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Re: [Xen-devel] [PATCH] x86-64: suppress some unneeded side effects of -
| To: | Jan Beulich <jbeulich@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] x86-64: suppress some unneeded side effects of -fPIC |
| From: | Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> |
| Date: | Wed, 13 Sep 2006 13:46:27 +0100 |
| Delivery-date: | Wed, 13 Sep 2006 05:45:30 -0700 |
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| Thread-topic: | [Xen-devel] [PATCH] x86-64: suppress some unneeded side effects of -fPIC |
| User-agent: | Microsoft-Entourage/11.2.5.060620 |
On 12/9/06 16:43, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > Full PIC mode isn't needed for Xen, namely is there no need to access data > objects via the GOT or call functions through the PLT. Adding > -fvisibility=hidden (if the compiler supports it) helps, although it doesn't > do > as good a job as would be desired (I'm in talks with our compiler guys to > understand why). > > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx> What overheads does this remove? Does it actually shorten code sequences? It seems that some gcc v3 compilers have -fvisibility=hidden too (e.g. My gcc-3.4.4 does). I thus checked in a patch that checks for availability of this feature in a 'test-gcc-flag' style of way (as defined in Config.mk), rather than doing a gcc version test. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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