//===- Reassociate.cpp - Reassociate binary expressions -------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
//
// This pass reassociates commutative expressions in an order that is designed
-// to promote better constant propogation, GCSE, LICM, PRE...
+// to promote better constant propagation, GCSE, LICM, PRE...
//
// For example: 4 + (x + 5) -> x + (4 + 5)
//
// (starting at 2), which effectively gives values in deep loops higher rank
// than values not in loops.
//
-// This code was originally written by Chris Lattner, and was then cleaned up
-// and perfected by Casey Carter.
-//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
#include "llvm/Pass.h"
#include "llvm/Constant.h"
#include "llvm/Support/CFG.h"
+#include "Support/Debug.h"
#include "Support/PostOrderIterator.h"
#include "Support/Statistic.h"
class Reassociate : public FunctionPass {
std::map<BasicBlock*, unsigned> RankMap;
+ std::map<Value*, unsigned> ValueRankMap;
public:
bool runOnFunction(Function &F);
Pass *createReassociatePass() { return new Reassociate(); }
void Reassociate::BuildRankMap(Function &F) {
- unsigned i = 1;
+ unsigned i = 2;
+
+ // Assign distinct ranks to function arguments
+ for (Function::aiterator I = F.abegin(), E = F.aend(); I != E; ++I)
+ ValueRankMap[I] = ++i;
+
ReversePostOrderTraversal<Function*> RPOT(&F);
for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
E = RPOT.end(); I != E; ++I)
- RankMap[*I] = ++i;
+ RankMap[*I] = ++i << 16;
}
unsigned Reassociate::getRank(Value *V) {
- if (isa<Argument>(V)) return 1; // Function argument...
+ if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument...
+
if (Instruction *I = dyn_cast<Instruction>(V)) {
- // If this is an expression, return the MAX(rank(LHS), rank(RHS)) so that we
- // can reassociate expressions for code motion! Since we do not recurse for
- // PHI nodes, we cannot have infinite recursion here, because there cannot
- // be loops in the value graph (except for PHI nodes).
+ // 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
+ // for PHI nodes, we cannot have infinite recursion here, because there
+ // cannot be loops in the value graph that do not go through PHI nodes.
//
- if (I->getOpcode() == Instruction::PHINode ||
+ if (I->getOpcode() == Instruction::PHI ||
I->getOpcode() == Instruction::Alloca ||
I->getOpcode() == Instruction::Malloc || isa<TerminatorInst>(I) ||
- I->hasSideEffects())
+ I->mayWriteToMemory()) // Cannot move inst if it writes to memory!
return RankMap[I->getParent()];
+ unsigned &CachedRank = ValueRankMap[I];
+ if (CachedRank) return CachedRank; // Rank already known?
+
+ // If not, compute it!
unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
for (unsigned i = 0, e = I->getNumOperands();
i != e && Rank != MaxRank; ++i)
Rank = std::max(Rank, getRank(I->getOperand(i)));
- return Rank;
+ DEBUG(std::cerr << "Calculated Rank[" << V->getName() << "] = "
+ << Rank+1 << "\n");
+
+ return CachedRank = Rank+1;
}
// Otherwise it's a global or constant, rank 0.
std::swap(LHSRank, RHSRank);
Changed = true;
++NumSwapped;
- DEBUG(std::cerr << "Transposed: " << I << " Result BB: " << I->getParent());
+ DEBUG(std::cerr << "Transposed: " << I
+ /* << " Result BB: " << I->getParent()*/);
}
// If the LHS is the same operator as the current one is, and if we are the
// only expression using it...
//
if (BinaryOperator *LHSI = dyn_cast<BinaryOperator>(LHS))
- if (LHSI->getOpcode() == I->getOpcode() && LHSI->use_size() == 1) {
+ if (LHSI->getOpcode() == I->getOpcode() && LHSI->hasOneUse()) {
// If the rank of our current RHS is less than the rank of the LHS's LHS,
// then we reassociate the two instructions...
- if (RHSRank < getRank(LHSI->getOperand(0))) {
- unsigned TakeOp = 0;
- if (BinaryOperator *IOp = dyn_cast<BinaryOperator>(LHSI->getOperand(0)))
- if (IOp->getOpcode() == LHSI->getOpcode())
- TakeOp = 1; // Hoist out non-tree portion
+ unsigned TakeOp = 0;
+ if (BinaryOperator *IOp = dyn_cast<BinaryOperator>(LHSI->getOperand(0)))
+ if (IOp->getOpcode() == LHSI->getOpcode())
+ TakeOp = 1; // Hoist out non-tree portion
+
+ if (RHSRank < getRank(LHSI->getOperand(TakeOp))) {
// Convert ((a + 12) + 10) into (a + (12 + 10))
I->setOperand(0, LHSI->getOperand(TakeOp));
+ LHSI->setOperand(TakeOp, RHS);
+ I->setOperand(1, LHSI);
// Move the LHS expression forward, to ensure that it is dominated by
// its operands.
- std::string Name = LHSI->getName();
- LHSI->setName("");
- BinaryOperator *NewLHS =
- BinaryOperator::create(LHSI->getOpcode(),
- LHSI->getOperand(0), LHSI->getOperand(1),
- Name, I);
-
- NewLHS->setOperand(TakeOp, RHS);
- I->setOperand(1, NewLHS);
-
- assert(LHSI->use_size() == 0 && "References to LHS shouldn't exist!");
- LHSI->getParent()->getInstList().erase(LHSI);
+ LHSI->getParent()->getInstList().remove(LHSI);
+ I->getParent()->getInstList().insert(I, LHSI);
++NumChanged;
- DEBUG(std::cerr << "Reassociated: " << I << " Result BB: "
- << I->getParent());
+ DEBUG(std::cerr << "Reassociated: " << I/* << " Result BB: "
+ << I->getParent()*/);
// Since we modified the RHS instruction, make sure that we recheck it.
- ReassociateExpr(NewLHS);
+ ReassociateExpr(LHSI);
+ ReassociateExpr(I);
return true;
}
}
// 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 unneccesary negation instructions...
+ // we introduce tons of unnecessary negation instructions...
//
if (Instruction *I = dyn_cast<Instruction>(V))
- if (I->getOpcode() == Instruction::Add && I->use_size() == 1) {
+ if (I->getOpcode() == Instruction::Add && I->hasOneUse()) {
Value *RHS = NegateValue(I->getOperand(1), BI);
Value *LHS = NegateValue(I->getOperand(0), BI);
bool Changed = false;
for (BasicBlock::iterator BI = BB->begin(); BI != BB->end(); ++BI) {
+ DEBUG(std::cerr << "Processing: " << *BI);
if (BI->getOpcode() == Instruction::Sub && !BinaryOperator::isNeg(BI)) {
// Convert a subtract into an add and a neg instruction... so that sub
// instructions can be commuted with other add instructions...
New->setOperand(1, NegateValue(New->getOperand(1), BI));
Changed = true;
- DEBUG(std::cerr << "Negated: " << New << " Result BB: " << BB);
+ DEBUG(std::cerr << "Negated: " << New /*<< " Result BB: " << BB*/);
}
// If this instruction is a commutative binary operator, and the ranks of
// the two operands are sorted incorrectly, fix it now.
//
if (BI->isAssociative()) {
- BinaryOperator *I = cast<BinaryOperator>(&*BI);
+ BinaryOperator *I = cast<BinaryOperator>(BI);
if (!I->use_empty()) {
// Make sure that we don't have a tree-shaped computation. If we do,
// linearize it. Convert (A+B)+(C+D) into ((A+B)+C)+D
Instruction *RHSI = dyn_cast<Instruction>(I->getOperand(1));
if (LHSI && (int)LHSI->getOpcode() == I->getOpcode() &&
RHSI && (int)RHSI->getOpcode() == I->getOpcode() &&
- RHSI->use_size() == 1) {
+ RHSI->hasOneUse()) {
// Insert a new temporary instruction... (A+B)+C
BinaryOperator *Tmp = BinaryOperator::create(I->getOpcode(), LHSI,
RHSI->getOperand(0),
I = Tmp;
++NumLinear;
Changed = true;
- DEBUG(std::cerr << "Linearized: " << I << " Result BB: " << BB);
+ DEBUG(std::cerr << "Linearized: " << I/* << " Result BB: " << BB*/);
}
// Make sure that this expression is correctly reassociated with respect
// We are done with the rank map...
RankMap.clear();
+ ValueRankMap.clear();
return Changed;
}
projects / oota-llvm.git / blobdiff