-//===- InstructionCombining.cpp - Combine multiple instructions -------------=//
+//===- InstructionCombining.cpp - Combine multiple instructions -----------===//
//
// InstructionCombining - Combine instructions to form fewer, simple
-// instructions. This pass does not modify the CFG, and has a tendancy to
-// make instructions dead, so a subsequent DIE pass is useful. This pass is
-// where algebraic simplification happens.
+// instructions. This pass does not modify the CFG This pass is where algebraic
+// simplification happens.
//
// This pass combines things like:
// %Y = add int 1, %X
//
//===----------------------------------------------------------------------===//
-#include "llvm/Transforms/Scalar/InstructionCombining.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ConstantHandling.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/Pass.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/Support/InstVisitor.h"
-#include "../TransformInternals.h"
+#include "Support/StatisticReporter.h"
+#include <algorithm>
+static Statistic<> NumCombined ("instcombine\t- Number of insts combined");
+static Statistic<> NumConstProp("instcombine\t- Number of constant folds");
+static Statistic<> NumDeadInst ("instcombine\t- Number of dead inst eliminate");
namespace {
class InstCombiner : public FunctionPass,
// Worklist of all of the instructions that need to be simplified.
std::vector<Instruction*> WorkList;
- void AddUsesToWorkList(Instruction *I) {
+ 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();
+ for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
UI != UE; ++UI)
WorkList.push_back(cast<Instruction>(*UI));
}
+ // removeFromWorkList - remove all instances of I from the worklist.
+ void removeFromWorkList(Instruction *I);
public:
- const char *getPassName() const { return "Instruction Combining"; }
-
- virtual bool runOnFunction(Function *F);
+ virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.preservesCFG();
// instruction types. The semantics are as follows:
// Return Value:
// null - No change was made
- // I - Change was made, I is still valid
+ // I - Change was made, I is still valid, I may be dead though
// otherwise - Change was made, replace I with returned instruction
//
- Instruction *visitNot(UnaryOperator *I);
- Instruction *visitAdd(BinaryOperator *I);
- Instruction *visitSub(BinaryOperator *I);
- Instruction *visitMul(BinaryOperator *I);
- Instruction *visitDiv(BinaryOperator *I);
- Instruction *visitRem(BinaryOperator *I);
- Instruction *visitAnd(BinaryOperator *I);
- Instruction *visitOr (BinaryOperator *I);
- Instruction *visitXor(BinaryOperator *I);
- Instruction *visitSetCondInst(BinaryOperator *I);
- Instruction *visitShiftInst(Instruction *I);
- Instruction *visitCastInst(CastInst *CI);
- Instruction *visitPHINode(PHINode *PN);
- Instruction *visitGetElementPtrInst(GetElementPtrInst *GEP);
- Instruction *visitMemAccessInst(MemAccessInst *MAI);
+ Instruction *visitAdd(BinaryOperator &I);
+ Instruction *visitSub(BinaryOperator &I);
+ Instruction *visitMul(BinaryOperator &I);
+ Instruction *visitDiv(BinaryOperator &I);
+ Instruction *visitRem(BinaryOperator &I);
+ Instruction *visitAnd(BinaryOperator &I);
+ Instruction *visitOr (BinaryOperator &I);
+ Instruction *visitXor(BinaryOperator &I);
+ Instruction *visitSetCondInst(BinaryOperator &I);
+ Instruction *visitShiftInst(Instruction &I);
+ Instruction *visitCastInst(CastInst &CI);
+ Instruction *visitPHINode(PHINode &PN);
+ Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
// visitInstruction - Specify what to return for unhandled instructions...
- Instruction *visitInstruction(Instruction *I) { return 0; }
- };
-}
-
-
-Instruction *InstCombiner::visitNot(UnaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
+ Instruction *visitInstruction(Instruction &I) { return 0; }
+
+ // InsertNewInstBefore - insert an instruction New before instruction Old
+ // in the program. Add the new instruction to the worklist.
+ //
+ void InsertNewInstBefore(Instruction *New, Instruction &Old) {
+ assert(New && New->getParent() == 0 &&
+ "New instruction already inserted into a basic block!");
+ BasicBlock *BB = Old.getParent();
+ BB->getInstList().insert(&Old, New); // Insert inst
+ WorkList.push_back(New); // Add to worklist
+ }
- // not (not X) = X
- if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(0)))
- if (Op->getOpcode() == Instruction::Not) {
+ // ReplaceInstUsesWith - This method is to be used when an instruction is
+ // found to be dead, replacable with another preexisting expression. Here
+ // we add all uses of I to the worklist, replace all uses of I with the new
+ // value, then return I, so that the inst combiner will know that I was
+ // modified.
+ //
+ Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op->getOperand(0));
- return I;
+ I.replaceAllUsesWith(V);
+ return &I;
}
- return 0;
+ };
+
+ RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
}
// 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)))
- return !I->swapOperands();
+static bool SimplifyBinOp(BinaryOperator &I) {
+ if (isa<Constant>(I.getOperand(0)) && !isa<Constant>(I.getOperand(1)))
+ return !I.swapOperands();
return false;
}
return 0;
}
-Instruction *InstCombiner::visitAdd(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead add instructions...
+static inline Value *dyn_castNotInst(Value *V) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I || I->getOpcode() != Instruction::Xor) return 0;
+
+ if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(I->getOperand(1)))
+ if (CI->isAllOnesValue())
+ return I->getOperand(0);
+ return 0;
+}
+
+Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyBinOp(I);
- Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
+ Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// Eliminate 'add int %X, 0'
- if (I->getType()->isIntegral() &&
- RHS == Constant::getNullValue(I->getType())) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(LHS);
- return I;
- }
+ if (RHS == Constant::getNullValue(I.getType()))
+ return ReplaceInstUsesWith(I, LHS);
- // -B + A --> A - B
+ // -A + B --> B - A
if (Value *V = dyn_castNegInst(LHS))
- return BinaryOperator::create(Instruction::Sub, RHS, LHS);
+ return BinaryOperator::create(Instruction::Sub, RHS, V);
// A + -B --> A - B
if (Value *V = dyn_castNegInst(RHS))
- return BinaryOperator::create(Instruction::Sub, LHS, RHS);
+ return BinaryOperator::create(Instruction::Sub, LHS, V);
// Simplify add instructions with a constant RHS...
if (Constant *Op2 = dyn_cast<Constant>(RHS)) {
// %Z = add int %X, 2
//
if (Constant *Val = *Op2 + *cast<Constant>(ILHS->getOperand(1))) {
- I->setOperand(0, ILHS->getOperand(0));
- I->setOperand(1, Val);
- return I;
+ I.setOperand(0, ILHS->getOperand(0));
+ I.setOperand(1, Val);
+ return &I;
}
}
}
}
- return Changed ? I : 0;
+ return Changed ? &I : 0;
}
-Instruction *InstCombiner::visitSub(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead add instructions...
- Value *Op0 = I->getOperand(0), *Op1 = I->getOperand(1);
+Instruction *InstCombiner::visitSub(BinaryOperator &I) {
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
- if (Op0 == Op1) { // sub X, X -> 0
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
- return I;
- }
+ if (Op0 == Op1) // sub X, X -> 0
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// 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>(Op1))
- if (Constant *RHS = *Constant::getNullValue(I->getType()) - *Op2) // 0 - RHS
- return BinaryOperator::create(Instruction::Add, Op0, RHS, I->getName());
+ if (Constant *RHS = *Constant::getNullValue(I.getType()) - *Op2) // 0 - RHS
+ return BinaryOperator::create(Instruction::Add, Op0, RHS, I.getName());
- // If this is a 'C = -B', check to see if 'B = -A', so that C = A...
- if (Op0 == Constant::getNullValue(I->getType()))
- if (Value *V = dyn_castNegInst(Op1)) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(V);
- return I;
- }
+ // If this is a 'B = x-(-A)', change to B = x+A...
+ if (Value *V = dyn_castNegInst(Op1))
+ return BinaryOperator::create(Instruction::Add, Op0, V);
+ // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression is
+ // not used by anyone else...
+ //
+ if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
+ if (Op1I->use_size() == 1 && Op1I->getOpcode() == Instruction::Sub) {
+ // Swap the two operands of the subexpr...
+ Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
+ Op1I->setOperand(0, IIOp1);
+ Op1I->setOperand(1, IIOp0);
+
+ // Create the new top level add instruction...
+ return BinaryOperator::create(Instruction::Add, Op0, Op1);
+ }
return 0;
}
-Instruction *InstCombiner::visitMul(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
+Instruction *InstCombiner::visitMul(BinaryOperator &I) {
bool Changed = SimplifyBinOp(I);
- Value *Op1 = I->getOperand(0);
+ 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;
+ // Simplify mul instructions with a constant RHS...
+ if (Constant *Op2 = dyn_cast<Constant>(I.getOperand(1))) {
+ if (I.getType()->isInteger() && cast<ConstantInt>(Op2)->equalsInt(1))
+ return ReplaceInstUsesWith(I, Op1); // Eliminate 'mul int %X, 1'
- } else if (I->getType()->isIntegral() &&
- cast<ConstantInt>(Op2)->equalsInt(2)) {
+ if (I.getType()->isInteger() && cast<ConstantInt>(Op2)->equalsInt(2))
// Convert 'mul int %X, 2' to 'add int %X, %X'
- return BinaryOperator::create(Instruction::Add, Op1, Op1, I->getName());
+ return BinaryOperator::create(Instruction::Add, Op1, Op1, I.getName());
- } else if (Op2->isNullValue()) {
- // Eliminate 'mul int %X, 0'
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op2); // Set this value to zero directly
- return I;
- }
+ if (Op2->isNullValue())
+ return ReplaceInstUsesWith(I, Op2); // Eliminate 'mul int %X, 0'
}
- return Changed ? I : 0;
+ return Changed ? &I : 0;
}
-Instruction *InstCombiner::visitDiv(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
-
+Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
// div X, 1 == X
- if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1)))
- if (RHS->equalsInt(1)) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(I->getOperand(0));
- return I;
- }
+ if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1)))
+ if (RHS->equalsInt(1))
+ return ReplaceInstUsesWith(I, I.getOperand(0));
return 0;
}
-Instruction *InstCombiner::visitRem(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
-
+Instruction *InstCombiner::visitRem(BinaryOperator &I) {
// rem X, 1 == 0
- if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1)))
- if (RHS->equalsInt(1)) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
- return I;
- }
+ if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1)))
+ if (RHS->equalsInt(1))
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+
return 0;
}
-static Constant *getMaxValue(const Type *Ty) {
- assert(Ty == Type::BoolTy || Ty->isIntegral());
- if (Ty == Type::BoolTy)
- return ConstantBool::True;
-
- if (Ty->isSigned())
- return ConstantSInt::get(Ty, -1);
- else if (Ty->isUnsigned()) {
+// isMaxValueMinusOne - return true if this is Max-1
+static bool isMaxValueMinusOne(const ConstantInt *C) {
+ if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
// Calculate -1 casted to the right type...
- unsigned TypeBits = Ty->getPrimitiveSize()*8;
- uint64_t Val = (uint64_t)-1LL; // All ones
+ unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
+ uint64_t Val = ~0ULL; // All ones
Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
- return ConstantUInt::get(Ty, Val);
+ return CU->getValue() == Val-1;
}
- return 0;
+
+ const ConstantSInt *CS = cast<ConstantSInt>(C);
+
+ // Calculate 0111111111..11111
+ unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
+ int64_t Val = INT64_MAX; // All ones
+ Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
+ return CS->getValue() == Val-1;
+}
+
+// isMinValuePlusOne - return true if this is Min+1
+static bool isMinValuePlusOne(const ConstantInt *C) {
+ if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
+ return CU->getValue() == 1;
+
+ const ConstantSInt *CS = cast<ConstantSInt>(C);
+
+ // Calculate 1111111111000000000000
+ unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
+ int64_t Val = -1; // All ones
+ Val <<= TypeBits-1; // Shift over to the right spot
+ return CS->getValue() == Val+1;
}
-Instruction *InstCombiner::visitAnd(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
+Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
bool Changed = SimplifyBinOp(I);
- Value *Op0 = I->getOperand(0), *Op1 = I->getOperand(1);
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// and X, X = X and X, 0 == 0
- if (Op0 == Op1 || Op1 == Constant::getNullValue(I->getType())) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op1);
- return I;
- }
+ if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
+ return ReplaceInstUsesWith(I, Op1);
// and X, -1 == X
- if (Constant *RHS = dyn_cast<Constant>(Op1))
- if (RHS == getMaxValue(I->getType())) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op0);
- return I;
- }
+ if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1))
+ if (RHS->isAllOnesValue())
+ return ReplaceInstUsesWith(I, Op0);
+
+ // and (not A), (not B) == not (or A, B)
+ if (Op0->use_size() == 1 && Op1->use_size() == 1)
+ if (Value *A = dyn_castNotInst(Op0))
+ if (Value *B = dyn_castNotInst(Op1)) {
+ Instruction *Or = BinaryOperator::create(Instruction::Or, A, B,
+ I.getName()+".demorgan");
+ InsertNewInstBefore(Or, I);
+ return BinaryOperator::createNot(Or, I.getName());
+ }
- return Changed ? I : 0;
+ return Changed ? &I : 0;
}
-Instruction *InstCombiner::visitOr(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
+Instruction *InstCombiner::visitOr(BinaryOperator &I) {
bool Changed = SimplifyBinOp(I);
- Value *Op0 = I->getOperand(0), *Op1 = I->getOperand(1);
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// or X, X = X or X, 0 == X
- if (Op0 == Op1 || Op1 == Constant::getNullValue(I->getType())) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op0);
- return I;
- }
+ if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
+ return ReplaceInstUsesWith(I, Op0);
// or X, -1 == -1
- if (Constant *RHS = dyn_cast<Constant>(Op1))
- if (RHS == getMaxValue(I->getType())) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op1);
- return I;
- }
+ if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1))
+ if (RHS->isAllOnesValue())
+ return ReplaceInstUsesWith(I, Op1);
- return Changed ? I : 0;
+ return Changed ? &I : 0;
}
-Instruction *InstCombiner::visitXor(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
+Instruction *InstCombiner::visitXor(BinaryOperator &I) {
bool Changed = SimplifyBinOp(I);
- Value *Op0 = I->getOperand(0), *Op1 = I->getOperand(1);
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// xor X, X = 0
- if (Op0 == Op1) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
- return I;
+ if (Op0 == Op1)
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+
+ if (ConstantIntegral *Op1C = dyn_cast<ConstantIntegral>(Op1)) {
+ // xor X, 0 == X
+ if (Op1C->isNullValue())
+ return ReplaceInstUsesWith(I, Op0);
+
+ // Is this a "NOT" instruction?
+ if (Op1C->isAllOnesValue()) {
+ // xor (xor X, -1), -1 = not (not X) = X
+ if (Value *X = dyn_castNotInst(Op0))
+ return ReplaceInstUsesWith(I, X);
+
+ // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
+ if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0))
+ if (SCI->use_size() == 1)
+ return new SetCondInst(SCI->getInverseCondition(),
+ SCI->getOperand(0), SCI->getOperand(1));
+ }
}
- // xor X, 0 == X
- if (Op1 == Constant::getNullValue(I->getType())) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op0);
- return I;
- }
+ return Changed ? &I : 0;
+}
- return Changed ? I : 0;
+// AddOne, SubOne - Add or subtract a constant one from an integer constant...
+static Constant *AddOne(ConstantInt *C) {
+ Constant *Result = *C + *ConstantInt::get(C->getType(), 1);
+ assert(Result && "Constant folding integer addition failed!");
+ return Result;
+}
+static Constant *SubOne(ConstantInt *C) {
+ Constant *Result = *C - *ConstantInt::get(C->getType(), 1);
+ assert(Result && "Constant folding integer addition failed!");
+ return Result;
}
-Instruction *InstCombiner::visitSetCondInst(BinaryOperator *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
+// isTrueWhenEqual - Return true if the specified setcondinst instruction is
+// true when both operands are equal...
+//
+static bool isTrueWhenEqual(Instruction &I) {
+ return I.getOpcode() == Instruction::SetEQ ||
+ I.getOpcode() == Instruction::SetGE ||
+ I.getOpcode() == Instruction::SetLE;
+}
+
+Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
bool Changed = SimplifyBinOp(I);
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ const Type *Ty = Op0->getType();
// setcc X, X
- if (I->getOperand(0) == I->getOperand(1)) {
- bool NewVal = I->getOpcode() == Instruction::SetEQ ||
- I->getOpcode() == Instruction::SetGE ||
- I->getOpcode() == Instruction::SetLE;
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(ConstantBool::get(NewVal));
- return I;
+ if (Op0 == Op1)
+ return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
+
+ // setcc <global*>, 0 - Global value addresses are never null!
+ if (isa<GlobalValue>(Op0) && isa<ConstantPointerNull>(Op1))
+ return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
+
+ // setcc's with boolean values can always be turned into bitwise operations
+ if (Ty == Type::BoolTy) {
+ // If this is <, >, or !=, we can change this into a simple xor instruction
+ if (!isTrueWhenEqual(I))
+ return BinaryOperator::create(Instruction::Xor, Op0, Op1, I.getName());
+
+ // Otherwise we need to make a temporary intermediate instruction and insert
+ // it into the instruction stream. This is what we are after:
+ //
+ // seteq bool %A, %B -> ~(A^B)
+ // setle bool %A, %B -> ~A | B
+ // setge bool %A, %B -> A | ~B
+ //
+ if (I.getOpcode() == Instruction::SetEQ) { // seteq case
+ Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
+ I.getName()+"tmp");
+ InsertNewInstBefore(Xor, I);
+ return BinaryOperator::createNot(Xor, I.getName());
+ }
+
+ // Handle the setXe cases...
+ assert(I.getOpcode() == Instruction::SetGE ||
+ I.getOpcode() == Instruction::SetLE);
+
+ if (I.getOpcode() == Instruction::SetGE)
+ std::swap(Op0, Op1); // Change setge -> setle
+
+ // Now we just have the SetLE case.
+ Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
+ InsertNewInstBefore(Not, I);
+ return BinaryOperator::create(Instruction::Or, Not, Op1, I.getName());
}
- return Changed ? I : 0;
+ // Check to see if we are doing one of many comparisons against constant
+ // integers at the end of their ranges...
+ //
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
+ // Check to see if we are comparing against the minimum or maximum value...
+ if (CI->isMinValue()) {
+ if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
+ return ReplaceInstUsesWith(I, ConstantBool::False);
+ if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
+ return ReplaceInstUsesWith(I, ConstantBool::True);
+ if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
+ return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
+ if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
+ return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
+
+ } else if (CI->isMaxValue()) {
+ if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
+ return ReplaceInstUsesWith(I, ConstantBool::False);
+ if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
+ return ReplaceInstUsesWith(I, ConstantBool::True);
+ if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
+ return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
+ if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
+ return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
+
+ // Comparing against a value really close to min or max?
+ } else if (isMinValuePlusOne(CI)) {
+ if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
+ return BinaryOperator::create(Instruction::SetEQ, Op0,
+ SubOne(CI), I.getName());
+ if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
+ return BinaryOperator::create(Instruction::SetNE, Op0,
+ SubOne(CI), I.getName());
+
+ } else if (isMaxValueMinusOne(CI)) {
+ if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
+ return BinaryOperator::create(Instruction::SetEQ, Op0,
+ AddOne(CI), I.getName());
+ if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
+ return BinaryOperator::create(Instruction::SetNE, Op0,
+ AddOne(CI), I.getName());
+ }
+ }
+
+ return Changed ? &I : 0;
}
-Instruction *InstCombiner::visitShiftInst(Instruction *I) {
- if (I->use_empty()) return 0; // Don't fix dead instructions...
- assert(I->getOperand(1)->getType() == Type::UByteTy);
- Value *Op0 = I->getOperand(0), *Op1 = I->getOperand(1);
+Instruction *InstCombiner::visitShiftInst(Instruction &I) {
+ assert(I.getOperand(1)->getType() == Type::UByteTy);
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// shl X, 0 == X and shr X, 0 == X
// shl 0, X == 0 and shr 0, X == 0
if (Op1 == Constant::getNullValue(Type::UByteTy) ||
- Op0 == Constant::getNullValue(Op0->getType())) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Op0);
- return I;
- }
+ Op0 == Constant::getNullValue(Op0->getType()))
+ return ReplaceInstUsesWith(I, Op0);
- // shl int X, 32 = 0 and shr sbyte Y, 9 = 0, ... just don't eliminate shr of
+ // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr of
// a signed value.
//
if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
- unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
- if (CUI->getValue() >= TypeBits &&
- !(Op0->getType()->isSigned() && I->getOpcode() == Instruction::Shr)) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I->replaceAllUsesWith(Constant::getNullValue(Op0->getType()));
- return I;
+ if (I.getOpcode() == Instruction::Shr) {
+ unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
+ if (CUI->getValue() >= TypeBits && !(Op0->getType()->isSigned()))
+ return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
}
+
+ // Check to see if we are shifting left by 1. If so, turn it into an add
+ // instruction.
+ if (I.getOpcode() == Instruction::Shl && CUI->equalsInt(1))
+ // Convert 'shl int %X, 2' to 'add int %X, %X'
+ return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
+
}
return 0;
}
// isEliminableCastOfCast - Return true if it is valid to eliminate the CI
// instruction.
//
-static inline bool isEliminableCastOfCast(const CastInst *CI,
+static inline bool isEliminableCastOfCast(const CastInst &CI,
const CastInst *CSrc) {
- assert(CI->getOperand(0) == CSrc);
+ assert(CI.getOperand(0) == CSrc);
const Type *SrcTy = CSrc->getOperand(0)->getType();
const Type *MidTy = CSrc->getType();
- const Type *DstTy = CI->getType();
+ const Type *DstTy = CI.getType();
- // It is legal to eliminate the instruction if casting A->B->A
- if (SrcTy == DstTy) return true;
+ // It is legal to eliminate the instruction if casting A->B->A if the sizes
+ // are identical and the bits don't get reinterpreted (for example
+ // int->float->int would not be allowed)
+ if (SrcTy == DstTy && SrcTy->isLosslesslyConvertableTo(MidTy))
+ return true;
// Allow free casting and conversion of sizes as long as the sign doesn't
// change...
- if (SrcTy->isSigned() == MidTy->isSigned() &&
- MidTy->isSigned() == DstTy->isSigned())
- return true;
+ if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
+ unsigned SrcSize = SrcTy->getPrimitiveSize();
+ unsigned MidSize = MidTy->getPrimitiveSize();
+ unsigned DstSize = DstTy->getPrimitiveSize();
+
+ // Cases where we are monotonically decreasing the size of the type are
+ // always ok, regardless of what sign changes are going on.
+ //
+ if (SrcSize >= MidSize && MidSize >= DstSize)
+ return true;
+
+ // If we are monotonically growing, things are more complex.
+ //
+ if (SrcSize <= MidSize && MidSize <= DstSize) {
+ // We have eight combinations of signedness to worry about. Here's the
+ // table:
+ static const int SignTable[8] = {
+ // CODE, SrcSigned, MidSigned, DstSigned, Comment
+ 1, // U U U Always ok
+ 1, // U U S Always ok
+ 3, // U S U Ok iff SrcSize != MidSize
+ 3, // U S S Ok iff SrcSize != MidSize
+ 0, // S U U Never ok
+ 2, // S U S Ok iff MidSize == DstSize
+ 1, // S S U Always ok
+ 1, // S S S Always ok
+ };
+
+ // Choose an action based on the current entry of the signtable that this
+ // cast of cast refers to...
+ unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
+ switch (SignTable[Row]) {
+ case 0: return false; // Never ok
+ case 1: return true; // Always ok
+ case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
+ case 3: // Ok iff SrcSize != MidSize
+ return SrcSize != MidSize || SrcTy == Type::BoolTy;
+ default: assert(0 && "Bad entry in sign table!");
+ }
+ }
+ }
// Otherwise, we cannot succeed. Specifically we do not want to allow things
// like: short -> ushort -> uint, because this can create wrong results if
// CastInst simplification
//
-Instruction *InstCombiner::visitCastInst(CastInst *CI) {
- if (CI->use_empty()) return 0; // Don't fix dead instructions...
-
+Instruction *InstCombiner::visitCastInst(CastInst &CI) {
// If the user is casting a value to the same type, eliminate this cast
// instruction...
- 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;
- }
-
+ if (CI.getType() == CI.getOperand(0)->getType())
+ return ReplaceInstUsesWith(CI, CI.getOperand(0));
// If casting the result of another cast instruction, try to eliminate this
// one!
//
- if (CastInst *CSrc = dyn_cast<CastInst>(CI->getOperand(0)))
+ if (CastInst *CSrc = dyn_cast<CastInst>(CI.getOperand(0))) {
if (isEliminableCastOfCast(CI, CSrc)) {
// This instruction now refers directly to the cast's src operand. This
// has a good chance of making CSrc dead.
- CI->setOperand(0, CSrc->getOperand(0));
- return CI;
+ CI.setOperand(0, CSrc->getOperand(0));
+ return &CI;
}
+ // If this is an A->B->A cast, and we are dealing with integral types, try
+ // to convert this into a logical 'and' instruction.
+ //
+ if (CSrc->getOperand(0)->getType() == CI.getType() &&
+ CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
+ CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
+ CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
+ assert(CSrc->getType() != Type::ULongTy &&
+ "Cannot have type bigger than ulong!");
+ 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 (PN->use_empty()) return 0; // Don't fix dead instructions...
-
+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;
- }
+ if (PN.getNumIncomingValues() == 0)
+ return ReplaceInstUsesWith(PN, Constant::getNullValue(PN.getType()));
+ if (PN.getNumIncomingValues() == 1)
+ return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
+
+ // Otherwise if all of the incoming values are the same for the PHI, replace
+ // the PHI node with the incoming value.
+ //
+ Value *InVal = 0;
+ for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
+ if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
+ if (InVal && PN.getIncomingValue(i) != InVal)
+ return 0; // Not the same, bail out.
+ else
+ InVal = PN.getIncomingValue(i);
+
+ // The only case that could cause InVal to be null is if we have a PHI node
+ // that only has entries for itself. In this case, there is no entry into the
+ // loop, so kill the PHI.
+ //
+ if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
- return 0;
+ // All of the incoming values are the same, replace the PHI node now.
+ return ReplaceInstUsesWith(PN, InVal);
}
-Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst *GEP) {
- // Is it getelementptr %P, uint 0
- // If so, elminate the noop.
- if (GEP->getNumOperands() == 2 && !GEP->use_empty() &&
- GEP->getOperand(1) == Constant::getNullValue(Type::UIntTy)) {
- AddUsesToWorkList(GEP); // Add all modified instrs to worklist
- GEP->replaceAllUsesWith(GEP->getOperand(0));
- return GEP;
- }
+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)
+ return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
- return visitMemAccessInst(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.getOperand(0))) {
+ 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());
-// Combine Indices - If the source pointer to this mem access instruction is a
-// getelementptr instruction, combine the indices of the GEP into this
-// instruction
-//
-Instruction *InstCombiner::visitMemAccessInst(MemAccessInst *MAI) {
- GetElementPtrInst *Src =
- dyn_cast<GetElementPtrInst>(MAI->getPointerOperand());
- if (!Src) return 0;
+ } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
+ // GEP of global variable. If all of the indices for this GEP are
+ // constants, we can promote this to a constexpr instead of an instruction.
- std::vector<Value *> Indices;
-
- // Only special case we have to watch out for is pointer arithmetic on the
- // 0th index of MAI.
- unsigned FirstIdx = MAI->getFirstIndexOperandNumber();
- if (FirstIdx == MAI->getNumOperands() ||
- (FirstIdx == MAI->getNumOperands()-1 &&
- MAI->getOperand(FirstIdx) == ConstantUInt::get(Type::UIntTy, 0))) {
- // Replace the index list on this MAI with the index on the getelementptr
- Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
- } else if (*MAI->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(), MAI->idx_begin()+1, MAI->idx_end());
- }
+ // Scan for nonconstants...
+ std::vector<Constant*> Indices;
+ User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
+ for (; I != E && isa<Constant>(*I); ++I)
+ Indices.push_back(cast<Constant>(*I));
+
+ if (I == E) { // If they are all constants...
+ ConstantExpr *CE =
+ ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
- if (Indices.empty()) return 0; // Can't do the fold?
-
- switch (MAI->getOpcode()) {
- case Instruction::GetElementPtr:
- return new GetElementPtrInst(Src->getOperand(0), Indices, MAI->getName());
- case Instruction::Load:
- return new LoadInst(Src->getOperand(0), Indices, MAI->getName());
- case Instruction::Store:
- return new StoreInst(MAI->getOperand(0), Src->getOperand(0), Indices);
- default:
- assert(0 && "Unknown memaccessinst!");
- break;
+ // Replace all uses of the GEP with the new constexpr...
+ return ReplaceInstUsesWith(GEP, CE);
+ }
}
- abort();
+
return 0;
}
-bool InstCombiner::runOnFunction(Function *F) {
+void InstCombiner::removeFromWorkList(Instruction *I) {
+ WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
+ WorkList.end());
+}
+
+bool InstCombiner::runOnFunction(Function &F) {
bool Changed = false;
WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
Instruction *I = WorkList.back(); // Get an instruction from the worklist
WorkList.pop_back();
+ // Check to see if we can DCE or ConstantPropogate the instruction...
+ // Check to see if we can DIE the instruction...
+ if (isInstructionTriviallyDead(I)) {
+ // Add operands to the worklist...
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
+ WorkList.push_back(Op);
+
+ ++NumDeadInst;
+ BasicBlock::iterator BBI = I;
+ if (dceInstruction(BBI)) {
+ removeFromWorkList(I);
+ continue;
+ }
+ }
+
+ // Instruction isn't dead, see if we can constant propogate it...
+ if (Constant *C = ConstantFoldInstruction(I)) {
+ // Add operands to the worklist...
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
+ WorkList.push_back(Op);
+ I->replaceAllUsesWith(C);
+ ++NumConstProp;
+ BasicBlock::iterator BBI = I;
+ if (dceInstruction(BBI)) {
+ removeFromWorkList(I);
+ continue;
+ }
+ }
+
// Now that we have an instruction, try combining it to simplify it...
- Instruction *Result = visit(I);
- if (Result) {
+ if (Instruction *Result = visit(*I)) {
+ ++NumCombined;
// Should we replace the old instruction with a new one?
- if (Result != I)
+ 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.
+ removeFromWorkList(I);
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.
+ removeFromWorkList(I);
+ Result = 0;
+ }
+ }
- WorkList.push_back(Result);
- AddUsesToWorkList(Result);
+ if (Result) {
+ WorkList.push_back(Result);
+ AddUsesToWorkList(*Result);
+ }
Changed = true;
}
}
projects / oota-llvm.git / blobdiff