35 lines
1.3 KiB
Diff
35 lines
1.3 KiB
Diff
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# HG changeset patch
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# User Jan Beulich <jbeulich@suse.com>
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# Date 1353946839 -3600
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# Node ID 16bf7f3069a77c8a15b785cfdb5f2f634661d7fc
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# Parent 0049de3827bcfe3488dc6c7b7a60327a562aee5c
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x86/time: fix scale_delta() inline assembly
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The way it was coded, it clobbered %rdx without telling the compiler.
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This generally didn't cause any problems except when there are two back
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to back invocations (as in plt_overflow()), as in that case the
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compiler may validly assume that it can re-use for the second instance
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the value loaded into %rdx before the first one.
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Once at it, also properly relax the second operand of "mul" (there's no
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need for it to be in %rdx, or a register at all), and switch away from
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using explicit register names in the instruction operands.
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Signed-off-by: Jan Beulich <jbeulich@suse.com>
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Acked-by: Keir Fraser <keir@xen.org>
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--- a/xen/arch/x86/time.c
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+++ b/xen/arch/x86/time.c
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@@ -142,8 +142,9 @@ static inline u64 scale_delta(u64 delta,
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: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (scale->mul_frac) );
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#else
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asm (
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- "mul %%rdx ; shrd $32,%%rdx,%%rax"
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- : "=a" (product) : "0" (delta), "d" ((u64)scale->mul_frac) );
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+ "mul %2 ; shrd $32,%1,%0"
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+ : "=a" (product), "=d" (delta)
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+ : "rm" (delta), "0" ((u64)scale->mul_frac) );
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#endif
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return product;
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