#include "llvm/Function.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
-#include "llvm/InstrTypes.h"
+#include "llvm/iOperators.h"
#include "llvm/Pass.h"
#include "llvm/Support/InstIterator.h"
+#include "llvm/Support/InstVisitor.h"
#include "../TransformInternals.h"
-static Instruction *CombineBinOp(BinaryOperator *I) {
- bool Changed = false;
- // First thing we do is make sure that this instruction has a constant on the
- // right hand side if it has any constant arguments.
- //
+namespace {
+ class InstCombiner : public MethodPass,
+ public InstVisitor<InstCombiner, Instruction*> {
+ // Worklist of all of the instructions that need to be simplified.
+ std::vector<Instruction*> WorkList;
+
+ void AddUsesToWorkList(Instruction *I) {
+ // The instruction was simplified, add all users of the instruction to
+ // the work lists because they might get more simplified now...
+ //
+ for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
+ UI != UE; ++UI)
+ WorkList.push_back(cast<Instruction>(*UI));
+ }
+
+ public:
+
+
+ virtual bool runOnMethod(Function *F);
+
+ // Visitation implementation - Implement instruction combining for different
+ // instruction types. The semantics are as follows:
+ // Return Value:
+ // null - No change was made
+ // I - Change was made, I is still valid
+ // otherwise - Change was made, replace I with returned instruction
+ //
+
+ Instruction *visitAdd(BinaryOperator *I);
+ Instruction *visitSub(BinaryOperator *I);
+ Instruction *visitMul(BinaryOperator *I);
+ Instruction *visitCastInst(CastInst *CI);
+ Instruction *visitMemAccessInst(MemAccessInst *MAI);
+
+ // visitInstruction - Specify what to return for unhandled instructions...
+ Instruction *visitInstruction(Instruction *I) { return 0; }
+ };
+}
+
+
+
+// Make sure that this instruction has a constant on the right hand side if it
+// has any constant arguments. If not, fix it an return true.
+//
+static bool SimplifyBinOp(BinaryOperator *I) {
if (isa<Constant>(I->getOperand(0)) && !isa<Constant>(I->getOperand(1)))
if (!I->swapOperands())
- Changed = true;
+ return true;
+ return false;
+}
- bool LocalChange = true;
- while (LocalChange) {
- LocalChange = false;
- Value *Op1 = I->getOperand(0);
- if (Constant *Op2 = dyn_cast<Constant>(I->getOperand(1))) {
- switch (I->getOpcode()) {
- case Instruction::Add:
- if (I->getType()->isIntegral() && cast<ConstantInt>(Op2)->equalsInt(0)){
- // Eliminate 'add int %X, 0'
- I->replaceAllUsesWith(Op1); // FIXME: This breaks the worklist
- Changed = true;
+Instruction *InstCombiner::visitAdd(BinaryOperator *I) {
+ if (I->use_empty()) return 0; // Don't fix dead add instructions...
+ bool Changed = SimplifyBinOp(I);
+ Value *Op1 = I->getOperand(0);
+
+ // Simplify add instructions with a constant RHS...
+ if (Constant *Op2 = dyn_cast<Constant>(I->getOperand(1))) {
+ // Eliminate 'add int %X, 0'
+ if (I->getType()->isIntegral() && Op2->isNullValue()) {
+ AddUsesToWorkList(I); // Add all modified instrs to worklist
+ I->replaceAllUsesWith(Op1);
+ return I;
+ }
+
+ if (BinaryOperator *IOp1 = dyn_cast<BinaryOperator>(Op1)) {
+ Changed |= SimplifyBinOp(IOp1);
+
+ if (IOp1->getOpcode() == Instruction::Add &&
+ isa<Constant>(IOp1->getOperand(1))) {
+ // Fold:
+ // %Y = add int %X, 1
+ // %Z = add int %Y, 1
+ // into:
+ // %Z = add int %X, 2
+ //
+ if (Constant *Val = *Op2 + *cast<Constant>(IOp1->getOperand(1))) {
+ I->setOperand(0, IOp1->getOperand(0));
+ I->setOperand(1, Val);
return I;
}
+ }
+ }
+ }
- if (Instruction *IOp1 = dyn_cast<Instruction>(Op1)) {
- if (IOp1->getOpcode() == Instruction::Add &&
- isa<Constant>(IOp1->getOperand(1))) {
- // Fold:
- // %Y = add int %X, 1
- // %Z = add int %Y, 1
- // into:
- // %Z = add int %X, 2
- //
- // Constant fold both constants...
- Constant *Val = *Op2 + *cast<Constant>(IOp1->getOperand(1));
-
- if (Val) {
- I->setOperand(0, IOp1->getOperand(0));
- I->setOperand(1, Val);
- LocalChange = true;
- break;
- }
- }
-
- }
- break;
-
- case Instruction::Mul:
- if (I->getType()->isIntegral() && cast<ConstantInt>(Op2)->equalsInt(1)){
- // Eliminate 'mul int %X, 1'
- I->replaceAllUsesWith(Op1); // FIXME: This breaks the worklist
- LocalChange = true;
- break;
- }
+ return Changed ? I : 0;
+}
- default:
- break;
- }
+Instruction *InstCombiner::visitSub(BinaryOperator *I) {
+ if (I->use_empty()) return 0; // Don't fix dead add instructions...
+ bool Changed = SimplifyBinOp(I);
+
+ // If this is a subtract instruction with a constant RHS, convert it to an add
+ // instruction of a negative constant
+ //
+ if (Constant *Op2 = dyn_cast<Constant>(I->getOperand(1)))
+ // Calculate 0 - RHS
+ if (Constant *RHS = *Constant::getNullConstant(I->getType()) - *Op2) {
+ return BinaryOperator::create(Instruction::Add, I->getOperand(0), RHS,
+ I->getName());
+ }
+
+ return Changed ? I : 0;
+}
+
+Instruction *InstCombiner::visitMul(BinaryOperator *I) {
+ if (I->use_empty()) return 0; // Don't fix dead add instructions...
+ bool Changed = SimplifyBinOp(I);
+ Value *Op1 = I->getOperand(0);
+
+ // Simplify add instructions with a constant RHS...
+ if (Constant *Op2 = dyn_cast<Constant>(I->getOperand(1))) {
+ if (I->getType()->isIntegral() && cast<ConstantInt>(Op2)->equalsInt(1)){
+ // Eliminate 'mul int %X, 1'
+ AddUsesToWorkList(I); // Add all modified instrs to worklist
+ I->replaceAllUsesWith(Op1);
+ return I;
}
- Changed |= LocalChange;
}
- if (!Changed) return 0;
- return I;
+ return Changed ? I : 0;
+}
+
+
+// CastInst simplification - If the user is casting a value to the same type,
+// eliminate this cast instruction...
+//
+Instruction *InstCombiner::visitCastInst(CastInst *CI) {
+ if (CI->getType() == CI->getOperand(0)->getType() && !CI->use_empty()) {
+ AddUsesToWorkList(CI); // Add all modified instrs to worklist
+ CI->replaceAllUsesWith(CI->getOperand(0));
+ return CI;
+ }
+ return 0;
}
// Combine Indices - If the source pointer to this mem access instruction is a
// getelementptr instruction, combine the indices of the GEP into this
// instruction
//
-static Instruction *CombineIndicies(MemAccessInst *MAI) {
+Instruction *InstCombiner::visitMemAccessInst(MemAccessInst *MAI) {
GetElementPtrInst *Src =
dyn_cast<GetElementPtrInst>(MAI->getPointerOperand());
if (!Src) return 0;
return 0;
}
-static bool CombineInstruction(Instruction *I) {
- Instruction *Result = 0;
- if (BinaryOperator *BOP = dyn_cast<BinaryOperator>(I))
- Result = CombineBinOp(BOP);
- else if (MemAccessInst *MAI = dyn_cast<MemAccessInst>(I))
- Result = CombineIndicies(MAI);
- else if (CastInst *CI = dyn_cast<CastInst>(I)) {
- if (CI->getType() == CI->getOperand(0)->getType() && !CI->use_empty()) {
- CI->replaceAllUsesWith(CI->getOperand(0));
- return true;
- }
-
- }
-
- if (!Result) return false;
- if (Result == I) return true;
- // If we get to here, we are to replace I with Result.
- ReplaceInstWithInst(I, Result);
- return true;
-}
+bool InstCombiner::runOnMethod(Function *F) {
+ bool Changed = false;
-static bool doInstCombining(Function *M) {
- // Start the worklist out with all of the instructions in the function in it.
- std::vector<Instruction*> WorkList(inst_begin(M), inst_end(M));
+ 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 (CombineInstruction(I)) {
- // The instruction was simplified, add all users of the instruction to
- // the work lists because they might get more simplified now...
- //
- for (Value::use_iterator UI = I->use_begin(), UE = I->use_end();
- UI != UE; ++UI)
- if (Instruction *User = dyn_cast<Instruction>(*UI))
- WorkList.push_back(User);
+ Instruction *Result = visit(I);
+ if (Result) {
+ // Should we replace the old instruction with a new one?
+ if (Result != I)
+ ReplaceInstWithInst(I, Result);
+
+ WorkList.push_back(Result);
+ AddUsesToWorkList(Result);
+ Changed = true;
}
}
- return false;
-}
-
-namespace {
- struct InstructionCombining : public MethodPass {
- virtual bool runOnMethod(Function *F) { return doInstCombining(F); }
- };
+ return Changed;
}
Pass *createInstructionCombiningPass() {
- return new InstructionCombining();
+ return new InstCombiner();
}
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