[PATCH] Fix PR ipa/61190, 2nd edition‏

[Bernd Edlinger <bernd dot edlinger at hotmail dot de>]

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.

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