//===----------------------------------------------------------------------===//
//
// This pass reassociates commutative expressions in an order that is designed
-// to promote better constant propagation, GCSE, LICM, PRE...
+// to promote better constant propagation, GCSE, LICM, PRE, etc.
//
// For example: 4 + (x + 5) -> x + (4 + 5)
//
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/DenseMap.h"
#include <algorithm>
-#include <map>
using namespace llvm;
STATISTIC(NumLinear , "Number of insts linearized");
///
static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
Module *M = I->getParent()->getParent()->getParent();
- errs() << Instruction::getOpcodeName(I->getOpcode()) << " "
+ dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
<< *Ops[0].Op->getType() << '\t';
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
- errs() << "[ ";
- WriteAsOperand(errs(), Ops[i].Op, false, M);
- errs() << ", #" << Ops[i].Rank << "] ";
+ dbgs() << "[ ";
+ WriteAsOperand(dbgs(), Ops[i].Op, false, M);
+ dbgs() << ", #" << Ops[i].Rank << "] ";
}
}
#endif
namespace {
class Reassociate : public FunctionPass {
- std::map<BasicBlock*, unsigned> RankMap;
-
std::map<AssertingVH<>, unsigned> ValueRankMap;
+ DenseMap<BasicBlock*, unsigned> RankMap;
+
DenseMap<AssertingVH<>, unsigned> ValueRankMap;
bool MadeChange;
public:
static char ID; // Pass identification, replacement for typeid
}
unsigned Reassociate::getRank(Value *V) {
- if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument...
-
Instruction *I = dyn_cast<Instruction>(V);
- if (I == 0) return 0; // Otherwise it's a global or constant, rank 0.
+ if (I == 0) {
+ if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
+ return 0; // Otherwise it's a global or constant, rank 0.
+ }
- unsigned &CachedRank = ValueRankMap[I];
- if (CachedRank) return CachedRank; // Rank already known?
+ if (unsigned Rank = ValueRankMap[I])
+ return Rank; // Rank already known?
// If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
// we can reassociate expressions for code motion! Since we do not recurse
(!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I)))
++Rank;
- //DEBUG(errs() << "Calculated Rank[" << V->getName() << "] = "
+ //DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = "
// << Rank << "\n");
- return CachedRank = Rank;
+ return ValueRankMap[I] = Rank;
}
/// isReassociableOp - Return true if V is an instruction of the specified
/// LowerNegateToMultiply - Replace 0-X with X*-1.
///
static Instruction *LowerNegateToMultiply(Instruction *Neg,
-
std::map<AssertingVH<>, unsigned> &ValueRankMap) {
+
DenseMap<AssertingVH<>, unsigned> &ValueRankMap) {
Constant *Cst = Constant::getAllOnesValue(Neg->getType());
Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
isReassociableOp(RHS, I->getOpcode()) &&
"Not an expression that needs linearization?");
- DEBUG(errs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n');
+ DEBUG(dbgs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n');
// Move the RHS instruction to live immediately before I, avoiding breaking
// dominator properties.
++NumLinear;
MadeChange = true;
- DEBUG(errs() << "Linearized: " << *I << '\n');
+ DEBUG(dbgs() << "Linearized: " << *I << '\n');
// If D is part of this expression tree, tail recurse.
if (isReassociableOp(I->getOperand(1), I->getOpcode()))
if (I->getOperand(0) != Ops[i].Op ||
I->getOperand(1) != Ops[i+1].Op) {
Value *OldLHS = I->getOperand(0);
- DEBUG(errs() << "RA: " << *I << '\n');
+ DEBUG(dbgs() << "RA: " << *I << '\n');
I->setOperand(0, Ops[i].Op);
I->setOperand(1, Ops[i+1].Op);
- DEBUG(errs() << "TO: " << *I << '\n');
+ DEBUG(dbgs() << "TO: " << *I << '\n');
MadeChange = true;
++NumChanged;
assert(i+2 < Ops.size() && "Ops index out of range!");
if (I->getOperand(1) != Ops[i].Op) {
- DEBUG(errs() << "RA: " << *I << '\n');
+ DEBUG(dbgs() << "RA: " << *I << '\n');
I->setOperand(1, Ops[i].Op);
- DEBUG(errs() << "TO: " << *I << '\n');
+ DEBUG(dbgs() << "TO: " << *I << '\n');
MadeChange = true;
++NumChanged;
}
// 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,
// X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
// so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
// the constants. We assume that instcombine will clean up the mess later if
- // we introduce tons of unnecessary negation instructions...
+ // we introduce tons of unnecessary negation instructions.
//
if (Instruction *I = dyn_cast<Instruction>(V))
if (I->getOpcode() == Instruction::Add && I->hasOneUse()) {
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;
+
+ // 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);
+
+ // 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)) {
+ InsertPt = II->getNormalDest()->begin();
+ } else {
+ InsertPt = InstInput;
+ ++InsertPt;
+ }
+ while (isa<PHINode>(InsertPt)) ++InsertPt;
+ } else {
+ InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
+ }
+ TheNeg->moveBefore(InsertPt);
+ return TheNeg;
+ }
// Insert a 'neg' instruction that subtracts the value from zero to get the
// negation.
- //
return BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI);
}
/// only used by an add, transform this into (X+(0-Y)) to promote better
/// reassociation.
static Instruction *BreakUpSubtract(Instruction *Sub,
-
std::map<AssertingVH<>, unsigned> &ValueRankMap) {
- // Convert a subtract into an add and a neg instruction... so that sub
- // instructions can be commuted with other add instructions...
+
DenseMap<AssertingVH<>, unsigned> &ValueRankMap) {
+ // Convert a subtract into an add and a neg instruction. This allows sub
+ // instructions to be commuted with other add instructions.
//
- // Calculate the negative value of Operand 1 of the sub instruction...
- // and set it as the RHS of the add instruction we just made...
+ // Calculate the negative value of Operand 1 of the sub instruction,
+ // and set it as the RHS of the add instruction we just made.
//
Value *NegVal = NegateValue(Sub->getOperand(1), Sub);
Instruction *New =
Sub->replaceAllUsesWith(New);
Sub->eraseFromParent();
- DEBUG(errs() << "Negated: " << *New << '\n');
+ DEBUG(dbgs() << "Negated: " << *New << '\n');
return New;
}
/// by one, change this into a multiply by a constant to assist with further
/// reassociation.
static Instruction *ConvertShiftToMul(Instruction *Shl,
-
std::map<AssertingVH<>, unsigned> &ValueRankMap) {
+
DenseMap<AssertingVH<>, 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) ||
}
// 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.
+// 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;
for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j)
if (Ops[j].Op == X)
return j;
- // Scan backwards
+ // Scan backwards.
for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j)
if (Ops[j].Op == X)
return j;
LinearizeExprTree(BO, Factors);
bool FoundFactor = false;
- for (unsigned i = 0, e = Factors.size(); i != e; ++i)
+ bool NeedsNegate = false;
+ for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
if (Factors[i].Op == Factor) {
FoundFactor = true;
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))
+ if (FC1->getValue() == -FC2->getValue()) {
+ FoundFactor = NeedsNegate = true;
+ Factors.erase(Factors.begin()+i);
+ 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();
- return Factors[0].Op;
+ V = Factors[0].Op;
+ } else {
+ RewriteExprTree(BO, Factors);
+ V = BO;
}
- RewriteExprTree(BO, Factors);
- return BO;
+ if (NeedsNegate)
+ V = BinaryOperator::CreateNeg(V, "neg", InsertPt);
+
+ return V;
}
/// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
assert(i < Ops.size());
if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
if (Opcode == Instruction::And || Opcode == Instruction::Or) {
- // Drop duplicate values.
+ // Drop duplicate values for And and Or.
Ops.erase(Ops.begin()+i);
--i; --e;
++NumAnnihil;
- } else {
- assert(Opcode == Instruction::Xor);
- if (e == 2)
- return Constant::getNullValue(Ops[0].Op->getType());
-
- // ... X^X -> ...
- Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
- i -= 1; e -= 2;
- ++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;
+ ++NumAnnihil;
}
}
return 0;
/// is returned, otherwise the Ops list is mutated as necessary.
Value *Reassociate::OptimizeAdd(Instruction *I,
SmallVectorImpl<ValueEntry> &Ops) {
- SmallPtrSet<Value*, 8> OperandsSeen;
-
-Restart:
- OperandsSeen.clear();
-
// Scan the operand lists looking for X and -X pairs. If we find any, we
// can simplify the expression. X+-X == 0. While we're at it, scan for any
// duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
+ //
+ // TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1".
+ //
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
Value *TheOp = Ops[i].Op;
// Check to see if we've seen this operand before. If so, we factor all
- // instances of the operand together.
- if (!OperandsSeen.insert(TheOp)) {
- // Rescan the list, removing all instances of this operand from the expr.
+ // instances of the operand together. Due to our sorting criteria, we know
+ // that these need to be next to each other in the vector.
+ if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
+ // Rescan the list, remove all instances of this operand from the expr.
unsigned NumFound = 0;
- for (unsigned j = 0, je = Ops.size(); j != je; ++j) {
- if (Ops[j].Op != TheOp) continue;
+ do {
+ Ops.erase(Ops.begin()+i);
++NumFound;
- Ops.erase(Ops.begin()+j);
- --j; --je;
- }
-
+ } 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);
// "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));
- goto Restart;
+
+ --i;
+ e = Ops.size();
+ continue;
}
// Check for X and -X in the operand list.
assert(Factors.size() > 1 && "Bad linearize!");
// Add one to FactorOccurrences for each unique factor in this op.
- if (Factors.size() == 2) {
- unsigned Occ = ++FactorOccurrences[Factors[0]];
- if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[0]; }
- if (Factors[0] != Factors[1]) { // Don't double count A*A.
- Occ = ++FactorOccurrences[Factors[1]];
- if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[1]; }
- }
- } else {
- SmallPtrSet<Value*, 4> Duplicates;
- for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
- if (!Duplicates.insert(Factors[i])) continue;
-
- unsigned Occ = ++FactorOccurrences[Factors[i]];
- if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[i]; }
- }
+ 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()) {
+ 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; }
+ }
}
}
// Create the multiply.
Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
- // FIXME: Should rerun 'ReassociateExpression' on the mul too??
+ // 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));
// 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)".
switch (Opcode) {
default: break;
case Instruction::And:
- if (CstVal->isZero()) // ... & 0 -> 0
+ if (CstVal->isZero()) // X & 0 -> 0
return CstVal;
- if (CstVal->isAllOnesValue()) // ... & -1 -> ...
+ if (CstVal->isAllOnesValue()) // X & -1 -> X
Ops.pop_back();
break;
case Instruction::Mul:
- if (CstVal->isZero()) { // ... * 0 -> 0
+ if (CstVal->isZero()) { // X * 0 -> 0
++NumAnnihil;
return CstVal;
}
if (cast<ConstantInt>(CstVal)->isOne())
- Ops.pop_back(); // ... * 1 -> ...
+ Ops.pop_back(); // X * 1 -> X
break;
case Instruction::Or:
- if (CstVal->isAllOnesValue()) // ... | -1 -> -1
+ if (CstVal->isAllOnesValue()) // X | -1 -> -1
return CstVal;
// FALLTHROUGH!
case Instruction::Add:
case Instruction::Xor:
- if (CstVal->isZero()) // ... [|^+] 0 -> ...
+ if (CstVal->isZero()) // X [|^+] 0 -> X
Ops.pop_back();
break;
}
SmallVector<ValueEntry, 8> Ops;
LinearizeExprTree(I, Ops);
- DEBUG(errs() << "RAIn:\t"; PrintOps(I, Ops); errs() << '\n');
+ 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
if (Value *V = OptimizeExpression(I, Ops)) {
// This expression tree simplified to something that isn't a tree,
// eliminate it.
- DEBUG(errs() << "Reassoc to scalar: " << *V << '\n');
+ DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
I->replaceAllUsesWith(V);
RemoveDeadBinaryOp(I);
++NumAnnihil;
Ops.insert(Ops.begin(), Tmp);
}
- DEBUG(errs() << "RAOut:\t"; PrintOps(I, Ops); errs() << '\n');
+ DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
if (Ops.size() == 1) {
// This expression tree simplified to something that isn't a tree,
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
ReassociateBB(FI);
- // We are done with the rank map...
+ // We are done with the rank map.
RankMap.clear();
ValueRankMap.clear();
return MadeChange;
projects / oota-llvm.git / blobdiff