Revert r219832.

llvm-svn: 219884

1 files changed, 0 insertions, 31 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index e158c11b1fd..ac0c01e3c7b 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2075,37 +2075,6 @@ Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
 
 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
   Value *Cond = SI.getCondition();
-  unsigned BitWidth = cast<IntegerType>(Cond->getType())->getBitWidth();
-  APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
-  computeKnownBits(Cond, KnownZero, KnownOne);
-  unsigned LeadingKnownZeros = KnownZero.countLeadingOnes();
-  unsigned LeadingKnownOnes = KnownOne.countLeadingOnes();
-
-  // Compute the number of leading bits we can ignore.
-  for (auto &C : SI.cases()) {
-    LeadingKnownZeros = std::min(
-        LeadingKnownZeros, C.getCaseValue()->getValue().countLeadingZeros());
-    LeadingKnownOnes = std::min(
-        LeadingKnownOnes, C.getCaseValue()->getValue().countLeadingOnes());
-  }
-
-  unsigned NewWidth = BitWidth - std::max(LeadingKnownZeros, LeadingKnownOnes);
-
-  // Truncate the condition operand if the new type is equal to or larger than
-  // the largest legal integer type. We need to be conservative here since
-  // x86 generates redundant zero-extenstion instructions if the operand is
-  // truncated to i8 or i16.
-  if (BitWidth > NewWidth && NewWidth >= DL->getLargestLegalIntTypeSize()) {
-    IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth);
-    Builder->SetInsertPoint(&SI);
-    Value *NewCond = Builder->CreateTrunc(SI.getCondition(), Ty, "trunc");
-    SI.setCondition(NewCond);
-
-    for (auto &C : SI.cases())
-      static_cast<SwitchInst::CaseIt *>(&C)->setValue(
-          ConstantInt::get(Ty, C.getCaseValue()->getValue().getZExtValue()));
-  }
-
   if (Instruction *I = dyn_cast<Instruction>(Cond)) {
     if (I->getOpcode() == Instruction::Add)
       if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {