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[C++ patch] do not make extern inlines as needed when not optimizing
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: gcc-patches at gcc dot gnu dot org, jason at redhat dot com
- Date: Mon, 15 Dec 2014 00:14:07 +0100
- Subject: [C++ patch] do not make extern inlines as needed when not optimizing
- Authentication-results: sourceware.org; auth=none
Hi,
while looking into PR ipa/61324 I noticed that extern inline functions are
produced by C++ FE even at -O0. This seems like considerable waste especially
because these may trigger instantiations.
Bootstrepped/regtested x86_64-linux, OK?
Honza
* decl2.c (decl_needed_p): When not optimizing, extern decls are not
needed.
Index: cp/decl2.c
===================================================================
--- cp/decl2.c (revision 218701)
+++ cp/decl2.c (working copy)
@@ -1996,19 +1996,31 @@ decl_needed_p (tree decl)
COMDAT until that point. */
gcc_assert (at_eof);
- /* All entities with external linkage that are not COMDAT should be
+ /* All entities with external linkage that are not COMDAT/EXTERN should be
emitted; they may be referred to from other object files. */
- if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl))
+ if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl)
+ && (!DECL_EXTERNAL (decl) || DECL_NOT_REALLY_EXTERN (decl)))
return true;
- /* If this entity was used, let the back end see it; it will decide
- whether or not to emit it into the object file. */
- if (TREE_USED (decl))
- return true;
/* Functions marked "dllexport" must be emitted so that they are
visible to other DLLs. */
if (flag_keep_inline_dllexport
&& lookup_attribute ("dllexport", DECL_ATTRIBUTES (decl)))
return true;
+
+ /* When not optimizing, do not bother to produce definitions for extern
+ symbols. */
+ if (DECL_EXTERNAL (decl) && !DECL_NOT_REALLY_EXTERN (decl)
+ && ((TREE_CODE (decl) != FUNCTION_DECL
+ && !optimize)
+ || (TREE_CODE (decl) == FUNCTION_DECL
+ && !opt_for_fn (decl, optimize)))
+ && !lookup_attribute ("always_inline", decl))
+ return false;
+
+ /* If this entity was used, let the back end see it; it will decide
+ whether or not to emit it into the object file. */
+ if (TREE_USED (decl))
+ return true;
/* Virtual functions might be needed for devirtualization. */
if (flag_devirtualize
&& TREE_CODE (decl) == FUNCTION_DECL