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    Subject[PATCH] MIPS: Make BUG() __noreturn.
    MIPS: Make BUG() __noreturn.

    Often we do things like put BUG() in the default clause of a case
    statement. Since it was not declared __noreturn, this could sometimes
    lead to bogus compiler warnings that variables were used
    uninitialized.

    There is a small problem in that we have to put a magic while(1); loop to
    fool GCC into really thinking it is noreturn. This makes the new
    BUG() function 3 instructions long instead of just 1, but I think it
    is worth it as it is now unnecessary to do extra work to silence the
    'used uninitialized' warnings.

    I also re-wrote BUG_ON so that if it is given a constant condition, it
    just does BUG() instead of loading a constant value in to a register
    and testing it.


    Signed-off-by: David Daney <ddaney@caviumnetworks.com>
    ---
    arch/mips/include/asm/bug.h | 29 ++++++++++++++++++++---------
    1 files changed, 20 insertions(+), 9 deletions(-)

    diff --git a/arch/mips/include/asm/bug.h b/arch/mips/include/asm/bug.h
    index 7eb63de..08ea468 100644
    --- a/arch/mips/include/asm/bug.h
    +++ b/arch/mips/include/asm/bug.h
    @@ -7,20 +7,31 @@

    #include <asm/break.h>

    -#define BUG() \
    -do { \
    - __asm__ __volatile__("break %0" : : "i" (BRK_BUG)); \
    -} while (0)
    +static inline void __noreturn BUG(void)
    +{
    + __asm__ __volatile__("break %0" : : "i" (BRK_BUG));
    + /* Fool GCC into thinking the function doesn't return. */
    + while (1)
    + ;
    +}

    #define HAVE_ARCH_BUG

    #if (_MIPS_ISA > _MIPS_ISA_MIPS1)

    -#define BUG_ON(condition) \
    -do { \
    - __asm__ __volatile__("tne $0, %0, %1" \
    - : : "r" (condition), "i" (BRK_BUG)); \
    -} while (0)
    +static inline void __BUG_ON(unsigned long condition)
    +{
    + if (__builtin_constant_p(condition)) {
    + if (condition)
    + BUG();
    + else
    + return;
    + }
    + __asm__ __volatile__("tne $0, %0, %1"
    + : : "r" (condition), "i" (BRK_BUG));
    +}
    +
    +#define BUG_ON(C) __BUG_ON((unsigned long)(C))

    #define HAVE_ARCH_BUG_ON


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