• Anton Blanchard's avatar
    powerpc: Fix bad inline asm constraint in create_zero_mask() · 420b214c
    Anton Blanchard authored
    [ Upstream commit b4c11211 ]
    
    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: d0cebfa6 ("powerpc: word-at-a-time optimization for 64-bit Little Endian")
    Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
    420b214c
word-at-a-time.h 4.71 KB