[Bug tree-optimization/94877] New: Failure to simplify ~(x + 1) to -2 - x

[gabravier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94877

            Bug ID: 94877
           Summary: Failure to simplify ~(x + 1) to -2 - x
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

int f(int x)
{
    return ~(x + 1);
}

With -O3, LLVM outputs this : 

f(int): # @f(int)
  mov eax, -2
  sub eax, edi
  ret

GCC outputs this :

f(int):
  lea eax, [rdi+1]
  not eax
  ret

`~x - 1` is already simplified to `-2 - x`, so optimizing this looks like it
would make sense too.