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Implement SCCP/phitest.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10763 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-01-12 03:57:30 +00:00
parent ff2ab4db20
commit 1daee8b010
1 changed files with 115 additions and 14 deletions
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129
lib/Transforms/Scalar/SCCP.cpp
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@ -75,7 +75,10 @@ public:
inline bool isConstant() const { return LatticeValue == constant; }
inline bool isOverdefined() const { return LatticeValue == overdefined; }
inline Constant *getConstant() const { return ConstantVal; }
inline Constant *getConstant() const {
assert(isConstant() && "Cannot get the constant of a non-constant!");
return ConstantVal;
}
};
} // end anonymous namespace
@ -94,6 +97,10 @@ class SCCP : public FunctionPass, public InstVisitor<SCCP> {
std::vector<Instruction*> InstWorkList;// The instruction work list
std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
/// UsersOfOverdefinedPHIs - Keep track of any users of PHI nodes that are not
/// overdefined, despite the fact that the PHI node is overdefined.
std::multimap<PHINode*, Instruction*> UsersOfOverdefinedPHIs;
/// KnownFeasibleEdges - Entries in this set are edges which have already had
/// PHI nodes retriggered.
typedef std::pair<BasicBlock*,BasicBlock*> Edge;
@ -463,7 +470,23 @@ bool SCCP::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
//
void SCCP::visitPHINode(PHINode &PN) {
InstVal &PNIV = getValueState(&PN);
if (PNIV.isOverdefined()) return; // Quick exit
if (PNIV.isOverdefined()) {
// There may be instructions using this PHI node that are not overdefined
// themselves. If so, make sure that they know that the PHI node operand
// changed.
std::multimap<PHINode*, Instruction*>::iterator I, E;
tie(I, E) = UsersOfOverdefinedPHIs.equal_range(&PN);
if (I != E) {
std::vector<Instruction*> Users;
Users.reserve(std::distance(I, E));
for (; I != E; ++I) Users.push_back(I->second);
while (!Users.empty()) {
visit(Users.back());
Users.pop_back();
}
}
return; // Quick exit
}
// Look at all of the executable operands of the PHI node. If any of them
// are overdefined, the PHI becomes overdefined as well. If they are all
@ -540,24 +563,102 @@ void SCCP::visitCastInst(CastInst &I) {
// Handle BinaryOperators and Shift Instructions...
void SCCP::visitBinaryOperator(Instruction &I) {
InstVal &IV = ValueState[&I];
if (IV.isOverdefined()) return;
InstVal &V1State = getValueState(I.getOperand(0));
InstVal &V2State = getValueState(I.getOperand(1));
if (V1State.isOverdefined() || V2State.isOverdefined()) {
markOverdefined(&I);
// If both operands are PHI nodes, it is possible that this instruction has
// a constant value, despite the fact that the PHI node doesn't. Check for
// this condition now.
if (PHINode *PN1 = dyn_cast<PHINode>(I.getOperand(0)))
if (PHINode *PN2 = dyn_cast<PHINode>(I.getOperand(1)))
if (PN1->getParent() == PN2->getParent()) {
// Since the two PHI nodes are in the same basic block, they must have
// entries for the same predecessors. Walk the predecessor list, and
// if all of the incoming values are constants, and the result of
// evaluating this expression with all incoming value pairs is the
// same, then this expression is a constant even though the PHI node
// is not a constant!
InstVal Result;
for (unsigned i = 0, e = PN1->getNumIncomingValues(); i != e; ++i) {
InstVal &In1 = getValueState(PN1->getIncomingValue(i));
BasicBlock *InBlock = PN1->getIncomingBlock(i);
InstVal &In2 =getValueState(PN2->getIncomingValueForBlock(InBlock));
if (In1.isOverdefined() || In2.isOverdefined()) {
Result.markOverdefined();
break; // Cannot fold this operation over the PHI nodes!
} else if (In1.isConstant() && In2.isConstant()) {
Constant *Val = 0;
if (isa<BinaryOperator>(I))
Val = ConstantExpr::get(I.getOpcode(), In1.getConstant(),
In2.getConstant());
else {
assert(isa<ShiftInst>(I) &&
"Can only handle binops and shifts here!");
Val = ConstantExpr::getShift(I.getOpcode(), In1.getConstant(),
In2.getConstant());
}
if (Result.isUndefined())
Result.markConstant(Val);
else if (Result.isConstant() && Result.getConstant() != Val) {
Result.markOverdefined();
break;
}
}
}
// If we found a constant value here, then we know the instruction is
// constant despite the fact that the PHI nodes are overdefined.
if (Result.isConstant()) {
markConstant(IV, &I, Result.getConstant());
// Remember that this instruction is virtually using the PHI node
// operands.
UsersOfOverdefinedPHIs.insert(std::make_pair(PN1, &I));
UsersOfOverdefinedPHIs.insert(std::make_pair(PN2, &I));
return;
} else if (Result.isUndefined()) {
return;
}
// Okay, this really is overdefined now. Since we might have
// speculatively thought that this was not overdefined before, and
// added ourselves to the UsersOfOverdefinedPHIs list for the PHIs,
// make sure to clean out any entries that we put there, for
// efficiency.
std::multimap<PHINode*, Instruction*>::iterator It, E;
tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN1);
while (It != E) {
if (It->second == &I) {
UsersOfOverdefinedPHIs.erase(It++);
} else
++It;
}
tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN2);
while (It != E) {
if (It->second == &I) {
UsersOfOverdefinedPHIs.erase(It++);
} else
++It;
}
}
markOverdefined(IV, &I);
} else if (V1State.isConstant() && V2State.isConstant()) {
Constant *Result = 0;
if (isa<BinaryOperator>(I))
Result = ConstantFoldBinaryInstruction(I.getOpcode(),
V1State.getConstant(),
V2State.getConstant());
else if (isa<ShiftInst>(I))
Result = ConstantFoldShiftInstruction(I.getOpcode(),
V1State.getConstant(),
V2State.getConstant());
if (Result)
markConstant(&I, Result); // This instruction constant folds!
else
markOverdefined(&I); // Don't know how to fold this instruction. :(
Result = ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
V2State.getConstant());
else {
assert (isa<ShiftInst>(I) && "Can only handle binops and shifts here!");
Result = ConstantExpr::getShift(I.getOpcode(), V1State.getConstant(),
V2State.getConstant());
}
markConstant(IV, &I, Result); // This instruction constant folds!
}
}