[Bug middle-end/127073] Missed LLVM's or disjoint detection for RISC-V

[kaelfandrew at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127073

Kael Franco <kaelfandrew at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://github.com/llvm/llv
                   |                            |m-project/issues/218553

--- Comment #2 from Kael Franco <kaelfandrew at gmail dot com> ---
(In reply to Robin Dapp from comment #1)
> Does llvm optimize the add case?

No. That would be https://github.com/llvm/llvm-project/issues/218553

https://godbolt.org/z/aah18xx7s

RISC-V 64 bit clang trunk with -O2:

src_add:
        add     a0, a0, a1
        zext.b  a0, a0
        ret

LLVM IR -O2:
```
define dso_local noundef zeroext i8 @src_add(i8 noundef zeroext %x, i8 noundef
zeroext %y) local_unnamed_addr {
entry:
  %and8 = and i8 %y, %x
  %cmp.not = icmp eq i8 %and8, 0
  tail call void @llvm.assume(i1 %cmp.not)
  %add = add i8 %y, %x
  ret i8 %add
}
```