[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] x86/time: fix scale_delta() inline assembly
The way it was coded, it clobbered %rdx without telling the compiler. This generally didn't cause any problems except when there are two back to back invocations (as in plt_overflow()), as in that case the compiler may validly assume that it can re-use for the second instance the value loaded into %rdx before the first one. Once at it, also properly relax the second operand of "mul" (there's no need for it to be in %rdx, or a register at all), and switch away from using explicit register names in the instruction operands. Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -127,8 +127,9 @@ static inline u64 scale_delta(u64 delta, delta <<= scale->shift; asm ( - "mul %%rdx ; shrd $32,%%rdx,%%rax" - : "=a" (product) : "0" (delta), "d" ((u64)scale->mul_frac) ); + "mul %2 ; shrd $32,%1,%0" + : "=a" (product), "=d" (delta) + : "rm" (delta), "0" ((u64)scale->mul_frac) ); return product; } Attachment:
x86-time-scale-asm.patch _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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