On Sat, 3 Jul 2010, Shinya Kuribayashi wrote:
> Ok, now I've come to the same conclusion. Revised patch will be like
> this. Malta is a development platform supporting various types of
> MIPS32/MIPS64 cores, hence use cpu_has_clo_clz directly. The same goes
> to MIPSSim.
Malta also supports a couple of MIPS IV processors too, so please be
careful about such assumptions.
> + if (__builtin_constant_p(cpu_has_clo_clz) && cpu_has_clo_clz) {
> + int x;
> + __asm__(
> + " .set push \n"
> + " .set mips32 \n"
> + " clz %0, %1 \n"
> + " .set pop \n"
> + : "=r" (x)
> + : "r" (pending));
> +
> + return -x + 31 - CAUSEB_IP;
> + }
Hmm, ".set mips32" looks dodgy here. For pre-MIPS32/64 platforms this
code should never make it to the assembler and if it did, then a
build-time error is better than a run-time problem.
It might be simpler just to use __builtin_ffs() for this variant though.
Inline assembly is better avoided unless absolutely required. Not even
mentioning readability.
Maciej
