mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-07-19 19:30:10 +00:00
8fd217cb29
Implement feature: Cast's can now be converted to bitwise AND expressions. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3225 91177308-0d34-0410-b5e6-96231b3b80d8
585 lines
19 KiB
C++
585 lines
19 KiB
C++
//===- InstructionCombining.cpp - Combine multiple instructions -------------=//
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//
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// InstructionCombining - Combine instructions to form fewer, simple
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// instructions. This pass does not modify the CFG, and has a tendancy to
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// make instructions dead, so a subsequent DIE pass is useful. This pass is
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// where algebraic simplification happens.
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//
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// This pass combines things like:
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// %Y = add int 1, %X
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// %Z = add int 1, %Y
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// into:
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// %Z = add int 2, %X
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//
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// This is a simple worklist driven algorithm.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ConstantHandling.h"
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#include "llvm/iMemory.h"
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#include "llvm/iOther.h"
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#include "llvm/iPHINode.h"
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#include "llvm/iOperators.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/InstIterator.h"
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#include "llvm/Support/InstVisitor.h"
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#include "Support/StatisticReporter.h"
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#include <algorithm>
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static Statistic<> NumCombined("instcombine\t- Number of insts combined");
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namespace {
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class InstCombiner : public FunctionPass,
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public InstVisitor<InstCombiner, Instruction*> {
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// Worklist of all of the instructions that need to be simplified.
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std::vector<Instruction*> WorkList;
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void AddUsesToWorkList(Instruction &I) {
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// The instruction was simplified, add all users of the instruction to
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// the work lists because they might get more simplified now...
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//
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for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
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UI != UE; ++UI)
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WorkList.push_back(cast<Instruction>(*UI));
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}
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public:
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virtual bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.preservesCFG();
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}
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// Visitation implementation - Implement instruction combining for different
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// instruction types. The semantics are as follows:
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// Return Value:
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// null - No change was made
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// I - Change was made, I is still valid
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// otherwise - Change was made, replace I with returned instruction
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//
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Instruction *visitNot(UnaryOperator &I);
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Instruction *visitAdd(BinaryOperator &I);
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Instruction *visitSub(BinaryOperator &I);
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Instruction *visitMul(BinaryOperator &I);
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Instruction *visitDiv(BinaryOperator &I);
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Instruction *visitRem(BinaryOperator &I);
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Instruction *visitAnd(BinaryOperator &I);
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Instruction *visitOr (BinaryOperator &I);
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Instruction *visitXor(BinaryOperator &I);
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Instruction *visitSetCondInst(BinaryOperator &I);
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Instruction *visitShiftInst(Instruction &I);
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Instruction *visitCastInst(CastInst &CI);
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Instruction *visitPHINode(PHINode &PN);
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Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
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// visitInstruction - Specify what to return for unhandled instructions...
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Instruction *visitInstruction(Instruction &I) { return 0; }
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};
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RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
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}
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Instruction *InstCombiner::visitNot(UnaryOperator &I) {
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// not (not X) = X
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if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(0)))
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if (Op->getOpcode() == Instruction::Not) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op->getOperand(0));
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return &I;
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}
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return 0;
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}
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// Make sure that this instruction has a constant on the right hand side if it
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// has any constant arguments. If not, fix it an return true.
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//
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static bool SimplifyBinOp(BinaryOperator &I) {
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if (isa<Constant>(I.getOperand(0)) && !isa<Constant>(I.getOperand(1)))
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return !I.swapOperands();
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return false;
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}
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// dyn_castNegInst - Given a 'sub' instruction, return the RHS of the
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// instruction if the LHS is a constant zero (which is the 'negate' form).
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//
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static inline Value *dyn_castNegInst(Value *V) {
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I || I->getOpcode() != Instruction::Sub) return 0;
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if (I->getOperand(0) == Constant::getNullValue(I->getType()))
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return I->getOperand(1);
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return 0;
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}
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Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
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bool Changed = SimplifyBinOp(I);
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Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
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// Eliminate 'add int %X, 0'
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if (RHS == Constant::getNullValue(I.getType())) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(LHS);
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return &I;
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}
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// -A + B --> B - A
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if (Value *V = dyn_castNegInst(LHS))
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return BinaryOperator::create(Instruction::Sub, RHS, V);
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// A + -B --> A - B
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if (Value *V = dyn_castNegInst(RHS))
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return BinaryOperator::create(Instruction::Sub, LHS, V);
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// Simplify add instructions with a constant RHS...
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if (Constant *Op2 = dyn_cast<Constant>(RHS)) {
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if (BinaryOperator *ILHS = dyn_cast<BinaryOperator>(LHS)) {
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if (ILHS->getOpcode() == Instruction::Add &&
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isa<Constant>(ILHS->getOperand(1))) {
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// Fold:
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// %Y = add int %X, 1
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// %Z = add int %Y, 1
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// into:
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// %Z = add int %X, 2
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//
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if (Constant *Val = *Op2 + *cast<Constant>(ILHS->getOperand(1))) {
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I.setOperand(0, ILHS->getOperand(0));
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I.setOperand(1, Val);
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return &I;
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}
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}
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}
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}
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return Changed ? &I : 0;
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}
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Instruction *InstCombiner::visitSub(BinaryOperator &I) {
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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if (Op0 == Op1) { // sub X, X -> 0
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Constant::getNullValue(I.getType()));
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return &I;
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}
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// If this is a subtract instruction with a constant RHS, convert it to an add
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// instruction of a negative constant
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//
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if (Constant *Op2 = dyn_cast<Constant>(Op1))
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if (Constant *RHS = *Constant::getNullValue(I.getType()) - *Op2) // 0 - RHS
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return BinaryOperator::create(Instruction::Add, Op0, RHS, I.getName());
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// If this is a 'C = x-B', check to see if 'B = -A', so that C = x+A...
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if (Value *V = dyn_castNegInst(Op1))
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return BinaryOperator::create(Instruction::Add, Op0, V);
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// Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression is
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// not used by anyone else...
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//
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if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
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if (Op1I->use_size() == 1 && Op1I->getOpcode() == Instruction::Sub) {
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// Swap the two operands of the subexpr...
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Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
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Op1I->setOperand(0, IIOp1);
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Op1I->setOperand(1, IIOp0);
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// Create the new top level add instruction...
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return BinaryOperator::create(Instruction::Add, Op0, Op1);
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}
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return 0;
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}
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Instruction *InstCombiner::visitMul(BinaryOperator &I) {
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bool Changed = SimplifyBinOp(I);
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Value *Op1 = I.getOperand(0);
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// Simplify add instructions with a constant RHS...
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if (Constant *Op2 = dyn_cast<Constant>(I.getOperand(1))) {
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if (I.getType()->isIntegral() && cast<ConstantInt>(Op2)->equalsInt(1)){
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// Eliminate 'mul int %X, 1'
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op1);
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return &I;
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} else if (I.getType()->isIntegral() &&
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cast<ConstantInt>(Op2)->equalsInt(2)) {
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// Convert 'mul int %X, 2' to 'add int %X, %X'
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return BinaryOperator::create(Instruction::Add, Op1, Op1, I.getName());
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} else if (Op2->isNullValue()) {
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// Eliminate 'mul int %X, 0'
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op2); // Set this value to zero directly
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return &I;
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}
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}
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return Changed ? &I : 0;
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}
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Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
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// div X, 1 == X
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if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1)))
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if (RHS->equalsInt(1)) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(I.getOperand(0));
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return &I;
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}
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return 0;
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}
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Instruction *InstCombiner::visitRem(BinaryOperator &I) {
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// rem X, 1 == 0
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if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1)))
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if (RHS->equalsInt(1)) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Constant::getNullValue(I.getType()));
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return &I;
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}
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return 0;
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}
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static Constant *getMaxValue(const Type *Ty) {
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assert(Ty == Type::BoolTy || Ty->isIntegral());
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if (Ty == Type::BoolTy)
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return ConstantBool::True;
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if (Ty->isSigned())
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return ConstantSInt::get(Ty, -1);
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else if (Ty->isUnsigned()) {
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// Calculate -1 casted to the right type...
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unsigned TypeBits = Ty->getPrimitiveSize()*8;
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uint64_t Val = (uint64_t)-1LL; // All ones
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Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
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return ConstantUInt::get(Ty, Val);
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}
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return 0;
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}
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Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
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bool Changed = SimplifyBinOp(I);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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// and X, X = X and X, 0 == 0
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if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType())) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op1);
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return &I;
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}
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// and X, -1 == X
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if (Constant *RHS = dyn_cast<Constant>(Op1))
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if (RHS == getMaxValue(I.getType())) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op0);
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return &I;
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}
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return Changed ? &I : 0;
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}
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Instruction *InstCombiner::visitOr(BinaryOperator &I) {
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bool Changed = SimplifyBinOp(I);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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// or X, X = X or X, 0 == X
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if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType())) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op0);
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return &I;
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}
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// or X, -1 == -1
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if (Constant *RHS = dyn_cast<Constant>(Op1))
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if (RHS == getMaxValue(I.getType())) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op1);
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return &I;
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}
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return Changed ? &I : 0;
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}
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Instruction *InstCombiner::visitXor(BinaryOperator &I) {
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bool Changed = SimplifyBinOp(I);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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// xor X, X = 0
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if (Op0 == Op1) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Constant::getNullValue(I.getType()));
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return &I;
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}
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// xor X, 0 == X
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if (Op1 == Constant::getNullValue(I.getType())) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op0);
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return &I;
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}
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return Changed ? &I : 0;
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}
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// isTrueWhenEqual - Return true if the specified setcondinst instruction is
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// true when both operands are equal...
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//
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static bool isTrueWhenEqual(Instruction &I) {
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return I.getOpcode() == Instruction::SetEQ ||
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I.getOpcode() == Instruction::SetGE ||
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I.getOpcode() == Instruction::SetLE;
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}
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Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
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bool Changed = SimplifyBinOp(I);
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// setcc X, X
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if (I.getOperand(0) == I.getOperand(1)) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(ConstantBool::get(isTrueWhenEqual(I)));
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return &I;
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}
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// setcc <global*>, 0 - Global value addresses are never null!
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if (isa<GlobalValue>(I.getOperand(0)) &&
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isa<ConstantPointerNull>(I.getOperand(1))) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(ConstantBool::get(!isTrueWhenEqual(I)));
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return &I;
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}
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return Changed ? &I : 0;
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}
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Instruction *InstCombiner::visitShiftInst(Instruction &I) {
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assert(I.getOperand(1)->getType() == Type::UByteTy);
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Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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// shl X, 0 == X and shr X, 0 == X
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// shl 0, X == 0 and shr 0, X == 0
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if (Op1 == Constant::getNullValue(Type::UByteTy) ||
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Op0 == Constant::getNullValue(Op0->getType())) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Op0);
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return &I;
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}
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// shl int X, 32 = 0 and shr sbyte Y, 9 = 0, ... just don't eliminate shr of
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// a signed value.
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//
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if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
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unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
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if (CUI->getValue() >= TypeBits &&
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!(Op0->getType()->isSigned() && I.getOpcode() == Instruction::Shr)) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I.replaceAllUsesWith(Constant::getNullValue(Op0->getType()));
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return &I;
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}
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}
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return 0;
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}
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// isEliminableCastOfCast - Return true if it is valid to eliminate the CI
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// instruction.
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//
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static inline bool isEliminableCastOfCast(const CastInst &CI,
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const CastInst *CSrc) {
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assert(CI.getOperand(0) == CSrc);
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const Type *SrcTy = CSrc->getOperand(0)->getType();
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const Type *MidTy = CSrc->getType();
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const Type *DstTy = CI.getType();
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// It is legal to eliminate the instruction if casting A->B->A if the sizes
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// are identical and the bits don't get reinterpreted (for example
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// int->float->int)
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if (SrcTy == DstTy && SrcTy->isLosslesslyConvertableTo(MidTy))
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return true;
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// Allow free casting and conversion of sizes as long as the sign doesn't
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// change...
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if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral() &&
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SrcTy->isSigned() == MidTy->isSigned() &&
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MidTy->isSigned() == DstTy->isSigned()) {
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// Only accept cases where we are either monotonically increasing the type
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// size, or monotonically decreasing it.
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//
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unsigned SrcSize = SrcTy->getPrimitiveSize();
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unsigned MidSize = MidTy->getPrimitiveSize();
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unsigned DstSize = DstTy->getPrimitiveSize();
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if (SrcSize < MidSize && MidSize < DstSize)
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return true;
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if (SrcSize > MidSize && MidSize > DstSize)
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return true;
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}
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// Otherwise, we cannot succeed. Specifically we do not want to allow things
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// like: short -> ushort -> uint, because this can create wrong results if
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// the input short is negative!
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//
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return false;
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}
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// CastInst simplification
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//
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Instruction *InstCombiner::visitCastInst(CastInst &CI) {
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// If the user is casting a value to the same type, eliminate this cast
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// instruction...
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if (CI.getType() == CI.getOperand(0)->getType()) {
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AddUsesToWorkList(CI); // Add all modified instrs to worklist
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CI.replaceAllUsesWith(CI.getOperand(0));
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return &CI;
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}
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// If casting the result of another cast instruction, try to eliminate this
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// one!
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//
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if (CastInst *CSrc = dyn_cast<CastInst>(CI.getOperand(0))) {
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if (isEliminableCastOfCast(CI, CSrc)) {
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// This instruction now refers directly to the cast's src operand. This
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// has a good chance of making CSrc dead.
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CI.setOperand(0, CSrc->getOperand(0));
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return &CI;
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}
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// If this is an A->B->A cast, and we are dealing with integral types, try
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// to convert this into a logical 'and' instruction.
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//
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if (CSrc->getOperand(0)->getType() == CI.getType() &&
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CI.getType()->isIntegral() && CSrc->getType()->isIntegral() &&
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CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
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CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
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assert(CSrc->getType() != Type::ULongTy &&
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"Cannot have type bigger than ulong!");
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|
unsigned AndValue = (1U << CSrc->getType()->getPrimitiveSize()*8)-1;
|
|
Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
|
|
return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
|
|
AndOp);
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
// PHINode simplification
|
|
//
|
|
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
|
|
// If the PHI node only has one incoming value, eliminate the PHI node...
|
|
if (PN.getNumIncomingValues() == 1) {
|
|
AddUsesToWorkList(PN); // Add all modified instrs to worklist
|
|
PN.replaceAllUsesWith(PN.getIncomingValue(0));
|
|
return &PN;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
|
|
// Is it 'getelementptr %P, uint 0' or 'getelementptr %P'
|
|
// If so, eliminate the noop.
|
|
if ((GEP.getNumOperands() == 2 &&
|
|
GEP.getOperand(1) == Constant::getNullValue(Type::UIntTy)) ||
|
|
GEP.getNumOperands() == 1) {
|
|
AddUsesToWorkList(GEP); // Add all modified instrs to worklist
|
|
GEP.replaceAllUsesWith(GEP.getOperand(0));
|
|
return &GEP;
|
|
}
|
|
|
|
// Combine Indices - If the source pointer to this getelementptr instruction
|
|
// is a getelementptr instruction, combine the indices of the two
|
|
// getelementptr instructions into a single instruction.
|
|
//
|
|
if (GetElementPtrInst *Src =
|
|
dyn_cast<GetElementPtrInst>(GEP.getPointerOperand())) {
|
|
std::vector<Value *> Indices;
|
|
|
|
// Can we combine the two pointer arithmetics offsets?
|
|
if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
|
|
isa<Constant>(GEP.getOperand(1))) {
|
|
// Replace the index list on this GEP with the index on the getelementptr
|
|
Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
|
|
Indices[0] = *cast<Constant>(Src->getOperand(1)) +
|
|
*cast<Constant>(GEP.getOperand(1));
|
|
assert(Indices[0] != 0 && "Constant folding of uint's failed!?");
|
|
|
|
} else if (*GEP.idx_begin() == ConstantUInt::get(Type::UIntTy, 0)) {
|
|
// Otherwise we can do the fold if the first index of the GEP is a zero
|
|
Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
|
|
Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
|
|
}
|
|
|
|
if (!Indices.empty())
|
|
return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
bool InstCombiner::runOnFunction(Function &F) {
|
|
bool Changed = false;
|
|
|
|
WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
|
|
|
|
while (!WorkList.empty()) {
|
|
Instruction *I = WorkList.back(); // Get an instruction from the worklist
|
|
WorkList.pop_back();
|
|
|
|
// Now that we have an instruction, try combining it to simplify it...
|
|
if (Instruction *Result = visit(*I)) {
|
|
++NumCombined;
|
|
// Should we replace the old instruction with a new one?
|
|
if (Result != I) {
|
|
// Instructions can end up on the worklist more than once. Make sure
|
|
// we do not process an instruction that has been deleted.
|
|
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
|
|
WorkList.end());
|
|
|
|
ReplaceInstWithInst(I, Result);
|
|
} else {
|
|
BasicBlock::iterator II = I;
|
|
|
|
// If the instruction was modified, it's possible that it is now dead.
|
|
// if so, remove it.
|
|
if (dceInstruction(II)) {
|
|
// Instructions may end up in the worklist more than once. Erase them
|
|
// all.
|
|
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
|
|
WorkList.end());
|
|
Result = 0;
|
|
}
|
|
}
|
|
|
|
if (Result) {
|
|
WorkList.push_back(Result);
|
|
AddUsesToWorkList(*Result);
|
|
}
|
|
Changed = true;
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
Pass *createInstructionCombiningPass() {
|
|
return new InstCombiner();
|
|
}
|