[Bug ipa/67307] New: FE considers 'inline int foo ()' as always-inline, inlining not disabled via -fno-early-inlining

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67307

            Bug ID: 67307
           Summary: FE considers 'inline int foo ()' as always-inline,
                    inlining not disabled via -fno-early-inlining
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
                CC: hubicka at gcc dot gnu.org, jsm28 at gcc dot gnu.org
  Target Milestone: ---

inline int foo (int i) { return i; }

runs into c-decl.c

  /* For GNU C extern inline functions disregard inline limits.  */
  if (DECL_EXTERNAL (fndecl)
      && DECL_DECLARED_INLINE_P (fndecl))
    DECL_DISREGARD_INLINE_LIMITS (fndecl) = 1;


but not with -std=gnu89, only with -std=gnu99.  This means it is considered
"always-inline" by inline_always_inline_functions which means it is still
inlined early even with -fno-early-inlining.

Not sure if the FE behavior is desired - we have DECL_DECLARED_INLINE_P
to guide general inlining.  DECL_DISREGARD_INLINE_LIMITS should really
be only used if "always-inline" semantics are to be wanted by the FE.