https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110334
--- Comment #11 from Jan Hubicka <hubicka at ucw dot cz> ---
Hi,
what about this. It should make at least quite basic inlining to happen
to always_inline. I do not think many critical always_inlines have
indirect calls in them. The test for lto is quite bad and I can
work on solving this incrementally (it would be nice to have this
tested and possibly backport it).
diff --git a/gcc/ipa-inline.cc b/gcc/ipa-inline.cc
index efc8df7d4e0..dcec07e49e1 100644
--- a/gcc/ipa-inline.cc
+++ b/gcc/ipa-inline.cc
@@ -702,6 +702,38 @@ can_early_inline_edge_p (struct cgraph_edge *e)
if (!can_inline_edge_p (e, true, true)
|| !can_inline_edge_by_limits_p (e, true, false, true))
return false;
+ /* When inlining regular functions into always-inline functions
+ during early inlining watch for possible inline cycles. */
+ if (DECL_DISREGARD_INLINE_LIMITS (caller->decl)
+ && lookup_attribute ("always_inline", DECL_ATTRIBUTES (caller->decl))
+ && (!DECL_DISREGARD_INLINE_LIMITS (callee->decl)
+ || !lookup_attribute ("always_inline", DECL_ATTRIBUTES
(callee->decl))))
+ {
+ /* If there are indirect calls, inlining may produce direct call.
+ TODO: We may lift this restriction if we avoid errors on formely
+ indirect calls to always_inline functions. Taking address
+ of always_inline function is generally bad idea and should
+ have been declared as undefined, but sadly we allow this. */
+ if (caller->indirect_calls || e->callee->indirect_calls)
+ return false;
+ for (cgraph_edge *e2 = callee->callees; e2; e2 = e2->next_callee)
+ {
+ struct cgraph_node *callee2 = e2->callee->ultimate_alias_target ();
+ /* As early inliner runs in RPO order, we will see uninlined
+ always_inline calls only in the case of cyclic graphs. */
+ if (DECL_DISREGARD_INLINE_LIMITS (callee2->decl)
+ || lookup_attribute ("always_inline", callee2->decl))
+ return false;
+ /* With LTO watch for case where function is later replaced
+ by always_inline definition.
+ TODO: We may either stop treating noninlined cross-module always
+ inlines as errors, or we can extend decl merging to produce
+ syntacic alias and honor always inline only in units it has
+ been declared as such. */
+ if (flag_lto && callee2->externally_visible)
+ return false;
+ }
+ }
return true;
}
@@ -3034,18 +3066,7 @@ early_inliner (function *fun)
if (!optimize
|| flag_no_inline
- || !flag_early_inlining
- /* Never inline regular functions into always-inline functions
- during incremental inlining. This sucks as functions calling
- always inline functions will get less optimized, but at the
- same time inlining of functions calling always inline
- function into an always inline function might introduce
- cycles of edges to be always inlined in the callgraph.
-
- We might want to be smarter and just avoid this type of inlining. */
- || (DECL_DISREGARD_INLINE_LIMITS (node->decl)
- && lookup_attribute ("always_inline",
- DECL_ATTRIBUTES (node->decl))))
+ || !flag_early_inlining)
;
else if (lookup_attribute ("flatten",
DECL_ATTRIBUTES (node->decl)) != NULL)
