[InstCombine] Relax the one-use constraints for `icmp pred (binop X, Z), (binop Y, Z)` (#76384)
This patch relaxes the one-use constraints for `icmp pred (binop X, Z),
(binop Y, Z)`. It will enable more optimizations with pointer
arithmetic.
One example in `boost::match_results::set_size`:
```
declare void @use(i64)
define i1 @src(ptr %a1, ptr %a2, ptr %add.ptr.i66, i64 %sub.ptr.rhs.cast.i) {
%sub.ptr.lhs.cast.i = ptrtoint ptr %a1 to i64
%sub.ptr.rhs.cast.i = ptrtoint ptr %a2 to i64
%sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
%sub.ptr.div.i = sdiv exact i64 %sub.ptr.sub.i, 24
call void @use(i64 %sub.ptr.div.i)
%sub.ptr.lhs.cast.i.i = ptrtoint ptr %add.ptr.i66 to i64
%sub.ptr.sub.i.i = sub i64 %sub.ptr.lhs.cast.i.i, %sub.ptr.rhs.cast.i
%sub.ptr.div.i.i = sdiv exact i64 %sub.ptr.sub.i.i, 24
%cmp.i.not.i.i = icmp eq i64 %sub.ptr.div.i.i, %sub.ptr.div.i
ret i1 %cmp.i.not.i.i
}
define i1 @tgt(ptr %a1, ptr %a2, ptr %add.ptr.i66, i64 %sub.ptr.rhs.cast.i) {
%sub.ptr.lhs.cast.i = ptrtoint ptr %a1 to i64
%sub.ptr.rhs.cast.i = ptrtoint ptr %a2 to i64
%sub.ptr.sub.i = sub i64 %sub.ptr.lhs.cast.i, %sub.ptr.rhs.cast.i
%sub.ptr.div.i = sdiv exact i64 %sub.ptr.sub.i, 24
call void @use(i64 %sub.ptr.div.i)
%cmp.i.not.i.i = icmp eq i64 %sub.ptr.sub.i.i, %sub.ptr.sub.i
ret i1 %cmp.i.not.i.i
}
```
parent
fd1c156e
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