Messages in this thread | | | Date | Wed, 09 Apr 2008 15:33:08 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [patch 13/17] Immediate Values - x86 Optimization (updated) |
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Mathieu Desnoyers wrote: > > Hrm, since even the nmi-safe version supports REX-prefixed instructions, > there is no need for an =q constraint on single-byte immediate values > anymore. (thanks to your "discard" section used in the nmi-safe version) >
WRONG!
Using =r for single-byte values is incorrect for 32-bit code -- that would permit %spl, %bpl, %sil, %dil which are illegal in 32-bit mode. That is not the incorrect bit, it's the description that is confused.
-hpa
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