bdadcf593d
kvm-unit-tests uses the following code on x86/x86-64:
static inline u64 scale_delta(u64 delta, u64 mul_frac)
{
u64 product, unused;
__asm__ (
"mul %3"
: "=d" (product), "=a" (unused) : "1" (delta), "rm" ((u64)mul_frac) );
return product;
}
The "mul" instruction does not have a suffix that indicates the width of
the data being multiplied. When the data is passed in a register, there
is no need to specify the width, but with some gcc versions, the data is
passed as a memory reference, and therefore the assembler does not know
the width of the data to be multiplied. It causes the following build
failure:
x86/hyperv_clock.c: Assembler messages:
x86/hyperv_clock.c:21: Error: no instruction mnemonic suffix given and no register operands; can't size instruction
Since the data being multiplied is 64 bit, we explicitly specify the
instruction as being "mulq".
Fixes:
http://autobuild.buildroot.net/results/a4a65d01f049db83a93de92660f228dd18532625/
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
36 lines
1.1 KiB
Diff
36 lines
1.1 KiB
Diff
From 022ae220d6e7b5bd064bc8698c271dca4dac7d8c Mon Sep 17 00:00:00 2001
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From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
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Date: Mon, 8 May 2017 22:27:25 +0200
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Subject: [PATCH] x86/hyperv_clock: be explicit about mul instruction data size
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With gcc 4.7.2, the build fails with:
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x86/hyperv_clock.c: Assembler messages:
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x86/hyperv_clock.c:21: Error: no instruction mnemonic suffix given and no register operands; can't size instruction
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In order to avoid this, make the mul instruction data size explicit by
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adding the appropriate suffix. It operates on 64-bit data, so use
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"mulq".
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Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
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---
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x86/hyperv_clock.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/x86/hyperv_clock.c b/x86/hyperv_clock.c
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index 8b1deba..6c4dd56 100644
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--- a/x86/hyperv_clock.c
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+++ b/x86/hyperv_clock.c
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@@ -19,7 +19,7 @@ static inline u64 scale_delta(u64 delta, u64 mul_frac)
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u64 product, unused;
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__asm__ (
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- "mul %3"
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+ "mulq %3"
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: "=d" (product), "=a" (unused) : "1" (delta), "rm" ((u64)mul_frac) );
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return product;
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--
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2.7.4
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