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https://github.com/c64scene-ar/llvm-6502.git
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Convert SCCP over to use InstVisitor instead of hand crafted switch
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2286 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
parent
d59b0af98b
commit
2a632551a7
@ -25,6 +25,7 @@
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#include "llvm/iTerminators.h"
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#include "llvm/iOther.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/InstVisitor.h"
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#include "Support/STLExtras.h"
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#include <algorithm>
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#include <map>
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@ -84,7 +85,7 @@ public:
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// This class does all of the work of Sparse Conditional Constant Propogation.
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// It's public interface consists of a constructor and a doSCCP() method.
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//
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class SCCP {
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class SCCP : public InstVisitor<SCCP> {
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Function *M; // The function that we are working on
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std::set<BasicBlock*> BBExecutable;// The basic blocks that are executable
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@ -109,6 +110,7 @@ public:
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// The implementation of this class
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//
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private:
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friend class InstVisitor<SCCP>; // Allow callbacks from visitor
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// markValueOverdefined - Make a value be marked as "constant". If the value
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// is not already a constant, add it to the instruction work list so that
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@ -168,11 +170,34 @@ private:
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}
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// UpdateInstruction - Something changed in this instruction... Either an
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// visit implementations - Something changed in this instruction... Either an
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// operand made a transition, or the instruction is newly executable. Change
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// the value type of I to reflect these changes if appropriate.
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//
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void UpdateInstruction(Instruction *I);
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void visitPHINode(PHINode *I);
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// Terminators
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void visitReturnInst(ReturnInst *I) { /*does not have an effect*/ }
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void visitBranchInst(BranchInst *I);
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void visitSwitchInst(SwitchInst *I);
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void visitUnaryOperator(Instruction *I);
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void visitCastInst(CastInst *I) { visitUnaryOperator(I); }
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void visitBinaryOperator(Instruction *I);
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void visitShiftInst(ShiftInst *I) { visitBinaryOperator(I); }
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// Instructions that cannot be folded away...
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void visitMemAccessInst (Instruction *I) { markOverdefined(I); }
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void visitCallInst (Instruction *I) { markOverdefined(I); }
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void visitInvokeInst (Instruction *I) { markOverdefined(I); }
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void visitAllocationInst(Instruction *I) { markOverdefined(I); }
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void visitFreeInst (Instruction *I) { markOverdefined(I); }
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void visitInstruction(Instruction *I) {
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// If a new instruction is added to LLVM that we don't handle...
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cerr << "SCCP: Don't know how to handle: " << I;
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markOverdefined(I); // Just in case
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}
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// OperandChangedState - This method is invoked on all of the users of an
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// instruction that was just changed state somehow.... Based on this
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@ -225,10 +250,9 @@ bool SCCP::doSCCP() {
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if (BB->getTerminator()->getNumSuccessors() == 1)
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markExecutable(BB->getTerminator()->getSuccessor(0));
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// Loop over all of the instructions and notify them that they are newly
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// executable...
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for_each(BB->begin(), BB->end(),
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bind_obj(this, &SCCP::UpdateInstruction));
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// Notify all instructions in this basic block that they are newly
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// executable.
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visit(BB);
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}
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}
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@ -284,7 +308,7 @@ bool SCCP::doSCCP() {
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}
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// UpdateInstruction - Something changed in this instruction... Either an
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// visit Implementations - Something changed in this instruction... Either an
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// operand made a transition, or the instruction is newly executable. Change
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// the value type of I to reflect these changes if appropriate. This method
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// makes sure to do the following actions:
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@ -302,199 +326,130 @@ bool SCCP::doSCCP() {
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// 7. If a conditional branch has a value that is overdefined, make all
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// successors executable.
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//
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void SCCP::UpdateInstruction(Instruction *I) {
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InstVal &IValue = ValueState[I];
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if (IValue.isOverdefined())
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return; // If already overdefined, we aren't going to effect anything
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switch (I->getOpcode()) {
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//===-----------------------------------------------------------------===//
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// Handle PHI nodes...
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//
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case Instruction::PHINode: {
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PHINode *PN = cast<PHINode>(I);
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unsigned NumValues = PN->getNumIncomingValues(), i;
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InstVal *OperandIV = 0;
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void SCCP::visitPHINode(PHINode *PN) {
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unsigned NumValues = PN->getNumIncomingValues(), i;
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InstVal *OperandIV = 0;
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// Look at all of the executable operands of the PHI node. If any of them
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// are overdefined, the PHI becomes overdefined as well. If they are all
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// constant, and they agree with each other, the PHI becomes the identical
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// constant. If they are constant and don't agree, the PHI is overdefined.
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// If there are no executable operands, the PHI remains undefined.
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//
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for (i = 0; i < NumValues; ++i) {
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if (BBExecutable.count(PN->getIncomingBlock(i))) {
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InstVal &IV = getValueState(PN->getIncomingValue(i));
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if (IV.isUndefined()) continue; // Doesn't influence PHI node.
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if (IV.isOverdefined()) { // PHI node becomes overdefined!
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markOverdefined(PN);
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return;
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}
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// Look at all of the executable operands of the PHI node. If any of them
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// are overdefined, the PHI becomes overdefined as well. If they are all
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// constant, and they agree with each other, the PHI becomes the identical
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// constant. If they are constant and don't agree, the PHI is overdefined.
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// If there are no executable operands, the PHI remains undefined.
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//
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for (i = 0; i < NumValues; ++i) {
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if (BBExecutable.count(PN->getIncomingBlock(i))) {
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InstVal &IV = getValueState(PN->getIncomingValue(i));
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if (IV.isUndefined()) continue; // Doesn't influence PHI node.
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if (IV.isOverdefined()) { // PHI node becomes overdefined!
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markOverdefined(PN);
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return;
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}
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if (OperandIV == 0) { // Grab the first value...
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OperandIV = &IV;
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} else { // Another value is being merged in!
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// There is already a reachable operand. If we conflict with it,
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// then the PHI node becomes overdefined. If we agree with it, we
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// can continue on.
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if (OperandIV == 0) { // Grab the first value...
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OperandIV = &IV;
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} else { // Another value is being merged in!
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// There is already a reachable operand. If we conflict with it,
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// then the PHI node becomes overdefined. If we agree with it, we
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// can continue on.
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// Check to see if there are two different constants merging...
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if (IV.getConstant() != OperandIV->getConstant()) {
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// Yes there is. This means the PHI node is not constant.
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// You must be overdefined poor PHI.
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//
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markOverdefined(I); // The PHI node now becomes overdefined
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return; // I'm done analyzing you
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}
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// Check to see if there are two different constants merging...
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if (IV.getConstant() != OperandIV->getConstant()) {
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// Yes there is. This means the PHI node is not constant.
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// You must be overdefined poor PHI.
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//
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markOverdefined(PN); // The PHI node now becomes overdefined
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return; // I'm done analyzing you
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}
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}
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}
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// If we exited the loop, this means that the PHI node only has constant
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// arguments that agree with each other(and OperandIV is a pointer to one
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// of their InstVal's) or OperandIV is null because there are no defined
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// incoming arguments. If this is the case, the PHI remains undefined.
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//
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if (OperandIV) {
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assert(OperandIV->isConstant() && "Should only be here for constants!");
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markConstant(I, OperandIV->getConstant()); // Aquire operand value
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}
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return;
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}
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//===-----------------------------------------------------------------===//
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// Handle instructions that unconditionally provide overdefined values...
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//
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case Instruction::Malloc:
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case Instruction::Free:
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case Instruction::Alloca:
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case Instruction::Load:
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case Instruction::Store:
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// TODO: getfield
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case Instruction::Call:
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case Instruction::Invoke:
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markOverdefined(I); // Memory and call's are all overdefined
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return;
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//===-----------------------------------------------------------------===//
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// Handle Terminator instructions...
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//
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case Instruction::Ret: return; // Function return doesn't affect anything
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case Instruction::Br: { // Handle conditional branches...
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BranchInst *BI = cast<BranchInst>(I);
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if (BI->isUnconditional())
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return; // Unconditional branches are already handled!
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InstVal &BCValue = getValueState(BI->getCondition());
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if (BCValue.isOverdefined()) {
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// Overdefined condition variables mean the branch could go either way.
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markExecutable(BI->getSuccessor(0));
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markExecutable(BI->getSuccessor(1));
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} else if (BCValue.isConstant()) {
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// Constant condition variables mean the branch can only go a single way.
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ConstantBool *CPB = cast<ConstantBool>(BCValue.getConstant());
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if (CPB->getValue()) // If the branch condition is TRUE...
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markExecutable(BI->getSuccessor(0));
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else // Else if the br cond is FALSE...
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markExecutable(BI->getSuccessor(1));
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}
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return;
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}
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case Instruction::Switch: {
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SwitchInst *SI = cast<SwitchInst>(I);
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InstVal &SCValue = getValueState(SI->getCondition());
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if (SCValue.isOverdefined()) { // Overdefined condition? All dests are exe
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for(unsigned i = 0; BasicBlock *Succ = SI->getSuccessor(i); ++i)
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markExecutable(Succ);
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} else if (SCValue.isConstant()) {
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Constant *CPV = SCValue.getConstant();
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// Make sure to skip the "default value" which isn't a value
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for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i) {
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if (SI->getSuccessorValue(i) == CPV) {// Found the right branch...
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markExecutable(SI->getSuccessor(i));
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return;
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}
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}
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// Constant value not equal to any of the branches... must execute
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// default branch then...
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markExecutable(SI->getDefaultDest());
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}
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return;
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}
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default: break; // Handle math operators as groups.
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} // end switch(I->getOpcode())
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//===-------------------------------------------------------------------===//
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// Handle Unary and cast instructions...
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// If we exited the loop, this means that the PHI node only has constant
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// arguments that agree with each other(and OperandIV is a pointer to one
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// of their InstVal's) or OperandIV is null because there are no defined
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// incoming arguments. If this is the case, the PHI remains undefined.
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//
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if (isa<UnaryOperator>(I) || isa<CastInst>(I)) {
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Value *V = I->getOperand(0);
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InstVal &VState = getValueState(V);
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if (VState.isOverdefined()) { // Inherit overdefinedness of operand
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markOverdefined(I);
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} else if (VState.isConstant()) { // Propogate constant value
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Constant *Result = isa<CastInst>(I)
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? ConstantFoldCastInstruction(VState.getConstant(), I->getType())
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: ConstantFoldUnaryInstruction(I->getOpcode(), VState.getConstant());
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if (Result) {
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// This instruction constant folds!
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markConstant(I, Result);
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} else {
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markOverdefined(I); // Don't know how to fold this instruction. :(
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}
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}
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return;
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if (OperandIV) {
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assert(OperandIV->isConstant() && "Should only be here for constants!");
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markConstant(PN, OperandIV->getConstant()); // Aquire operand value
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}
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//===-----------------------------------------------------------------===//
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// Handle GetElementPtr instructions...
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//
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if (isa<GetElementPtrInst>(I)) {
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markOverdefined(I);
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return;
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}
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//===-----------------------------------------------------------------===//
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// Handle Binary instructions...
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//
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if (isa<BinaryOperator>(I) || isa<ShiftInst>(I)) {
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Value *V1 = I->getOperand(0);
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Value *V2 = I->getOperand(1);
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InstVal &V1State = getValueState(V1);
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InstVal &V2State = getValueState(V2);
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if (V1State.isOverdefined() || V2State.isOverdefined()) {
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markOverdefined(I);
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} else if (V1State.isConstant() && V2State.isConstant()) {
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Constant *Result =
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ConstantFoldBinaryInstruction(I->getOpcode(),
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V1State.getConstant(),
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V2State.getConstant());
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if (Result) {
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// This instruction constant folds!
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markConstant(I, Result);
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} else {
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markOverdefined(I); // Don't know how to fold this instruction. :(
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}
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}
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return;
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}
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// Shouldn't get here... either the switch statement or one of the group
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// handlers should have kicked in...
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//
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cerr << "SCCP: Don't know how to handle: " << I;
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markOverdefined(I); // Just in case
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}
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void SCCP::visitBranchInst(BranchInst *BI) {
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if (BI->isUnconditional())
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return; // Unconditional branches are already handled!
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InstVal &BCValue = getValueState(BI->getCondition());
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if (BCValue.isOverdefined()) {
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// Overdefined condition variables mean the branch could go either way.
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markExecutable(BI->getSuccessor(0));
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markExecutable(BI->getSuccessor(1));
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} else if (BCValue.isConstant()) {
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// Constant condition variables mean the branch can only go a single way.
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if (BCValue.getConstant() == ConstantBool::True)
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markExecutable(BI->getSuccessor(0));
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else
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markExecutable(BI->getSuccessor(1));
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}
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}
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void SCCP::visitSwitchInst(SwitchInst *SI) {
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InstVal &SCValue = getValueState(SI->getCondition());
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if (SCValue.isOverdefined()) { // Overdefined condition? All dests are exe
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for(unsigned i = 0; BasicBlock *Succ = SI->getSuccessor(i); ++i)
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markExecutable(Succ);
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} else if (SCValue.isConstant()) {
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Constant *CPV = SCValue.getConstant();
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// Make sure to skip the "default value" which isn't a value
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for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i) {
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if (SI->getSuccessorValue(i) == CPV) {// Found the right branch...
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markExecutable(SI->getSuccessor(i));
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return;
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}
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}
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// Constant value not equal to any of the branches... must execute
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// default branch then...
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markExecutable(SI->getDefaultDest());
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}
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}
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void SCCP::visitUnaryOperator(Instruction *I) {
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Value *V = I->getOperand(0);
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InstVal &VState = getValueState(V);
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if (VState.isOverdefined()) { // Inherit overdefinedness of operand
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markOverdefined(I);
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} else if (VState.isConstant()) { // Propogate constant value
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Constant *Result = isa<CastInst>(I)
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? ConstantFoldCastInstruction(VState.getConstant(), I->getType())
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: ConstantFoldUnaryInstruction(I->getOpcode(), VState.getConstant());
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if (Result) {
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// This instruction constant folds!
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markConstant(I, Result);
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} else {
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markOverdefined(I); // Don't know how to fold this instruction. :(
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}
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}
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}
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// Handle BinaryOperators and Shift Instructions...
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void SCCP::visitBinaryOperator(Instruction *I) {
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InstVal &V1State = getValueState(I->getOperand(0));
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InstVal &V2State = getValueState(I->getOperand(1));
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if (V1State.isOverdefined() || V2State.isOverdefined()) {
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markOverdefined(I);
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} else if (V1State.isConstant() && V2State.isConstant()) {
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Constant *Result = ConstantFoldBinaryInstruction(I->getOpcode(),
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V1State.getConstant(),
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V2State.getConstant());
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if (Result)
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markConstant(I, Result); // This instruction constant fold!s
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else
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markOverdefined(I); // Don't know how to fold this instruction. :(
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}
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}
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// OperandChangedState - This method is invoked on all of the users of an
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// instruction that was just changed state somehow.... Based on this
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@ -505,7 +460,7 @@ void SCCP::OperandChangedState(User *U) {
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Instruction *I = cast<Instruction>(U);
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if (!BBExecutable.count(I->getParent())) return; // Inst not executable yet!
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UpdateInstruction(I);
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visit(I);
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}
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namespace {
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