Re: Structure vs purism ?

Stefan Monnier (monnier+lists/linux/kernel/news/@tequila.cs.yale.edu)
22 Jan 1999 12:46:15 -0500


>>>>> "Helge" == Helge Hafting <helge.hafting@daldata.no> writes:
> Changing the C language won't be easy, but an asymmetric if could be
> implemented by putting #pragma probable_if, #pragma improbable_if

Profiling-feedback is much easier for the programmer, doesn't require
any compiler-dependant source code changes and is less error prone (an `if'
can change from being very likely taken to very likely not-taken by changes in
other places of the code).
Compilers generally don't have this kind of hint anyway because:
1 - as said above, profile-feedback is better and more generally useful
2 - some old Fortran compiler used to povide such hints and the story says that
they compiler ended up interpreting the hints in the opposite direction
because people tended to add incorrect hints (it's not as easy as it seems
to predict the profile of your code)

Stefan

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