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Re: EGCS: pointer to member functions.
- To: Alexandre Oliva <oliva at dcc dot unicamp dot br>
- Subject: Re: EGCS: pointer to member functions.
- From: Richard Henderson <rth at cygnus dot com>
- Date: Wed, 23 Jun 1999 15:41:12 -0700
- Cc: Jason Merrill <jason at cygnus dot com>, Mike Stump <mrs at wrs dot com>, brendan at dgs dot monash dot edu dot au, egcs at egcs dot cygnus dot com, martin at mira dot isdn dot cs dot tu-berlin dot de, egcs-patches at egcs dot cygnus dot com
- References: <199906171530.IAA14508@kankakee.wrs.com> <oriu8h1gr1.fsf@saci.lsd.dcc.unicamp.br> <u9pv2or9pf.fsf@yorick.cygnus.com> <or909b4f6h.fsf@saci.lsd.dcc.unicamp.br>
On Wed, Jun 23, 1999 at 03:13:58AM -0300, Alexandre Oliva wrote:
> Moreover, even if the test cost is close to zero, it would still have
> to branch, and, given that the `thunk' I have in mind is as simple as
> a `trampoline', I don't see how it could be less efficient than the
> current approach. Only if branches with good prediction were much
> cheaper than a 100% certain jump; is this the case?
Indirect branches are often not predicted at all, and are typically
horrible for performance. Most every target besides ia32 and m68k
would need to use an indirect branch in the thunk because a pc-relative
branch won't reach.
r~