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Convert SCCP over to use InstVisitor instead of hand crafted switch

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2286 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-04-18 15:13:15 +00:00
parent d59b0af98b
commit 2a632551a7
1 changed files with 143 additions and 188 deletions
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331
lib/Transforms/Scalar/SCCP.cpp
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@ -25,6 +25,7 @@
#include "llvm/iTerminators.h" #include "llvm/iTerminators.h"
#include "llvm/iOther.h" #include "llvm/iOther.h"
#include "llvm/Pass.h" #include "llvm/Pass.h"
#include "llvm/Support/InstVisitor.h"
#include "Support/STLExtras.h" #include "Support/STLExtras.h"
#include <algorithm> #include <algorithm>
#include <map> #include <map>
@ -84,7 +85,7 @@ public:
// This class does all of the work of Sparse Conditional Constant Propogation. // This class does all of the work of Sparse Conditional Constant Propogation.
// It's public interface consists of a constructor and a doSCCP() method. // It's public interface consists of a constructor and a doSCCP() method.
// //
class SCCP { class SCCP : public InstVisitor<SCCP> {
Function *M; // The function that we are working on Function *M; // The function that we are working on
std::set<BasicBlock*> BBExecutable;// The basic blocks that are executable std::set<BasicBlock*> BBExecutable;// The basic blocks that are executable
@ -109,6 +110,7 @@ public:
// The implementation of this class // The implementation of this class
// //
private: private:
friend class InstVisitor<SCCP>; // Allow callbacks from visitor
// markValueOverdefined - Make a value be marked as "constant". If the value // markValueOverdefined - Make a value be marked as "constant". If the value
// is not already a constant, add it to the instruction work list so that // is not already a constant, add it to the instruction work list so that
@ -168,11 +170,34 @@ private:
} }
// UpdateInstruction - Something changed in this instruction... Either an // visit implementations - Something changed in this instruction... Either an
// operand made a transition, or the instruction is newly executable. Change // operand made a transition, or the instruction is newly executable. Change
// the value type of I to reflect these changes if appropriate. // the value type of I to reflect these changes if appropriate.
// //
void UpdateInstruction(Instruction *I); void visitPHINode(PHINode *I);
// Terminators
void visitReturnInst(ReturnInst *I) { /*does not have an effect*/ }
void visitBranchInst(BranchInst *I);
void visitSwitchInst(SwitchInst *I);
void visitUnaryOperator(Instruction *I);
void visitCastInst(CastInst *I) { visitUnaryOperator(I); }
void visitBinaryOperator(Instruction *I);
void visitShiftInst(ShiftInst *I) { visitBinaryOperator(I); }
// Instructions that cannot be folded away...
void visitMemAccessInst (Instruction *I) { markOverdefined(I); }
void visitCallInst (Instruction *I) { markOverdefined(I); }
void visitInvokeInst (Instruction *I) { markOverdefined(I); }
void visitAllocationInst(Instruction *I) { markOverdefined(I); }
void visitFreeInst (Instruction *I) { markOverdefined(I); }
void visitInstruction(Instruction *I) {
// If a new instruction is added to LLVM that we don't handle...
cerr << "SCCP: Don't know how to handle: " << I;
markOverdefined(I); // Just in case
}
// OperandChangedState - This method is invoked on all of the users of an // OperandChangedState - This method is invoked on all of the users of an
// instruction that was just changed state somehow.... Based on this // instruction that was just changed state somehow.... Based on this
@ -225,10 +250,9 @@ bool SCCP::doSCCP() {
if (BB->getTerminator()->getNumSuccessors() == 1) if (BB->getTerminator()->getNumSuccessors() == 1)
markExecutable(BB->getTerminator()->getSuccessor(0)); markExecutable(BB->getTerminator()->getSuccessor(0));
// Loop over all of the instructions and notify them that they are newly // Notify all instructions in this basic block that they are newly
// executable... // executable.
for_each(BB->begin(), BB->end(), visit(BB);
bind_obj(this, &SCCP::UpdateInstruction));
} }
} }
@ -284,7 +308,7 @@ bool SCCP::doSCCP() {
} }
// UpdateInstruction - Something changed in this instruction... Either an // visit Implementations - Something changed in this instruction... Either an
// operand made a transition, or the instruction is newly executable. Change // operand made a transition, or the instruction is newly executable. Change
// the value type of I to reflect these changes if appropriate. This method // the value type of I to reflect these changes if appropriate. This method
// makes sure to do the following actions: // makes sure to do the following actions:
@ -302,199 +326,130 @@ bool SCCP::doSCCP() {
// 7. If a conditional branch has a value that is overdefined, make all // 7. If a conditional branch has a value that is overdefined, make all
// successors executable. // successors executable.
// //
void SCCP::UpdateInstruction(Instruction *I) {
InstVal &IValue = ValueState[I];
if (IValue.isOverdefined())
return; // If already overdefined, we aren't going to effect anything
switch (I->getOpcode()) { void SCCP::visitPHINode(PHINode *PN) {
//===-----------------------------------------------------------------===// unsigned NumValues = PN->getNumIncomingValues(), i;
// Handle PHI nodes... InstVal *OperandIV = 0;
//
case Instruction::PHINode: {
PHINode *PN = cast<PHINode>(I);
unsigned NumValues = PN->getNumIncomingValues(), i;
InstVal *OperandIV = 0;
// Look at all of the executable operands of the PHI node. If any of them // 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 // are overdefined, the PHI becomes overdefined as well. If they are all
// constant, and they agree with each other, the PHI becomes the identical // constant, and they agree with each other, the PHI becomes the identical
// constant. If they are constant and don't agree, the PHI is overdefined. // constant. If they are constant and don't agree, the PHI is overdefined.
// If there are no executable operands, the PHI remains undefined. // If there are no executable operands, the PHI remains undefined.
// //
for (i = 0; i < NumValues; ++i) { for (i = 0; i < NumValues; ++i) {
if (BBExecutable.count(PN->getIncomingBlock(i))) { if (BBExecutable.count(PN->getIncomingBlock(i))) {
InstVal &IV = getValueState(PN->getIncomingValue(i)); InstVal &IV = getValueState(PN->getIncomingValue(i));
if (IV.isUndefined()) continue; // Doesn't influence PHI node. if (IV.isUndefined()) continue; // Doesn't influence PHI node.
if (IV.isOverdefined()) { // PHI node becomes overdefined! if (IV.isOverdefined()) { // PHI node becomes overdefined!
markOverdefined(PN); markOverdefined(PN);
return; return;
} }
if (OperandIV == 0) { // Grab the first value... if (OperandIV == 0) { // Grab the first value...
OperandIV = &IV; OperandIV = &IV;
} else { // Another value is being merged in! } else { // Another value is being merged in!
// There is already a reachable operand. If we conflict with it, // There is already a reachable operand. If we conflict with it,
// then the PHI node becomes overdefined. If we agree with it, we // then the PHI node becomes overdefined. If we agree with it, we
// can continue on. // can continue on.
// Check to see if there are two different constants merging... // Check to see if there are two different constants merging...
if (IV.getConstant() != OperandIV->getConstant()) { if (IV.getConstant() != OperandIV->getConstant()) {
// Yes there is. This means the PHI node is not constant. // Yes there is. This means the PHI node is not constant.
// You must be overdefined poor PHI. // You must be overdefined poor PHI.
// //
markOverdefined(I); // The PHI node now becomes overdefined markOverdefined(PN); // The PHI node now becomes overdefined
return; // I'm done analyzing you return; // I'm done analyzing you
}
} }
} }
} }
// If we exited the loop, this means that the PHI node only has constant
// arguments that agree with each other(and OperandIV is a pointer to one
// of their InstVal's) or OperandIV is null because there are no defined
// incoming arguments. If this is the case, the PHI remains undefined.
//
if (OperandIV) {
assert(OperandIV->isConstant() && "Should only be here for constants!");
markConstant(I, OperandIV->getConstant()); // Aquire operand value
}
return;
} }
//===-----------------------------------------------------------------===// // If we exited the loop, this means that the PHI node only has constant
// Handle instructions that unconditionally provide overdefined values... // arguments that agree with each other(and OperandIV is a pointer to one
// // of their InstVal's) or OperandIV is null because there are no defined
case Instruction::Malloc: // incoming arguments. If this is the case, the PHI remains undefined.
case Instruction::Free:
case Instruction::Alloca:
case Instruction::Load:
case Instruction::Store:
// TODO: getfield
case Instruction::Call:
case Instruction::Invoke:
markOverdefined(I); // Memory and call's are all overdefined
return;
//===-----------------------------------------------------------------===//
// Handle Terminator instructions...
//
case Instruction::Ret: return; // Function return doesn't affect anything
case Instruction::Br: { // Handle conditional branches...
BranchInst *BI = cast<BranchInst>(I);
if (BI->isUnconditional())
return; // Unconditional branches are already handled!
InstVal &BCValue = getValueState(BI->getCondition());
if (BCValue.isOverdefined()) {
// Overdefined condition variables mean the branch could go either way.
markExecutable(BI->getSuccessor(0));
markExecutable(BI->getSuccessor(1));
} else if (BCValue.isConstant()) {
// Constant condition variables mean the branch can only go a single way.
ConstantBool *CPB = cast<ConstantBool>(BCValue.getConstant());
if (CPB->getValue()) // If the branch condition is TRUE...
markExecutable(BI->getSuccessor(0));
else // Else if the br cond is FALSE...
markExecutable(BI->getSuccessor(1));
}
return;
}
case Instruction::Switch: {
SwitchInst *SI = cast<SwitchInst>(I);
InstVal &SCValue = getValueState(SI->getCondition());
if (SCValue.isOverdefined()) { // Overdefined condition? All dests are exe
for(unsigned i = 0; BasicBlock *Succ = SI->getSuccessor(i); ++i)
markExecutable(Succ);
} else if (SCValue.isConstant()) {
Constant *CPV = SCValue.getConstant();
// Make sure to skip the "default value" which isn't a value
for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i) {
if (SI->getSuccessorValue(i) == CPV) {// Found the right branch...
markExecutable(SI->getSuccessor(i));
return;
}
}
// Constant value not equal to any of the branches... must execute
// default branch then...
markExecutable(SI->getDefaultDest());
}
return;
}
default: break; // Handle math operators as groups.
} // end switch(I->getOpcode())
//===-------------------------------------------------------------------===//
// Handle Unary and cast instructions...
// //
if (isa<UnaryOperator>(I) || isa<CastInst>(I)) { if (OperandIV) {
Value *V = I->getOperand(0); assert(OperandIV->isConstant() && "Should only be here for constants!");
InstVal &VState = getValueState(V); markConstant(PN, OperandIV->getConstant()); // Aquire operand value
if (VState.isOverdefined()) { // Inherit overdefinedness of operand
markOverdefined(I);
} else if (VState.isConstant()) { // Propogate constant value
Constant *Result = isa<CastInst>(I)
? ConstantFoldCastInstruction(VState.getConstant(), I->getType())
: ConstantFoldUnaryInstruction(I->getOpcode(), VState.getConstant());
if (Result) {
// This instruction constant folds!
markConstant(I, Result);
} else {
markOverdefined(I); // Don't know how to fold this instruction. :(
}
}
return;
} }
//===-----------------------------------------------------------------===//
// Handle GetElementPtr instructions...
//
if (isa<GetElementPtrInst>(I)) {
markOverdefined(I);
return;
}
//===-----------------------------------------------------------------===//
// Handle Binary instructions...
//
if (isa<BinaryOperator>(I) || isa<ShiftInst>(I)) {
Value *V1 = I->getOperand(0);
Value *V2 = I->getOperand(1);
InstVal &V1State = getValueState(V1);
InstVal &V2State = getValueState(V2);
if (V1State.isOverdefined() || V2State.isOverdefined()) {
markOverdefined(I);
} else if (V1State.isConstant() && V2State.isConstant()) {
Constant *Result =
ConstantFoldBinaryInstruction(I->getOpcode(),
V1State.getConstant(),
V2State.getConstant());
if (Result) {
// This instruction constant folds!
markConstant(I, Result);
} else {
markOverdefined(I); // Don't know how to fold this instruction. :(
}
}
return;
}
// Shouldn't get here... either the switch statement or one of the group
// handlers should have kicked in...
//
cerr << "SCCP: Don't know how to handle: " << I;
markOverdefined(I); // Just in case
} }
void SCCP::visitBranchInst(BranchInst *BI) {
if (BI->isUnconditional())
return; // Unconditional branches are already handled!
InstVal &BCValue = getValueState(BI->getCondition());
if (BCValue.isOverdefined()) {
// Overdefined condition variables mean the branch could go either way.
markExecutable(BI->getSuccessor(0));
markExecutable(BI->getSuccessor(1));
} else if (BCValue.isConstant()) {
// Constant condition variables mean the branch can only go a single way.
if (BCValue.getConstant() == ConstantBool::True)
markExecutable(BI->getSuccessor(0));
else
markExecutable(BI->getSuccessor(1));
}
}
void SCCP::visitSwitchInst(SwitchInst *SI) {
InstVal &SCValue = getValueState(SI->getCondition());
if (SCValue.isOverdefined()) { // Overdefined condition? All dests are exe
for(unsigned i = 0; BasicBlock *Succ = SI->getSuccessor(i); ++i)
markExecutable(Succ);
} else if (SCValue.isConstant()) {
Constant *CPV = SCValue.getConstant();
// Make sure to skip the "default value" which isn't a value
for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i) {
if (SI->getSuccessorValue(i) == CPV) {// Found the right branch...
markExecutable(SI->getSuccessor(i));
return;
}
}
// Constant value not equal to any of the branches... must execute
// default branch then...
markExecutable(SI->getDefaultDest());
}
}
void SCCP::visitUnaryOperator(Instruction *I) {
Value *V = I->getOperand(0);
InstVal &VState = getValueState(V);
if (VState.isOverdefined()) { // Inherit overdefinedness of operand
markOverdefined(I);
} else if (VState.isConstant()) { // Propogate constant value
Constant *Result = isa<CastInst>(I)
? ConstantFoldCastInstruction(VState.getConstant(), I->getType())
: ConstantFoldUnaryInstruction(I->getOpcode(), VState.getConstant());
if (Result) {
// This instruction constant folds!
markConstant(I, Result);
} else {
markOverdefined(I); // Don't know how to fold this instruction. :(
}
}
}
// Handle BinaryOperators and Shift Instructions...
void SCCP::visitBinaryOperator(Instruction *I) {
InstVal &V1State = getValueState(I->getOperand(0));
InstVal &V2State = getValueState(I->getOperand(1));
if (V1State.isOverdefined() || V2State.isOverdefined()) {
markOverdefined(I);
} else if (V1State.isConstant() && V2State.isConstant()) {
Constant *Result = ConstantFoldBinaryInstruction(I->getOpcode(),
V1State.getConstant(),
V2State.getConstant());
if (Result)
markConstant(I, Result); // This instruction constant fold!s
else
markOverdefined(I); // Don't know how to fold this instruction. :(
}
}
// OperandChangedState - This method is invoked on all of the users of an // OperandChangedState - This method is invoked on all of the users of an
// instruction that was just changed state somehow.... Based on this // instruction that was just changed state somehow.... Based on this
@ -505,7 +460,7 @@ void SCCP::OperandChangedState(User *U) {
Instruction *I = cast<Instruction>(U); Instruction *I = cast<Instruction>(U);
if (!BBExecutable.count(I->getParent())) return; // Inst not executable yet! if (!BBExecutable.count(I->getParent())) return; // Inst not executable yet!
UpdateInstruction(I); visit(I);
} }
namespace { namespace {