Re: Merging identical functions in GCC

[Roman Kononov <kononov195-far at yahoo dot com>]

On 09/15/2006 04:32 PM, Ross Ridge wrote:
> Also, I don't think it's safe if you merge only functions in COMDAT
> sections.
>
> Consider:
>
> 	#include <assert.h>
>
> 	template <class T> T foo(T a) { return a; }
> 	template <class T> T bar(T a) { return a; }
>
> 	int
> 	main() {
> 		assert((int (*)(int)) foo<int> != (int (*)(int)) bar<int>);
> 	}
>
> Both foo<int> and bar<int> get put in their own COMDAT section and their
> RTL and assembly are the same, but it's not safe to merge them.

Merge can be safely done like this:
If both functions A and B are not inlined functions, and they have single 
entry points, and memcmp of their asm code is zero, and the code is large 
enough, then the asm code of the functions B is replaced by "jmp A" instruction.

Regards,

Roman