Revert rL326898: "Teach CorrelatedValuePropagation to reduce the width of udiv/urem instructions."

Breaks bootstrap builds: clang built with this patch asserts while
building MCDwarf.cpp: Assertion `castIsValid(op, S, Ty) && "Invalid
cast!"' failed.

llvm-svn: 326900

1 files changed, 0 insertions, 52 deletions

diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 6985632c7a2..db24fe05e86 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -58,7 +58,6 @@ STATISTIC(NumCmps,      "Number of comparisons propagated");
 STATISTIC(NumReturns,   "Number of return values propagated");
 STATISTIC(NumDeadCases, "Number of switch cases removed");
 STATISTIC(NumSDivs,     "Number of sdiv converted to udiv");
-STATISTIC(NumUDivs,     "Number of udivs whose width was decreased");
 STATISTIC(NumAShrs,     "Number of ashr converted to lshr");
 STATISTIC(NumSRems,     "Number of srem converted to urem");
 STATISTIC(NumOverflows, "Number of overflow checks removed");
@@ -433,46 +432,6 @@ static bool hasPositiveOperands(BinaryOperator *SDI, LazyValueInfo *LVI) {
   return true;
 }
 
-/// Try to shrink a udiv/urem's width down to the smallest power of two that's
-/// sufficient to contain its operands.
-static bool processUDivOrURem(BinaryOperator *Instr, LazyValueInfo *LVI) {
-  assert(Instr->getOpcode() == Instruction::UDiv ||
-         Instr->getOpcode() == Instruction::URem);
-  if (Instr->getType()->isVectorTy())
-    return false;
-
-  // Find the smallest power of two bitwidth that's sufficient to hold Instr's
-  // operands.
-  auto OrigWidth = Instr->getType()->getIntegerBitWidth();
-  ConstantRange OperandRange(OrigWidth, /*isFullset=*/false);
-  for (Value *Operand : Instr->operands()) {
-    OperandRange = OperandRange.unionWith(
-        LVI->getConstantRange(Operand, Instr->getParent()));
-  }
-  // Don't shrink below 8 bits wide.
-  unsigned NewWidth = std::max<unsigned>(
-      PowerOf2Ceil(OperandRange.getUnsignedMax().getActiveBits()), 8);
-  if (NewWidth == OrigWidth)
-    return false;
-
-  ++NumUDivs;
-  auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
-  auto *LHS = CastInst::Create(Instruction::Trunc, Instr->getOperand(0), TruncTy,
-                               Instr->getName() + ".lhs.trunc", Instr);
-  auto *RHS = CastInst::Create(Instruction::Trunc, Instr->getOperand(1), TruncTy,
-                               Instr->getName() + ".rhs.trunc", Instr);
-  auto *BO =
-      BinaryOperator::Create(Instr->getOpcode(), LHS, RHS, Instr->getName(), Instr);
-  auto *Zext = CastInst::Create(Instruction::ZExt, BO, Instr->getType(),
-                                Instr->getName() + ".zext", Instr);
-  if (BO->getOpcode() == Instruction::UDiv)
-    BO->setIsExact(Instr->isExact());
-
-  Instr->replaceAllUsesWith(Zext);
-  Instr->eraseFromParent();
-  return true;
-}
-
 static bool processSRem(BinaryOperator *SDI, LazyValueInfo *LVI) {
   if (SDI->getType()->isVectorTy() || !hasPositiveOperands(SDI, LVI))
     return false;
@@ -482,10 +441,6 @@ static bool processSRem(BinaryOperator *SDI, LazyValueInfo *LVI) {
                                         SDI->getName(), SDI);
   SDI->replaceAllUsesWith(BO);
   SDI->eraseFromParent();
-
-  // Try to process our new urem.
-  processUDivOrURem(BO, LVI);
-
   return true;
 }
 
@@ -505,9 +460,6 @@ static bool processSDiv(BinaryOperator *SDI, LazyValueInfo *LVI) {
   SDI->replaceAllUsesWith(BO);
   SDI->eraseFromParent();
 
-  // Try to simplify our new udiv.
-  processUDivOrURem(BO, LVI);
-
   return true;
 }
 
@@ -643,10 +595,6 @@ static bool runImpl(Function &F, LazyValueInfo *LVI, const SimplifyQuery &SQ) {
       case Instruction::SDiv:
         BBChanged |= processSDiv(cast<BinaryOperator>(II), LVI);
         break;
-      case Instruction::UDiv:
-      case Instruction::URem:
-        BBChanged |= processUDivOrURem(cast<BinaryOperator>(II), LVI);
-        break;
       case Instruction::AShr:
         BBChanged |= processAShr(cast<BinaryOperator>(II), LVI);
         break;