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Postings from March 2008
On Fri, Mar 21, 2008 at 12:21:53PM +0000, Nicholas Clark wrote:
>
> It made me wonder. Currently the perl 5 runloop looks like this:
>
> int
> Perl_runops_standard(pTHX)
> {
> dVAR;
> while ((PL_op = CALL_FPTR(PL_op->op_ppaddr)(aTHX))) {
> PERL_ASYNC_CHECK();
> }
>
> # 3 "PERL_ASYNC_CHECK expands to"
> if ((my_perl->Isig_pending)) Perl_despatch_signals(my_perl)
>
> We do the check after every op. I wondered, if we did the check
I think there's more to gain by adding branch prediction to the code.
It seems the config side is done, so it's ready to use:
perl.h:# define EXPECT(expr,val) __builtin_expect(expr,val)
perl.h:# define EXPECT(expr,val) (expr)
perl.h:#define LIKELY(cond) EXPECT(cond,1)
perl.h:#define UNLIKELY(cond) EXPECT(cond,0)
Tim.
p.s. I think they'd look much less noisy in the code if they were in lowercase.
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