[Bug tree-optimization/81953] New: Code sinking results in increased use of callee saved registers

["pthaugen at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81953

            Bug ID: 81953
           Summary: Code sinking results in increased use of callee saved
                    registers
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pthaugen at gcc dot gnu.org
                CC: dje.gcc at gmail dot com, wschmidt at gcc dot gnu.org
  Target Milestone: ---
              Host: powerpc64le-unknown-linux-gnu
            Target: powerpc64le-unknown-linux-gnu
             Build: powerpc64le-unknown-linux-gnu

void bar();
int j;
void foo(int a, int b, int c, int d, int e, int f)
{
  int l;
  l = a + b + c + d +e + f;
  if (a != 5)
    {
      bar();
      j = l;
    }
}


The whole expression "l = a + b + c..." is moved past the call to bar(), which
means we now need to use 6 callee-saved regs to hold the parm values across the
call.