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Hi,
I found that g++4.9.0 have -fdevirtualize switch and wanted to play with
that feature for a while. I wrote simple, non-trivial program to check
how g++ will behave in obvious case:
==== SOURCE BEGIN ====
#include <iostream>
class B final
{
public:
virtual void test() { std::cout << "Test" << std::endl; }
};
int main()
{
B test;
test.test();
return 0;
}
==== SOURCE ENDS ====
I compiled this code with
g++ -std=c++11 -fdevirtualize simple1.cpp
and then objdumped symbols:
objdump -t a.out | c++filt | grep vtable
and noticed that vtable is present (I would expect it will be removed)
00000000006012c0 w O .bss 0000000000000058 vtable for
__cxxabiv1::__class_type_info@@CXXABI_1.3
0000000000400b20 w O .rodata 0000000000000018 vtable for B
I found some examples in testsuite (opt/ and ipa/) but for those
examples I checked, I can "reproduce" devirtualization.
Is there a documentation somewhere to see what is the current status of
devirtualiztion in g++ 4.9? I mean, beside the source code. Or maybe
someone could explain me why this case can't be devirtualized?
Best regards
Robert
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