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

["Maciej W. Rozycki" <macro@linux-mips.org>]

On Fri, 21 Nov 2008, Ralf Baechle wrote:

> MIPS ISA newer than MIPS I also have conditional break codes allowing
> something like this:
> 
> #define BUG_ON(condition)                                               \
> do {                                                                    \
>         __asm__ __volatile__("tne $0, %0, %1"                           \
>                              : : "r" (condition), "i" (BRK_BUG));       \
> } while (0)
> 
> that is test of condition and the trap as a single instruction.  Note there
> are break and trap instructions on MIPS and they are basically doing the
> same job ...

 GCC is actually smart enough to combine sequences like:

if (something)
        __builtin_trap();

into appropriate conditional trap instructions on MIPS.  As noted by David 
trap codes other than the default cannot be emitted this way though.

  Maciej