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author | Anton Blanchard <anton@samba.org> | 2016-04-30 01:29:27 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-05-11 12:21:20 +0300 |
commit | beac678d0908ee0a14200e1412f98a89b765c0aa (patch) | |
tree | 7457c857d4a896702e5a00afe30fcdfa5f6ffe5a /arch/powerpc | |
parent | ee3e27f14e40bc3c95a175af482d6bbf35ab78bc (diff) | |
download | linux-beac678d0908ee0a14200e1412f98a89b765c0aa.tar.xz |
powerpc: Fix bad inline asm constraint in create_zero_mask()
commit b4c112114aab9aff5ed4568ca5e662bb02cdfe74 upstream.
In create_zero_mask() we have:
addi %1,%2,-1
andc %1,%1,%2
popcntd %0,%1
using the "r" constraint for %2. r0 is a valid register in the "r" set,
but addi X,r0,X turns it into an li:
li r7,-1
andc r7,r7,r0
popcntd r4,r7
Fix this by using the "b" constraint, for which r0 is not a valid
register.
This was found with a kernel build using gcc trunk, narrowed down to
when -frename-registers was enabled at -O2. It is just luck however
that we aren't seeing this on older toolchains.
Thanks to Segher for working with me to find this issue.
Fixes: d0cebfa650a0 ("powerpc: word-at-a-time optimization for 64-bit Little Endian")
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r-- | arch/powerpc/include/asm/word-at-a-time.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/word-at-a-time.h b/arch/powerpc/include/asm/word-at-a-time.h index e4396a7d0f7c..4afe66aa1400 100644 --- a/arch/powerpc/include/asm/word-at-a-time.h +++ b/arch/powerpc/include/asm/word-at-a-time.h @@ -82,7 +82,7 @@ static inline unsigned long create_zero_mask(unsigned long bits) "andc %1,%1,%2\n\t" "popcntd %0,%1" : "=r" (leading_zero_bits), "=&r" (trailing_zero_bit_mask) - : "r" (bits)); + : "b" (bits)); return leading_zero_bits; } |