• Daniel Jacobowitz's avatar
    [ARM] 3759/2: Remove uses of %? · 6a39dd62
    Daniel Jacobowitz authored
    Patch from Daniel Jacobowitz
    
    The ARM kernel has several uses of asm("foo%?").  %? is a GCC internal
    modifier used to output conditional execution predicates.  However, no
    version of GCC supports conditionalizing asm statements.  GCC 4.2 will
    correctly expand %? to the empty string in user asms.  Earlier versions may
    reuse the condition from the previous instruction.  In 'if (foo) asm
    ("bar%?");' this is somewhat likely to be right... but not reliable.
    
    So, the only safe thing to do is to remove the uses of %?.  I believe
    the tlbflush.h occurances were supposed to be removed before, based
    on the comment about %? not working at the top of that file.
    
    Old versions of GCC could omit branches around user asms if the asm didn't
    mark the condition codes as clobbered.  This problem hasn't been seen on any
    recent (3.x or 4.x) GCC, but it could theoretically happen.  So, where
    %? was removed a cc clobber was added.
    Signed-off-by: default avatarDaniel Jacobowitz <dan@codesourcery.com>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    6a39dd62
dc21285.c 9.09 KB