On Tue, Dec 25, 2012 at 6:54 AM, Mike Frysinger <vap...@gentoo.org> wrote: > On Monday 24 December 2012 17:26:47 Leif Ekblad wrote: >> In the case of cpuid, the code is hardly performance sensitive, and >> probably runs only at startup. An alternative solution for the broken code >> here is to move the result from rbx to another register, and to >> save/restore rbx. Currently, this is the only place in libgcc and newlib >> affected by this problem. > > it's not a question of performance. i can't remember how many various > projects i've had to tweak the inline asm code to work with __PIC__ (either > because it's going into shared library code or it's being built as a PIE). > Andi's point is now we have to redo all of that work a 2nd time and handle two > different cases depending on gcc version ? it'd be a _lot_ better if gcc were > intelligent and end users didn't have to code crap like stuffing %ebx > somewhere > temporarily.
Please note that we are not talking about 32bit code, where this would make a difference, but for 64bit targets with -mcmodel=medium and -mcmodel=large exclusively. The default x64_64 -mcmodel=small doesn't use PIC register, other code models are rarely used, so I sincerely doubt that any %rbx workarounds were needed in the past for x86_64. Uros.
