[Bug middle-end/100323] New: #pragma and attribute optimize don't enable inlining

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100323

            Bug ID: 100323
           Summary: #pragma and attribute optimize don't enable inlining
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

I expected the effect of the attribute and the #pragma on the calls to f() in
both g() and h() to be to inline them.  They aren't.  With #pragma clang
optimize on, Clang inlines the call in h().

If this should be the expected behavior in GCC it should be documented.


$ cat a.c && gcc -O0 -S -Wall -fdump-tree-optimized=/dev/stdout a.c
static int f (void) { return 0; }

__attribute__ ((optimize (2)))
int g (void) { return f (); }

#pragma GCC optimize ("2")
int h (void) { return f (); }

;; Function f (f, funcdef_no=0, decl_uid=1943, cgraph_uid=1, symbol_order=0)

int f ()
{
  int D.1952;
  int _1;

  <bb 2> :
  _1 = 0;

  <bb 3> :
<L0>:
  return _1;

}



;; Function g (g, funcdef_no=1, decl_uid=1946, cgraph_uid=2, symbol_order=1)

__attribute__((optimize (2)))
int g ()
{
  int _3;

  <bb 2> [local count: 1073741824]:
  _3 = f (); [tail call]
  return _3;

}



;; Function h (h, funcdef_no=2, decl_uid=1949, cgraph_uid=3, symbol_order=2)

__attribute__((optimize ("2")))
int h ()
{
  int _3;

  <bb 2> [local count: 1073741824]:
  _3 = f (); [tail call]
  return _3;

}