Re: Linux 2.4.10-pre11 -- __builtin_expect

Andreas Schwab
2001-09-27T16:28:10Z

James Antill <james@and.org> writes:

|> Andreas Schwab <schwab@suse.de> writes:
|>
|> > James Antill <james@and.org> writes:
|> >
|> > |> unlikely() also needs to be...
|> > |>
|> > |> #define unlikely(x) __builtin_expect(!(x), 1)
|> > |>
|> > |> ...or...
|> > |>
|> > |> #define unlikely(x) __builtin_expect(!!(x), 0)
|> >
|> > This is not needed, since only 0 is the likely value and !! does not
|> > change that.
|>
|> Yes it is, given the code...
|>
|> struct blah *ptr = NULL;
|>
|> if (unlikely(ptr))
|>
|> ...you'll get a warning from gcc because you are implicitly converting
|> from a pointer to a long.

You're right, seems like __builtin_expect is really only defined for pure
boolean values.

Andreas.

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