[Bug tree-optimization/103216] New: missed optimization, phiopt/vrp?

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103216

            Bug ID: 103216
           Summary: missed optimization, phiopt/vrp?
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

signed char f(unsigned char a)
{
  unsigned char b;
  signed char c, d, v;
  b = a & 127;
  c = (signed char) b;
  d = (signed char) a;
  v = c;
  if (d < 0)
    v = c | -128;
  return v;
}

This should just be optimized to return (signed char)a;

Reduced from the testcase provided by
https://twitter.com/__phantomderp/status/1459247957904080901 .