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Re: [Xen-devel] [PATCH] x86: fix variable_test_bit() asmconstraints
| To: | Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] x86: fix variable_test_bit() asmconstraints |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Fri, 14 Mar 2008 14:04:14 +0000 |
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx |
| Delivery-date: | Fri, 14 Mar 2008 07:05:27 -0700 |
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| Thread-topic: | [Xen-devel] [PATCH] x86: fix variable_test_bit() asmconstraints |
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On 14/3/08 13:59, "Samuel Thibault" <samuel.thibault@xxxxxxxxxxxxx> wrote: >> Atomic ops imply a barrier (otherwise the compiler can defeat the >> purpose of the atomic operation). The non-atomic ones don't need a >> dummy operand, but one that precisely describes the place in memory >> that changes. > > Mmm, won't that unnecessarily make the compiler put code to compute that > place? x86 has enough fancy addressing modes that usually the compiler can emit the effective address without pre-computing any part of it. It's not guaranteed to do this, though, it's true. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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