diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index e00a96161cd..b02d2923b8e 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -3423,11 +3423,17 @@ static bool EliminateDeadSwitchCases(SwitchInst *SI, AssumptionCache *AC, } // If we can prove that the cases must cover all possible values, the - // default destination becomes dead and we can remove it. + // default destination becomes dead and we can remove it. If we know some + // of the bits in the value, we can use that to more precisely compute the + // number of possible unique case values. bool HasDefault = !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg()); - if (HasDefault && Bits < 64 /* avoid overflow */ && - SI->getNumCases() == (1ULL << Bits)) { + const unsigned NumUnknownBits = Bits - + (KnownZero.Or(KnownOne)).countPopulation(); + assert(0 <= NumUnknownBits && NumUnknownBits <= Bits); + if (HasDefault && DeadCases.empty() && + NumUnknownBits < 64 /* avoid overflow */ && + SI->getNumCases() == (1ULL << NumUnknownBits)) { DEBUG(dbgs() << "SimplifyCFG: switch default is dead.\n"); BasicBlock *NewDefault = SplitBlockPredecessors(SI->getDefaultDest(), SI->getParent(), ""); |
