Would you mind reporting a bug in llvm.org/bugs?
Thanks
On 24 December 2013 17:42, Jasper Neumann <jasper.neumann at web.de>
wrote:> Hello all,
>
> in SelectionDAGBuilder::handleBTSplitSwitchCase
> (lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp) seems to be a quirk
which
> can effectively create an else-if chain from a very sparse switch statement
> instead of a balanced binary tree.
>
> A possible solution is to weight an isolated single switch label with 0. To
> do this one can replace the assignments to LDensity und RDensity by:
> volatile double LDensity > (double)(LSize-1).roundToDouble()
/
> (LEnd - First + 1ULL).roundToDouble();
> volatile double RDensity > (double)(RSize-1).roundToDouble() /
> (Last - RBegin + 1ULL).roundToDouble();
>
> I replaced ?Size by (?Size-1).
>
> Here is a more or less stupid test program (translate with "clang -O3
-S
> test.cpp" and then look at test.s):
>
> int main(int argc, char **argv) {
> switch (argc) {
> case 100: return 1;
> case 200: return 2;
> case 300: return 3;
> case 400: return 4;
> case 500: return 5;
> case 600: return 6;
> case 700: return 7;
> case 800: return 8;
> case 900: return 9;
> default: return 0;
> }
> }
>
> Best regards
> Jasper Neumann
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev