[llvm] r193068 - Fix the predecessor removal logic in r193045.

[Rafael Espíndola]

testcase?

On 21 October 2013 01:20, Michael Gottesman <mgottesman at apple.com> wrote:
> Author: mgottesman
> Date: Mon Oct 21 00:20:11 2013
> New Revision: 193068
>
> URL: http://llvm.org/viewvc/llvm-project?rev=193068&view=rev
> Log:
> Fix the predecessor removal logic in r193045.
>
> Additionally some small comment/stylistic fixes are included as well.
>
> Modified:
>     llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>
> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=193068&r1=193067&r2=193068&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon Oct 21 00:20:11 2013
> @@ -3741,18 +3741,20 @@ static bool SwitchToLookupTable(SwitchIn
>
>    // Compute the maximum table size representable by the integer type we are
>    // switching upon.
> -  const unsigned CaseSize = MinCaseVal->getType()->getPrimitiveSizeInBits();
> -  const uint64_t MaxTableSize = CaseSize > 63? UINT64_MAX : 1ULL << CaseSize;
> +  unsigned CaseSize = MinCaseVal->getType()->getPrimitiveSizeInBits();
> +  uint64_t MaxTableSize = CaseSize > 63? UINT64_MAX : 1ULL << CaseSize;
>    assert(MaxTableSize >= TableSize &&
>           "It is impossible for a switch to have more entries than the max "
>           "representable value of its input integer type's size.");
>
> -  // If we have a covered lookup table, unconditionally branch to the lookup table
> -  // BB. Otherwise, check if the condition value is within the case range. If it
> -  // is so, branch to the new BB. Otherwise branch to SI's default destination.
> +  // If we have a fully covered lookup table, unconditionally branch to the
> +  // lookup table BB. Otherwise, check if the condition value is within the case
> +  // range. If it is so, branch to the new BB. Otherwise branch to SI's default
> +  // destination.
>    const bool GeneratingCoveredLookupTable = MaxTableSize == TableSize;
>    if (GeneratingCoveredLookupTable) {
>      Builder.CreateBr(LookupBB);
> +    SI->getDefaultDest()->removePredecessor(SI->getParent());
>    } else {
>      Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get(
>                                           MinCaseVal->getType(), TableSize));
> @@ -3786,14 +3788,10 @@ static bool SwitchToLookupTable(SwitchIn
>      Builder.CreateBr(CommonDest);
>
>    // Remove the switch.
> -  for (unsigned i = 0; i < SI->getNumSuccessors(); ++i) {
> +  for (unsigned i = 0, e = SI->getNumSuccessors(); i < e; ++i) {
>      BasicBlock *Succ = SI->getSuccessor(i);
>
> -    // If we are not generating a covered lookup table, we will have a
> -    // conditional branch from SI's parent BB to SI's default destination if our
> -    // input value lies outside of our case range. Thus in that case leave the
> -    // default destination BB as a predecessor of SI's parent BB.
> -    if (Succ == SI->getDefaultDest() && !GeneratingCoveredLookupTable)
> +    if (Succ == SI->getDefaultDest())
>        continue;
>      Succ->removePredecessor(SI->getParent());
>    }
>
>
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