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1286 lines
52 KiB
C++
1286 lines
52 KiB
C++
//===- InstCombineSimplifyDemanded.cpp ------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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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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//===----------------------------------------------------------------------===//
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//
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// This file contains logic for simplifying instructions based on information
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// about how they are used.
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//
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//===----------------------------------------------------------------------===//
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#include "InstCombine.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/Support/PatternMatch.h"
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using namespace llvm;
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using namespace llvm::PatternMatch;
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/// ShrinkDemandedConstant - Check to see if the specified operand of the
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/// specified instruction is a constant integer. If so, check to see if there
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/// are any bits set in the constant that are not demanded. If so, shrink the
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/// constant and return true.
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static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
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APInt Demanded) {
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assert(I && "No instruction?");
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assert(OpNo < I->getNumOperands() && "Operand index too large");
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// If the operand is not a constant integer, nothing to do.
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ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
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if (!OpC) return false;
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// If there are no bits set that aren't demanded, nothing to do.
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Demanded = Demanded.zextOrTrunc(OpC->getValue().getBitWidth());
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if ((~Demanded & OpC->getValue()) == 0)
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return false;
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// This instruction is producing bits that are not demanded. Shrink the RHS.
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Demanded &= OpC->getValue();
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I->setOperand(OpNo, ConstantInt::get(OpC->getType(), Demanded));
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return true;
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}
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/// SimplifyDemandedInstructionBits - Inst is an integer instruction that
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/// SimplifyDemandedBits knows about. See if the instruction has any
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/// properties that allow us to simplify its operands.
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bool InstCombiner::SimplifyDemandedInstructionBits(Instruction &Inst) {
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unsigned BitWidth = Inst.getType()->getScalarSizeInBits();
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APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
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APInt DemandedMask(APInt::getAllOnesValue(BitWidth));
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Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask,
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KnownZero, KnownOne, 0);
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if (V == 0) return false;
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if (V == &Inst) return true;
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ReplaceInstUsesWith(Inst, V);
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return true;
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}
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/// SimplifyDemandedBits - This form of SimplifyDemandedBits simplifies the
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/// specified instruction operand if possible, updating it in place. It returns
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/// true if it made any change and false otherwise.
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bool InstCombiner::SimplifyDemandedBits(Use &U, APInt DemandedMask,
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APInt &KnownZero, APInt &KnownOne,
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unsigned Depth) {
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Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask,
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KnownZero, KnownOne, Depth);
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if (NewVal == 0) return false;
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U = NewVal;
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return true;
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}
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/// SimplifyDemandedUseBits - This function attempts to replace V with a simpler
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/// value based on the demanded bits. When this function is called, it is known
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/// that only the bits set in DemandedMask of the result of V are ever used
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/// downstream. Consequently, depending on the mask and V, it may be possible
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/// to replace V with a constant or one of its operands. In such cases, this
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/// function does the replacement and returns true. In all other cases, it
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/// returns false after analyzing the expression and setting KnownOne and known
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/// to be one in the expression. KnownZero contains all the bits that are known
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/// to be zero in the expression. These are provided to potentially allow the
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/// caller (which might recursively be SimplifyDemandedBits itself) to simplify
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/// the expression. KnownOne and KnownZero always follow the invariant that
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/// KnownOne & KnownZero == 0. That is, a bit can't be both 1 and 0. Note that
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/// the bits in KnownOne and KnownZero may only be accurate for those bits set
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/// in DemandedMask. Note also that the bitwidth of V, DemandedMask, KnownZero
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/// and KnownOne must all be the same.
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///
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/// This returns null if it did not change anything and it permits no
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/// simplification. This returns V itself if it did some simplification of V's
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/// operands based on the information about what bits are demanded. This returns
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/// some other non-null value if it found out that V is equal to another value
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/// in the context where the specified bits are demanded, but not for all users.
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Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
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APInt &KnownZero, APInt &KnownOne,
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unsigned Depth) {
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assert(V != 0 && "Null pointer of Value???");
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assert(Depth <= 6 && "Limit Search Depth");
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uint32_t BitWidth = DemandedMask.getBitWidth();
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Type *VTy = V->getType();
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assert((TD || !VTy->isPointerTy()) &&
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"SimplifyDemandedBits needs to know bit widths!");
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assert((!TD || TD->getTypeSizeInBits(VTy->getScalarType()) == BitWidth) &&
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(!VTy->isIntOrIntVectorTy() ||
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VTy->getScalarSizeInBits() == BitWidth) &&
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KnownZero.getBitWidth() == BitWidth &&
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KnownOne.getBitWidth() == BitWidth &&
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"Value *V, DemandedMask, KnownZero and KnownOne "
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"must have same BitWidth");
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
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// We know all of the bits for a constant!
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KnownOne = CI->getValue() & DemandedMask;
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KnownZero = ~KnownOne & DemandedMask;
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return 0;
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}
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if (isa<ConstantPointerNull>(V)) {
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// We know all of the bits for a constant!
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KnownOne.clearAllBits();
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KnownZero = DemandedMask;
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return 0;
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}
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KnownZero.clearAllBits();
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KnownOne.clearAllBits();
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if (DemandedMask == 0) { // Not demanding any bits from V.
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if (isa<UndefValue>(V))
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return 0;
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return UndefValue::get(VTy);
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}
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if (Depth == 6) // Limit search depth.
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return 0;
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APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
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APInt RHSKnownZero(BitWidth, 0), RHSKnownOne(BitWidth, 0);
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I) {
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ComputeMaskedBits(V, KnownZero, KnownOne, Depth);
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return 0; // Only analyze instructions.
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}
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// If there are multiple uses of this value and we aren't at the root, then
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// we can't do any simplifications of the operands, because DemandedMask
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// only reflects the bits demanded by *one* of the users.
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if (Depth != 0 && !I->hasOneUse()) {
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// Despite the fact that we can't simplify this instruction in all User's
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// context, we can at least compute the knownzero/knownone bits, and we can
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// do simplifications that apply to *just* the one user if we know that
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// this instruction has a simpler value in that context.
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if (I->getOpcode() == Instruction::And) {
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// If either the LHS or the RHS are Zero, the result is zero.
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ComputeMaskedBits(I->getOperand(1), RHSKnownZero, RHSKnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1);
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// If all of the demanded bits are known 1 on one side, return the other.
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// These bits cannot contribute to the result of the 'and' in this
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// context.
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if ((DemandedMask & ~LHSKnownZero & RHSKnownOne) ==
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(DemandedMask & ~LHSKnownZero))
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return I->getOperand(0);
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if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) ==
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(DemandedMask & ~RHSKnownZero))
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return I->getOperand(1);
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// If all of the demanded bits in the inputs are known zeros, return zero.
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if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask)
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return Constant::getNullValue(VTy);
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} else if (I->getOpcode() == Instruction::Or) {
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// We can simplify (X|Y) -> X or Y in the user's context if we know that
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// only bits from X or Y are demanded.
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// If either the LHS or the RHS are One, the result is One.
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ComputeMaskedBits(I->getOperand(1), RHSKnownZero, RHSKnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1);
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// If all of the demanded bits are known zero on one side, return the
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// other. These bits cannot contribute to the result of the 'or' in this
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// context.
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if ((DemandedMask & ~LHSKnownOne & RHSKnownZero) ==
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(DemandedMask & ~LHSKnownOne))
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return I->getOperand(0);
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if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) ==
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(DemandedMask & ~RHSKnownOne))
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return I->getOperand(1);
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// If all of the potentially set bits on one side are known to be set on
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// the other side, just use the 'other' side.
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if ((DemandedMask & (~RHSKnownZero) & LHSKnownOne) ==
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(DemandedMask & (~RHSKnownZero)))
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return I->getOperand(0);
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if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) ==
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(DemandedMask & (~LHSKnownZero)))
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return I->getOperand(1);
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} else if (I->getOpcode() == Instruction::Xor) {
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// We can simplify (X^Y) -> X or Y in the user's context if we know that
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// only bits from X or Y are demanded.
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ComputeMaskedBits(I->getOperand(1), RHSKnownZero, RHSKnownOne, Depth+1);
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ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1);
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// If all of the demanded bits are known zero on one side, return the
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// other.
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if ((DemandedMask & RHSKnownZero) == DemandedMask)
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return I->getOperand(0);
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if ((DemandedMask & LHSKnownZero) == DemandedMask)
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return I->getOperand(1);
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}
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// Compute the KnownZero/KnownOne bits to simplify things downstream.
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ComputeMaskedBits(I, KnownZero, KnownOne, Depth);
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return 0;
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}
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// If this is the root being simplified, allow it to have multiple uses,
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// just set the DemandedMask to all bits so that we can try to simplify the
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// operands. This allows visitTruncInst (for example) to simplify the
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// operand of a trunc without duplicating all the logic below.
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if (Depth == 0 && !V->hasOneUse())
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DemandedMask = APInt::getAllOnesValue(BitWidth);
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switch (I->getOpcode()) {
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default:
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ComputeMaskedBits(I, KnownZero, KnownOne, Depth);
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break;
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case Instruction::And:
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// If either the LHS or the RHS are Zero, the result is zero.
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if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
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RHSKnownZero, RHSKnownOne, Depth+1) ||
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SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownZero,
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LHSKnownZero, LHSKnownOne, Depth+1))
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return I;
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assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
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assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
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// If all of the demanded bits are known 1 on one side, return the other.
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// These bits cannot contribute to the result of the 'and'.
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if ((DemandedMask & ~LHSKnownZero & RHSKnownOne) ==
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(DemandedMask & ~LHSKnownZero))
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return I->getOperand(0);
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if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) ==
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(DemandedMask & ~RHSKnownZero))
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return I->getOperand(1);
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// If all of the demanded bits in the inputs are known zeros, return zero.
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if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask)
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return Constant::getNullValue(VTy);
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// If the RHS is a constant, see if we can simplify it.
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if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnownZero))
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return I;
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// Output known-1 bits are only known if set in both the LHS & RHS.
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KnownOne = RHSKnownOne & LHSKnownOne;
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// Output known-0 are known to be clear if zero in either the LHS | RHS.
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KnownZero = RHSKnownZero | LHSKnownZero;
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break;
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case Instruction::Or:
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// If either the LHS or the RHS are One, the result is One.
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if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
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RHSKnownZero, RHSKnownOne, Depth+1) ||
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SimplifyDemandedBits(I->getOperandUse(0), DemandedMask & ~RHSKnownOne,
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LHSKnownZero, LHSKnownOne, Depth+1))
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return I;
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assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
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assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
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// If all of the demanded bits are known zero on one side, return the other.
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// These bits cannot contribute to the result of the 'or'.
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if ((DemandedMask & ~LHSKnownOne & RHSKnownZero) ==
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(DemandedMask & ~LHSKnownOne))
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return I->getOperand(0);
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if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) ==
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(DemandedMask & ~RHSKnownOne))
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return I->getOperand(1);
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// If all of the potentially set bits on one side are known to be set on
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// the other side, just use the 'other' side.
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if ((DemandedMask & (~RHSKnownZero) & LHSKnownOne) ==
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(DemandedMask & (~RHSKnownZero)))
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return I->getOperand(0);
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if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) ==
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(DemandedMask & (~LHSKnownZero)))
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return I->getOperand(1);
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// If the RHS is a constant, see if we can simplify it.
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if (ShrinkDemandedConstant(I, 1, DemandedMask))
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return I;
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// Output known-0 bits are only known if clear in both the LHS & RHS.
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KnownZero = RHSKnownZero & LHSKnownZero;
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// Output known-1 are known to be set if set in either the LHS | RHS.
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KnownOne = RHSKnownOne | LHSKnownOne;
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break;
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case Instruction::Xor: {
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if (SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
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RHSKnownZero, RHSKnownOne, Depth+1) ||
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SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
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LHSKnownZero, LHSKnownOne, Depth+1))
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return I;
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assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
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assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
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// If all of the demanded bits are known zero on one side, return the other.
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// These bits cannot contribute to the result of the 'xor'.
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if ((DemandedMask & RHSKnownZero) == DemandedMask)
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return I->getOperand(0);
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if ((DemandedMask & LHSKnownZero) == DemandedMask)
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return I->getOperand(1);
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// If all of the demanded bits are known to be zero on one side or the
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// other, turn this into an *inclusive* or.
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// e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
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if ((DemandedMask & ~RHSKnownZero & ~LHSKnownZero) == 0) {
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Instruction *Or =
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BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1),
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I->getName());
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return InsertNewInstWith(Or, *I);
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}
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// If all of the demanded bits on one side are known, and all of the set
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// bits on that side are also known to be set on the other side, turn this
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// into an AND, as we know the bits will be cleared.
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// e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
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if ((DemandedMask & (RHSKnownZero|RHSKnownOne)) == DemandedMask) {
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// all known
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if ((RHSKnownOne & LHSKnownOne) == RHSKnownOne) {
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Constant *AndC = Constant::getIntegerValue(VTy,
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~RHSKnownOne & DemandedMask);
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Instruction *And = BinaryOperator::CreateAnd(I->getOperand(0), AndC);
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return InsertNewInstWith(And, *I);
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}
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}
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// If the RHS is a constant, see if we can simplify it.
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// FIXME: for XOR, we prefer to force bits to 1 if they will make a -1.
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if (ShrinkDemandedConstant(I, 1, DemandedMask))
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return I;
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// If our LHS is an 'and' and if it has one use, and if any of the bits we
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// are flipping are known to be set, then the xor is just resetting those
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// bits to zero. We can just knock out bits from the 'and' and the 'xor',
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// simplifying both of them.
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if (Instruction *LHSInst = dyn_cast<Instruction>(I->getOperand(0)))
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if (LHSInst->getOpcode() == Instruction::And && LHSInst->hasOneUse() &&
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isa<ConstantInt>(I->getOperand(1)) &&
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isa<ConstantInt>(LHSInst->getOperand(1)) &&
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(LHSKnownOne & RHSKnownOne & DemandedMask) != 0) {
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ConstantInt *AndRHS = cast<ConstantInt>(LHSInst->getOperand(1));
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ConstantInt *XorRHS = cast<ConstantInt>(I->getOperand(1));
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APInt NewMask = ~(LHSKnownOne & RHSKnownOne & DemandedMask);
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Constant *AndC =
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ConstantInt::get(I->getType(), NewMask & AndRHS->getValue());
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Instruction *NewAnd = BinaryOperator::CreateAnd(I->getOperand(0), AndC);
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InsertNewInstWith(NewAnd, *I);
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Constant *XorC =
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ConstantInt::get(I->getType(), NewMask & XorRHS->getValue());
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Instruction *NewXor = BinaryOperator::CreateXor(NewAnd, XorC);
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return InsertNewInstWith(NewXor, *I);
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}
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// Output known-0 bits are known if clear or set in both the LHS & RHS.
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KnownZero= (RHSKnownZero & LHSKnownZero) | (RHSKnownOne & LHSKnownOne);
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// Output known-1 are known to be set if set in only one of the LHS, RHS.
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KnownOne = (RHSKnownZero & LHSKnownOne) | (RHSKnownOne & LHSKnownZero);
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break;
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}
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case Instruction::Select:
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if (SimplifyDemandedBits(I->getOperandUse(2), DemandedMask,
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RHSKnownZero, RHSKnownOne, Depth+1) ||
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SimplifyDemandedBits(I->getOperandUse(1), DemandedMask,
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LHSKnownZero, LHSKnownOne, Depth+1))
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return I;
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assert(!(RHSKnownZero & RHSKnownOne) && "Bits known to be one AND zero?");
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assert(!(LHSKnownZero & LHSKnownOne) && "Bits known to be one AND zero?");
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// If the operands are constants, see if we can simplify them.
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if (ShrinkDemandedConstant(I, 1, DemandedMask) ||
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ShrinkDemandedConstant(I, 2, DemandedMask))
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return I;
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// Only known if known in both the LHS and RHS.
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KnownOne = RHSKnownOne & LHSKnownOne;
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KnownZero = RHSKnownZero & LHSKnownZero;
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break;
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case Instruction::Trunc: {
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unsigned truncBf = I->getOperand(0)->getType()->getScalarSizeInBits();
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DemandedMask = DemandedMask.zext(truncBf);
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KnownZero = KnownZero.zext(truncBf);
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KnownOne = KnownOne.zext(truncBf);
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if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
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KnownZero, KnownOne, Depth+1))
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return I;
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DemandedMask = DemandedMask.trunc(BitWidth);
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KnownZero = KnownZero.trunc(BitWidth);
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KnownOne = KnownOne.trunc(BitWidth);
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assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
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break;
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}
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case Instruction::BitCast:
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if (!I->getOperand(0)->getType()->isIntOrIntVectorTy())
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return 0; // vector->int or fp->int?
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|
|
if (VectorType *DstVTy = dyn_cast<VectorType>(I->getType())) {
|
|
if (VectorType *SrcVTy =
|
|
dyn_cast<VectorType>(I->getOperand(0)->getType())) {
|
|
if (DstVTy->getNumElements() != SrcVTy->getNumElements())
|
|
// Don't touch a bitcast between vectors of different element counts.
|
|
return 0;
|
|
} else
|
|
// Don't touch a scalar-to-vector bitcast.
|
|
return 0;
|
|
} else if (I->getOperand(0)->getType()->isVectorTy())
|
|
// Don't touch a vector-to-scalar bitcast.
|
|
return 0;
|
|
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
|
|
KnownZero, KnownOne, Depth+1))
|
|
return I;
|
|
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
|
|
break;
|
|
case Instruction::ZExt: {
|
|
// Compute the bits in the result that are not present in the input.
|
|
unsigned SrcBitWidth =I->getOperand(0)->getType()->getScalarSizeInBits();
|
|
|
|
DemandedMask = DemandedMask.trunc(SrcBitWidth);
|
|
KnownZero = KnownZero.trunc(SrcBitWidth);
|
|
KnownOne = KnownOne.trunc(SrcBitWidth);
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMask,
|
|
KnownZero, KnownOne, Depth+1))
|
|
return I;
|
|
DemandedMask = DemandedMask.zext(BitWidth);
|
|
KnownZero = KnownZero.zext(BitWidth);
|
|
KnownOne = KnownOne.zext(BitWidth);
|
|
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
|
|
// The top bits are known to be zero.
|
|
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
|
|
break;
|
|
}
|
|
case Instruction::SExt: {
|
|
// Compute the bits in the result that are not present in the input.
|
|
unsigned SrcBitWidth =I->getOperand(0)->getType()->getScalarSizeInBits();
|
|
|
|
APInt InputDemandedBits = DemandedMask &
|
|
APInt::getLowBitsSet(BitWidth, SrcBitWidth);
|
|
|
|
APInt NewBits(APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth));
|
|
// If any of the sign extended bits are demanded, we know that the sign
|
|
// bit is demanded.
|
|
if ((NewBits & DemandedMask) != 0)
|
|
InputDemandedBits.setBit(SrcBitWidth-1);
|
|
|
|
InputDemandedBits = InputDemandedBits.trunc(SrcBitWidth);
|
|
KnownZero = KnownZero.trunc(SrcBitWidth);
|
|
KnownOne = KnownOne.trunc(SrcBitWidth);
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), InputDemandedBits,
|
|
KnownZero, KnownOne, Depth+1))
|
|
return I;
|
|
InputDemandedBits = InputDemandedBits.zext(BitWidth);
|
|
KnownZero = KnownZero.zext(BitWidth);
|
|
KnownOne = KnownOne.zext(BitWidth);
|
|
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
|
|
|
|
// If the sign bit of the input is known set or clear, then we know the
|
|
// top bits of the result.
|
|
|
|
// If the input sign bit is known zero, or if the NewBits are not demanded
|
|
// convert this into a zero extension.
|
|
if (KnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits) {
|
|
// Convert to ZExt cast
|
|
CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName());
|
|
return InsertNewInstWith(NewCast, *I);
|
|
} else if (KnownOne[SrcBitWidth-1]) { // Input sign bit known set
|
|
KnownOne |= NewBits;
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::Add: {
|
|
// Figure out what the input bits are. If the top bits of the and result
|
|
// are not demanded, then the add doesn't demand them from its input
|
|
// either.
|
|
unsigned NLZ = DemandedMask.countLeadingZeros();
|
|
|
|
// If there is a constant on the RHS, there are a variety of xformations
|
|
// we can do.
|
|
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
|
// If null, this should be simplified elsewhere. Some of the xforms here
|
|
// won't work if the RHS is zero.
|
|
if (RHS->isZero())
|
|
break;
|
|
|
|
// If the top bit of the output is demanded, demand everything from the
|
|
// input. Otherwise, we demand all the input bits except NLZ top bits.
|
|
APInt InDemandedBits(APInt::getLowBitsSet(BitWidth, BitWidth - NLZ));
|
|
|
|
// Find information about known zero/one bits in the input.
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), InDemandedBits,
|
|
LHSKnownZero, LHSKnownOne, Depth+1))
|
|
return I;
|
|
|
|
// If the RHS of the add has bits set that can't affect the input, reduce
|
|
// the constant.
|
|
if (ShrinkDemandedConstant(I, 1, InDemandedBits))
|
|
return I;
|
|
|
|
// Avoid excess work.
|
|
if (LHSKnownZero == 0 && LHSKnownOne == 0)
|
|
break;
|
|
|
|
// Turn it into OR if input bits are zero.
|
|
if ((LHSKnownZero & RHS->getValue()) == RHS->getValue()) {
|
|
Instruction *Or =
|
|
BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1),
|
|
I->getName());
|
|
return InsertNewInstWith(Or, *I);
|
|
}
|
|
|
|
// We can say something about the output known-zero and known-one bits,
|
|
// depending on potential carries from the input constant and the
|
|
// unknowns. For example if the LHS is known to have at most the 0x0F0F0
|
|
// bits set and the RHS constant is 0x01001, then we know we have a known
|
|
// one mask of 0x00001 and a known zero mask of 0xE0F0E.
|
|
|
|
// To compute this, we first compute the potential carry bits. These are
|
|
// the bits which may be modified. I'm not aware of a better way to do
|
|
// this scan.
|
|
const APInt &RHSVal = RHS->getValue();
|
|
APInt CarryBits((~LHSKnownZero + RHSVal) ^ (~LHSKnownZero ^ RHSVal));
|
|
|
|
// Now that we know which bits have carries, compute the known-1/0 sets.
|
|
|
|
// Bits are known one if they are known zero in one operand and one in the
|
|
// other, and there is no input carry.
|
|
KnownOne = ((LHSKnownZero & RHSVal) |
|
|
(LHSKnownOne & ~RHSVal)) & ~CarryBits;
|
|
|
|
// Bits are known zero if they are known zero in both operands and there
|
|
// is no input carry.
|
|
KnownZero = LHSKnownZero & ~RHSVal & ~CarryBits;
|
|
} else {
|
|
// If the high-bits of this ADD are not demanded, then it does not demand
|
|
// the high bits of its LHS or RHS.
|
|
if (DemandedMask[BitWidth-1] == 0) {
|
|
// Right fill the mask of bits for this ADD to demand the most
|
|
// significant bit and all those below it.
|
|
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
|
|
LHSKnownZero, LHSKnownOne, Depth+1) ||
|
|
SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps,
|
|
LHSKnownZero, LHSKnownOne, Depth+1))
|
|
return I;
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::Sub:
|
|
// If the high-bits of this SUB are not demanded, then it does not demand
|
|
// the high bits of its LHS or RHS.
|
|
if (DemandedMask[BitWidth-1] == 0) {
|
|
// Right fill the mask of bits for this SUB to demand the most
|
|
// significant bit and all those below it.
|
|
uint32_t NLZ = DemandedMask.countLeadingZeros();
|
|
APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedFromOps,
|
|
LHSKnownZero, LHSKnownOne, Depth+1) ||
|
|
SimplifyDemandedBits(I->getOperandUse(1), DemandedFromOps,
|
|
LHSKnownZero, LHSKnownOne, Depth+1))
|
|
return I;
|
|
}
|
|
|
|
// Otherwise just hand the sub off to ComputeMaskedBits to fill in
|
|
// the known zeros and ones.
|
|
ComputeMaskedBits(V, KnownZero, KnownOne, Depth);
|
|
|
|
// Turn this into a xor if LHS is 2^n-1 and the remaining bits are known
|
|
// zero.
|
|
if (ConstantInt *C0 = dyn_cast<ConstantInt>(I->getOperand(0))) {
|
|
APInt I0 = C0->getValue();
|
|
if ((I0 + 1).isPowerOf2() && (I0 | KnownZero).isAllOnesValue()) {
|
|
Instruction *Xor = BinaryOperator::CreateXor(I->getOperand(1), C0);
|
|
return InsertNewInstWith(Xor, *I);
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::Shl:
|
|
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
|
{
|
|
Value *VarX; ConstantInt *C1;
|
|
if (match(I->getOperand(0), m_Shr(m_Value(VarX), m_ConstantInt(C1)))) {
|
|
Instruction *Shr = cast<Instruction>(I->getOperand(0));
|
|
Value *R = SimplifyShrShlDemandedBits(Shr, I, DemandedMask,
|
|
KnownZero, KnownOne);
|
|
if (R)
|
|
return R;
|
|
}
|
|
}
|
|
|
|
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
|
|
APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
|
|
|
|
// If the shift is NUW/NSW, then it does demand the high bits.
|
|
ShlOperator *IOp = cast<ShlOperator>(I);
|
|
if (IOp->hasNoSignedWrap())
|
|
DemandedMaskIn |= APInt::getHighBitsSet(BitWidth, ShiftAmt+1);
|
|
else if (IOp->hasNoUnsignedWrap())
|
|
DemandedMaskIn |= APInt::getHighBitsSet(BitWidth, ShiftAmt);
|
|
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
|
|
KnownZero, KnownOne, Depth+1))
|
|
return I;
|
|
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
|
|
KnownZero <<= ShiftAmt;
|
|
KnownOne <<= ShiftAmt;
|
|
// low bits known zero.
|
|
if (ShiftAmt)
|
|
KnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
|
|
}
|
|
break;
|
|
case Instruction::LShr:
|
|
// For a logical shift right
|
|
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
|
uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
|
|
|
|
// Unsigned shift right.
|
|
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
|
|
|
|
// If the shift is exact, then it does demand the low bits (and knows that
|
|
// they are zero).
|
|
if (cast<LShrOperator>(I)->isExact())
|
|
DemandedMaskIn |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
|
|
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
|
|
KnownZero, KnownOne, Depth+1))
|
|
return I;
|
|
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
|
|
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
|
|
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
|
|
if (ShiftAmt) {
|
|
// Compute the new bits that are at the top now.
|
|
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
|
|
KnownZero |= HighBits; // high bits known zero.
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::AShr:
|
|
// If this is an arithmetic shift right and only the low-bit is set, we can
|
|
// always convert this into a logical shr, even if the shift amount is
|
|
// variable. The low bit of the shift cannot be an input sign bit unless
|
|
// the shift amount is >= the size of the datatype, which is undefined.
|
|
if (DemandedMask == 1) {
|
|
// Perform the logical shift right.
|
|
Instruction *NewVal = BinaryOperator::CreateLShr(
|
|
I->getOperand(0), I->getOperand(1), I->getName());
|
|
return InsertNewInstWith(NewVal, *I);
|
|
}
|
|
|
|
// If the sign bit is the only bit demanded by this ashr, then there is no
|
|
// need to do it, the shift doesn't change the high bit.
|
|
if (DemandedMask.isSignBit())
|
|
return I->getOperand(0);
|
|
|
|
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
|
uint32_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
|
|
|
|
// Signed shift right.
|
|
APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
|
|
// If any of the "high bits" are demanded, we should set the sign bit as
|
|
// demanded.
|
|
if (DemandedMask.countLeadingZeros() <= ShiftAmt)
|
|
DemandedMaskIn.setBit(BitWidth-1);
|
|
|
|
// If the shift is exact, then it does demand the low bits (and knows that
|
|
// they are zero).
|
|
if (cast<AShrOperator>(I)->isExact())
|
|
DemandedMaskIn |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
|
|
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), DemandedMaskIn,
|
|
KnownZero, KnownOne, Depth+1))
|
|
return I;
|
|
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
|
|
// Compute the new bits that are at the top now.
|
|
APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
|
|
KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
|
|
KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
|
|
|
|
// Handle the sign bits.
|
|
APInt SignBit(APInt::getSignBit(BitWidth));
|
|
// Adjust to where it is now in the mask.
|
|
SignBit = APIntOps::lshr(SignBit, ShiftAmt);
|
|
|
|
// If the input sign bit is known to be zero, or if none of the top bits
|
|
// are demanded, turn this into an unsigned shift right.
|
|
if (BitWidth <= ShiftAmt || KnownZero[BitWidth-ShiftAmt-1] ||
|
|
(HighBits & ~DemandedMask) == HighBits) {
|
|
// Perform the logical shift right.
|
|
BinaryOperator *NewVal = BinaryOperator::CreateLShr(I->getOperand(0),
|
|
SA, I->getName());
|
|
NewVal->setIsExact(cast<BinaryOperator>(I)->isExact());
|
|
return InsertNewInstWith(NewVal, *I);
|
|
} else if ((KnownOne & SignBit) != 0) { // New bits are known one.
|
|
KnownOne |= HighBits;
|
|
}
|
|
}
|
|
break;
|
|
case Instruction::SRem:
|
|
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
|
|
// X % -1 demands all the bits because we don't want to introduce
|
|
// INT_MIN % -1 (== undef) by accident.
|
|
if (Rem->isAllOnesValue())
|
|
break;
|
|
APInt RA = Rem->getValue().abs();
|
|
if (RA.isPowerOf2()) {
|
|
if (DemandedMask.ult(RA)) // srem won't affect demanded bits
|
|
return I->getOperand(0);
|
|
|
|
APInt LowBits = RA - 1;
|
|
APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), Mask2,
|
|
LHSKnownZero, LHSKnownOne, Depth+1))
|
|
return I;
|
|
|
|
// The low bits of LHS are unchanged by the srem.
|
|
KnownZero = LHSKnownZero & LowBits;
|
|
KnownOne = LHSKnownOne & LowBits;
|
|
|
|
// If LHS is non-negative or has all low bits zero, then the upper bits
|
|
// are all zero.
|
|
if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits))
|
|
KnownZero |= ~LowBits;
|
|
|
|
// If LHS is negative and not all low bits are zero, then the upper bits
|
|
// are all one.
|
|
if (LHSKnownOne[BitWidth-1] && ((LHSKnownOne & LowBits) != 0))
|
|
KnownOne |= ~LowBits;
|
|
|
|
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
|
|
}
|
|
}
|
|
|
|
// The sign bit is the LHS's sign bit, except when the result of the
|
|
// remainder is zero.
|
|
if (DemandedMask.isNegative() && KnownZero.isNonNegative()) {
|
|
APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
|
|
ComputeMaskedBits(I->getOperand(0), LHSKnownZero, LHSKnownOne, Depth+1);
|
|
// If it's known zero, our sign bit is also zero.
|
|
if (LHSKnownZero.isNegative())
|
|
KnownZero.setBit(KnownZero.getBitWidth() - 1);
|
|
}
|
|
break;
|
|
case Instruction::URem: {
|
|
APInt KnownZero2(BitWidth, 0), KnownOne2(BitWidth, 0);
|
|
APInt AllOnes = APInt::getAllOnesValue(BitWidth);
|
|
if (SimplifyDemandedBits(I->getOperandUse(0), AllOnes,
|
|
KnownZero2, KnownOne2, Depth+1) ||
|
|
SimplifyDemandedBits(I->getOperandUse(1), AllOnes,
|
|
KnownZero2, KnownOne2, Depth+1))
|
|
return I;
|
|
|
|
unsigned Leaders = KnownZero2.countLeadingOnes();
|
|
Leaders = std::max(Leaders,
|
|
KnownZero2.countLeadingOnes());
|
|
KnownZero = APInt::getHighBitsSet(BitWidth, Leaders) & DemandedMask;
|
|
break;
|
|
}
|
|
case Instruction::Call:
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::bswap: {
|
|
// If the only bits demanded come from one byte of the bswap result,
|
|
// just shift the input byte into position to eliminate the bswap.
|
|
unsigned NLZ = DemandedMask.countLeadingZeros();
|
|
unsigned NTZ = DemandedMask.countTrailingZeros();
|
|
|
|
// Round NTZ down to the next byte. If we have 11 trailing zeros, then
|
|
// we need all the bits down to bit 8. Likewise, round NLZ. If we
|
|
// have 14 leading zeros, round to 8.
|
|
NLZ &= ~7;
|
|
NTZ &= ~7;
|
|
// If we need exactly one byte, we can do this transformation.
|
|
if (BitWidth-NLZ-NTZ == 8) {
|
|
unsigned ResultBit = NTZ;
|
|
unsigned InputBit = BitWidth-NTZ-8;
|
|
|
|
// Replace this with either a left or right shift to get the byte into
|
|
// the right place.
|
|
Instruction *NewVal;
|
|
if (InputBit > ResultBit)
|
|
NewVal = BinaryOperator::CreateLShr(II->getArgOperand(0),
|
|
ConstantInt::get(I->getType(), InputBit-ResultBit));
|
|
else
|
|
NewVal = BinaryOperator::CreateShl(II->getArgOperand(0),
|
|
ConstantInt::get(I->getType(), ResultBit-InputBit));
|
|
NewVal->takeName(I);
|
|
return InsertNewInstWith(NewVal, *I);
|
|
}
|
|
|
|
// TODO: Could compute known zero/one bits based on the input.
|
|
break;
|
|
}
|
|
case Intrinsic::x86_sse42_crc32_64_64:
|
|
KnownZero = APInt::getHighBitsSet(64, 32);
|
|
return 0;
|
|
}
|
|
}
|
|
ComputeMaskedBits(V, KnownZero, KnownOne, Depth);
|
|
break;
|
|
}
|
|
|
|
// If the client is only demanding bits that we know, return the known
|
|
// constant.
|
|
if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask)
|
|
return Constant::getIntegerValue(VTy, KnownOne);
|
|
return 0;
|
|
}
|
|
|
|
/// Helper routine of SimplifyDemandedUseBits. It tries to simplify
|
|
/// "E1 = (X lsr C1) << C2", where the C1 and C2 are constant, into
|
|
/// "E2 = X << (C2 - C1)" or "E2 = X >> (C1 - C2)", depending on the sign
|
|
/// of "C2-C1".
|
|
///
|
|
/// Suppose E1 and E2 are generally different in bits S={bm, bm+1,
|
|
/// ..., bn}, without considering the specific value X is holding.
|
|
/// This transformation is legal iff one of following conditions is hold:
|
|
/// 1) All the bit in S are 0, in this case E1 == E2.
|
|
/// 2) We don't care those bits in S, per the input DemandedMask.
|
|
/// 3) Combination of 1) and 2). Some bits in S are 0, and we don't care the
|
|
/// rest bits.
|
|
///
|
|
/// Currently we only test condition 2).
|
|
///
|
|
/// As with SimplifyDemandedUseBits, it returns NULL if the simplification was
|
|
/// not successful.
|
|
Value *InstCombiner::SimplifyShrShlDemandedBits(Instruction *Shr,
|
|
Instruction *Shl, APInt DemandedMask, APInt &KnownZero, APInt &KnownOne) {
|
|
|
|
const APInt &ShlOp1 = cast<ConstantInt>(Shl->getOperand(1))->getValue();
|
|
const APInt &ShrOp1 = cast<ConstantInt>(Shr->getOperand(1))->getValue();
|
|
if (!ShlOp1 || !ShrOp1)
|
|
return 0; // Noop.
|
|
|
|
Value *VarX = Shr->getOperand(0);
|
|
Type *Ty = VarX->getType();
|
|
unsigned BitWidth = Ty->getIntegerBitWidth();
|
|
if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth))
|
|
return 0; // Undef.
|
|
|
|
unsigned ShlAmt = ShlOp1.getZExtValue();
|
|
unsigned ShrAmt = ShrOp1.getZExtValue();
|
|
|
|
KnownOne.clearAllBits();
|
|
KnownZero = APInt::getBitsSet(KnownZero.getBitWidth(), 0, ShlAmt-1);
|
|
KnownZero &= DemandedMask;
|
|
|
|
APInt BitMask1(APInt::getAllOnesValue(BitWidth));
|
|
APInt BitMask2(APInt::getAllOnesValue(BitWidth));
|
|
|
|
bool isLshr = (Shr->getOpcode() == Instruction::LShr);
|
|
BitMask1 = isLshr ? (BitMask1.lshr(ShrAmt) << ShlAmt) :
|
|
(BitMask1.ashr(ShrAmt) << ShlAmt);
|
|
|
|
if (ShrAmt <= ShlAmt) {
|
|
BitMask2 <<= (ShlAmt - ShrAmt);
|
|
} else {
|
|
BitMask2 = isLshr ? BitMask2.lshr(ShrAmt - ShlAmt):
|
|
BitMask2.ashr(ShrAmt - ShlAmt);
|
|
}
|
|
|
|
// Check if condition-2 (see the comment to this function) is satified.
|
|
if ((BitMask1 & DemandedMask) == (BitMask2 & DemandedMask)) {
|
|
if (ShrAmt == ShlAmt)
|
|
return VarX;
|
|
|
|
if (!Shr->hasOneUse())
|
|
return 0;
|
|
|
|
BinaryOperator *New;
|
|
if (ShrAmt < ShlAmt) {
|
|
Constant *Amt = ConstantInt::get(VarX->getType(), ShlAmt - ShrAmt);
|
|
New = BinaryOperator::CreateShl(VarX, Amt);
|
|
BinaryOperator *Orig = cast<BinaryOperator>(Shl);
|
|
New->setHasNoSignedWrap(Orig->hasNoSignedWrap());
|
|
New->setHasNoUnsignedWrap(Orig->hasNoUnsignedWrap());
|
|
} else {
|
|
Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt);
|
|
New = isLshr ? BinaryOperator::CreateLShr(VarX, Amt) :
|
|
BinaryOperator::CreateAShr(VarX, Amt);
|
|
if (cast<BinaryOperator>(Shr)->isExact())
|
|
New->setIsExact(true);
|
|
}
|
|
|
|
return InsertNewInstWith(New, *Shl);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/// SimplifyDemandedVectorElts - The specified value produces a vector with
|
|
/// any number of elements. DemandedElts contains the set of elements that are
|
|
/// actually used by the caller. This method analyzes which elements of the
|
|
/// operand are undef and returns that information in UndefElts.
|
|
///
|
|
/// If the information about demanded elements can be used to simplify the
|
|
/// operation, the operation is simplified, then the resultant value is
|
|
/// returned. This returns null if no change was made.
|
|
Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
|
|
APInt &UndefElts,
|
|
unsigned Depth) {
|
|
unsigned VWidth = cast<VectorType>(V->getType())->getNumElements();
|
|
APInt EltMask(APInt::getAllOnesValue(VWidth));
|
|
assert((DemandedElts & ~EltMask) == 0 && "Invalid DemandedElts!");
|
|
|
|
if (isa<UndefValue>(V)) {
|
|
// If the entire vector is undefined, just return this info.
|
|
UndefElts = EltMask;
|
|
return 0;
|
|
}
|
|
|
|
if (DemandedElts == 0) { // If nothing is demanded, provide undef.
|
|
UndefElts = EltMask;
|
|
return UndefValue::get(V->getType());
|
|
}
|
|
|
|
UndefElts = 0;
|
|
|
|
// Handle ConstantAggregateZero, ConstantVector, ConstantDataSequential.
|
|
if (Constant *C = dyn_cast<Constant>(V)) {
|
|
// Check if this is identity. If so, return 0 since we are not simplifying
|
|
// anything.
|
|
if (DemandedElts.isAllOnesValue())
|
|
return 0;
|
|
|
|
Type *EltTy = cast<VectorType>(V->getType())->getElementType();
|
|
Constant *Undef = UndefValue::get(EltTy);
|
|
|
|
SmallVector<Constant*, 16> Elts;
|
|
for (unsigned i = 0; i != VWidth; ++i) {
|
|
if (!DemandedElts[i]) { // If not demanded, set to undef.
|
|
Elts.push_back(Undef);
|
|
UndefElts.setBit(i);
|
|
continue;
|
|
}
|
|
|
|
Constant *Elt = C->getAggregateElement(i);
|
|
if (Elt == 0) return 0;
|
|
|
|
if (isa<UndefValue>(Elt)) { // Already undef.
|
|
Elts.push_back(Undef);
|
|
UndefElts.setBit(i);
|
|
} else { // Otherwise, defined.
|
|
Elts.push_back(Elt);
|
|
}
|
|
}
|
|
|
|
// If we changed the constant, return it.
|
|
Constant *NewCV = ConstantVector::get(Elts);
|
|
return NewCV != C ? NewCV : 0;
|
|
}
|
|
|
|
// Limit search depth.
|
|
if (Depth == 10)
|
|
return 0;
|
|
|
|
// If multiple users are using the root value, proceed with
|
|
// simplification conservatively assuming that all elements
|
|
// are needed.
|
|
if (!V->hasOneUse()) {
|
|
// Quit if we find multiple users of a non-root value though.
|
|
// They'll be handled when it's their turn to be visited by
|
|
// the main instcombine process.
|
|
if (Depth != 0)
|
|
// TODO: Just compute the UndefElts information recursively.
|
|
return 0;
|
|
|
|
// Conservatively assume that all elements are needed.
|
|
DemandedElts = EltMask;
|
|
}
|
|
|
|
Instruction *I = dyn_cast<Instruction>(V);
|
|
if (!I) return 0; // Only analyze instructions.
|
|
|
|
bool MadeChange = false;
|
|
APInt UndefElts2(VWidth, 0);
|
|
Value *TmpV;
|
|
switch (I->getOpcode()) {
|
|
default: break;
|
|
|
|
case Instruction::InsertElement: {
|
|
// If this is a variable index, we don't know which element it overwrites.
|
|
// demand exactly the same input as we produce.
|
|
ConstantInt *Idx = dyn_cast<ConstantInt>(I->getOperand(2));
|
|
if (Idx == 0) {
|
|
// Note that we can't propagate undef elt info, because we don't know
|
|
// which elt is getting updated.
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
|
|
UndefElts2, Depth+1);
|
|
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
|
|
break;
|
|
}
|
|
|
|
// If this is inserting an element that isn't demanded, remove this
|
|
// insertelement.
|
|
unsigned IdxNo = Idx->getZExtValue();
|
|
if (IdxNo >= VWidth || !DemandedElts[IdxNo]) {
|
|
Worklist.Add(I);
|
|
return I->getOperand(0);
|
|
}
|
|
|
|
// Otherwise, the element inserted overwrites whatever was there, so the
|
|
// input demanded set is simpler than the output set.
|
|
APInt DemandedElts2 = DemandedElts;
|
|
DemandedElts2.clearBit(IdxNo);
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts2,
|
|
UndefElts, Depth+1);
|
|
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
|
|
|
|
// The inserted element is defined.
|
|
UndefElts.clearBit(IdxNo);
|
|
break;
|
|
}
|
|
case Instruction::ShuffleVector: {
|
|
ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(I);
|
|
uint64_t LHSVWidth =
|
|
cast<VectorType>(Shuffle->getOperand(0)->getType())->getNumElements();
|
|
APInt LeftDemanded(LHSVWidth, 0), RightDemanded(LHSVWidth, 0);
|
|
for (unsigned i = 0; i < VWidth; i++) {
|
|
if (DemandedElts[i]) {
|
|
unsigned MaskVal = Shuffle->getMaskValue(i);
|
|
if (MaskVal != -1u) {
|
|
assert(MaskVal < LHSVWidth * 2 &&
|
|
"shufflevector mask index out of range!");
|
|
if (MaskVal < LHSVWidth)
|
|
LeftDemanded.setBit(MaskVal);
|
|
else
|
|
RightDemanded.setBit(MaskVal - LHSVWidth);
|
|
}
|
|
}
|
|
}
|
|
|
|
APInt UndefElts4(LHSVWidth, 0);
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), LeftDemanded,
|
|
UndefElts4, Depth+1);
|
|
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
|
|
|
|
APInt UndefElts3(LHSVWidth, 0);
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(1), RightDemanded,
|
|
UndefElts3, Depth+1);
|
|
if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
|
|
|
|
bool NewUndefElts = false;
|
|
for (unsigned i = 0; i < VWidth; i++) {
|
|
unsigned MaskVal = Shuffle->getMaskValue(i);
|
|
if (MaskVal == -1u) {
|
|
UndefElts.setBit(i);
|
|
} else if (!DemandedElts[i]) {
|
|
NewUndefElts = true;
|
|
UndefElts.setBit(i);
|
|
} else if (MaskVal < LHSVWidth) {
|
|
if (UndefElts4[MaskVal]) {
|
|
NewUndefElts = true;
|
|
UndefElts.setBit(i);
|
|
}
|
|
} else {
|
|
if (UndefElts3[MaskVal - LHSVWidth]) {
|
|
NewUndefElts = true;
|
|
UndefElts.setBit(i);
|
|
}
|
|
}
|
|
}
|
|
|
|
if (NewUndefElts) {
|
|
// Add additional discovered undefs.
|
|
SmallVector<Constant*, 16> Elts;
|
|
for (unsigned i = 0; i < VWidth; ++i) {
|
|
if (UndefElts[i])
|
|
Elts.push_back(UndefValue::get(Type::getInt32Ty(I->getContext())));
|
|
else
|
|
Elts.push_back(ConstantInt::get(Type::getInt32Ty(I->getContext()),
|
|
Shuffle->getMaskValue(i)));
|
|
}
|
|
I->setOperand(2, ConstantVector::get(Elts));
|
|
MadeChange = true;
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::Select: {
|
|
APInt LeftDemanded(DemandedElts), RightDemanded(DemandedElts);
|
|
if (ConstantVector* CV = dyn_cast<ConstantVector>(I->getOperand(0))) {
|
|
for (unsigned i = 0; i < VWidth; i++) {
|
|
if (CV->getAggregateElement(i)->isNullValue())
|
|
LeftDemanded.clearBit(i);
|
|
else
|
|
RightDemanded.clearBit(i);
|
|
}
|
|
}
|
|
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(1), LeftDemanded,
|
|
UndefElts, Depth+1);
|
|
if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
|
|
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(2), RightDemanded,
|
|
UndefElts2, Depth+1);
|
|
if (TmpV) { I->setOperand(2, TmpV); MadeChange = true; }
|
|
|
|
// Output elements are undefined if both are undefined.
|
|
UndefElts &= UndefElts2;
|
|
break;
|
|
}
|
|
case Instruction::BitCast: {
|
|
// Vector->vector casts only.
|
|
VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType());
|
|
if (!VTy) break;
|
|
unsigned InVWidth = VTy->getNumElements();
|
|
APInt InputDemandedElts(InVWidth, 0);
|
|
unsigned Ratio;
|
|
|
|
if (VWidth == InVWidth) {
|
|
// If we are converting from <4 x i32> -> <4 x f32>, we demand the same
|
|
// elements as are demanded of us.
|
|
Ratio = 1;
|
|
InputDemandedElts = DemandedElts;
|
|
} else if (VWidth > InVWidth) {
|
|
// Untested so far.
|
|
break;
|
|
|
|
// If there are more elements in the result than there are in the source,
|
|
// then an input element is live if any of the corresponding output
|
|
// elements are live.
|
|
Ratio = VWidth/InVWidth;
|
|
for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) {
|
|
if (DemandedElts[OutIdx])
|
|
InputDemandedElts.setBit(OutIdx/Ratio);
|
|
}
|
|
} else {
|
|
// Untested so far.
|
|
break;
|
|
|
|
// If there are more elements in the source than there are in the result,
|
|
// then an input element is live if the corresponding output element is
|
|
// live.
|
|
Ratio = InVWidth/VWidth;
|
|
for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
|
|
if (DemandedElts[InIdx/Ratio])
|
|
InputDemandedElts.setBit(InIdx);
|
|
}
|
|
|
|
// div/rem demand all inputs, because they don't want divide by zero.
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), InputDemandedElts,
|
|
UndefElts2, Depth+1);
|
|
if (TmpV) {
|
|
I->setOperand(0, TmpV);
|
|
MadeChange = true;
|
|
}
|
|
|
|
UndefElts = UndefElts2;
|
|
if (VWidth > InVWidth) {
|
|
llvm_unreachable("Unimp");
|
|
// If there are more elements in the result than there are in the source,
|
|
// then an output element is undef if the corresponding input element is
|
|
// undef.
|
|
for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx)
|
|
if (UndefElts2[OutIdx/Ratio])
|
|
UndefElts.setBit(OutIdx);
|
|
} else if (VWidth < InVWidth) {
|
|
llvm_unreachable("Unimp");
|
|
// If there are more elements in the source than there are in the result,
|
|
// then a result element is undef if all of the corresponding input
|
|
// elements are undef.
|
|
UndefElts = ~0ULL >> (64-VWidth); // Start out all undef.
|
|
for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
|
|
if (!UndefElts2[InIdx]) // Not undef?
|
|
UndefElts.clearBit(InIdx/Ratio); // Clear undef bit.
|
|
}
|
|
break;
|
|
}
|
|
case Instruction::And:
|
|
case Instruction::Or:
|
|
case Instruction::Xor:
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
case Instruction::Mul:
|
|
// div/rem demand all inputs, because they don't want divide by zero.
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
|
|
UndefElts, Depth+1);
|
|
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(1), DemandedElts,
|
|
UndefElts2, Depth+1);
|
|
if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
|
|
|
|
// Output elements are undefined if both are undefined. Consider things
|
|
// like undef&0. The result is known zero, not undef.
|
|
UndefElts &= UndefElts2;
|
|
break;
|
|
case Instruction::FPTrunc:
|
|
case Instruction::FPExt:
|
|
TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
|
|
UndefElts, Depth+1);
|
|
if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
|
|
break;
|
|
|
|
case Instruction::Call: {
|
|
IntrinsicInst *II = dyn_cast<IntrinsicInst>(I);
|
|
if (!II) break;
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
|
|
// Binary vector operations that work column-wise. A dest element is a
|
|
// function of the corresponding input elements from the two inputs.
|
|
case Intrinsic::x86_sse_sub_ss:
|
|
case Intrinsic::x86_sse_mul_ss:
|
|
case Intrinsic::x86_sse_min_ss:
|
|
case Intrinsic::x86_sse_max_ss:
|
|
case Intrinsic::x86_sse2_sub_sd:
|
|
case Intrinsic::x86_sse2_mul_sd:
|
|
case Intrinsic::x86_sse2_min_sd:
|
|
case Intrinsic::x86_sse2_max_sd:
|
|
TmpV = SimplifyDemandedVectorElts(II->getArgOperand(0), DemandedElts,
|
|
UndefElts, Depth+1);
|
|
if (TmpV) { II->setArgOperand(0, TmpV); MadeChange = true; }
|
|
TmpV = SimplifyDemandedVectorElts(II->getArgOperand(1), DemandedElts,
|
|
UndefElts2, Depth+1);
|
|
if (TmpV) { II->setArgOperand(1, TmpV); MadeChange = true; }
|
|
|
|
// If only the low elt is demanded and this is a scalarizable intrinsic,
|
|
// scalarize it now.
|
|
if (DemandedElts == 1) {
|
|
switch (II->getIntrinsicID()) {
|
|
default: break;
|
|
case Intrinsic::x86_sse_sub_ss:
|
|
case Intrinsic::x86_sse_mul_ss:
|
|
case Intrinsic::x86_sse2_sub_sd:
|
|
case Intrinsic::x86_sse2_mul_sd:
|
|
// TODO: Lower MIN/MAX/ABS/etc
|
|
Value *LHS = II->getArgOperand(0);
|
|
Value *RHS = II->getArgOperand(1);
|
|
// Extract the element as scalars.
|
|
LHS = InsertNewInstWith(ExtractElementInst::Create(LHS,
|
|
ConstantInt::get(Type::getInt32Ty(I->getContext()), 0U)), *II);
|
|
RHS = InsertNewInstWith(ExtractElementInst::Create(RHS,
|
|
ConstantInt::get(Type::getInt32Ty(I->getContext()), 0U)), *II);
|
|
|
|
switch (II->getIntrinsicID()) {
|
|
default: llvm_unreachable("Case stmts out of sync!");
|
|
case Intrinsic::x86_sse_sub_ss:
|
|
case Intrinsic::x86_sse2_sub_sd:
|
|
TmpV = InsertNewInstWith(BinaryOperator::CreateFSub(LHS, RHS,
|
|
II->getName()), *II);
|
|
break;
|
|
case Intrinsic::x86_sse_mul_ss:
|
|
case Intrinsic::x86_sse2_mul_sd:
|
|
TmpV = InsertNewInstWith(BinaryOperator::CreateFMul(LHS, RHS,
|
|
II->getName()), *II);
|
|
break;
|
|
}
|
|
|
|
Instruction *New =
|
|
InsertElementInst::Create(
|
|
UndefValue::get(II->getType()), TmpV,
|
|
ConstantInt::get(Type::getInt32Ty(I->getContext()), 0U, false),
|
|
II->getName());
|
|
InsertNewInstWith(New, *II);
|
|
return New;
|
|
}
|
|
}
|
|
|
|
// Output elements are undefined if both are undefined. Consider things
|
|
// like undef&0. The result is known zero, not undef.
|
|
UndefElts &= UndefElts2;
|
|
break;
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
return MadeChange ? I : 0;
|
|
}
|