//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "instcombine"
#include "InstCombine.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
using namespace llvm;
using namespace PatternMatch;
+#define DEBUG_TYPE "instcombine"
+
Instruction *InstCombiner::commonShiftTransforms(BinaryOperator &I) {
assert(I.getOperand(1)->getType() == I.getOperand(0)->getType());
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
return &I;
}
- return 0;
+ return nullptr;
}
/// CanEvaluateShifted - See if we can compute the specified value, but shifted
/// this succeeds, the GetShiftedValue function will be called to produce the
/// value.
static bool CanEvaluateShifted(Value *V, unsigned NumBits, bool isLeftShift,
- InstCombiner &IC) {
+ InstCombiner &IC, Instruction *CxtI) {
// We can always evaluate constants shifted.
if (isa<Constant>(V))
return true;
// if the needed bits are already zero in the input. This allows us to reuse
// the value which means that we don't care if the shift has multiple uses.
// TODO: Handle opposite shift by exact value.
- ConstantInt *CI = 0;
+ ConstantInt *CI = nullptr;
if ((isLeftShift && match(I, m_LShr(m_Value(), m_ConstantInt(CI)))) ||
(!isLeftShift && match(I, m_Shl(m_Value(), m_ConstantInt(CI))))) {
if (CI->getZExtValue() == NumBits) {
case Instruction::Or:
case Instruction::Xor:
// Bitwise operators can all arbitrarily be arbitrarily evaluated shifted.
- return CanEvaluateShifted(I->getOperand(0), NumBits, isLeftShift, IC) &&
- CanEvaluateShifted(I->getOperand(1), NumBits, isLeftShift, IC);
+ return CanEvaluateShifted(I->getOperand(0), NumBits, isLeftShift, IC, I) &&
+ CanEvaluateShifted(I->getOperand(1), NumBits, isLeftShift, IC, I);
case Instruction::Shl: {
// We can often fold the shift into shifts-by-a-constant.
CI = dyn_cast<ConstantInt>(I->getOperand(1));
- if (CI == 0) return false;
+ if (!CI) return false;
// We can always fold shl(c1)+shl(c2) -> shl(c1+c2).
if (isLeftShift) return true;
// profitable unless we know the and'd out bits are already zero.
if (CI->getZExtValue() > NumBits) {
unsigned LowBits = TypeWidth - CI->getZExtValue();
- if (MaskedValueIsZero(I->getOperand(0),
- APInt::getLowBitsSet(TypeWidth, NumBits) << LowBits))
+ if (IC.MaskedValueIsZero(I->getOperand(0),
+ APInt::getLowBitsSet(TypeWidth, NumBits) << LowBits,
+ 0, CxtI))
return true;
}
case Instruction::LShr: {
// We can often fold the shift into shifts-by-a-constant.
CI = dyn_cast<ConstantInt>(I->getOperand(1));
- if (CI == 0) return false;
+ if (!CI) return false;
// We can always fold lshr(c1)+lshr(c2) -> lshr(c1+c2).
if (!isLeftShift) return true;
// profitable unless we know the and'd out bits are already zero.
if (CI->getValue().ult(TypeWidth) && CI->getZExtValue() > NumBits) {
unsigned LowBits = CI->getZExtValue() - NumBits;
- if (MaskedValueIsZero(I->getOperand(0),
- APInt::getLowBitsSet(TypeWidth, NumBits) << LowBits))
+ if (IC.MaskedValueIsZero(I->getOperand(0),
+ APInt::getLowBitsSet(TypeWidth, NumBits) << LowBits,
+ 0, CxtI))
return true;
}
}
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
- return CanEvaluateShifted(SI->getTrueValue(), NumBits, isLeftShift, IC) &&
- CanEvaluateShifted(SI->getFalseValue(), NumBits, isLeftShift, IC);
+ return CanEvaluateShifted(SI->getTrueValue(), NumBits, isLeftShift,
+ IC, SI) &&
+ CanEvaluateShifted(SI->getFalseValue(), NumBits, isLeftShift, IC, SI);
}
case Instruction::PHI: {
// We can change a phi if we can change all operands. Note that we never
// instructions with a single use.
PHINode *PN = cast<PHINode>(I);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (!CanEvaluateShifted(PN->getIncomingValue(i), NumBits, isLeftShift,IC))
+ if (!CanEvaluateShifted(PN->getIncomingValue(i), NumBits, isLeftShift,
+ IC, PN))
return false;
return true;
}
// See if we can propagate this shift into the input, this covers the trivial
// cast of lshr(shl(x,c1),c2) as well as other more complex cases.
if (I.getOpcode() != Instruction::AShr &&
- CanEvaluateShifted(Op0, COp1->getZExtValue(), isLeftShift, *this)) {
+ CanEvaluateShifted(Op0, COp1->getZExtValue(), isLeftShift, *this, &I)) {
DEBUG(dbgs() << "ICE: GetShiftedValue propagating shift through expression"
" to eliminate shift:\n IN: " << *Op0 << "\n SH: " << I <<"\n");
GetShiftedValue(Op0, COp1->getZExtValue(), isLeftShift, *this));
}
-
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint32_t TypeBits = Op0->getType()->getScalarSizeInBits();
- // shl i32 X, 32 = 0 and srl i8 Y, 9 = 0, ... just don't eliminate
- // a signed shift.
- //
- if (COp1->uge(TypeBits)) {
- if (I.getOpcode() != Instruction::AShr)
- return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
- // ashr i32 X, 32 --> ashr i32 X, 31
- I.setOperand(1, ConstantInt::get(I.getType(), TypeBits-1));
- return &I;
- }
+ assert(!COp1->uge(TypeBits) &&
+ "Shift over the type width should have been removed already");
// ((X*C1) << C2) == (X * (C1 << C2))
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
}
- // If the operand is an bitwise operator with a constant RHS, and the
+ // If the operand is a bitwise operator with a constant RHS, and the
// shift is the only use, we can pull it out of the shift.
if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
bool isValid = true; // Valid only for And, Or, Xor
// Find out if this is a shift of a shift by a constant.
BinaryOperator *ShiftOp = dyn_cast<BinaryOperator>(Op0);
if (ShiftOp && !ShiftOp->isShift())
- ShiftOp = 0;
+ ShiftOp = nullptr;
if (ShiftOp && isa<ConstantInt>(ShiftOp->getOperand(1))) {
uint32_t ShiftAmt1 = ShiftAmt1C->getLimitedValue(TypeBits);
uint32_t ShiftAmt2 = COp1->getLimitedValue(TypeBits);
assert(ShiftAmt2 != 0 && "Should have been simplified earlier");
- if (ShiftAmt1 == 0) return 0; // Will be simplified in the future.
+ if (ShiftAmt1 == 0) return nullptr; // Will be simplified in the future.
Value *X = ShiftOp->getOperand(0);
IntegerType *Ty = cast<IntegerType>(I.getType());
}
}
}
- return 0;
+ return nullptr;
}
Instruction *InstCombiner::visitShl(BinaryOperator &I) {
+ if (Value *V = SimplifyVectorOp(I))
+ return ReplaceInstUsesWith(I, V);
+
if (Value *V = SimplifyShlInst(I.getOperand(0), I.getOperand(1),
I.hasNoSignedWrap(), I.hasNoUnsignedWrap(),
- DL))
+ DL, TLI, DT, AT))
return ReplaceInstUsesWith(I, V);
if (Instruction *V = commonShiftTransforms(I))
// If the shifted-out value is known-zero, then this is a NUW shift.
if (!I.hasNoUnsignedWrap() &&
MaskedValueIsZero(I.getOperand(0),
- APInt::getHighBitsSet(Op1C->getBitWidth(), ShAmt))) {
+ APInt::getHighBitsSet(Op1C->getBitWidth(), ShAmt),
+ 0, &I)) {
I.setHasNoUnsignedWrap();
return &I;
}
// If the shifted out value is all signbits, this is a NSW shift.
if (!I.hasNoSignedWrap() &&
- ComputeNumSignBits(I.getOperand(0)) > ShAmt) {
+ ComputeNumSignBits(I.getOperand(0), 0, &I) > ShAmt) {
I.setHasNoSignedWrap();
return &I;
}
match(I.getOperand(1), m_Constant(C2)))
return BinaryOperator::CreateShl(ConstantExpr::getShl(C1, C2), A);
- return 0;
+ return nullptr;
}
Instruction *InstCombiner::visitLShr(BinaryOperator &I) {
+ if (Value *V = SimplifyVectorOp(I))
+ return ReplaceInstUsesWith(I, V);
+
if (Value *V = SimplifyLShrInst(I.getOperand(0), I.getOperand(1),
- I.isExact(), DL))
+ I.isExact(), DL, TLI, DT, AT))
return ReplaceInstUsesWith(I, V);
if (Instruction *R = commonShiftTransforms(I))
// If the shifted-out value is known-zero, then this is an exact shift.
if (!I.isExact() &&
- MaskedValueIsZero(Op0,APInt::getLowBitsSet(Op1C->getBitWidth(),ShAmt))){
+ MaskedValueIsZero(Op0, APInt::getLowBitsSet(Op1C->getBitWidth(), ShAmt),
+ 0, &I)){
I.setIsExact();
return &I;
}
}
- return 0;
+ return nullptr;
}
Instruction *InstCombiner::visitAShr(BinaryOperator &I) {
+ if (Value *V = SimplifyVectorOp(I))
+ return ReplaceInstUsesWith(I, V);
+
if (Value *V = SimplifyAShrInst(I.getOperand(0), I.getOperand(1),
- I.isExact(), DL))
+ I.isExact(), DL, TLI, DT, AT))
return ReplaceInstUsesWith(I, V);
if (Instruction *R = commonShiftTransforms(I))
// have a sign-extend idiom.
Value *X;
if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1)))) {
- // If the left shift is just shifting out partial signbits, delete the
- // extension.
- if (cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap())
- return ReplaceInstUsesWith(I, X);
-
// If the input is an extension from the shifted amount value, e.g.
// %x = zext i8 %A to i32
// %y = shl i32 %x, 24
// If the shifted-out value is known-zero, then this is an exact shift.
if (!I.isExact() &&
- MaskedValueIsZero(Op0,APInt::getLowBitsSet(Op1C->getBitWidth(),ShAmt))){
+ MaskedValueIsZero(Op0,APInt::getLowBitsSet(Op1C->getBitWidth(),ShAmt),
+ 0, &I)){
I.setIsExact();
return &I;
}
// See if we can turn a signed shr into an unsigned shr.
if (MaskedValueIsZero(Op0,
- APInt::getSignBit(I.getType()->getScalarSizeInBits())))
+ APInt::getSignBit(I.getType()->getScalarSizeInBits()),
+ 0, &I))
return BinaryOperator::CreateLShr(Op0, Op1);
- // Arithmetic shifting an all-sign-bit value is a no-op.
- unsigned NumSignBits = ComputeNumSignBits(Op0);
- if (NumSignBits == Op0->getType()->getScalarSizeInBits())
- return ReplaceInstUsesWith(I, Op0);
-
- return 0;
+ return nullptr;
}
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