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//===- InstCombineCasts.cpp -----------------------------------------------===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This file implements the visit functions for cast operations.
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//===----------------------------------------------------------------------===//
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#include "InstCombine.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Support/PatternMatch.h"
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using namespace PatternMatch;
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/// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear
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/// expression. If so, decompose it, returning some value X, such that Val is
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static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
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assert(Val->getType()->isIntegerTy(32) && "Unexpected allocation size type!");
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if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) {
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Offset = CI->getZExtValue();
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return ConstantInt::get(Type::getInt32Ty(Val->getContext()), 0);
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if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
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if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
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if (I->getOpcode() == Instruction::Shl) {
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// This is a value scaled by '1 << the shift amt'.
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Scale = 1U << RHS->getZExtValue();
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return I->getOperand(0);
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if (I->getOpcode() == Instruction::Mul) {
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// This value is scaled by 'RHS'.
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Scale = RHS->getZExtValue();
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return I->getOperand(0);
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if (I->getOpcode() == Instruction::Add) {
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// We have X+C. Check to see if we really have (X*C2)+C1,
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// where C1 is divisible by C2.
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DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset);
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Offset += RHS->getZExtValue();
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// Otherwise, we can't look past this.
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/// PromoteCastOfAllocation - If we find a cast of an allocation instruction,
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/// try to eliminate the cast by moving the type information into the alloc.
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Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
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// This requires TargetData to get the alloca alignment and size information.
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const PointerType *PTy = cast<PointerType>(CI.getType());
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BuilderTy AllocaBuilder(*Builder);
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AllocaBuilder.SetInsertPoint(AI.getParent(), &AI);
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// Get the type really allocated and the type casted to.
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const Type *AllocElTy = AI.getAllocatedType();
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const Type *CastElTy = PTy->getElementType();
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if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0;
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unsigned AllocElTyAlign = TD->getABITypeAlignment(AllocElTy);
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unsigned CastElTyAlign = TD->getABITypeAlignment(CastElTy);
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if (CastElTyAlign < AllocElTyAlign) return 0;
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// If the allocation has multiple uses, only promote it if we are strictly
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// increasing the alignment of the resultant allocation. If we keep it the
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// same, we open the door to infinite loops of various kinds. (A reference
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// from a dbg.declare doesn't count as a use for this purpose.)
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if (!AI.hasOneUse() && !hasOneUsePlusDeclare(&AI) &&
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CastElTyAlign == AllocElTyAlign) return 0;
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uint64_t AllocElTySize = TD->getTypeAllocSize(AllocElTy);
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uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy);
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if (CastElTySize == 0 || AllocElTySize == 0) return 0;
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// See if we can satisfy the modulus by pulling a scale out of the array
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unsigned ArraySizeScale;
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Value *NumElements = // See if the array size is a decomposable linear expr.
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DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset);
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// If we can now satisfy the modulus, by using a non-1 scale, we really can
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if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
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(AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0;
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unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
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Amt = ConstantInt::get(Type::getInt32Ty(CI.getContext()), Scale);
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// Insert before the alloca, not before the cast.
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Amt = AllocaBuilder.CreateMul(Amt, NumElements, "tmp");
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if (int Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
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Value *Off = ConstantInt::get(Type::getInt32Ty(CI.getContext()),
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Amt = AllocaBuilder.CreateAdd(Amt, Off, "tmp");
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AllocaInst *New = AllocaBuilder.CreateAlloca(CastElTy, Amt);
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New->setAlignment(AI.getAlignment());
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// If the allocation has one real use plus a dbg.declare, just remove the
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if (DbgDeclareInst *DI = hasOneUsePlusDeclare(&AI)) {
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EraseInstFromFunction(*(Instruction*)DI);
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// If the allocation has multiple real uses, insert a cast and change all
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// things that used it to use the new cast. This will also hack on CI, but it
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else if (!AI.hasOneUse()) {
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// New is the allocation instruction, pointer typed. AI is the original
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// allocation instruction, also pointer typed. Thus, cast to use is BitCast.
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Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast");
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AI.replaceAllUsesWith(NewCast);
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return ReplaceInstUsesWith(CI, New);
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/// EvaluateInDifferentType - Given an expression that
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/// CanEvaluateTruncated or CanEvaluateSExtd returns true for, actually
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/// insert the code to evaluate the expression.
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Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
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if (Constant *C = dyn_cast<Constant>(V)) {
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C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/);
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// If we got a constantexpr back, try to simplify it with TD info.
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
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C = ConstantFoldConstantExpression(CE, TD);
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// Otherwise, it must be an instruction.
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Instruction *I = cast<Instruction>(V);
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Instruction *Res = 0;
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unsigned Opc = I->getOpcode();
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case Instruction::Add:
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case Instruction::Sub:
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case Instruction::Mul:
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case Instruction::And:
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case Instruction::Or:
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case Instruction::Xor:
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case Instruction::AShr:
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case Instruction::LShr:
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case Instruction::Shl:
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case Instruction::UDiv:
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case Instruction::URem: {
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Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
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Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
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Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
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case Instruction::Trunc:
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case Instruction::ZExt:
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case Instruction::SExt:
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// If the source type of the cast is the type we're trying for then we can
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// just return the source. There's no need to insert it because it is not
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if (I->getOperand(0)->getType() == Ty)
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return I->getOperand(0);
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// Otherwise, must be the same type of cast, so just reinsert a new one.
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// This also handles the case of zext(trunc(x)) -> zext(x).
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Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty,
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Opc == Instruction::SExt);
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case Instruction::Select: {
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Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
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Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned);
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Res = SelectInst::Create(I->getOperand(0), True, False);
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case Instruction::PHI: {
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PHINode *OPN = cast<PHINode>(I);
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PHINode *NPN = PHINode::Create(Ty);
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for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) {
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Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned);
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NPN->addIncoming(V, OPN->getIncomingBlock(i));
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// TODO: Can handle more cases here.
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llvm_unreachable("Unreachable!");
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return InsertNewInstBefore(Res, *I);
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/// This function is a wrapper around CastInst::isEliminableCastPair. It
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/// simply extracts arguments and returns what that function returns.
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static Instruction::CastOps
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isEliminableCastPair(
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const CastInst *CI, ///< The first cast instruction
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unsigned opcode, ///< The opcode of the second cast instruction
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const Type *DstTy, ///< The target type for the second cast instruction
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TargetData *TD ///< The target data for pointer size
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const Type *SrcTy = CI->getOperand(0)->getType(); // A from above
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const Type *MidTy = CI->getType(); // B from above
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// Get the opcodes of the two Cast instructions
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Instruction::CastOps firstOp = Instruction::CastOps(CI->getOpcode());
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Instruction::CastOps secondOp = Instruction::CastOps(opcode);
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unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy,
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TD ? TD->getIntPtrType(CI->getContext()) : 0);
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// We don't want to form an inttoptr or ptrtoint that converts to an integer
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// type that differs from the pointer size.
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if ((Res == Instruction::IntToPtr &&
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(!TD || SrcTy != TD->getIntPtrType(CI->getContext()))) ||
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(Res == Instruction::PtrToInt &&
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(!TD || DstTy != TD->getIntPtrType(CI->getContext()))))
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return Instruction::CastOps(Res);
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/// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
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/// results in any code being generated and is interesting to optimize out. If
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/// the cast can be eliminated by some other simple transformation, we prefer
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/// to do the simplification first.
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bool InstCombiner::ShouldOptimizeCast(Instruction::CastOps opc, const Value *V,
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// Noop casts and casts of constants should be eliminated trivially.
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if (V->getType() == Ty || isa<Constant>(V)) return false;
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// If this is another cast that can be eliminated, we prefer to have it
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if (const CastInst *CI = dyn_cast<CastInst>(V))
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if (isEliminableCastPair(CI, opc, Ty, TD))
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// If this is a vector sext from a compare, then we don't want to break the
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// idiom where each element of the extended vector is either zero or all ones.
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if (opc == Instruction::SExt && isa<CmpInst>(V) && Ty->isVectorTy())
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/// @brief Implement the transforms common to all CastInst visitors.
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Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
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Value *Src = CI.getOperand(0);
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// Many cases of "cast of a cast" are eliminable. If it's eliminable we just
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if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
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if (Instruction::CastOps opc =
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isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), TD)) {
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// The first cast (CSrc) is eliminable so we need to fix up or replace
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// the second cast (CI). CSrc will then have a good chance of being dead.
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return CastInst::Create(opc, CSrc->getOperand(0), CI.getType());
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// If we are casting a select then fold the cast into the select
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if (SelectInst *SI = dyn_cast<SelectInst>(Src))
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if (Instruction *NV = FoldOpIntoSelect(CI, SI))
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// If we are casting a PHI then fold the cast into the PHI
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if (isa<PHINode>(Src)) {
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// We don't do this if this would create a PHI node with an illegal type if
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// it is currently legal.
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if (!Src->getType()->isIntegerTy() ||
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!CI.getType()->isIntegerTy() ||
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ShouldChangeType(CI.getType(), Src->getType()))
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if (Instruction *NV = FoldOpIntoPhi(CI))
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/// CanEvaluateTruncated - Return true if we can evaluate the specified
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/// expression tree as type Ty instead of its larger type, and arrive with the
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/// same value. This is used by code that tries to eliminate truncates.
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/// Ty will always be a type smaller than V. We should return true if trunc(V)
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/// can be computed by computing V in the smaller type. If V is an instruction,
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/// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only
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/// makes sense if x and y can be efficiently truncated.
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/// This function works on both vectors and scalars.
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static bool CanEvaluateTruncated(Value *V, const Type *Ty) {
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// We can always evaluate constants in another type.
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if (isa<Constant>(V))
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I) return false;
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const Type *OrigTy = V->getType();
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// If this is an extension from the dest type, we can eliminate it, even if it
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// has multiple uses.
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if ((isa<ZExtInst>(I) || isa<SExtInst>(I)) &&
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I->getOperand(0)->getType() == Ty)
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// We can't extend or shrink something that has multiple uses: doing so would
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// require duplicating the instruction in general, which isn't profitable.
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if (!I->hasOneUse()) return false;
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unsigned Opc = I->getOpcode();
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case Instruction::Add:
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case Instruction::Sub:
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case Instruction::Mul:
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case Instruction::And:
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case Instruction::Or:
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case Instruction::Xor:
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// These operators can all arbitrarily be extended or truncated.
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return CanEvaluateTruncated(I->getOperand(0), Ty) &&
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CanEvaluateTruncated(I->getOperand(1), Ty);
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case Instruction::UDiv:
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case Instruction::URem: {
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// UDiv and URem can be truncated if all the truncated bits are zero.
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uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
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uint32_t BitWidth = Ty->getScalarSizeInBits();
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if (BitWidth < OrigBitWidth) {
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APInt Mask = APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth);
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if (MaskedValueIsZero(I->getOperand(0), Mask) &&
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MaskedValueIsZero(I->getOperand(1), Mask)) {
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return CanEvaluateTruncated(I->getOperand(0), Ty) &&
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CanEvaluateTruncated(I->getOperand(1), Ty);
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case Instruction::Shl:
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// If we are truncating the result of this SHL, and if it's a shift of a
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// constant amount, we can always perform a SHL in a smaller type.
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if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
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uint32_t BitWidth = Ty->getScalarSizeInBits();
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if (CI->getLimitedValue(BitWidth) < BitWidth)
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return CanEvaluateTruncated(I->getOperand(0), Ty);
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case Instruction::LShr:
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// If this is a truncate of a logical shr, we can truncate it to a smaller
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// lshr iff we know that the bits we would otherwise be shifting in are
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if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
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uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
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uint32_t BitWidth = Ty->getScalarSizeInBits();
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if (MaskedValueIsZero(I->getOperand(0),
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APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth)) &&
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CI->getLimitedValue(BitWidth) < BitWidth) {
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return CanEvaluateTruncated(I->getOperand(0), Ty);
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case Instruction::Trunc:
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// trunc(trunc(x)) -> trunc(x)
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case Instruction::Select: {
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SelectInst *SI = cast<SelectInst>(I);
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return CanEvaluateTruncated(SI->getTrueValue(), Ty) &&
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CanEvaluateTruncated(SI->getFalseValue(), Ty);
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case Instruction::PHI: {
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// We can change a phi if we can change all operands. Note that we never
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// get into trouble with cyclic PHIs here because we only consider
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// instructions with a single use.
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PHINode *PN = cast<PHINode>(I);
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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if (!CanEvaluateTruncated(PN->getIncomingValue(i), Ty))
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// TODO: Can handle more cases here.
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Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
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if (Instruction *Result = commonCastTransforms(CI))
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// See if we can simplify any instructions used by the input whose sole
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// purpose is to compute bits we don't care about.
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if (SimplifyDemandedInstructionBits(CI))
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Value *Src = CI.getOperand(0);
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const Type *DestTy = CI.getType(), *SrcTy = Src->getType();
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// Attempt to truncate the entire input expression tree to the destination
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// type. Only do this if the dest type is a simple type, don't convert the
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// expression tree to something weird like i93 unless the source is also
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if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
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CanEvaluateTruncated(Src, DestTy)) {
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// If this cast is a truncate, evaluting in a different type always
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// eliminates the cast, so it is always a win.
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DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
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" to avoid cast: " << CI);
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Value *Res = EvaluateInDifferentType(Src, DestTy, false);
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assert(Res->getType() == DestTy);
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return ReplaceInstUsesWith(CI, Res);
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// Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0), likewise for vector.
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if (DestTy->getScalarSizeInBits() == 1) {
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Constant *One = ConstantInt::get(Src->getType(), 1);
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Src = Builder->CreateAnd(Src, One, "tmp");
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Value *Zero = Constant::getNullValue(Src->getType());
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return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero);
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/// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations
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/// in order to eliminate the icmp.
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Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI,
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// If we are just checking for a icmp eq of a single bit and zext'ing it
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// to an integer, then shift the bit to the appropriate place and then
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// cast to integer to avoid the comparison.
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if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
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const APInt &Op1CV = Op1C->getValue();
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// zext (x <s 0) to i32 --> x>>u31 true if signbit set.
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// zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
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if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
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(ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) {
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if (!DoXform) return ICI;
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Value *In = ICI->getOperand(0);
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Value *Sh = ConstantInt::get(In->getType(),
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In->getType()->getScalarSizeInBits()-1);
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In = Builder->CreateLShr(In, Sh, In->getName()+".lobit");
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if (In->getType() != CI.getType())
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In = Builder->CreateIntCast(In, CI.getType(), false/*ZExt*/, "tmp");
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if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
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Constant *One = ConstantInt::get(In->getType(), 1);
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In = Builder->CreateXor(In, One, In->getName()+".not");
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return ReplaceInstUsesWith(CI, In);
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// zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
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// zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
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// zext (X == 1) to i32 --> X iff X has only the low bit set.
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// zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set.
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// zext (X != 0) to i32 --> X iff X has only the low bit set.
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// zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set.
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// zext (X != 1) to i32 --> X^1 iff X has only the low bit set.
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// zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
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if ((Op1CV == 0 || Op1CV.isPowerOf2()) &&
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// This only works for EQ and NE
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// If Op1C some other power of two, convert:
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uint32_t BitWidth = Op1C->getType()->getBitWidth();
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APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
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APInt TypeMask(APInt::getAllOnesValue(BitWidth));
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ComputeMaskedBits(ICI->getOperand(0), TypeMask, KnownZero, KnownOne);
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APInt KnownZeroMask(~KnownZero);
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if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
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if (!DoXform) return ICI;
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bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE;
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if (Op1CV != 0 && (Op1CV != KnownZeroMask)) {
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// (X&4) == 2 --> false
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// (X&4) != 2 --> true
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Constant *Res = ConstantInt::get(Type::getInt1Ty(CI.getContext()),
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Res = ConstantExpr::getZExt(Res, CI.getType());
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return ReplaceInstUsesWith(CI, Res);
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uint32_t ShiftAmt = KnownZeroMask.logBase2();
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Value *In = ICI->getOperand(0);
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// Perform a logical shr by shiftamt.
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// Insert the shift to put the result in the low bit.
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In = Builder->CreateLShr(In, ConstantInt::get(In->getType(),ShiftAmt),
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In->getName()+".lobit");
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if ((Op1CV != 0) == isNE) { // Toggle the low bit.
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Constant *One = ConstantInt::get(In->getType(), 1);
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In = Builder->CreateXor(In, One, "tmp");
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if (CI.getType() == In->getType())
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return ReplaceInstUsesWith(CI, In);
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return CastInst::CreateIntegerCast(In, CI.getType(), false/*ZExt*/);
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// icmp ne A, B is equal to xor A, B when A and B only really have one bit.
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// It is also profitable to transform icmp eq into not(xor(A, B)) because that
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// may lead to additional simplifications.
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if (ICI->isEquality() && CI.getType() == ICI->getOperand(0)->getType()) {
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if (const IntegerType *ITy = dyn_cast<IntegerType>(CI.getType())) {
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uint32_t BitWidth = ITy->getBitWidth();
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Value *LHS = ICI->getOperand(0);
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Value *RHS = ICI->getOperand(1);
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APInt KnownZeroLHS(BitWidth, 0), KnownOneLHS(BitWidth, 0);
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APInt KnownZeroRHS(BitWidth, 0), KnownOneRHS(BitWidth, 0);
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APInt TypeMask(APInt::getAllOnesValue(BitWidth));
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ComputeMaskedBits(LHS, TypeMask, KnownZeroLHS, KnownOneLHS);
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ComputeMaskedBits(RHS, TypeMask, KnownZeroRHS, KnownOneRHS);
563
if (KnownZeroLHS == KnownZeroRHS && KnownOneLHS == KnownOneRHS) {
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APInt KnownBits = KnownZeroLHS | KnownOneLHS;
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APInt UnknownBit = ~KnownBits;
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if (UnknownBit.countPopulation() == 1) {
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if (!DoXform) return ICI;
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Value *Result = Builder->CreateXor(LHS, RHS);
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// Mask off any bits that are set and won't be shifted away.
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if (KnownOneLHS.uge(UnknownBit))
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Result = Builder->CreateAnd(Result,
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ConstantInt::get(ITy, UnknownBit));
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// Shift the bit we're testing down to the lsb.
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Result = Builder->CreateLShr(
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Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros()));
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if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
581
Result = Builder->CreateXor(Result, ConstantInt::get(ITy, 1));
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Result->takeName(ICI);
583
return ReplaceInstUsesWith(CI, Result);
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/// CanEvaluateZExtd - Determine if the specified value can be computed in the
593
/// specified wider type and produce the same low bits. If not, return false.
595
/// If this function returns true, it can also return a non-zero number of bits
596
/// (in BitsToClear) which indicates that the value it computes is correct for
597
/// the zero extend, but that the additional BitsToClear bits need to be zero'd
598
/// out. For example, to promote something like:
600
/// %B = trunc i64 %A to i32
601
/// %C = lshr i32 %B, 8
602
/// %E = zext i32 %C to i64
604
/// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be
605
/// set to 8 to indicate that the promoted value needs to have bits 24-31
606
/// cleared in addition to bits 32-63. Since an 'and' will be generated to
607
/// clear the top bits anyway, doing this has no extra cost.
609
/// This function works on both vectors and scalars.
610
static bool CanEvaluateZExtd(Value *V, const Type *Ty, unsigned &BitsToClear) {
612
if (isa<Constant>(V))
615
Instruction *I = dyn_cast<Instruction>(V);
616
if (!I) return false;
618
// If the input is a truncate from the destination type, we can trivially
619
// eliminate it, even if it has multiple uses.
620
// FIXME: This is currently disabled until codegen can handle this without
621
// pessimizing code, PR5997.
622
if (0 && isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty)
625
// We can't extend or shrink something that has multiple uses: doing so would
626
// require duplicating the instruction in general, which isn't profitable.
627
if (!I->hasOneUse()) return false;
629
unsigned Opc = I->getOpcode(), Tmp;
631
case Instruction::ZExt: // zext(zext(x)) -> zext(x).
632
case Instruction::SExt: // zext(sext(x)) -> sext(x).
633
case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x)
635
case Instruction::And:
636
case Instruction::Or:
637
case Instruction::Xor:
638
case Instruction::Add:
639
case Instruction::Sub:
640
case Instruction::Mul:
641
case Instruction::Shl:
642
if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear) ||
643
!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp))
645
// These can all be promoted if neither operand has 'bits to clear'.
646
if (BitsToClear == 0 && Tmp == 0)
649
// If the operation is an AND/OR/XOR and the bits to clear are zero in the
650
// other side, BitsToClear is ok.
652
(Opc == Instruction::And || Opc == Instruction::Or ||
653
Opc == Instruction::Xor)) {
654
// We use MaskedValueIsZero here for generality, but the case we care
655
// about the most is constant RHS.
656
unsigned VSize = V->getType()->getScalarSizeInBits();
657
if (MaskedValueIsZero(I->getOperand(1),
658
APInt::getHighBitsSet(VSize, BitsToClear)))
662
// Otherwise, we don't know how to analyze this BitsToClear case yet.
665
case Instruction::LShr:
666
// We can promote lshr(x, cst) if we can promote x. This requires the
667
// ultimate 'and' to clear out the high zero bits we're clearing out though.
668
if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) {
669
if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear))
671
BitsToClear += Amt->getZExtValue();
672
if (BitsToClear > V->getType()->getScalarSizeInBits())
673
BitsToClear = V->getType()->getScalarSizeInBits();
676
// Cannot promote variable LSHR.
678
case Instruction::Select:
679
if (!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp) ||
680
!CanEvaluateZExtd(I->getOperand(2), Ty, BitsToClear) ||
681
// TODO: If important, we could handle the case when the BitsToClear are
682
// known zero in the disagreeing side.
687
case Instruction::PHI: {
688
// We can change a phi if we can change all operands. Note that we never
689
// get into trouble with cyclic PHIs here because we only consider
690
// instructions with a single use.
691
PHINode *PN = cast<PHINode>(I);
692
if (!CanEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear))
694
for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
695
if (!CanEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp) ||
696
// TODO: If important, we could handle the case when the BitsToClear
697
// are known zero in the disagreeing input.
703
// TODO: Can handle more cases here.
708
Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
709
// If this zero extend is only used by a truncate, let the truncate by
710
// eliminated before we try to optimize this zext.
711
if (CI.hasOneUse() && isa<TruncInst>(CI.use_back()))
714
// If one of the common conversion will work, do it.
715
if (Instruction *Result = commonCastTransforms(CI))
718
// See if we can simplify any instructions used by the input whose sole
719
// purpose is to compute bits we don't care about.
720
if (SimplifyDemandedInstructionBits(CI))
723
Value *Src = CI.getOperand(0);
724
const Type *SrcTy = Src->getType(), *DestTy = CI.getType();
726
// Attempt to extend the entire input expression tree to the destination
727
// type. Only do this if the dest type is a simple type, don't convert the
728
// expression tree to something weird like i93 unless the source is also
730
unsigned BitsToClear;
731
if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
732
CanEvaluateZExtd(Src, DestTy, BitsToClear)) {
733
assert(BitsToClear < SrcTy->getScalarSizeInBits() &&
734
"Unreasonable BitsToClear");
736
// Okay, we can transform this! Insert the new expression now.
737
DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
738
" to avoid zero extend: " << CI);
739
Value *Res = EvaluateInDifferentType(Src, DestTy, false);
740
assert(Res->getType() == DestTy);
742
uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear;
743
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
745
// If the high bits are already filled with zeros, just replace this
746
// cast with the result.
747
if (MaskedValueIsZero(Res, APInt::getHighBitsSet(DestBitSize,
748
DestBitSize-SrcBitsKept)))
749
return ReplaceInstUsesWith(CI, Res);
751
// We need to emit an AND to clear the high bits.
752
Constant *C = ConstantInt::get(Res->getType(),
753
APInt::getLowBitsSet(DestBitSize, SrcBitsKept));
754
return BinaryOperator::CreateAnd(Res, C);
757
// If this is a TRUNC followed by a ZEXT then we are dealing with integral
758
// types and if the sizes are just right we can convert this into a logical
759
// 'and' which will be much cheaper than the pair of casts.
760
if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast
761
// TODO: Subsume this into EvaluateInDifferentType.
763
// Get the sizes of the types involved. We know that the intermediate type
764
// will be smaller than A or C, but don't know the relation between A and C.
765
Value *A = CSrc->getOperand(0);
766
unsigned SrcSize = A->getType()->getScalarSizeInBits();
767
unsigned MidSize = CSrc->getType()->getScalarSizeInBits();
768
unsigned DstSize = CI.getType()->getScalarSizeInBits();
769
// If we're actually extending zero bits, then if
770
// SrcSize < DstSize: zext(a & mask)
771
// SrcSize == DstSize: a & mask
772
// SrcSize > DstSize: trunc(a) & mask
773
if (SrcSize < DstSize) {
774
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
775
Constant *AndConst = ConstantInt::get(A->getType(), AndValue);
776
Value *And = Builder->CreateAnd(A, AndConst, CSrc->getName()+".mask");
777
return new ZExtInst(And, CI.getType());
780
if (SrcSize == DstSize) {
781
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
782
return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(),
785
if (SrcSize > DstSize) {
786
Value *Trunc = Builder->CreateTrunc(A, CI.getType(), "tmp");
787
APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize));
788
return BinaryOperator::CreateAnd(Trunc,
789
ConstantInt::get(Trunc->getType(),
794
if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src))
795
return transformZExtICmp(ICI, CI);
797
BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src);
798
if (SrcI && SrcI->getOpcode() == Instruction::Or) {
799
// zext (or icmp, icmp) --> or (zext icmp), (zext icmp) if at least one
800
// of the (zext icmp) will be transformed.
801
ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0));
802
ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1));
803
if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() &&
804
(transformZExtICmp(LHS, CI, false) ||
805
transformZExtICmp(RHS, CI, false))) {
806
Value *LCast = Builder->CreateZExt(LHS, CI.getType(), LHS->getName());
807
Value *RCast = Builder->CreateZExt(RHS, CI.getType(), RHS->getName());
808
return BinaryOperator::Create(Instruction::Or, LCast, RCast);
812
// zext(trunc(t) & C) -> (t & zext(C)).
813
if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse())
814
if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
815
if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) {
816
Value *TI0 = TI->getOperand(0);
817
if (TI0->getType() == CI.getType())
819
BinaryOperator::CreateAnd(TI0,
820
ConstantExpr::getZExt(C, CI.getType()));
823
// zext((trunc(t) & C) ^ C) -> ((t & zext(C)) ^ zext(C)).
824
if (SrcI && SrcI->getOpcode() == Instruction::Xor && SrcI->hasOneUse())
825
if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1)))
826
if (BinaryOperator *And = dyn_cast<BinaryOperator>(SrcI->getOperand(0)))
827
if (And->getOpcode() == Instruction::And && And->hasOneUse() &&
828
And->getOperand(1) == C)
829
if (TruncInst *TI = dyn_cast<TruncInst>(And->getOperand(0))) {
830
Value *TI0 = TI->getOperand(0);
831
if (TI0->getType() == CI.getType()) {
832
Constant *ZC = ConstantExpr::getZExt(C, CI.getType());
833
Value *NewAnd = Builder->CreateAnd(TI0, ZC, "tmp");
834
return BinaryOperator::CreateXor(NewAnd, ZC);
838
// zext (xor i1 X, true) to i32 --> xor (zext i1 X to i32), 1
840
if (SrcI && SrcI->hasOneUse() && SrcI->getType()->isIntegerTy(1) &&
841
match(SrcI, m_Not(m_Value(X))) &&
842
(!X->hasOneUse() || !isa<CmpInst>(X))) {
843
Value *New = Builder->CreateZExt(X, CI.getType());
844
return BinaryOperator::CreateXor(New, ConstantInt::get(CI.getType(), 1));
850
/// CanEvaluateSExtd - Return true if we can take the specified value
851
/// and return it as type Ty without inserting any new casts and without
852
/// changing the value of the common low bits. This is used by code that tries
853
/// to promote integer operations to a wider types will allow us to eliminate
856
/// This function works on both vectors and scalars.
858
static bool CanEvaluateSExtd(Value *V, const Type *Ty) {
859
assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() &&
860
"Can't sign extend type to a smaller type");
861
// If this is a constant, it can be trivially promoted.
862
if (isa<Constant>(V))
865
Instruction *I = dyn_cast<Instruction>(V);
866
if (!I) return false;
868
// If this is a truncate from the dest type, we can trivially eliminate it,
869
// even if it has multiple uses.
870
// FIXME: This is currently disabled until codegen can handle this without
871
// pessimizing code, PR5997.
872
if (0 && isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty)
875
// We can't extend or shrink something that has multiple uses: doing so would
876
// require duplicating the instruction in general, which isn't profitable.
877
if (!I->hasOneUse()) return false;
879
switch (I->getOpcode()) {
880
case Instruction::SExt: // sext(sext(x)) -> sext(x)
881
case Instruction::ZExt: // sext(zext(x)) -> zext(x)
882
case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x)
884
case Instruction::And:
885
case Instruction::Or:
886
case Instruction::Xor:
887
case Instruction::Add:
888
case Instruction::Sub:
889
case Instruction::Mul:
890
// These operators can all arbitrarily be extended if their inputs can.
891
return CanEvaluateSExtd(I->getOperand(0), Ty) &&
892
CanEvaluateSExtd(I->getOperand(1), Ty);
894
//case Instruction::Shl: TODO
895
//case Instruction::LShr: TODO
897
case Instruction::Select:
898
return CanEvaluateSExtd(I->getOperand(1), Ty) &&
899
CanEvaluateSExtd(I->getOperand(2), Ty);
901
case Instruction::PHI: {
902
// We can change a phi if we can change all operands. Note that we never
903
// get into trouble with cyclic PHIs here because we only consider
904
// instructions with a single use.
905
PHINode *PN = cast<PHINode>(I);
906
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
907
if (!CanEvaluateSExtd(PN->getIncomingValue(i), Ty)) return false;
911
// TODO: Can handle more cases here.
918
Instruction *InstCombiner::visitSExt(SExtInst &CI) {
919
// If this sign extend is only used by a truncate, let the truncate by
920
// eliminated before we try to optimize this zext.
921
if (CI.hasOneUse() && isa<TruncInst>(CI.use_back()))
924
if (Instruction *I = commonCastTransforms(CI))
927
// See if we can simplify any instructions used by the input whose sole
928
// purpose is to compute bits we don't care about.
929
if (SimplifyDemandedInstructionBits(CI))
932
Value *Src = CI.getOperand(0);
933
const Type *SrcTy = Src->getType(), *DestTy = CI.getType();
935
// Attempt to extend the entire input expression tree to the destination
936
// type. Only do this if the dest type is a simple type, don't convert the
937
// expression tree to something weird like i93 unless the source is also
939
if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
940
CanEvaluateSExtd(Src, DestTy)) {
941
// Okay, we can transform this! Insert the new expression now.
942
DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
943
" to avoid sign extend: " << CI);
944
Value *Res = EvaluateInDifferentType(Src, DestTy, true);
945
assert(Res->getType() == DestTy);
947
uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
948
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
950
// If the high bits are already filled with sign bit, just replace this
951
// cast with the result.
952
if (ComputeNumSignBits(Res) > DestBitSize - SrcBitSize)
953
return ReplaceInstUsesWith(CI, Res);
955
// We need to emit a shl + ashr to do the sign extend.
956
Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize);
957
return BinaryOperator::CreateAShr(Builder->CreateShl(Res, ShAmt, "sext"),
961
// If this input is a trunc from our destination, then turn sext(trunc(x))
963
if (TruncInst *TI = dyn_cast<TruncInst>(Src))
964
if (TI->hasOneUse() && TI->getOperand(0)->getType() == DestTy) {
965
uint32_t SrcBitSize = SrcTy->getScalarSizeInBits();
966
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
968
// We need to emit a shl + ashr to do the sign extend.
969
Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize);
970
Value *Res = Builder->CreateShl(TI->getOperand(0), ShAmt, "sext");
971
return BinaryOperator::CreateAShr(Res, ShAmt);
975
// (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed
976
// (x >s -1) ? -1 : 0 -> ashr x, 31 -> all ones if not signed
978
ICmpInst::Predicate Pred; Value *CmpLHS; ConstantInt *CmpRHS;
979
if (match(Src, m_ICmp(Pred, m_Value(CmpLHS), m_ConstantInt(CmpRHS)))) {
980
// sext (x <s 0) to i32 --> x>>s31 true if signbit set.
981
// sext (x >s -1) to i32 --> (x>>s31)^-1 true if signbit clear.
982
if ((Pred == ICmpInst::ICMP_SLT && CmpRHS->isZero()) ||
983
(Pred == ICmpInst::ICMP_SGT && CmpRHS->isAllOnesValue())) {
984
Value *Sh = ConstantInt::get(CmpLHS->getType(),
985
CmpLHS->getType()->getScalarSizeInBits()-1);
986
Value *In = Builder->CreateAShr(CmpLHS, Sh, CmpLHS->getName()+".lobit");
987
if (In->getType() != CI.getType())
988
In = Builder->CreateIntCast(In, CI.getType(), true/*SExt*/, "tmp");
990
if (Pred == ICmpInst::ICMP_SGT)
991
In = Builder->CreateNot(In, In->getName()+".not");
992
return ReplaceInstUsesWith(CI, In);
998
// If the input is a shl/ashr pair of a same constant, then this is a sign
999
// extension from a smaller value. If we could trust arbitrary bitwidth
1000
// integers, we could turn this into a truncate to the smaller bit and then
1001
// use a sext for the whole extension. Since we don't, look deeper and check
1002
// for a truncate. If the source and dest are the same type, eliminate the
1003
// trunc and extend and just do shifts. For example, turn:
1004
// %a = trunc i32 %i to i8
1005
// %b = shl i8 %a, 6
1006
// %c = ashr i8 %b, 6
1007
// %d = sext i8 %c to i32
1009
// %a = shl i32 %i, 30
1010
// %d = ashr i32 %a, 30
1012
// TODO: Eventually this could be subsumed by EvaluateInDifferentType.
1013
ConstantInt *BA = 0, *CA = 0;
1014
if (match(Src, m_AShr(m_Shl(m_Trunc(m_Value(A)), m_ConstantInt(BA)),
1015
m_ConstantInt(CA))) &&
1016
BA == CA && A->getType() == CI.getType()) {
1017
unsigned MidSize = Src->getType()->getScalarSizeInBits();
1018
unsigned SrcDstSize = CI.getType()->getScalarSizeInBits();
1019
unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize;
1020
Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt);
1021
A = Builder->CreateShl(A, ShAmtV, CI.getName());
1022
return BinaryOperator::CreateAShr(A, ShAmtV);
1029
/// FitsInFPType - Return a Constant* for the specified FP constant if it fits
1030
/// in the specified FP type without changing its value.
1031
static Constant *FitsInFPType(ConstantFP *CFP, const fltSemantics &Sem) {
1033
APFloat F = CFP->getValueAPF();
1034
(void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo);
1036
return ConstantFP::get(CFP->getContext(), F);
1040
/// LookThroughFPExtensions - If this is an fp extension instruction, look
1041
/// through it until we get the source value.
1042
static Value *LookThroughFPExtensions(Value *V) {
1043
if (Instruction *I = dyn_cast<Instruction>(V))
1044
if (I->getOpcode() == Instruction::FPExt)
1045
return LookThroughFPExtensions(I->getOperand(0));
1047
// If this value is a constant, return the constant in the smallest FP type
1048
// that can accurately represent it. This allows us to turn
1049
// (float)((double)X+2.0) into x+2.0f.
1050
if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
1051
if (CFP->getType() == Type::getPPC_FP128Ty(V->getContext()))
1052
return V; // No constant folding of this.
1053
// See if the value can be truncated to float and then reextended.
1054
if (Value *V = FitsInFPType(CFP, APFloat::IEEEsingle))
1056
if (CFP->getType()->isDoubleTy())
1057
return V; // Won't shrink.
1058
if (Value *V = FitsInFPType(CFP, APFloat::IEEEdouble))
1060
// Don't try to shrink to various long double types.
1066
Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
1067
if (Instruction *I = commonCastTransforms(CI))
1070
// If we have fptrunc(fadd (fpextend x), (fpextend y)), where x and y are
1071
// smaller than the destination type, we can eliminate the truncate by doing
1072
// the add as the smaller type. This applies to fadd/fsub/fmul/fdiv as well
1073
// as many builtins (sqrt, etc).
1074
BinaryOperator *OpI = dyn_cast<BinaryOperator>(CI.getOperand(0));
1075
if (OpI && OpI->hasOneUse()) {
1076
switch (OpI->getOpcode()) {
1078
case Instruction::FAdd:
1079
case Instruction::FSub:
1080
case Instruction::FMul:
1081
case Instruction::FDiv:
1082
case Instruction::FRem:
1083
const Type *SrcTy = OpI->getType();
1084
Value *LHSTrunc = LookThroughFPExtensions(OpI->getOperand(0));
1085
Value *RHSTrunc = LookThroughFPExtensions(OpI->getOperand(1));
1086
if (LHSTrunc->getType() != SrcTy &&
1087
RHSTrunc->getType() != SrcTy) {
1088
unsigned DstSize = CI.getType()->getScalarSizeInBits();
1089
// If the source types were both smaller than the destination type of
1090
// the cast, do this xform.
1091
if (LHSTrunc->getType()->getScalarSizeInBits() <= DstSize &&
1092
RHSTrunc->getType()->getScalarSizeInBits() <= DstSize) {
1093
LHSTrunc = Builder->CreateFPExt(LHSTrunc, CI.getType());
1094
RHSTrunc = Builder->CreateFPExt(RHSTrunc, CI.getType());
1095
return BinaryOperator::Create(OpI->getOpcode(), LHSTrunc, RHSTrunc);
1104
Instruction *InstCombiner::visitFPExt(CastInst &CI) {
1105
return commonCastTransforms(CI);
1108
Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) {
1109
Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
1111
return commonCastTransforms(FI);
1113
// fptoui(uitofp(X)) --> X
1114
// fptoui(sitofp(X)) --> X
1115
// This is safe if the intermediate type has enough bits in its mantissa to
1116
// accurately represent all values of X. For example, do not do this with
1117
// i64->float->i64. This is also safe for sitofp case, because any negative
1118
// 'X' value would cause an undefined result for the fptoui.
1119
if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) &&
1120
OpI->getOperand(0)->getType() == FI.getType() &&
1121
(int)FI.getType()->getScalarSizeInBits() < /*extra bit for sign */
1122
OpI->getType()->getFPMantissaWidth())
1123
return ReplaceInstUsesWith(FI, OpI->getOperand(0));
1125
return commonCastTransforms(FI);
1128
Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) {
1129
Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0));
1131
return commonCastTransforms(FI);
1133
// fptosi(sitofp(X)) --> X
1134
// fptosi(uitofp(X)) --> X
1135
// This is safe if the intermediate type has enough bits in its mantissa to
1136
// accurately represent all values of X. For example, do not do this with
1137
// i64->float->i64. This is also safe for sitofp case, because any negative
1138
// 'X' value would cause an undefined result for the fptoui.
1139
if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) &&
1140
OpI->getOperand(0)->getType() == FI.getType() &&
1141
(int)FI.getType()->getScalarSizeInBits() <=
1142
OpI->getType()->getFPMantissaWidth())
1143
return ReplaceInstUsesWith(FI, OpI->getOperand(0));
1145
return commonCastTransforms(FI);
1148
Instruction *InstCombiner::visitUIToFP(CastInst &CI) {
1149
return commonCastTransforms(CI);
1152
Instruction *InstCombiner::visitSIToFP(CastInst &CI) {
1153
return commonCastTransforms(CI);
1156
Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
1157
// If the source integer type is not the intptr_t type for this target, do a
1158
// trunc or zext to the intptr_t type, then inttoptr of it. This allows the
1159
// cast to be exposed to other transforms.
1161
if (CI.getOperand(0)->getType()->getScalarSizeInBits() >
1162
TD->getPointerSizeInBits()) {
1163
Value *P = Builder->CreateTrunc(CI.getOperand(0),
1164
TD->getIntPtrType(CI.getContext()), "tmp");
1165
return new IntToPtrInst(P, CI.getType());
1167
if (CI.getOperand(0)->getType()->getScalarSizeInBits() <
1168
TD->getPointerSizeInBits()) {
1169
Value *P = Builder->CreateZExt(CI.getOperand(0),
1170
TD->getIntPtrType(CI.getContext()), "tmp");
1171
return new IntToPtrInst(P, CI.getType());
1175
if (Instruction *I = commonCastTransforms(CI))
1181
/// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint)
1182
Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
1183
Value *Src = CI.getOperand(0);
1185
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1186
// If casting the result of a getelementptr instruction with no offset, turn
1187
// this into a cast of the original pointer!
1188
if (GEP->hasAllZeroIndices()) {
1189
// Changing the cast operand is usually not a good idea but it is safe
1190
// here because the pointer operand is being replaced with another
1191
// pointer operand so the opcode doesn't need to change.
1193
CI.setOperand(0, GEP->getOperand(0));
1197
// If the GEP has a single use, and the base pointer is a bitcast, and the
1198
// GEP computes a constant offset, see if we can convert these three
1199
// instructions into fewer. This typically happens with unions and other
1200
// non-type-safe code.
1201
if (TD && GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0)) &&
1202
GEP->hasAllConstantIndices()) {
1203
// We are guaranteed to get a constant from EmitGEPOffset.
1204
ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(GEP));
1205
int64_t Offset = OffsetV->getSExtValue();
1207
// Get the base pointer input of the bitcast, and the type it points to.
1208
Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0);
1209
const Type *GEPIdxTy =
1210
cast<PointerType>(OrigBase->getType())->getElementType();
1211
SmallVector<Value*, 8> NewIndices;
1212
if (FindElementAtOffset(GEPIdxTy, Offset, NewIndices)) {
1213
// If we were able to index down into an element, create the GEP
1214
// and bitcast the result. This eliminates one bitcast, potentially
1216
Value *NGEP = cast<GEPOperator>(GEP)->isInBounds() ?
1217
Builder->CreateInBoundsGEP(OrigBase,
1218
NewIndices.begin(), NewIndices.end()) :
1219
Builder->CreateGEP(OrigBase, NewIndices.begin(), NewIndices.end());
1220
NGEP->takeName(GEP);
1222
if (isa<BitCastInst>(CI))
1223
return new BitCastInst(NGEP, CI.getType());
1224
assert(isa<PtrToIntInst>(CI));
1225
return new PtrToIntInst(NGEP, CI.getType());
1230
return commonCastTransforms(CI);
1233
Instruction *InstCombiner::visitPtrToInt(PtrToIntInst &CI) {
1234
// If the destination integer type is not the intptr_t type for this target,
1235
// do a ptrtoint to intptr_t then do a trunc or zext. This allows the cast
1236
// to be exposed to other transforms.
1238
if (CI.getType()->getScalarSizeInBits() < TD->getPointerSizeInBits()) {
1239
Value *P = Builder->CreatePtrToInt(CI.getOperand(0),
1240
TD->getIntPtrType(CI.getContext()),
1242
return new TruncInst(P, CI.getType());
1244
if (CI.getType()->getScalarSizeInBits() > TD->getPointerSizeInBits()) {
1245
Value *P = Builder->CreatePtrToInt(CI.getOperand(0),
1246
TD->getIntPtrType(CI.getContext()),
1248
return new ZExtInst(P, CI.getType());
1252
return commonPointerCastTransforms(CI);
1255
Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
1256
// If the operands are integer typed then apply the integer transforms,
1257
// otherwise just apply the common ones.
1258
Value *Src = CI.getOperand(0);
1259
const Type *SrcTy = Src->getType();
1260
const Type *DestTy = CI.getType();
1262
// Get rid of casts from one type to the same type. These are useless and can
1263
// be replaced by the operand.
1264
if (DestTy == Src->getType())
1265
return ReplaceInstUsesWith(CI, Src);
1267
if (const PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) {
1268
const PointerType *SrcPTy = cast<PointerType>(SrcTy);
1269
const Type *DstElTy = DstPTy->getElementType();
1270
const Type *SrcElTy = SrcPTy->getElementType();
1272
// If the address spaces don't match, don't eliminate the bitcast, which is
1273
// required for changing types.
1274
if (SrcPTy->getAddressSpace() != DstPTy->getAddressSpace())
1277
// If we are casting a alloca to a pointer to a type of the same
1278
// size, rewrite the allocation instruction to allocate the "right" type.
1279
// There is no need to modify malloc calls because it is their bitcast that
1280
// needs to be cleaned up.
1281
if (AllocaInst *AI = dyn_cast<AllocaInst>(Src))
1282
if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
1285
// If the source and destination are pointers, and this cast is equivalent
1286
// to a getelementptr X, 0, 0, 0... turn it into the appropriate gep.
1287
// This can enhance SROA and other transforms that want type-safe pointers.
1288
Constant *ZeroUInt =
1289
Constant::getNullValue(Type::getInt32Ty(CI.getContext()));
1290
unsigned NumZeros = 0;
1291
while (SrcElTy != DstElTy &&
1292
isa<CompositeType>(SrcElTy) && !SrcElTy->isPointerTy() &&
1293
SrcElTy->getNumContainedTypes() /* not "{}" */) {
1294
SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(ZeroUInt);
1298
// If we found a path from the src to dest, create the getelementptr now.
1299
if (SrcElTy == DstElTy) {
1300
SmallVector<Value*, 8> Idxs(NumZeros+1, ZeroUInt);
1301
return GetElementPtrInst::CreateInBounds(Src, Idxs.begin(), Idxs.end(),"",
1302
((Instruction*)NULL));
1306
if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
1307
if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) {
1308
Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType());
1309
return InsertElementInst::Create(UndefValue::get(DestTy), Elem,
1310
Constant::getNullValue(Type::getInt32Ty(CI.getContext())));
1311
// FIXME: Canonicalize bitcast(insertelement) -> insertelement(bitcast)
1315
if (const VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) {
1316
if (SrcVTy->getNumElements() == 1 && !DestTy->isVectorTy()) {
1318
Builder->CreateExtractElement(Src,
1319
Constant::getNullValue(Type::getInt32Ty(CI.getContext())));
1320
return CastInst::Create(Instruction::BitCast, Elem, DestTy);
1324
if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(Src)) {
1325
// Okay, we have (bitcast (shuffle ..)). Check to see if this is
1326
// a bitconvert to a vector with the same # elts.
1327
if (SVI->hasOneUse() && DestTy->isVectorTy() &&
1328
cast<VectorType>(DestTy)->getNumElements() ==
1329
SVI->getType()->getNumElements() &&
1330
SVI->getType()->getNumElements() ==
1331
cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements()) {
1333
// If either of the operands is a cast from CI.getType(), then
1334
// evaluating the shuffle in the casted destination's type will allow
1335
// us to eliminate at least one cast.
1336
if (((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(0))) &&
1337
Tmp->getOperand(0)->getType() == DestTy) ||
1338
((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(1))) &&
1339
Tmp->getOperand(0)->getType() == DestTy)) {
1340
Value *LHS = Builder->CreateBitCast(SVI->getOperand(0), DestTy);
1341
Value *RHS = Builder->CreateBitCast(SVI->getOperand(1), DestTy);
1342
// Return a new shuffle vector. Use the same element ID's, as we
1343
// know the vector types match #elts.
1344
return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2));
1349
if (SrcTy->isPointerTy())
1350
return commonPointerCastTransforms(CI);
1351
return commonCastTransforms(CI);
added
removed
libclamav/c++/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
