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Re: ppc-linux gcc configury patch
- To: Cort Dougan <cort at ppc dot kernel dot org>
- Subject: Re: ppc-linux gcc configury patch
- From: Richard Henderson <rth at cygnus dot com>
- Date: Fri, 4 Jun 1999 13:08:58 -0700
- Cc: Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>, egcs-patches at egcs dot cygnus dot com, geoffk at ozemail dot com dot au
- References: <19990531093346.A19882@cygnus.com> <99053122114300.00734@ns1102.munich.netsurf.de> <19990531154254.A20388@cygnus.com> <19990604124947.A19158@attis.cs.nmt.edu>
On Fri, Jun 04, 1999 at 12:49:47PM -0600, Cort Dougan wrote:
> I'm not willing to take a performance hit so AIX can add linux/ppc binary
> support. Aren't branches of that size rare, though?
Yes and no.
We attempt to map the libraries such that calls into them get to
use `b', or more usually `ba', instead of `addis+addi+mtctr+bctr'.
Thing is, I'm not sure how much we're losing because of the change.
We have moved the base of the program up, but that has left more
room in the bottom 26 bits for shared libraries, and so for calls
into them to use `ba'. I think the only place we lose is calls back
into the main application, which is really very rare.
It would be trivial to add a line to __elf_machine_fixup_plt to
collect some statistics on what's happening with real applications.
r~