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Re: Fix removal of ctors/dtors
- From: Martin Jambor <mjambor at suse dot cz>
- To: Jan Hubicka <hubicka at ucw dot cz>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 1 Nov 2010 15:48:37 +0100
- Subject: Re: Fix removal of ctors/dtors
- References: <20101026141604.GD20390@kam.mff.cuni.cz>
On Tue, Oct 26, 2010 at 04:16:04PM +0200, Jan Hubicka wrote:
> Finally both inliner and ipa-cp confuse handling of functions with
> address taken. ipa-cp is considering functions with address taken
> to be cloning candidates. This is wrong. We should clone only when
> we think original function is not called at all but we can't say for
> sure since it is externally visible. Clonning is of course
> possible, but current impementation leads to wrong code when
> updating call sites of calls promoted to be direct.
We have had similar issues before but so far managed to get around
them without such a big hammer. Do you have a testcase that will fail
if I remove the ipa-cp hunk?
> Bootstrapped/regtested x86_64-linux, lto-bootstrapped x86_64-linux and tested
> with Firefox builds. I also tested that tramp3d does not care about the
> inliner mertric fixes.
> * cgraph.c (cgraph_set_readonly_flag): Rename to...
> (cgraph_set_const_flags) ... this one; get also looping argument;
> clear constructor/destructor flags.
> (cgraph_set_pure_flag): Likewise.
> (cgraph_set_looping_const_or_pure_flag): Remove.
> (cgraph_can_remove_if_no_direct_calls_and_refs): Do not try
> to optimize away static ctors/dtors; it does not work on inline clones;
> external functions can always be rmeoved.
> (cgraph_will_be_removed_from_program_if_no_direct_calls): Assert on inline
> clones; in LTO external functions always can go.
> (cgraph_used_from_object_file_p): Handle EXTERNAL functions correctly.
> (cgraph_mark_address_taken_node): Assert that we are not taking address of
> inline clone.
> (cgraph_can_remove_if_no_direct_calls_p): We always eventually remove
> external functions.
> * ipa-cp.c (ipcp_cloning_candidate_p): Do not clone functions with address taken.
> (ipcp_initialize_node_lattices): Only local functions can be handled without cloning.
> * cgraph.h (cgraph_set_readonly_flag,
> cgraph_set_looping_const_or_pure_flag): Remove.
> (cgraph_set_const_flag): Declare.
> (cgraph_set_pure_flag): Update.
> * ipa-pure-const (propagate_pure_const, local_pure_const): Update
> flags setting code.
> * ipa.c (cgraph_remove_unreachable_nodes): Fix formating; do not look at inline
> clones; fix handling of external definitions.
> (cgraph_postorder): Do not look at inline clones in the first pass.
> (function_and_variable_visibility): Drop constructors/destructor
> flags at pure and const functions.
> * tree-profile.c (tree_profiling): Update.
> * ipa-inline.c (cgraph_clone_inlined_nodes): Always clone functions with
> address taken; external functions do not account to whole program size.
> (cgraph_decide_inlining): Likewise; do not try to inline functions already
> * testsuite/gcc.dg/lto/pr45736_0.c: New function.