#define DEBUG_TYPE "reassociate"
#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Pass.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/DenseMap.h"
#include <algorithm>
}
}
#endif
-
+
+namespace {
+ /// \brief Utility class representing a base and exponent pair which form one
+ /// factor of some product.
+ struct Factor {
+ Value *Base;
+ unsigned Power;
+
+ Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {}
+
+ /// \brief Sort factors by their Base.
+ struct BaseSorter {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Base < RHS.Base;
+ }
+ };
+
+ /// \brief Compare factors for equal bases.
+ struct BaseEqual {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Base == RHS.Base;
+ }
+ };
+
+ /// \brief Sort factors in descending order by their power.
+ struct PowerDescendingSorter {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Power > RHS.Power;
+ }
+ };
+
+ /// \brief Compare factors for equal powers.
+ struct PowerEqual {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Power == RHS.Power;
+ }
+ };
+ };
+}
+
namespace {
class Reassociate : public FunctionPass {
DenseMap<BasicBlock*, unsigned> RankMap;
- DenseMap<AssertingVH<>, unsigned> ValueRankMap;
+ DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
+ SmallVector<WeakVH, 8> RedoInsts;
+ SmallVector<WeakVH, 8> DeadInsts;
bool MadeChange;
public:
static char ID; // Pass identification, replacement for typeid
- Reassociate() : FunctionPass(&ID) {}
+ Reassociate() : FunctionPass(ID) {
+ initializeReassociatePass(*PassRegistry::getPassRegistry());
+ }
bool runOnFunction(Function &F);
Value *OptimizeExpression(BinaryOperator *I,
SmallVectorImpl<ValueEntry> &Ops);
Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
+ bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
+ SmallVectorImpl<Factor> &Factors);
+ Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
+ SmallVectorImpl<Factor> &Factors);
+ Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
void LinearizeExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
void LinearizeExpr(BinaryOperator *I);
Value *RemoveFactorFromExpression(Value *V, Value *Factor);
- void ReassociateBB(BasicBlock *BB);
-
+ void ReassociateInst(BasicBlock::iterator &BBI);
+
void RemoveDeadBinaryOp(Value *V);
};
}
char Reassociate::ID = 0;
-static RegisterPass<Reassociate> X("reassociate", "Reassociate expressions");
+INITIALIZE_PASS(Reassociate, "reassociate",
+ "Reassociate expressions", false, false)
// Public interface to the Reassociate pass
FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
void Reassociate::RemoveDeadBinaryOp(Value *V) {
Instruction *Op = dyn_cast<Instruction>(V);
- if (!Op || !isa<BinaryOperator>(Op) || !Op->use_empty())
+ if (!Op || !isa<BinaryOperator>(Op))
return;
-
+
Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
-
+
ValueRankMap.erase(Op);
- Op->eraseFromParent();
+ DeadInsts.push_back(Op);
RemoveDeadBinaryOp(LHS);
RemoveDeadBinaryOp(RHS);
}
-
static bool isUnmovableInstruction(Instruction *I) {
if (I->getOpcode() == Instruction::PHI ||
+ I->getOpcode() == Instruction::LandingPad ||
I->getOpcode() == Instruction::Alloca ||
I->getOpcode() == Instruction::Load ||
I->getOpcode() == Instruction::Invoke ||
(I->getOpcode() == Instruction::Call &&
!isa<DbgInfoIntrinsic>(I)) ||
- I->getOpcode() == Instruction::UDiv ||
+ I->getOpcode() == Instruction::UDiv ||
I->getOpcode() == Instruction::SDiv ||
I->getOpcode() == Instruction::FDiv ||
I->getOpcode() == Instruction::URem ||
/// LowerNegateToMultiply - Replace 0-X with X*-1.
///
static Instruction *LowerNegateToMultiply(Instruction *Neg,
- DenseMap<AssertingVH<>, unsigned> &ValueRankMap) {
+ DenseMap<AssertingVH<Value>, unsigned> &ValueRankMap) {
Constant *Cst = Constant::getAllOnesValue(Neg->getType());
Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
ValueRankMap.erase(Neg);
Res->takeName(Neg);
Neg->replaceAllUsesWith(Res);
+ Res->setDebugLoc(Neg->getDebugLoc());
Neg->eraseFromParent();
return Res;
}
// linearize it as well. Besides that case, this does not recurse into A,B, or
// C.
void Reassociate::LinearizeExpr(BinaryOperator *I) {
- BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
- BinaryOperator *RHS = cast<BinaryOperator>(I->getOperand(1));
- assert(isReassociableOp(LHS, I->getOpcode()) &&
- isReassociableOp(RHS, I->getOpcode()) &&
- "Not an expression that needs linearization?");
+ BinaryOperator *LHS = isReassociableOp(I->getOperand(0), I->getOpcode());
+ BinaryOperator *RHS = isReassociableOp(I->getOperand(1), I->getOpcode());
+ assert(LHS && RHS && "Not an expression that needs linearization?");
- DEBUG(dbgs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n');
+ DEBUG({
+ dbgs() << "Linear:\n";
+ dbgs() << '\t' << *LHS << "\t\n" << *RHS << "\t\n" << *I << '\n';
+ });
// Move the RHS instruction to live immediately before I, avoiding breaking
// dominator properties.
RHS->setOperand(0, LHS);
I->setOperand(0, RHS);
+ // Conservatively clear all the optional flags, which may not hold
+ // after the reassociation.
+ I->clearSubclassOptionalData();
+ LHS->clearSubclassOptionalData();
+ RHS->clearSubclassOptionalData();
+
++NumLinear;
MadeChange = true;
DEBUG(dbgs() << "Linearized: " << *I << '\n');
LinearizeExpr(I);
}
-
/// LinearizeExprTree - Given an associative binary expression tree, traverse
/// all of the uses putting it into canonical form. This forces a left-linear
/// form of the expression (((a+b)+c)+d), and collects information about the
// such, just remember these operands and their rank.
Ops.push_back(ValueEntry(getRank(LHS), LHS));
Ops.push_back(ValueEntry(getRank(RHS), RHS));
-
+
// Clear the leaves out.
I->setOperand(0, UndefValue::get(I->getType()));
I->setOperand(1, UndefValue::get(I->getType()));
return;
}
-
+
// Turn X+(Y+Z) -> (Y+Z)+X
std::swap(LHSBO, RHSBO);
std::swap(LHS, RHS);
bool Success = !I->swapOperands();
assert(Success && "swapOperands failed");
- Success = false;
+ (void)Success;
MadeChange = true;
} else if (RHSBO) {
// Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the RHS is not
// Remember the RHS operand and its rank.
Ops.push_back(ValueEntry(getRank(RHS), RHS));
-
+
// Clear the RHS leaf out.
I->setOperand(1, UndefValue::get(I->getType()));
}
DEBUG(dbgs() << "RA: " << *I << '\n');
I->setOperand(0, Ops[i].Op);
I->setOperand(1, Ops[i+1].Op);
+
+ // Clear all the optional flags, which may not hold after the
+ // reassociation if the expression involved more than just this operation.
+ if (Ops.size() != 2)
+ I->clearSubclassOptionalData();
+
DEBUG(dbgs() << "TO: " << *I << '\n');
MadeChange = true;
++NumChanged;
-
+
// If we reassociated a tree to fewer operands (e.g. (1+a+2) -> (a+3)
// delete the extra, now dead, nodes.
RemoveDeadBinaryOp(OldLHS);
if (I->getOperand(1) != Ops[i].Op) {
DEBUG(dbgs() << "RA: " << *I << '\n');
I->setOperand(1, Ops[i].Op);
+
+ // Conservatively clear all the optional flags, which may not hold
+ // after the reassociation.
+ I->clearSubclassOptionalData();
+
DEBUG(dbgs() << "TO: " << *I << '\n');
MadeChange = true;
++NumChanged;
}
-
+
BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
assert(LHS->getOpcode() == I->getOpcode() &&
"Improper expression tree!");
-
+
// Compactify the tree instructions together with each other to guarantee
// that the expression tree is dominated by all of Ops.
LHS->moveBefore(I);
RewriteExprTree(LHS, Ops, i+1);
}
-
-
-// NegateValue - Insert instructions before the instruction pointed to by BI,
-// that computes the negative version of the value specified. The negative
-// version of the value is returned, and BI is left pointing at the instruction
-// that should be processed next by the reassociation pass.
-//
+/// NegateValue - Insert instructions before the instruction pointed to by BI,
+/// that computes the negative version of the value specified. The negative
+/// version of the value is returned, and BI is left pointing at the instruction
+/// that should be processed next by the reassociation pass.
static Value *NegateValue(Value *V, Instruction *BI) {
if (Constant *C = dyn_cast<Constant>(V))
return ConstantExpr::getNeg(C);
-
+
// We are trying to expose opportunity for reassociation. One of the things
// that we want to do to achieve this is to push a negation as deep into an
// expression chain as possible, to expose the add instructions. In practice,
// We must move the add instruction here, because the neg instructions do
// not dominate the old add instruction in general. By moving it, we are
- // assured that the neg instructions we just inserted dominate the
+ // assured that the neg instructions we just inserted dominate the
// instruction we are about to insert after them.
//
I->moveBefore(BI);
I->setName(I->getName()+".neg");
return I;
}
-
+
// Okay, we need to materialize a negated version of V with an instruction.
// Scan the use lists of V to see if we have one already.
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
- if (!BinaryOperator::isNeg(*UI)) continue;
+ User *U = *UI;
+ if (!BinaryOperator::isNeg(U)) continue;
// We found one! Now we have to make sure that the definition dominates
// this use. We do this by moving it to the entry block (if it is a
// non-instruction value) or right after the definition. These negates will
// be zapped by reassociate later, so we don't need much finesse here.
- BinaryOperator *TheNeg = cast<BinaryOperator>(*UI);
+ BinaryOperator *TheNeg = cast<BinaryOperator>(U);
// Verify that the negate is in this function, V might be a constant expr.
if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
continue;
-
+
BasicBlock::iterator InsertPt;
if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
// If this is a negation, we can't split it up!
if (BinaryOperator::isNeg(Sub))
return false;
-
+
// Don't bother to break this up unless either the LHS is an associable add or
// subtract or if this is only used by one.
if (isReassociableOp(Sub->getOperand(0), Instruction::Add) ||
if (isReassociableOp(Sub->getOperand(1), Instruction::Add) ||
isReassociableOp(Sub->getOperand(1), Instruction::Sub))
return true;
- if (Sub->hasOneUse() &&
+ if (Sub->hasOneUse() &&
(isReassociableOp(Sub->use_back(), Instruction::Add) ||
isReassociableOp(Sub->use_back(), Instruction::Sub)))
return true;
-
+
return false;
}
/// only used by an add, transform this into (X+(0-Y)) to promote better
/// reassociation.
static Instruction *BreakUpSubtract(Instruction *Sub,
- DenseMap<AssertingVH<>, unsigned> &ValueRankMap) {
+ DenseMap<AssertingVH<Value>, unsigned> &ValueRankMap) {
// Convert a subtract into an add and a neg instruction. This allows sub
// instructions to be commuted with other add instructions.
//
// Everyone now refers to the add instruction.
ValueRankMap.erase(Sub);
Sub->replaceAllUsesWith(New);
+ New->setDebugLoc(Sub->getDebugLoc());
Sub->eraseFromParent();
DEBUG(dbgs() << "Negated: " << *New << '\n');
/// ConvertShiftToMul - If this is a shift of a reassociable multiply or is used
/// by one, change this into a multiply by a constant to assist with further
/// reassociation.
-static Instruction *ConvertShiftToMul(Instruction *Shl,
- DenseMap<AssertingVH<>, unsigned> &ValueRankMap) {
+static Instruction *ConvertShiftToMul(Instruction *Shl,
+ DenseMap<AssertingVH<Value>, unsigned> &ValueRankMap) {
// If an operand of this shift is a reassociable multiply, or if the shift
// is used by a reassociable multiply or add, turn into a multiply.
if (isReassociableOp(Shl->getOperand(0), Instruction::Mul) ||
- (Shl->hasOneUse() &&
+ (Shl->hasOneUse() &&
(isReassociableOp(Shl->use_back(), Instruction::Mul) ||
isReassociableOp(Shl->use_back(), Instruction::Add)))) {
Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
-
+
Instruction *Mul =
BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
ValueRankMap.erase(Shl);
Mul->takeName(Shl);
Shl->replaceAllUsesWith(Mul);
+ Mul->setDebugLoc(Shl->getDebugLoc());
Shl->eraseFromParent();
return Mul;
}
return 0;
}
-// Scan backwards and forwards among values with the same rank as element i to
-// see if X exists. If X does not exist, return i. This is useful when
-// scanning for 'x' when we see '-x' because they both get the same rank.
+/// FindInOperandList - Scan backwards and forwards among values with the same
+/// rank as element i to see if X exists. If X does not exist, return i. This
+/// is useful when scanning for 'x' when we see '-x' because they both get the
+/// same rank.
static unsigned FindInOperandList(SmallVectorImpl<ValueEntry> &Ops, unsigned i,
Value *X) {
unsigned XRank = Ops[i].Rank;
/// EmitAddTreeOfValues - Emit a tree of add instructions, summing Ops together
/// and returning the result. Insert the tree before I.
-static Value *EmitAddTreeOfValues(Instruction *I, SmallVectorImpl<Value*> &Ops){
+static Value *EmitAddTreeOfValues(Instruction *I,
+ SmallVectorImpl<WeakVH> &Ops){
if (Ops.size() == 1) return Ops.back();
-
+
Value *V1 = Ops.back();
Ops.pop_back();
Value *V2 = EmitAddTreeOfValues(I, Ops);
return BinaryOperator::CreateAdd(V2, V1, "tmp", I);
}
-/// RemoveFactorFromExpression - If V is an expression tree that is a
+/// RemoveFactorFromExpression - If V is an expression tree that is a
/// multiplication sequence, and if this sequence contains a multiply by Factor,
/// remove Factor from the tree and return the new tree.
Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) {
BinaryOperator *BO = isReassociableOp(V, Instruction::Mul);
if (!BO) return 0;
-
+
SmallVector<ValueEntry, 8> Factors;
LinearizeExprTree(BO, Factors);
Factors.erase(Factors.begin()+i);
break;
}
-
+
// If this is a negative version of this factor, remove it.
if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor))
if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
break;
}
}
-
+
if (!FoundFactor) {
// Make sure to restore the operands to the expression tree.
RewriteExprTree(BO, Factors);
return 0;
}
-
+
BasicBlock::iterator InsertPt = BO; ++InsertPt;
-
+
// If this was just a single multiply, remove the multiply and return the only
// remaining operand.
if (Factors.size() == 1) {
ValueRankMap.erase(BO);
- BO->eraseFromParent();
+ DeadInsts.push_back(BO);
V = Factors[0].Op;
} else {
RewriteExprTree(BO, Factors);
V = BO;
}
-
+
if (NeedsNegate)
V = BinaryOperator::CreateNeg(V, "neg", InsertPt);
-
+
return V;
}
/// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
/// add its operands as factors, otherwise add V to the list of factors.
+///
+/// Ops is the top-level list of add operands we're trying to factor.
static void FindSingleUseMultiplyFactors(Value *V,
- SmallVectorImpl<Value*> &Factors) {
+ SmallVectorImpl<Value*> &Factors,
+ const SmallVectorImpl<ValueEntry> &Ops,
+ bool IsRoot) {
BinaryOperator *BO;
- if ((!V->hasOneUse() && !V->use_empty()) ||
+ if (!(V->hasOneUse() || V->use_empty()) || // More than one use.
!(BO = dyn_cast<BinaryOperator>(V)) ||
BO->getOpcode() != Instruction::Mul) {
Factors.push_back(V);
return;
}
-
+
+ // If this value has a single use because it is another input to the add
+ // tree we're reassociating and we dropped its use, it actually has two
+ // uses and we can't factor it.
+ if (!IsRoot) {
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i)
+ if (Ops[i].Op == V) {
+ Factors.push_back(V);
+ return;
+ }
+ }
+
+
// Otherwise, add the LHS and RHS to the list of factors.
- FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
- FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
+ FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops, false);
+ FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops, false);
}
/// OptimizeAndOrXor - Optimize a series of operands to an 'and', 'or', or 'xor'
if (FoundX != i) {
if (Opcode == Instruction::And) // ...&X&~X = 0
return Constant::getNullValue(X->getType());
-
+
if (Opcode == Instruction::Or) // ...|X|~X = -1
return Constant::getAllOnesValue(X->getType());
}
}
-
+
// Next, check for duplicate pairs of values, which we assume are next to
// each other, due to our sorting criteria.
assert(i < Ops.size());
++NumAnnihil;
continue;
}
-
+
// Drop pairs of values for Xor.
assert(Opcode == Instruction::Xor);
if (e == 2)
return Constant::getNullValue(Ops[0].Op->getType());
-
+
// Y ^ X^X -> Y
Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
i -= 1; e -= 2;
Ops.erase(Ops.begin()+i);
++NumFound;
} while (i != Ops.size() && Ops[i].Op == TheOp);
-
+
DEBUG(errs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
++NumFactor;
-
+
// Insert a new multiply.
Value *Mul = ConstantInt::get(cast<IntegerType>(I->getType()), NumFound);
Mul = BinaryOperator::CreateMul(TheOp, Mul, "factor", I);
-
+
// Now that we have inserted a multiply, optimize it. This allows us to
// handle cases that require multiple factoring steps, such as this:
// (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
- Mul = ReassociateExpression(cast<BinaryOperator>(Mul));
-
+ RedoInsts.push_back(Mul);
+
// If every add operand was a duplicate, return the multiply.
if (Ops.empty())
return Mul;
-
+
// Otherwise, we had some input that didn't have the dupe, such as
// "A + A + B" -> "A*2 + B". Add the new multiply to the list of
// things being added by this operation.
Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
-
+
--i;
e = Ops.size();
continue;
}
-
+
// Check for X and -X in the operand list.
if (!BinaryOperator::isNeg(TheOp))
continue;
-
+
Value *X = BinaryOperator::getNegArgument(TheOp);
unsigned FoundX = FindInOperandList(Ops, i, X);
if (FoundX == i)
continue;
-
+
// Remove X and -X from the operand list.
if (Ops.size() == 2)
return Constant::getNullValue(X->getType());
-
+
Ops.erase(Ops.begin()+i);
if (i < FoundX)
--FoundX;
--i; // Revisit element.
e -= 2; // Removed two elements.
}
-
+
// Scan the operand list, checking to see if there are any common factors
// between operands. Consider something like A*A+A*B*C+D. We would like to
// reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
// To efficiently find this, we count the number of times a factor occurs
// for any ADD operands that are MULs.
DenseMap<Value*, unsigned> FactorOccurrences;
-
+
// Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
// where they are actually the same multiply.
unsigned MaxOcc = 0;
BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op);
if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
continue;
-
+
// Compute all of the factors of this added value.
SmallVector<Value*, 8> Factors;
- FindSingleUseMultiplyFactors(BOp, Factors);
+ FindSingleUseMultiplyFactors(BOp, Factors, Ops, true);
assert(Factors.size() > 1 && "Bad linearize!");
-
+
// Add one to FactorOccurrences for each unique factor in this op.
SmallPtrSet<Value*, 8> Duplicates;
for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
Value *Factor = Factors[i];
if (!Duplicates.insert(Factor)) continue;
-
+
unsigned Occ = ++FactorOccurrences[Factor];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; }
-
+
// If Factor is a negative constant, add the negated value as a factor
// because we can percolate the negate out. Watch for minint, which
// cannot be positivified.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor))
- if (CI->getValue().isNegative() && !CI->getValue().isMinSignedValue()) {
+ if (CI->isNegative() && !CI->isMinValue(true)) {
Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
assert(!Duplicates.count(Factor) &&
"Shouldn't have two constant factors, missed a canonicalize");
-
+
unsigned Occ = ++FactorOccurrences[Factor];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; }
}
}
}
-
+
// If any factor occurred more than one time, we can pull it out.
if (MaxOcc > 1) {
DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
// Create a new instruction that uses the MaxOccVal twice. If we don't do
// this, we could otherwise run into situations where removing a factor
- // from an expression will drop a use of maxocc, and this can cause
+ // from an expression will drop a use of maxocc, and this can cause
// RemoveFactorFromExpression on successive values to behave differently.
Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
- SmallVector<Value*, 4> NewMulOps;
- for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+ SmallVector<WeakVH, 4> NewMulOps;
+ for (unsigned i = 0; i != Ops.size(); ++i) {
// Only try to remove factors from expressions we're allowed to.
BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op);
if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
continue;
-
+
if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
- NewMulOps.push_back(V);
- Ops.erase(Ops.begin()+i);
- --i; --e;
+ // The factorized operand may occur several times. Convert them all in
+ // one fell swoop.
+ for (unsigned j = Ops.size(); j != i;) {
+ --j;
+ if (Ops[j].Op == Ops[i].Op) {
+ NewMulOps.push_back(V);
+ Ops.erase(Ops.begin()+j);
+ }
+ }
+ --i;
}
}
-
+
// No need for extra uses anymore.
delete DummyInst;
// A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
(void)NumAddedValues;
- V = ReassociateExpression(cast<BinaryOperator>(V));
+ RedoInsts.push_back(V);
// Create the multiply.
Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
// Rerun associate on the multiply in case the inner expression turned into
// a multiply. We want to make sure that we keep things in canonical form.
- V2 = ReassociateExpression(cast<BinaryOperator>(V2));
-
+ RedoInsts.push_back(V2);
+
// If every add operand included the factor (e.g. "A*B + A*C"), then the
// entire result expression is just the multiply "A*(B+C)".
if (Ops.empty())
return V2;
-
+
// Otherwise, we had some input that didn't have the factor, such as
// "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
// things being added by this operation.
Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
}
-
+
+ return 0;
+}
+
+namespace {
+ /// \brief Predicate tests whether a ValueEntry's op is in a map.
+ struct IsValueInMap {
+ const DenseMap<Value *, unsigned> ⤅
+
+ IsValueInMap(const DenseMap<Value *, unsigned> &Map) : Map(Map) {}
+
+ bool operator()(const ValueEntry &Entry) {
+ return Map.find(Entry.Op) != Map.end();
+ }
+ };
+}
+
+/// \brief Build up a vector of value/power pairs factoring a product.
+///
+/// Given a series of multiplication operands, build a vector of factors and
+/// the powers each is raised to when forming the final product. Sort them in
+/// the order of descending power.
+///
+/// (x*x) -> [(x, 2)]
+/// ((x*x)*x) -> [(x, 3)]
+/// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
+///
+/// \returns Whether any factors have a power greater than one.
+bool Reassociate::collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
+ SmallVectorImpl<Factor> &Factors) {
+ unsigned FactorPowerSum = 0;
+ DenseMap<Value *, unsigned> FactorCounts;
+ for (unsigned LastIdx = 0, Idx = 0, Size = Ops.size(); Idx < Size; ++Idx) {
+ // Note that 'use_empty' uses means the only use is in the linearized tree
+ // represented by Ops -- we remove the values from the actual operations to
+ // reduce their use count.
+ if (!Ops[Idx].Op->use_empty()) {
+ if (LastIdx == Idx)
+ ++LastIdx;
+ continue;
+ }
+ if (LastIdx == Idx || Ops[LastIdx].Op != Ops[Idx].Op) {
+ LastIdx = Idx;
+ continue;
+ }
+ // Track for simplification all factors which occur 2 or more times.
+ DenseMap<Value *, unsigned>::iterator CountIt;
+ bool Inserted;
+ llvm::tie(CountIt, Inserted)
+ = FactorCounts.insert(std::make_pair(Ops[Idx].Op, 2));
+ if (Inserted) {
+ FactorPowerSum += 2;
+ Factors.push_back(Factor(Ops[Idx].Op, 2));
+ } else {
+ ++CountIt->second;
+ ++FactorPowerSum;
+ }
+ }
+ // We can only simplify factors if the sum of the powers of our simplifiable
+ // factors is 4 or higher. When that is the case, we will *always* have
+ // a simplification. This is an important invariant to prevent cyclicly
+ // trying to simplify already minimal formations.
+ if (FactorPowerSum < 4)
+ return false;
+
+ // Remove all the operands which are in the map.
+ Ops.erase(std::remove_if(Ops.begin(), Ops.end(), IsValueInMap(FactorCounts)),
+ Ops.end());
+
+ // Record the adjusted power for the simplification factors. We add back into
+ // the Ops list any values with an odd power, and make the power even. This
+ // allows the outer-most multiplication tree to remain in tact during
+ // simplification.
+ unsigned OldOpsSize = Ops.size();
+ for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
+ Factors[Idx].Power = FactorCounts[Factors[Idx].Base];
+ if (Factors[Idx].Power & 1) {
+ Ops.push_back(ValueEntry(getRank(Factors[Idx].Base), Factors[Idx].Base));
+ --Factors[Idx].Power;
+ --FactorPowerSum;
+ }
+ }
+ // None of the adjustments above should have reduced the sum of factor powers
+ // below our mininum of '4'.
+ assert(FactorPowerSum >= 4);
+
+ // Patch up the sort of the ops vector by sorting the factors we added back
+ // onto the back, and merging the two sequences.
+ if (OldOpsSize != Ops.size()) {
+ SmallVectorImpl<ValueEntry>::iterator MiddleIt = Ops.begin() + OldOpsSize;
+ std::sort(MiddleIt, Ops.end());
+ std::inplace_merge(Ops.begin(), MiddleIt, Ops.end());
+ }
+
+ std::sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
+ return true;
+}
+
+/// \brief Build a tree of multiplies, computing the product of Ops.
+static Value *buildMultiplyTree(IRBuilder<> &Builder,
+ SmallVectorImpl<Value*> &Ops) {
+ if (Ops.size() == 1)
+ return Ops.back();
+
+ Value *LHS = Ops.pop_back_val();
+ do {
+ LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
+ } while (!Ops.empty());
+
+ return LHS;
+}
+
+/// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
+///
+/// Given a vector of values raised to various powers, where no two values are
+/// equal and the powers are sorted in decreasing order, compute the minimal
+/// DAG of multiplies to compute the final product, and return that product
+/// value.
+Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
+ SmallVectorImpl<Factor> &Factors) {
+ assert(Factors[0].Power);
+ SmallVector<Value *, 4> OuterProduct;
+ for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
+ Idx < Size && Factors[Idx].Power > 0; ++Idx) {
+ if (Factors[Idx].Power != Factors[LastIdx].Power) {
+ LastIdx = Idx;
+ continue;
+ }
+
+ // We want to multiply across all the factors with the same power so that
+ // we can raise them to that power as a single entity. Build a mini tree
+ // for that.
+ SmallVector<Value *, 4> InnerProduct;
+ InnerProduct.push_back(Factors[LastIdx].Base);
+ do {
+ InnerProduct.push_back(Factors[Idx].Base);
+ ++Idx;
+ } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
+
+ // Reset the base value of the first factor to the new expression tree.
+ // We'll remove all the factors with the same power in a second pass.
+ Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
+ RedoInsts.push_back(Factors[LastIdx].Base);
+
+ LastIdx = Idx;
+ }
+ // Unique factors with equal powers -- we've folded them into the first one's
+ // base.
+ Factors.erase(std::unique(Factors.begin(), Factors.end(),
+ Factor::PowerEqual()),
+ Factors.end());
+
+ // Iteratively collect the base of each factor with an add power into the
+ // outer product, and halve each power in preparation for squaring the
+ // expression.
+ for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
+ if (Factors[Idx].Power & 1)
+ OuterProduct.push_back(Factors[Idx].Base);
+ Factors[Idx].Power >>= 1;
+ }
+ if (Factors[0].Power) {
+ Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
+ OuterProduct.push_back(SquareRoot);
+ OuterProduct.push_back(SquareRoot);
+ }
+ if (OuterProduct.size() == 1)
+ return OuterProduct.front();
+
+ Value *V = buildMultiplyTree(Builder, OuterProduct);
+ RedoInsts.push_back(V);
+ return V;
+}
+
+Value *Reassociate::OptimizeMul(BinaryOperator *I,
+ SmallVectorImpl<ValueEntry> &Ops) {
+ // We can only optimize the multiplies when there is a chain of more than
+ // three, such that a balanced tree might require fewer total multiplies.
+ if (Ops.size() < 4)
+ return 0;
+
+ // Try to turn linear trees of multiplies without other uses of the
+ // intermediate stages into minimal multiply DAGs with perfect sub-expression
+ // re-use.
+ SmallVector<Factor, 4> Factors;
+ if (!collectMultiplyFactors(Ops, Factors))
+ return 0; // All distinct factors, so nothing left for us to do.
+
+ IRBuilder<> Builder(I);
+ Value *V = buildMinimalMultiplyDAG(Builder, Factors);
+ if (Ops.empty())
+ return V;
+
+ ValueEntry NewEntry = ValueEntry(getRank(V), V);
+ Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
return 0;
}
if (Ops.size() == 1) return Ops[0].Op;
unsigned Opcode = I->getOpcode();
-
+
if (Constant *V1 = dyn_cast<Constant>(Ops[Ops.size()-2].Op))
if (Constant *V2 = dyn_cast<Constant>(Ops.back().Op)) {
Ops.pop_back();
++NumAnnihil;
return CstVal;
}
-
+
if (cast<ConstantInt>(CstVal)->isOne())
Ops.pop_back(); // X * 1 -> X
break;
// Handle destructive annihilation due to identities between elements in the
// argument list here.
+ unsigned NumOps = Ops.size();
switch (Opcode) {
default: break;
case Instruction::And:
case Instruction::Or:
- case Instruction::Xor: {
- unsigned NumOps = Ops.size();
+ case Instruction::Xor:
if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
return Result;
- IterateOptimization |= Ops.size() != NumOps;
break;
- }
- case Instruction::Add: {
- unsigned NumOps = Ops.size();
+ case Instruction::Add:
if (Value *Result = OptimizeAdd(I, Ops))
return Result;
- IterateOptimization |= Ops.size() != NumOps;
- }
+ break;
+ case Instruction::Mul:
+ if (Value *Result = OptimizeMul(I, Ops))
+ return Result;
break;
- //case Instruction::Mul:
}
- if (IterateOptimization)
+ if (IterateOptimization || Ops.size() != NumOps)
return OptimizeExpression(I, Ops);
return 0;
}
+/// ReassociateInst - Inspect and reassociate the instruction at the
+/// given position, post-incrementing the position.
+void Reassociate::ReassociateInst(BasicBlock::iterator &BBI) {
+ Instruction *BI = BBI++;
+ if (BI->getOpcode() == Instruction::Shl &&
+ isa<ConstantInt>(BI->getOperand(1)))
+ if (Instruction *NI = ConvertShiftToMul(BI, ValueRankMap)) {
+ MadeChange = true;
+ BI = NI;
+ }
-/// ReassociateBB - Inspect all of the instructions in this basic block,
-/// reassociating them as we go.
-void Reassociate::ReassociateBB(BasicBlock *BB) {
- for (BasicBlock::iterator BBI = BB->begin(); BBI != BB->end(); ) {
- Instruction *BI = BBI++;
- if (BI->getOpcode() == Instruction::Shl &&
- isa<ConstantInt>(BI->getOperand(1)))
- if (Instruction *NI = ConvertShiftToMul(BI, ValueRankMap)) {
- MadeChange = true;
- BI = NI;
- }
+ // Floating point binary operators are not associative, but we can still
+ // commute (some) of them, to canonicalize the order of their operands.
+ // This can potentially expose more CSE opportunities, and makes writing
+ // other transformations simpler.
+ if (isa<BinaryOperator>(BI) &&
+ (BI->getType()->isFloatingPointTy() || BI->getType()->isVectorTy())) {
+ // FAdd and FMul can be commuted.
+ if (BI->getOpcode() != Instruction::FMul &&
+ BI->getOpcode() != Instruction::FAdd)
+ return;
- // Reject cases where it is pointless to do this.
- if (!isa<BinaryOperator>(BI) || BI->getType()->isFloatingPointTy() ||
- BI->getType()->isVectorTy())
- continue; // Floating point ops are not associative.
-
- // Do not reassociate boolean (i1) expressions. We want to preserve the
- // original order of evaluation for short-circuited comparisons that
- // SimplifyCFG has folded to AND/OR expressions. If the expression
- // is not further optimized, it is likely to be transformed back to a
- // short-circuited form for code gen, and the source order may have been
- // optimized for the most likely conditions.
- if (BI->getType()->isIntegerTy(1))
- continue;
+ Value *LHS = BI->getOperand(0);
+ Value *RHS = BI->getOperand(1);
+ unsigned LHSRank = getRank(LHS);
+ unsigned RHSRank = getRank(RHS);
- // If this is a subtract instruction which is not already in negate form,
- // see if we can convert it to X+-Y.
- if (BI->getOpcode() == Instruction::Sub) {
- if (ShouldBreakUpSubtract(BI)) {
- BI = BreakUpSubtract(BI, ValueRankMap);
- // Reset the BBI iterator in case BreakUpSubtract changed the
- // instruction it points to.
- BBI = BI;
- ++BBI;
+ // Sort the operands by rank.
+ if (RHSRank < LHSRank) {
+ BI->setOperand(0, RHS);
+ BI->setOperand(1, LHS);
+ }
+
+ return;
+ }
+
+ // Do not reassociate operations that we do not understand.
+ if (!isa<BinaryOperator>(BI))
+ return;
+
+ // Do not reassociate boolean (i1) expressions. We want to preserve the
+ // original order of evaluation for short-circuited comparisons that
+ // SimplifyCFG has folded to AND/OR expressions. If the expression
+ // is not further optimized, it is likely to be transformed back to a
+ // short-circuited form for code gen, and the source order may have been
+ // optimized for the most likely conditions.
+ if (BI->getType()->isIntegerTy(1))
+ return;
+
+ // If this is a subtract instruction which is not already in negate form,
+ // see if we can convert it to X+-Y.
+ if (BI->getOpcode() == Instruction::Sub) {
+ if (ShouldBreakUpSubtract(BI)) {
+ BI = BreakUpSubtract(BI, ValueRankMap);
+ // Reset the BBI iterator in case BreakUpSubtract changed the
+ // instruction it points to.
+ BBI = BI;
+ ++BBI;
+ MadeChange = true;
+ } else if (BinaryOperator::isNeg(BI)) {
+ // Otherwise, this is a negation. See if the operand is a multiply tree
+ // and if this is not an inner node of a multiply tree.
+ if (isReassociableOp(BI->getOperand(1), Instruction::Mul) &&
+ (!BI->hasOneUse() ||
+ !isReassociableOp(BI->use_back(), Instruction::Mul))) {
+ BI = LowerNegateToMultiply(BI, ValueRankMap);
MadeChange = true;
- } else if (BinaryOperator::isNeg(BI)) {
- // Otherwise, this is a negation. See if the operand is a multiply tree
- // and if this is not an inner node of a multiply tree.
- if (isReassociableOp(BI->getOperand(1), Instruction::Mul) &&
- (!BI->hasOneUse() ||
- !isReassociableOp(BI->use_back(), Instruction::Mul))) {
- BI = LowerNegateToMultiply(BI, ValueRankMap);
- MadeChange = true;
- }
}
}
+ }
- // If this instruction is a commutative binary operator, process it.
- if (!BI->isAssociative()) continue;
- BinaryOperator *I = cast<BinaryOperator>(BI);
+ // If this instruction is a commutative binary operator, process it.
+ if (!BI->isAssociative()) return;
+ BinaryOperator *I = cast<BinaryOperator>(BI);
- // If this is an interior node of a reassociable tree, ignore it until we
- // get to the root of the tree, to avoid N^2 analysis.
- if (I->hasOneUse() && isReassociableOp(I->use_back(), I->getOpcode()))
- continue;
+ // If this is an interior node of a reassociable tree, ignore it until we
+ // get to the root of the tree, to avoid N^2 analysis.
+ if (I->hasOneUse() && isReassociableOp(I->use_back(), I->getOpcode()))
+ return;
- // If this is an add tree that is used by a sub instruction, ignore it
- // until we process the subtract.
- if (I->hasOneUse() && I->getOpcode() == Instruction::Add &&
- cast<Instruction>(I->use_back())->getOpcode() == Instruction::Sub)
- continue;
+ // If this is an add tree that is used by a sub instruction, ignore it
+ // until we process the subtract.
+ if (I->hasOneUse() && I->getOpcode() == Instruction::Add &&
+ cast<Instruction>(I->use_back())->getOpcode() == Instruction::Sub)
+ return;
- ReassociateExpression(I);
- }
+ ReassociateExpression(I);
}
Value *Reassociate::ReassociateExpression(BinaryOperator *I) {
-
+
// First, walk the expression tree, linearizing the tree, collecting the
// operand information.
SmallVector<ValueEntry, 8> Ops;
LinearizeExprTree(I, Ops);
-
+
DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
-
+
// Now that we have linearized the tree to a list and have gathered all of
// the operands and their ranks, sort the operands by their rank. Use a
// stable_sort so that values with equal ranks will have their relative
// this sorts so that the highest ranking values end up at the beginning of
// the vector.
std::stable_sort(Ops.begin(), Ops.end());
-
+
// OptimizeExpression - Now that we have the expression tree in a convenient
// sorted form, optimize it globally if possible.
if (Value *V = OptimizeExpression(I, Ops)) {
// eliminate it.
DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
I->replaceAllUsesWith(V);
+ if (Instruction *VI = dyn_cast<Instruction>(V))
+ VI->setDebugLoc(I->getDebugLoc());
RemoveDeadBinaryOp(I);
++NumAnnihil;
return V;
}
-
+
// We want to sink immediates as deeply as possible except in the case where
// this is a multiply tree used only by an add, and the immediate is a -1.
// In this case we reassociate to put the negation on the outside so that we
ValueEntry Tmp = Ops.pop_back_val();
Ops.insert(Ops.begin(), Tmp);
}
-
+
DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
-
+
if (Ops.size() == 1) {
// This expression tree simplified to something that isn't a tree,
// eliminate it.
I->replaceAllUsesWith(Ops[0].Op);
+ if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
+ OI->setDebugLoc(I->getDebugLoc());
RemoveDeadBinaryOp(I);
return Ops[0].Op;
}
-
+
// Now that we ordered and optimized the expressions, splat them back into
// the expression tree, removing any unneeded nodes.
RewriteExprTree(I, Ops);
return I;
}
-
bool Reassociate::runOnFunction(Function &F) {
// Recalculate the rank map for F
BuildRankMap(F);
MadeChange = false;
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
- ReassociateBB(FI);
+ for (BasicBlock::iterator BBI = FI->begin(); BBI != FI->end(); )
+ ReassociateInst(BBI);
+
+ // Now that we're done, revisit any instructions which are likely to
+ // have secondary reassociation opportunities.
+ while (!RedoInsts.empty())
+ if (Value *V = RedoInsts.pop_back_val()) {
+ BasicBlock::iterator BBI = cast<Instruction>(V);
+ ReassociateInst(BBI);
+ }
+
+ // Now that we're done, delete any instructions which are no longer used.
+ while (!DeadInsts.empty())
+ if (Value *V = DeadInsts.pop_back_val())
+ RecursivelyDeleteTriviallyDeadInstructions(V);
// We are done with the rank map.
RankMap.clear();
ValueRankMap.clear();
return MadeChange;
}
-
projects / oota-llvm.git / blobdiff