-//===- 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.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/ConstantHandling.h"
-#include "llvm/iMemory.h"
-#include "llvm/iOther.h"
-#include "llvm/iPHINode.h"
-#include "llvm/iOperators.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Instructions.h"
#include "llvm/Pass.h"
+#include "llvm/Constants.h"
+#include "llvm/ConstantHandling.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/GlobalVariable.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/Support/InstVisitor.h"
-#include "Support/StatisticReporter.h"
+#include "llvm/Support/CallSite.h"
+#include "Support/Statistic.h"
#include <algorithm>
-static Statistic<> NumCombined("instcombine\t- Number of insts combined");
-
namespace {
+ Statistic<> NumCombined ("instcombine", "Number of insts combined");
+ Statistic<> NumConstProp("instcombine", "Number of constant folds");
+ Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
+
class InstCombiner : public FunctionPass,
public InstVisitor<InstCombiner, Instruction*> {
// Worklist of all of the instructions that need to be simplified.
WorkList.push_back(cast<Instruction>(*UI));
}
+ // removeFromWorkList - remove all instances of I from the worklist.
+ void removeFromWorkList(Instruction *I);
public:
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.preservesCFG();
+ AU.setPreservesCFG();
}
// 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
+ // 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 *visitOr (BinaryOperator &I);
Instruction *visitXor(BinaryOperator &I);
Instruction *visitSetCondInst(BinaryOperator &I);
- Instruction *visitShiftInst(Instruction &I);
+ Instruction *visitShiftInst(ShiftInst &I);
Instruction *visitCastInst(CastInst &CI);
+ Instruction *visitCallInst(CallInst &CI);
+ Instruction *visitInvokeInst(InvokeInst &II);
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
- Instruction *visitMemAccessInst(MemAccessInst &MAI);
+ Instruction *visitAllocationInst(AllocationInst &AI);
+ Instruction *visitLoadInst(LoadInst &LI);
+ Instruction *visitBranchInst(BranchInst &BI);
// visitInstruction - Specify what to return for unhandled instructions...
Instruction *visitInstruction(Instruction &I) { return 0; }
+
+ private:
+ bool transformConstExprCastCall(CallSite CS);
+
+ // 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
+ }
+
+ // 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(V);
+ return &I;
+ }
+
+ // SimplifyCommutative - This performs a few simplifications for commutative
+ // operators...
+ bool SimplifyCommutative(BinaryOperator &I);
};
RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
}
+// getComplexity: Assign a complexity or rank value to LLVM Values...
+// 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
+static unsigned getComplexity(Value *V) {
+ if (isa<Instruction>(V)) {
+ if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
+ return 2;
+ return 3;
+ }
+ if (isa<Argument>(V)) return 2;
+ return isa<Constant>(V) ? 0 : 1;
+}
-Instruction *InstCombiner::visitNot(UnaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead instructions...
+// isOnlyUse - Return true if this instruction will be deleted if we stop using
+// it.
+static bool isOnlyUse(Value *V) {
+ return V->use_size() == 1 || isa<Constant>(V);
+}
- // not (not X) = X
- if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(0)))
- if (Op->getOpcode() == Instruction::Not) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I.replaceAllUsesWith(Op->getOperand(0));
- return &I;
+// SimplifyCommutative - This performs a few simplifications for commutative
+// operators:
+//
+// 1. Order operands such that they are listed from right (least complex) to
+// left (most complex). This puts constants before unary operators before
+// binary operators.
+//
+// 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
+// 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
+//
+bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
+ bool Changed = false;
+ if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
+ Changed = !I.swapOperands();
+
+ if (!I.isAssociative()) return Changed;
+ Instruction::BinaryOps Opcode = I.getOpcode();
+ if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
+ if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
+ if (isa<Constant>(I.getOperand(1))) {
+ Constant *Folded = ConstantExpr::get(I.getOpcode(),
+ cast<Constant>(I.getOperand(1)),
+ cast<Constant>(Op->getOperand(1)));
+ I.setOperand(0, Op->getOperand(0));
+ I.setOperand(1, Folded);
+ return true;
+ } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
+ if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
+ isOnlyUse(Op) && isOnlyUse(Op1)) {
+ Constant *C1 = cast<Constant>(Op->getOperand(1));
+ Constant *C2 = cast<Constant>(Op1->getOperand(1));
+
+ // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
+ Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
+ Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
+ Op1->getOperand(0),
+ Op1->getName(), &I);
+ WorkList.push_back(New);
+ I.setOperand(0, New);
+ I.setOperand(1, Folded);
+ return true;
+ }
}
+ return Changed;
+}
+
+// dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
+// if the LHS is a constant zero (which is the 'negate' form).
+//
+static inline Value *dyn_castNegVal(Value *V) {
+ if (BinaryOperator::isNeg(V))
+ return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
+
+ // Constants can be considered to be negated values if they can be folded...
+ if (Constant *C = dyn_cast<Constant>(V))
+ return ConstantExpr::get(Instruction::Sub,
+ Constant::getNullValue(V->getType()), C);
return 0;
}
+static inline Value *dyn_castNotVal(Value *V) {
+ if (BinaryOperator::isNot(V))
+ return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
-// 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.
+ // Constants can be considered to be not'ed values...
+ if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
+ return ConstantExpr::get(Instruction::Xor,
+ ConstantIntegral::getAllOnesValue(C->getType()),C);
+ return 0;
+}
+
+// dyn_castFoldableMul - If this value is a multiply that can be folded into
+// other computations (because it has a constant operand), return the
+// non-constant operand of the multiply.
//
-static bool SimplifyBinOp(BinaryOperator &I) {
- if (isa<Constant>(I.getOperand(0)) && !isa<Constant>(I.getOperand(1)))
- return !I.swapOperands();
- return false;
+static inline Value *dyn_castFoldableMul(Value *V) {
+ if (V->use_size() == 1 && V->getType()->isInteger())
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ if (I->getOpcode() == Instruction::Mul)
+ if (isa<Constant>(I->getOperand(1)))
+ return I->getOperand(0);
+ return 0;
}
-// dyn_castNegInst - Given a 'sub' instruction, return the RHS of the
-// instruction if the LHS is a constant zero (which is the 'negate' form).
+// dyn_castMaskingAnd - If this value is an And instruction masking a value with
+// a constant, return the constant being anded with.
//
-static inline Value *dyn_castNegInst(Value *V) {
- Instruction *I = dyn_cast<Instruction>(V);
- if (!I || I->getOpcode() != Instruction::Sub) return 0;
+static inline Constant *dyn_castMaskingAnd(Value *V) {
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ if (I->getOpcode() == Instruction::And)
+ return dyn_cast<Constant>(I->getOperand(1));
- if (I->getOperand(0) == Constant::getNullValue(I->getType()))
- return I->getOperand(1);
- return 0;
+ // If this is a constant, it acts just like we were masking with it.
+ return dyn_cast<Constant>(V);
+}
+
+// Log2 - Calculate the log base 2 for the specified value if it is exactly a
+// power of 2.
+static unsigned Log2(uint64_t Val) {
+ assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
+ unsigned Count = 0;
+ while (Val != 1) {
+ if (Val & 1) return 0; // Multiple bits set?
+ Val >>= 1;
+ ++Count;
+ }
+ return Count;
}
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead add instructions...
- bool Changed = SimplifyBinOp(I);
+ bool Changed = SimplifyCommutative(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// Eliminate 'add int %X, 0'
- if (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);
// -A + B --> B - A
- if (Value *V = dyn_castNegInst(LHS))
+ if (Value *V = dyn_castNegVal(LHS))
return BinaryOperator::create(Instruction::Sub, RHS, V);
// A + -B --> A - B
- if (Value *V = dyn_castNegInst(RHS))
- return BinaryOperator::create(Instruction::Sub, LHS, V);
-
- // Simplify add instructions with a constant RHS...
- if (Constant *Op2 = dyn_cast<Constant>(RHS)) {
- if (BinaryOperator *ILHS = dyn_cast<BinaryOperator>(LHS)) {
- if (ILHS->getOpcode() == Instruction::Add &&
- isa<Constant>(ILHS->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>(ILHS->getOperand(1))) {
- I.setOperand(0, ILHS->getOperand(0));
- I.setOperand(1, Val);
- return &I;
- }
- }
- }
+ if (!isa<Constant>(RHS))
+ if (Value *V = dyn_castNegVal(RHS))
+ return BinaryOperator::create(Instruction::Sub, LHS, V);
+
+ // X*C + X --> X * (C+1)
+ if (dyn_castFoldableMul(LHS) == RHS) {
+ Constant *CP1 =
+ ConstantExpr::get(Instruction::Add,
+ cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
+ ConstantInt::get(I.getType(), 1));
+ return BinaryOperator::create(Instruction::Mul, RHS, CP1);
}
+ // X + X*C --> X * (C+1)
+ if (dyn_castFoldableMul(RHS) == LHS) {
+ Constant *CP1 =
+ ConstantExpr::get(Instruction::Add,
+ cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
+ ConstantInt::get(I.getType(), 1));
+ return BinaryOperator::create(Instruction::Mul, LHS, CP1);
+ }
+
+ // (A & C1)+(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
+ if (Constant *C1 = dyn_castMaskingAnd(LHS))
+ if (Constant *C2 = dyn_castMaskingAnd(RHS))
+ if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
+ return BinaryOperator::create(Instruction::Or, LHS, RHS);
+
return Changed ? &I : 0;
}
+// isSignBit - Return true if the value represented by the constant only has the
+// highest order bit set.
+static bool isSignBit(ConstantInt *CI) {
+ unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
+ return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
+}
+
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);
- if (Op0 == Op1) { // sub X, X -> 0
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I.replaceAllUsesWith(Constant::getNullValue(I.getType()));
- return &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>(Op1))
- if (Constant *RHS = *Constant::getNullValue(I.getType()) - *Op2) // 0 - RHS
- return BinaryOperator::create(Instruction::Add, Op0, RHS, I.getName());
+ if (Op0 == Op1) // sub X, X -> 0
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
- // If this is a 'C = x-B', check to see if 'B = -A', so that C = x+A...
- if (Value *V = dyn_castNegInst(Op1))
+ // If this is a 'B = x-(-A)', change to B = x+A...
+ if (Value *V = dyn_castNegVal(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...
- //
+ // Replace (-1 - A) with (~A)...
+ if (ConstantInt *C = dyn_cast<ConstantInt>(Op0))
+ if (C->isAllOnesValue())
+ return BinaryOperator::createNot(Op1);
+
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);
+ if (Op1I->use_size() == 1) {
+ // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
+ // is not used by anyone else...
+ //
+ if (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);
+ }
+
+ // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
+ //
+ if (Op1I->getOpcode() == Instruction::And &&
+ (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
+ Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
+
+ Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
+ return BinaryOperator::create(Instruction::And, Op0, NewNot);
+ }
+
+ // X - X*C --> X * (1-C)
+ if (dyn_castFoldableMul(Op1I) == Op0) {
+ Constant *CP1 =
+ ConstantExpr::get(Instruction::Sub,
+ ConstantInt::get(I.getType(), 1),
+ cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
+ assert(CP1 && "Couldn't constant fold 1-C?");
+ return BinaryOperator::create(Instruction::Mul, Op0, CP1);
+ }
}
+
+ // X*C - X --> X * (C-1)
+ if (dyn_castFoldableMul(Op0) == Op1) {
+ Constant *CP1 =
+ ConstantExpr::get(Instruction::Sub,
+ cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
+ ConstantInt::get(I.getType(), 1));
+ assert(CP1 && "Couldn't constant fold C - 1?");
+ return BinaryOperator::create(Instruction::Mul, Op1, CP1);
+ }
+
return 0;
}
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead 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;
-
- } else if (I.getType()->isIntegral() &&
- cast<ConstantInt>(Op2)->equalsInt(2)) {
- // Convert 'mul int %X, 2' to 'add int %X, %X'
- return BinaryOperator::create(Instruction::Add, Op1, Op1, I.getName());
+ bool Changed = SimplifyCommutative(I);
+ Value *Op0 = I.getOperand(0);
+
+ // Simplify mul instructions with a constant RHS...
+ if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
+ const Type *Ty = CI->getType();
+ int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
+ switch (Val) {
+ case -1: // X * -1 -> -X
+ return BinaryOperator::createNeg(Op0, I.getName());
+ case 0:
+ return ReplaceInstUsesWith(I, Op1); // Eliminate 'mul double %X, 0'
+ case 1:
+ return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul int %X, 1'
+ case 2: // Convert 'mul int %X, 2' to 'add int %X, %X'
+ return BinaryOperator::create(Instruction::Add, Op0, Op0, 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 (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
+ return new ShiftInst(Instruction::Shl, Op0,
+ ConstantUInt::get(Type::UByteTy, C));
+ } else {
+ ConstantFP *Op1F = cast<ConstantFP>(Op1);
+ if (Op1F->isNullValue())
+ return ReplaceInstUsesWith(I, Op1);
+
+ // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
+ // ANSI says we can drop signals, so we can do this anyway." (from GCC)
+ if (Op1F->getValue() == 1.0)
+ return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
}
}
+ if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
+ if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
+ return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
+
return Changed ? &I : 0;
}
-
Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead instructions...
-
// 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));
+
+ // Check to see if this is an unsigned division with an exact power of 2,
+ // if so, convert to a right shift.
+ if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
+ if (uint64_t Val = C->getValue()) // Don't break X / 0
+ if (uint64_t C = Log2(Val))
+ return new ShiftInst(Instruction::Shr, I.getOperand(0),
+ ConstantUInt::get(Type::UByteTy, C));
+ }
+
+ // 0 / X == 0, we don't need to preserve faults!
+ if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
+ if (LHS->equalsInt(0))
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+
return 0;
}
Instruction *InstCombiner::visitRem(BinaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead instructions...
+ if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
+ if (RHS->equalsInt(1)) // X % 1 == 0
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+
+ // Check to see if this is an unsigned remainder with an exact power of 2,
+ // if so, convert to a bitwise and.
+ if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
+ if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
+ if (Log2(Val))
+ return BinaryOperator::create(Instruction::And, I.getOperand(0),
+ ConstantUInt::get(I.getType(), Val-1));
+ }
+
+ // 0 % X == 0, we don't need to preserve faults!
+ if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
+ if (LHS->equalsInt(0))
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
- // 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;
- }
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...
- bool Changed = SimplifyBinOp(I);
+ bool Changed = SimplifyCommutative(I);
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);
+
+ // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
+ if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
+ if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
+ if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
+ std::string Op0Name = Op0I->getName(); Op0I->setName("");
+ Instruction *And = BinaryOperator::create(Instruction::And,
+ Op0I->getOperand(0), RHS,
+ Op0Name);
+ InsertNewInstBefore(And, I);
+ return BinaryOperator::create(Instruction::Xor, And, *RHS & *Op0CI);
+ }
+ }
+
+ Value *Op0NotVal = dyn_castNotVal(Op0);
+ Value *Op1NotVal = dyn_castNotVal(Op1);
+
+ // (~A & ~B) == (~(A | B)) - Demorgan's Law
+ if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
+ Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
+ Op1NotVal,I.getName()+".demorgan");
+ InsertNewInstBefore(Or, I);
+ return BinaryOperator::createNot(Or);
+ }
+
+ if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
+ return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitOr(BinaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead instructions...
- bool Changed = SimplifyBinOp(I);
+ bool Changed = SimplifyCommutative(I);
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);
+
+ if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
+ // (X & C1) | C2 --> (X | C2) & (C1|C2)
+ if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
+ if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
+ std::string Op0Name = Op0I->getName(); Op0I->setName("");
+ Instruction *Or = BinaryOperator::create(Instruction::Or,
+ Op0I->getOperand(0), RHS,
+ Op0Name);
+ InsertNewInstBefore(Or, I);
+ return BinaryOperator::create(Instruction::And, Or, *RHS | *Op0CI);
+ }
+
+ // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
+ if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
+ if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
+ std::string Op0Name = Op0I->getName(); Op0I->setName("");
+ Instruction *Or = BinaryOperator::create(Instruction::Or,
+ Op0I->getOperand(0), RHS,
+ Op0Name);
+ InsertNewInstBefore(Or, I);
+ return BinaryOperator::create(Instruction::Xor, Or, *Op0CI & *~*RHS);
+ }
}
+ }
+
+ Value *Op0NotVal = dyn_castNotVal(Op0);
+ Value *Op1NotVal = dyn_castNotVal(Op1);
+
+ if (Op1 == Op0NotVal) // ~A | A == -1
+ return ReplaceInstUsesWith(I,
+ ConstantIntegral::getAllOnesValue(I.getType()));
+
+ if (Op0 == Op1NotVal) // A | ~A == -1
+ return ReplaceInstUsesWith(I,
+ ConstantIntegral::getAllOnesValue(I.getType()));
+
+ // (~A | ~B) == (~(A & B)) - Demorgan's Law
+ if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
+ Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
+ Op1NotVal,I.getName()+".demorgan",
+ &I);
+ WorkList.push_back(And);
+ return BinaryOperator::createNot(And);
+ }
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitXor(BinaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead instructions...
- bool Changed = SimplifyBinOp(I);
+ bool Changed = SimplifyCommutative(I);
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_castNotVal(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;
- }
+ if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
+ if (X == Op1)
+ return ReplaceInstUsesWith(I,
+ ConstantIntegral::getAllOnesValue(I.getType()));
+
+ if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
+ if (X == Op0)
+ return ReplaceInstUsesWith(I,
+ ConstantIntegral::getAllOnesValue(I.getType()));
+
+ if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
+ if (Op1I->getOpcode() == Instruction::Or)
+ if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
+ cast<BinaryOperator>(Op1I)->swapOperands();
+ I.swapOperands();
+ std::swap(Op0, Op1);
+ } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
+ I.swapOperands();
+ std::swap(Op0, Op1);
+ }
+
+ if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
+ if (Op0I->getOpcode() == Instruction::Or && Op0I->use_size() == 1) {
+ if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
+ cast<BinaryOperator>(Op0I)->swapOperands();
+ if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
+ Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
+ WorkList.push_back(cast<Instruction>(NotB));
+ return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
+ NotB);
+ }
+ }
+
+ // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
+ if (Constant *C1 = dyn_castMaskingAnd(Op0))
+ if (Constant *C2 = dyn_castMaskingAnd(Op1))
+ if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
+ return BinaryOperator::create(Instruction::Or, Op0, Op1);
return Changed ? &I : 0;
}
+// AddOne, SubOne - Add or subtract a constant one from an integer constant...
+static Constant *AddOne(ConstantInt *C) {
+ Constant *Result = ConstantExpr::get(Instruction::Add, C,
+ ConstantInt::get(C->getType(), 1));
+ assert(Result && "Constant folding integer addition failed!");
+ return Result;
+}
+static Constant *SubOne(ConstantInt *C) {
+ Constant *Result = ConstantExpr::get(Instruction::Sub, C,
+ ConstantInt::get(C->getType(), 1));
+ assert(Result && "Constant folding integer addition failed!");
+ return Result;
+}
+
// isTrueWhenEqual - Return true if the specified setcondinst instruction is
// true when both operands are equal...
//
}
Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
- if (I.use_empty()) return 0; // Don't fix dead instructions...
- bool Changed = SimplifyBinOp(I);
+ bool Changed = SimplifyCommutative(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)) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I.replaceAllUsesWith(ConstantBool::get(isTrueWhenEqual(I)));
- return &I;
- }
+ if (Op0 == Op1)
+ return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
// setcc <global*>, 0 - Global value addresses are never null!
- if (isa<GlobalValue>(I.getOperand(0)) &&
- isa<ConstantPointerNull>(I.getOperand(1))) {
- AddUsesToWorkList(I); // Add all modified instrs to worklist
- I.replaceAllUsesWith(ConstantBool::get(!isTrueWhenEqual(I)));
- return &I;
+ 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());
+ }
+
+ // 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)) {
+ // Simplify seteq and setne instructions...
+ if (I.getOpcode() == Instruction::SetEQ ||
+ I.getOpcode() == Instruction::SetNE) {
+ bool isSetNE = I.getOpcode() == Instruction::SetNE;
+
+ if (CI->isNullValue()) { // Simplify [seteq|setne] X, 0
+ CastInst *Val = new CastInst(Op0, Type::BoolTy, I.getName()+".not");
+ if (isSetNE) return Val;
+
+ // seteq X, 0 -> not (cast X to bool)
+ InsertNewInstBefore(Val, I);
+ return BinaryOperator::createNot(Val, I.getName());
+ }
+
+ // If the first operand is (and|or|xor) with a constant, and the second
+ // operand is a constant, simplify a bit.
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
+ if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1)))
+ if (BO->getOpcode() == Instruction::Or) {
+ // If bits are being or'd in that are not present in the constant we
+ // are comparing against, then the comparison could never succeed!
+ if (!(*BOC & *~*CI)->isNullValue())
+ return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
+ } else if (BO->getOpcode() == Instruction::And) {
+ // If bits are being compared against that are and'd out, then the
+ // comparison can never succeed!
+ if (!(*CI & *~*BOC)->isNullValue())
+ return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
+ } else if (BO->getOpcode() == Instruction::Xor) {
+ // For the xor case, we can always just xor the two constants
+ // together, potentially eliminating the explicit xor.
+ return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
+ *CI ^ *BOC);
+ }
+ }
+
+ // 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...
+Instruction *InstCombiner::visitShiftInst(ShiftInst &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);
+
+ // If this is a shift of a shift, see if we can fold the two together...
+ if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0)) {
+ if (isa<Constant>(Op1) && isa<Constant>(Op0SI->getOperand(1))) {
+ ConstantUInt *ShiftAmt1C = cast<ConstantUInt>(Op0SI->getOperand(1));
+ unsigned ShiftAmt1 = ShiftAmt1C->getValue();
+ unsigned ShiftAmt2 = cast<ConstantUInt>(Op1)->getValue();
+
+ // Check for (A << c1) << c2 and (A >> c1) >> c2
+ if (I.getOpcode() == Op0SI->getOpcode()) {
+ unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
+ return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
+ ConstantUInt::get(Type::UByteTy, Amt));
+ }
+
+ if (I.getType()->isUnsigned()) { // Check for (A << c1) >> c2 or visaversa
+ // Calculate bitmask for what gets shifted off the edge...
+ Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
+ if (I.getOpcode() == Instruction::Shr)
+ C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
+ else
+ C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
+
+ Instruction *Mask =
+ BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
+ C, Op0SI->getOperand(0)->getName()+".mask",&I);
+ WorkList.push_back(Mask);
+
+ // Figure out what flavor of shift we should use...
+ if (ShiftAmt1 == ShiftAmt2)
+ return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
+ else if (ShiftAmt1 < ShiftAmt2) {
+ return new ShiftInst(I.getOpcode(), Mask,
+ ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
+ } else {
+ return new ShiftInst(Op0SI->getOpcode(), Mask,
+ ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
+ }
+ }
+ }
}
- // 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;
- }
+ (!Op0->getType()->isSigned() || I.getOpcode() == Instruction::Shl))
+ 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, 1' to 'add int %X, %X'
+ return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
+
}
+
+ // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
+ if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
+ if (I.getOpcode() == Instruction::Shr && CSI->isAllOnesValue())
+ return ReplaceInstUsesWith(I, CSI);
+
return 0;
}
const Type *MidTy = CSrc->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->isLosslesslyConvertibleTo(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;
+
+ // Cases where the source and destination type are the same, but the middle
+ // type is bigger are noops.
+ //
+ if (SrcSize == DstSize && MidSize > SrcSize)
+ 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...
+ Value *Src = CI.getOperand(0);
// 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() == Src->getType())
+ return ReplaceInstUsesWith(CI, Src);
// 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>(Src)) {
if (isEliminableCastOfCast(CI, CSrc)) {
// This instruction now refers directly to the cast's src operand. This
// has a good chance of making CSrc dead.
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!");
+ uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
+ Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
+ return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
+ AndOp);
+ }
+ }
+
+ // If casting the result of a getelementptr instruction with no offset, turn
+ // this into a cast of the original pointer!
+ //
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
+ bool AllZeroOperands = true;
+ for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
+ if (!isa<Constant>(GEP->getOperand(i)) ||
+ !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
+ AllZeroOperands = false;
+ break;
+ }
+ if (AllZeroOperands) {
+ CI.setOperand(0, GEP->getOperand(0));
+ return &CI;
+ }
+ }
+
+ // If this is a cast to bool (which is effectively a "!=0" test), then we can
+ // perform a few optimizations...
+ //
+ if (CI.getType() == Type::BoolTy) {
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Src)) {
+ Value *Op0 = BO->getOperand(0), *Op1 = BO->getOperand(1);
+
+ switch (BO->getOpcode()) {
+ case Instruction::Sub:
+ case Instruction::Xor:
+ // Replace (cast ([sub|xor] A, B) to bool) with (setne A, B)
+ return new SetCondInst(Instruction::SetNE, Op0, Op1);
+
+ // Replace (cast (add A, B) to bool) with (setne A, -B) if B is
+ // efficiently invertible, or if the add has just this one use.
+ case Instruction::Add:
+ if (Value *NegVal = dyn_castNegVal(Op1))
+ return new SetCondInst(Instruction::SetNE, Op0, NegVal);
+ else if (Value *NegVal = dyn_castNegVal(Op0))
+ return new SetCondInst(Instruction::SetNE, NegVal, Op1);
+ else if (BO->use_size() == 1) {
+ Instruction *Neg = BinaryOperator::createNeg(Op1, BO->getName());
+ BO->setName("");
+ InsertNewInstBefore(Neg, CI);
+ return new SetCondInst(Instruction::SetNE, Op0, Neg);
+ }
+ break;
+
+ case Instruction::And:
+ // Replace (cast (and X, (1 << size(X)-1)) to bool) with x < 0,
+ // converting X to be a signed value as appropriate. Don't worry about
+ // bool values, as they will be optimized other ways if they occur in
+ // this configuration.
+ if (ConstantInt *CInt = dyn_cast<ConstantInt>(Op1))
+ if (isSignBit(CInt)) {
+ // If 'X' is not signed, insert a cast now...
+ if (!CInt->getType()->isSigned()) {
+ const Type *DestTy;
+ switch (CInt->getType()->getPrimitiveID()) {
+ case Type::UByteTyID: DestTy = Type::SByteTy; break;
+ case Type::UShortTyID: DestTy = Type::ShortTy; break;
+ case Type::UIntTyID: DestTy = Type::IntTy; break;
+ case Type::ULongTyID: DestTy = Type::LongTy; break;
+ default: assert(0 && "Invalid unsigned integer type!"); abort();
+ }
+ CastInst *NewCI = new CastInst(Op0, DestTy,
+ Op0->getName()+".signed");
+ InsertNewInstBefore(NewCI, CI);
+ Op0 = NewCI;
+ }
+ return new SetCondInst(Instruction::SetLT, Op0,
+ Constant::getNullValue(Op0->getType()));
+ }
+ break;
+ default: break;
+ }
+ }
+ }
+
+ return 0;
+}
+
+// CallInst simplification
+//
+Instruction *InstCombiner::visitCallInst(CallInst &CI) {
+ if (transformConstExprCastCall(&CI)) return 0;
return 0;
}
+// InvokeInst simplification
+//
+Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
+ if (transformConstExprCastCall(&II)) return 0;
+ return 0;
+}
+
+// getPromotedType - Return the specified type promoted as it would be to pass
+// though a va_arg area...
+static const Type *getPromotedType(const Type *Ty) {
+ switch (Ty->getPrimitiveID()) {
+ case Type::SByteTyID:
+ case Type::ShortTyID: return Type::IntTy;
+ case Type::UByteTyID:
+ case Type::UShortTyID: return Type::UIntTy;
+ case Type::FloatTyID: return Type::DoubleTy;
+ default: return Ty;
+ }
+}
+
+// transformConstExprCastCall - If the callee is a constexpr cast of a function,
+// attempt to move the cast to the arguments of the call/invoke.
+//
+bool InstCombiner::transformConstExprCastCall(CallSite CS) {
+ if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
+ ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
+ if (CE->getOpcode() != Instruction::Cast ||
+ !isa<ConstantPointerRef>(CE->getOperand(0)))
+ return false;
+ ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
+ if (!isa<Function>(CPR->getValue())) return false;
+ Function *Callee = cast<Function>(CPR->getValue());
+ Instruction *Caller = CS.getInstruction();
+
+ // Okay, this is a cast from a function to a different type. Unless doing so
+ // would cause a type conversion of one of our arguments, change this call to
+ // be a direct call with arguments casted to the appropriate types.
+ //
+ const FunctionType *FT = Callee->getFunctionType();
+ const Type *OldRetTy = Caller->getType();
+
+ if (Callee->isExternal() &&
+ !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
+ return false; // Cannot transform this return value...
+
+ unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
+ unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
+
+ CallSite::arg_iterator AI = CS.arg_begin();
+ for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
+ const Type *ParamTy = FT->getParamType(i);
+ bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
+ if (Callee->isExternal() && !isConvertible) return false;
+ }
+
+ if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
+ Callee->isExternal())
+ return false; // Do not delete arguments unless we have a function body...
+
+ // Okay, we decided that this is a safe thing to do: go ahead and start
+ // inserting cast instructions as necessary...
+ std::vector<Value*> Args;
+ Args.reserve(NumActualArgs);
+
+ AI = CS.arg_begin();
+ for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
+ const Type *ParamTy = FT->getParamType(i);
+ if ((*AI)->getType() == ParamTy) {
+ Args.push_back(*AI);
+ } else {
+ Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
+ InsertNewInstBefore(Cast, *Caller);
+ Args.push_back(Cast);
+ }
+ }
+
+ // If the function takes more arguments than the call was taking, add them
+ // now...
+ for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
+ Args.push_back(Constant::getNullValue(FT->getParamType(i)));
+
+ // If we are removing arguments to the function, emit an obnoxious warning...
+ if (FT->getNumParams() < NumActualArgs)
+ if (!FT->isVarArg()) {
+ std::cerr << "WARNING: While resolving call to function '"
+ << Callee->getName() << "' arguments were dropped!\n";
+ } else {
+ // Add all of the arguments in their promoted form to the arg list...
+ for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
+ const Type *PTy = getPromotedType((*AI)->getType());
+ if (PTy != (*AI)->getType()) {
+ // Must promote to pass through va_arg area!
+ Instruction *Cast = new CastInst(*AI, PTy, "tmp");
+ InsertNewInstBefore(Cast, *Caller);
+ Args.push_back(Cast);
+ } else {
+ Args.push_back(*AI);
+ }
+ }
+ }
+
+ if (FT->getReturnType() == Type::VoidTy)
+ Caller->setName(""); // Void type should not have a name...
+
+ Instruction *NC;
+ if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
+ NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
+ Args, Caller->getName(), Caller);
+ } else {
+ NC = new CallInst(Callee, Args, Caller->getName(), Caller);
+ }
+
+ // Insert a cast of the return type as necessary...
+ Value *NV = NC;
+ if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
+ if (NV->getType() != Type::VoidTy) {
+ NV = NC = new CastInst(NC, Caller->getType(), "tmp");
+ InsertNewInstBefore(NC, *Caller);
+ AddUsesToWorkList(*Caller);
+ } else {
+ NV = Constant::getNullValue(Caller->getType());
+ }
+ }
+
+ if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
+ Caller->replaceAllUsesWith(NV);
+ Caller->getParent()->getInstList().erase(Caller);
+ removeFromWorkList(Caller);
+ return true;
+}
+
+
// PHINode simplification
//
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
- if (PN.use_empty()) return 0; // Don't fix dead instructions...
-
// 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() == 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
+ // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
// If so, eliminate 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;
+ if ((GEP.getNumOperands() == 2 &&
+ GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
+ GEP.getNumOperands() == 1)
+ return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
+
+ // 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: gep (gep %P, long C1), long C2, ...
+ // With: gep %P, long (C1+C2), ...
+ Value *Sum = ConstantExpr::get(Instruction::Add,
+ cast<Constant>(Src->getOperand(1)),
+ cast<Constant>(GEP.getOperand(1)));
+ assert(Sum && "Constant folding of longs failed!?");
+ GEP.setOperand(0, Src->getOperand(0));
+ GEP.setOperand(1, Sum);
+ AddUsesToWorkList(*Src); // Reduce use count of Src
+ return &GEP;
+ } else if (Src->getNumOperands() == 2) {
+ // Replace: gep (gep %P, long B), long A, ...
+ // With: T = long A+B; gep %P, T, ...
+ //
+ Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
+ GEP.getOperand(1),
+ Src->getName()+".sum", &GEP);
+ GEP.setOperand(0, Src->getOperand(0));
+ GEP.setOperand(1, Sum);
+ WorkList.push_back(cast<Instruction>(Sum));
+ return &GEP;
+ } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
+ Src->getNumOperands() != 1) {
+ // 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());
+ } else if (Src->getOperand(Src->getNumOperands()-1) ==
+ Constant::getNullValue(Type::LongTy)) {
+ // If the src gep ends with a constant array index, merge this get into
+ // it, even if we have a non-zero array index.
+ Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
+ Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
+ }
+
+ if (!Indices.empty())
+ return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
+
+ } 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.
+
+ // 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...
+ Constant *CE =
+ ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
+
+ // Replace all uses of the GEP with the new constexpr...
+ return ReplaceInstUsesWith(GEP, CE);
+ }
}
- return visitMemAccessInst(GEP);
+ return 0;
}
+Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
+ // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
+ if (AI.isArrayAllocation()) // Check C != 1
+ if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
+ const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
+ AllocationInst *New = 0;
+
+ // Create and insert the replacement instruction...
+ if (isa<MallocInst>(AI))
+ New = new MallocInst(NewTy, 0, AI.getName(), &AI);
+ else {
+ assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
+ New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
+ }
+
+ // Scan to the end of the allocation instructions, to skip over a block of
+ // allocas if possible...
+ //
+ BasicBlock::iterator It = New;
+ while (isa<AllocationInst>(*It)) ++It;
-// 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) {
- return 0; // DISABLE FOLDING. GEP is now the only MAI!
+ // Now that I is pointing to the first non-allocation-inst in the block,
+ // insert our getelementptr instruction...
+ //
+ std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
+ Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
- GetElementPtrInst *Src =
- dyn_cast<GetElementPtrInst>(MAI.getPointerOperand());
- if (!Src) return 0;
+ // Now make everything use the getelementptr instead of the original
+ // allocation.
+ ReplaceInstUsesWith(AI, V);
+ return &AI;
+ }
+ return 0;
+}
- 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());
- }
+/// GetGEPGlobalInitializer - Given a constant, and a getelementptr
+/// constantexpr, return the constant value being addressed by the constant
+/// expression, or null if something is funny.
+///
+static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
+ if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
+ return 0; // Do not allow stepping over the value!
+
+ // Loop over all of the operands, tracking down which value we are
+ // addressing...
+ for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
+ if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
+ ConstantStruct *CS = cast<ConstantStruct>(C);
+ if (CU->getValue() >= CS->getValues().size()) return 0;
+ C = cast<Constant>(CS->getValues()[CU->getValue()]);
+ } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
+ ConstantArray *CA = cast<ConstantArray>(C);
+ if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
+ C = cast<Constant>(CA->getValues()[CS->getValue()]);
+ } else
+ return 0;
+ return C;
+}
- 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;
- }
- abort();
+Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
+ Value *Op = LI.getOperand(0);
+ if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
+ Op = CPR->getValue();
+
+ // Instcombine load (constant global) into the value loaded...
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
+ if (GV->isConstant() && !GV->isExternal())
+ return ReplaceInstUsesWith(LI, GV->getInitializer());
+
+ // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
+ if (CE->getOpcode() == Instruction::GetElementPtr)
+ if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
+ if (GV->isConstant() && !GV->isExternal())
+ if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
+ return ReplaceInstUsesWith(LI, V);
return 0;
}
+Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
+ // Change br (not X), label True, label False to: br X, label False, True
+ if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
+ if (Value *V = dyn_castNotVal(BI.getCondition())) {
+ BasicBlock *TrueDest = BI.getSuccessor(0);
+ BasicBlock *FalseDest = BI.getSuccessor(1);
+ // Swap Destinations and condition...
+ BI.setCondition(V);
+ BI.setSuccessor(0, FalseDest);
+ BI.setSuccessor(1, TrueDest);
+ return &BI;
+ }
+ return 0;
+}
+
+
+void InstCombiner::removeFromWorkList(Instruction *I) {
+ WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
+ WorkList.end());
+}
+
bool InstCombiner::runOnFunction(Function &F) {
bool Changed = false;
Instruction *I = WorkList.back(); // Get an instruction from the worklist
WorkList.pop_back();
+ // Check to see if we can DCE or ConstantPropagate 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 propagate 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);
+ ReplaceInstUsesWith(*I, 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) {
// Instructions can end up on the worklist more than once. Make sure
// we do not process an instruction that has been deleted.
- std::vector<Instruction*>::iterator It = std::find(WorkList.begin(),
- WorkList.end(), I);
- while (It != WorkList.end()) {
- It = WorkList.erase(It);
- It = std::find(It, WorkList.end(), I);
- }
-
+ removeFromWorkList(I);
ReplaceInstWithInst(I, Result);
} else {
- // FIXME:
- // FIXME:
- // FIXME: This should DCE the instruction to simplify the cases above.
- // FIXME:
- // FIXME:
+ 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;
}
}