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authorAnton Blanchard <anton@samba.org>2016-04-30 08:29:27 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2016-05-02 11:10:25 +1000
commitb4c112114aab9aff5ed4568ca5e662bb02cdfe74 (patch)
treefabfb14d64976dd601e42038cf3dad800a8bb5d2 /arch
parentd701cca6744fe0d67c86346dcfc9b128b17b5045 (diff)
powerpc: Fix bad inline asm constraint in create_zero_mask()
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. Cc: stable@vger.kernel.org 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>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/include/asm/word-at-a-time.h2
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;
}