Submit a bug here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63970
Wei. On Wed, Nov 19, 2014 at 2:18 AM, Richard Biener <richard.guent...@gmail.com> wrote: > On Wed, Nov 19, 2014 at 8:21 AM, Richard Biener > <richard.guent...@gmail.com> wrote: >> On November 19, 2014 8:13:09 AM CET, Wei Mi <w...@google.com> wrote: >>>We see an inline problem as below caused by r201408 >>>(https://gcc.gnu.org/ml/gcc-patches/2013-08/msg00027.html). >>> >>>hoo() { >>> foo(); >>> ... >>>} >>> >>>foo { >>> goo(); >>> ... >>>} >>> >>>foo is func splitted, so its body changes to >>> >>>foo { >>> goo(); >>> ... >>> foo.part(); >>>} >>> >>>and the used_as_abstract_origin of cgraph node of foo will be set to >>>true after func splitting. >>> >>>In ipa-inline, when inlining foo into hoo, the original node of foo >>>will not be reused as clone node because used_as_abstract_origin of >>>cgraph node of foo is true and can_remove_node_now_p_1 will return >>>false, so that a new clone node of foo will be created. This is the >>>case in gcc-4_9. >>>In gcc-4_8, the original node of foo will be reused as clone node. >>> >>>gcc-4_8 >>>foo >>> | >>>goo >>> >>>gcc-4_9 >>>foo foo_clone >>> \ / >>> goo >>> >>>Because of the difference of whether to create a new clone for foo, >>>when inlining goo to foo, the overall growth of inlining all callsites >>>of goo in gcc-4_8 will be less than gcc-4_9 (goo has two callsites in >>>gcc-4_9 but only one in gcc-4_8). If we have many cases like this, >>>gcc-4_8 will actually have more inline growth budget than gcc-4_9 and >>>will inline more aggressively than gcc-4_9. >>> >>>I don't understand the exact usage of the check about >>>node->used_as_abstract_origin in can_remove_node_now_p_1, but I feel >>>puzzled about following two points: >>> >>>1. https://gcc.gnu.org/ml/gcc-patches/2013-08/msg00027.html said the >>>patch was to ensure all abstract origin functions do have nodes >>>attached. However, even if the node of origin function is reused as a >>>clone node, a new clone node will be created in following code in >>>symbol_table::remove_unreachable_nodes if only the node that needs >>>abstract origin is reachable. >>> >>> if (TREE_CODE (node->decl) == FUNCTION_DECL >>> && DECL_ABSTRACT_ORIGIN (node->decl)) >>> { >>> struct cgraph_node *origin_node >>> = cgraph_node::get_create (DECL_ABSTRACT_ORIGIN (node->decl)); >>> origin_node->used_as_abstract_origin = true; >>> enqueue_node (origin_node, &first, &reachable); >>> } >>> >>>2. DECL_ABSTRACT_ORIGIN(decl) seems only useful for debug info of >>>clone nodes. But now the check of used_as_abstract_origin affect >>>inline decisions, which should be the same with or without keeping >>>debug info. >> >> I think we need to keep the functions but do not need to account for them in >> the unit size if we otherwise could remove them > > Btw - please make sure to open a bug so this issue doesn't get lost. > > Thanks, > Richard. > >> Richard. >> >>>Thanks, >>>Wei. >> >>
