Messages in this thread | | | Date | Wed, 27 Oct 2004 17:47:50 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] Remove some divide instructions |
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On Wed, 27 Oct 2004, Linus Torvalds wrote: > > I could add a sparse check for "no side effects", if anybody cares (so > that you could do > > __builtin_warning( > !__builtin_nosideeffects(base), > "expression has side effects"); > > in macros like these.. Sparse already has the logic internally..
Done. Except I called it __builtin_safe_p().
The kernel sources already know about "__builtin_warning()" (and pre-process it away on gcc), so if you have a new sparse setup (as of two minutes ago ;), you can use this thing to check that arguments to macros do not have side effects.
Useful? You be the judge. But it was just a couple of lines in sparse, and doing so also made it obvious how to clean up __builtin_constant_p() a lot at the same time by just re-organizing things a bit.
My inliner and statement simplificator isn't perfect, so inline functions sadly are not considered constant (or safe) even if they _do_ end up returning a constant value (or be safe internally).
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