[Bug tree-optimization/96167] New: fails to detect ROL pattern in simple case, but succeeds when operand goes through memcpy

[nok.raven at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96167

            Bug ID: 96167
           Summary: fails to detect ROL pattern in simple case, but
                    succeeds when operand goes through memcpy
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nok.raven at gmail dot com
  Target Milestone: ---

inline void swap(int &x, int &y)
{
  int tmp = x;
  x = y;
  y = tmp;
}

void foo(int (&x)[2])
{
  swap(x[0], x[1]);
}

void bar(int (&x)[2])
{
  int y[2];
  __builtin_memcpy(&y, &x, sizeof x);
  swap(y[0], y[1]);
  __builtin_memcpy(&x, &y, sizeof x);
}


foo:
  movl (%rdi), %eax
  movl 4(%rdi), %edx
  movl %eax, 4(%rdi)
  movl %edx, (%rdi)
  ret

bar:
  rolq $32, (%rdi)
  ret

https://godbolt.org/z/Tcz7YG