? It says (pending) on my screen, but I don't know why, but it may mean that it hasn't been uploaded. So I'll reply here again.
> 
> I think it is necessary. because Select ICmp is must be "X (comp) Y". here is example:
> 
> ```
> define i32 @src_select_xor_max_positive_int(i32 %x, i32 %y) {
> ; CHECK-LABEL: @src_select_xor_max_positive_int(
> ; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
> ; CHECK-NEXT:    [[XOR0:%.*]] = icmp eq i32 [[XOR]], 2147483647
> ; CHECK-NEXT:    [[AND:%.*]] = and i32 [[X]], [[Y]]
> ; CHECK-NEXT:    [[OR:%.*]] = or i32 [[X]], [[Y]]
> ; CHECK-NEXT:    [[COND:%.*]] = select i1 [[XOR0]], i32 [[AND]], i32 [[OR]]
> ; CHECK-NEXT:    ret i32 [[COND]]
> ;
>   %xor = xor i32 %x, %y
>   %xor0 = icmp eq i32 %xor, 2147483647
>   %and = and i32 %x, %y
>   %or = or i32 %x, %y
>   %cond = select i1 %xor0, i32 %and, i32 %or
>   ret i32 %cond
> }
> ```
> 
> without `if (match(CmpLHS, m_Value(X)) && match(CmpRHS, m_Value(Y))) {` condition then `%and = and i32 %x, %y %or = or i32 %x, %y` will match case.
> 
> am I right?

`match(CmpLHS, m_Value(X))` is equivalent to the following code :(
```
bool match(...) {
  X = CmpLHS;
  return true;
}
```



https://github.com/llvm/llvm-project/pull/73362