Hi Honza,
as you know, we have a wrong code bug, when a pure or const method is called
via a virtual thunk.
I had some more Ideas, how to fix that, but all of them had some serious
draw-backs, so I leave the details out...
But now I have a new insight, why the "obvious" fix for this serious code
generation bug did not work
in the first place.
And the reason was, that if ipa-pure-const.c calls set_const_flag or
set_pure_flag for a thunk, it calls the same
function later for the called method, and this overwrites the flags of _all_
associated thunks and aliases.
However that should at least not be done for virtual thunks, as these need to
be IPA_NEITHER, even if
the method itself has different attributes, that is because the assembler thunk
accesses the vtable, while
other thunks do not.
So I re-factored set_const_flag and set_pure_flag to exclude the virtual
thunks, taking care that other
users of call_for_symbol_thunks_and_aliases do not get a different behavior
than before this patch.
The attached patch was boot-strapped and
regression-tested on x86_64-linux-gnu.
Ok for trunk?
PS: As a side-note, there are two identical functions, named
"call_for_symbol_and_aliases", in
class symtab_node and in class cgraph_node, which inherits from symtab_node.
Both functions are
not declared virtual. Is that what's intended? Usually this could lead to
errors, or at least some serious
compiler warnings.
Thanks
Bernd.
2014-10-07 Bernd Edlinger <bernd.edlin...@hotmail.de>
PR ipa/61190
* cgraph.h (symtab_node::call_for_symbol_and_aliases): Fix comment.
(cgraph_node::call_for_symbol_and_aliases): Likewise.
(cgraph_node::call_for_symbol_thunks_and_aliases_1): New function.
(cgraph_node::call_for_symbol_thunks_and_aliases): Adjust comment.
Call call_for_symbol_thunks_and_aliases_1.
* cgraph.c (cgraph_node::call_for_symbol_thunks_and_aliases): Renamed
to cgraph_node::call_for_symbol_thunks_and_aliases_1. Added new
parameter exclude_virtual_thunks.
(cgraph_node::set_const_flag): Don't propagate to virtual thunks.
(cgraph_node::set_pure_flag): Likewise.
* ipa-pure-const.c (analyze_function): For virtual thunks
set pure_const_state to IPA_NEITHER.
testsuite/ChangeLog:
2014-10-07 Bernd Edlinger <bernd.edlin...@hotmail.de>
PR ipa/61190
* g++.old-deja/g++.mike/p4736b.C: Use -O2.
patch-pr61190.diff
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