[llvm-commits] [LLVM, SwitchInst, case ranges] Auxiliary patch #1

[Stepan Dyatkovskiy]

Hi, Duncan.

Well, on instruction selection level switch cases are already grouped to switch ranges. I don't think that case ranges increases complexity of existing optimizers. I think that its useful when we work with front-ends like Fortran, since we doesn't need to split fortran's case-ranges and combine them again during switch lowering procedure.

-Stepan

28.10.2011, 16:19, "Duncan Sands" <baldrick at free.fr>:
> Hi Stepan, I have to ask: what are switch case ranges good for?  Will they
> actually result in better code, or just more complexity in the optimizers
> and code generators?  Sorry to ask at this late date.  I know I'm the one
> that first suggested adding case ranges, but I've since come to wonder
> whether they are really useful.
>
> Ciao, Duncan.
>
>>  Hi all. The main discussion branch of this feature is here:
>>  http://llvm.org/bugs/show_bug.cgi?id=1255
>>
>>  We need change SwitchInst internals: replace case value type from "ConstantInt"
>>  to "APInt", then move case values out from operands collection. To do that we
>>  need add APInt::isInitialized feature. We also need extend SmallSet class adding
>>  Compare parameter to this template:
>>  template <typename T, unsigned N, typename C = std::less<T> >
>>
>>  Please find attached patches for review.
>>
>>  Regards,
>>  Stepan.
>>
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