//===- InstructionCombining.cpp - Combine multiple instructions -----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
//
// InstructionCombining - Combine instructions to form fewer, simple
// instructions. This pass does not modify the CFG This pass is where algebraic
//
// This is a simple worklist driven algorithm.
//
+// This pass guarantees that the following canonicalizations are performed on
+// the program:
+// 1. If a binary operator has a constant operand, it is moved to the RHS
+// 2. Bitwise operators with constant operands are always grouped so that
+// shifts are performed first, then or's, then and's, then xor's.
+// 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
+// 4. All SetCC instructions on boolean values are replaced with logical ops
+// 5. add X, X is represented as (X*2) => (X << 1)
+// 6. Multiplies with a power-of-two constant argument are transformed into
+// shifts.
+// N. This list is incomplete
+//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.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/Target/TargetData.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/InstIterator.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/CallSite.h"
#include "Support/Statistic.h"
#include <algorithm>
+using namespace llvm;
namespace {
Statistic<> NumCombined ("instcombine", "Number of insts combined");
public InstVisitor<InstCombiner, Instruction*> {
// Worklist of all of the instructions that need to be simplified.
std::vector<Instruction*> WorkList;
+ TargetData *TD;
void AddUsesToWorkList(Instruction &I) {
// The instruction was simplified, add all users of the instruction to
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetData>();
AU.setPreservesCFG();
}
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitAllocationInst(AllocationInst &AI);
+ Instruction *visitFreeInst(FreeInst &FI);
Instruction *visitLoadInst(LoadInst &LI);
Instruction *visitBranchInst(BranchInst &BI);
Instruction *visitInstruction(Instruction &I) { return 0; }
private:
+ Instruction *visitCallSite(CallSite CS);
bool transformConstExprCastCall(CallSite CS);
// InsertNewInstBefore - insert an instruction New before instruction Old
WorkList.push_back(New); // Add to worklist
}
+ public:
// 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
I.replaceAllUsesWith(V);
return &I;
}
+ private:
+ /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
+ /// InsertBefore instruction. This is specialized a bit to avoid inserting
+ /// casts that are known to not do anything...
+ ///
+ Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
+ Instruction *InsertBefore);
// SimplifyCommutative - This performs a few simplifications for commutative
// operators...
bool SimplifyCommutative(BinaryOperator &I);
+
+ Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
+ ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
};
RegisterOpt<InstCombiner> X("instcombine", "Combine redundant 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);
+ return V->hasOneUse() || isa<Constant>(V);
}
// SimplifyCommutative - This performs a few simplifications for commutative
// non-constant operand of the multiply.
//
static inline Value *dyn_castFoldableMul(Value *V) {
- if (V->use_size() == 1 && V->getType()->isInteger())
+ if (V->hasOneUse() && V->getType()->isInteger())
if (Instruction *I = dyn_cast<Instruction>(V))
if (I->getOpcode() == Instruction::Mul)
if (isa<Constant>(I->getOperand(1)))
// dyn_castMaskingAnd - If this value is an And instruction masking a value with
// a constant, return the constant being anded with.
//
-static inline Constant *dyn_castMaskingAnd(Value *V) {
+template<class ValueType>
+static inline Constant *dyn_castMaskingAnd(ValueType *V) {
if (Instruction *I = dyn_cast<Instruction>(V))
if (I->getOpcode() == Instruction::And)
return dyn_cast<Constant>(I->getOperand(1));
return Count;
}
+
+/// AssociativeOpt - Perform an optimization on an associative operator. This
+/// function is designed to check a chain of associative operators for a
+/// potential to apply a certain optimization. Since the optimization may be
+/// applicable if the expression was reassociated, this checks the chain, then
+/// reassociates the expression as necessary to expose the optimization
+/// opportunity. This makes use of a special Functor, which must define
+/// 'shouldApply' and 'apply' methods.
+///
+template<typename Functor>
+Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
+ unsigned Opcode = Root.getOpcode();
+ Value *LHS = Root.getOperand(0);
+
+ // Quick check, see if the immediate LHS matches...
+ if (F.shouldApply(LHS))
+ return F.apply(Root);
+
+ // Otherwise, if the LHS is not of the same opcode as the root, return.
+ Instruction *LHSI = dyn_cast<Instruction>(LHS);
+ while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
+ // Should we apply this transform to the RHS?
+ bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
+
+ // If not to the RHS, check to see if we should apply to the LHS...
+ if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
+ cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
+ ShouldApply = true;
+ }
+
+ // If the functor wants to apply the optimization to the RHS of LHSI,
+ // reassociate the expression from ((? op A) op B) to (? op (A op B))
+ if (ShouldApply) {
+ BasicBlock *BB = Root.getParent();
+ // All of the instructions have a single use and have no side-effects,
+ // because of this, we can pull them all into the current basic block.
+ if (LHSI->getParent() != BB) {
+ // Move all of the instructions from root to LHSI into the current
+ // block.
+ Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
+ Instruction *LastUse = &Root;
+ while (TmpLHSI->getParent() == BB) {
+ LastUse = TmpLHSI;
+ TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
+ }
+
+ // Loop over all of the instructions in other blocks, moving them into
+ // the current one.
+ Value *TmpLHS = TmpLHSI;
+ do {
+ TmpLHSI = cast<Instruction>(TmpLHS);
+ // Remove from current block...
+ TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
+ // Insert before the last instruction...
+ BB->getInstList().insert(LastUse, TmpLHSI);
+ TmpLHS = TmpLHSI->getOperand(0);
+ } while (TmpLHSI != LHSI);
+ }
+
+ // Now all of the instructions are in the current basic block, go ahead
+ // and perform the reassociation.
+ Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
+
+ // First move the selected RHS to the LHS of the root...
+ Root.setOperand(0, LHSI->getOperand(1));
+
+ // Make what used to be the LHS of the root be the user of the root...
+ Value *ExtraOperand = TmpLHSI->getOperand(1);
+ Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
+ TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
+ BB->getInstList().remove(&Root); // Remove root from the BB
+ BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
+
+ // Now propagate the ExtraOperand down the chain of instructions until we
+ // get to LHSI.
+ while (TmpLHSI != LHSI) {
+ Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
+ Value *NextOp = NextLHSI->getOperand(1);
+ NextLHSI->setOperand(1, ExtraOperand);
+ TmpLHSI = NextLHSI;
+ ExtraOperand = NextOp;
+ }
+
+ // Now that the instructions are reassociated, have the functor perform
+ // the transformation...
+ return F.apply(Root);
+ }
+
+ LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
+ }
+ return 0;
+}
+
+
+// AddRHS - Implements: X + X --> X << 1
+struct AddRHS {
+ Value *RHS;
+ AddRHS(Value *rhs) : RHS(rhs) {}
+ bool shouldApply(Value *LHS) const { return LHS == RHS; }
+ Instruction *apply(BinaryOperator &Add) const {
+ return new ShiftInst(Instruction::Shl, Add.getOperand(0),
+ ConstantInt::get(Type::UByteTy, 1));
+ }
+};
+
+// AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
+// iff C1&C2 == 0
+struct AddMaskingAnd {
+ Constant *C2;
+ AddMaskingAnd(Constant *c) : C2(c) {}
+ bool shouldApply(Value *LHS) const {
+ if (Constant *C1 = dyn_castMaskingAnd(LHS))
+ return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
+ return false;
+ }
+ Instruction *apply(BinaryOperator &Add) const {
+ return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
+ Add.getOperand(1));
+ }
+};
+
+
+
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
- // Eliminate 'add int %X, 0'
+ // X + 0 --> X
if (RHS == Constant::getNullValue(I.getType()))
return ReplaceInstUsesWith(I, LHS);
+ // X + X --> X << 1
+ if (I.getType()->isInteger())
+ if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
+
// -A + B --> B - A
if (Value *V = dyn_castNegVal(LHS))
return BinaryOperator::create(Instruction::Sub, RHS, V);
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);
+ // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
+ if (Constant *C2 = dyn_castMaskingAnd(RHS))
+ if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
+
+ if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
+ if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
+ switch (ILHS->getOpcode()) {
+ case Instruction::Xor:
+ // ~X + C --> (C-1) - X
+ if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
+ if (XorRHS->isAllOnesValue())
+ return BinaryOperator::create(Instruction::Sub,
+ *CRHS - *ConstantInt::get(I.getType(), 1),
+ ILHS->getOperand(0));
+ break;
+ default: break;
+ }
+ }
+ }
return Changed ? &I : 0;
}
return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
}
+static unsigned getTypeSizeInBits(const Type *Ty) {
+ return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
+}
+
Instruction *InstCombiner::visitSub(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = dyn_castNegVal(Op1))
return BinaryOperator::create(Instruction::Add, Op0, V);
- // Replace (-1 - A) with (~A)...
- if (ConstantInt *C = dyn_cast<ConstantInt>(Op0))
+ if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
+ // Replace (-1 - A) with (~A)...
if (C->isAllOnesValue())
return BinaryOperator::createNot(Op1);
+ // C - ~X == X + (1+C)
+ if (BinaryOperator::isNot(Op1))
+ return BinaryOperator::create(Instruction::Add,
+ BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
+ *C + *ConstantInt::get(I.getType(), 1));
+ }
+
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
- if (Op1I->use_size() == 1) {
+ if (Op1I->hasOneUse()) {
// Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
// is not used by anyone else...
//
// 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
+
+ // ((X << C1)*C2) == (X * (C2 << C1))
+ if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
+ if (SI->getOpcode() == Instruction::Shl)
+ if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
+ return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
+ *CI << *ShOp);
+
+ if (CI->isNullValue())
+ return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
+ if (CI->equalsInt(1)) // X * 1 == X
+ return ReplaceInstUsesWith(I, Op0);
+ if (CI->isAllOnesValue()) // X * -1 == 0 - 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());
- }
+ int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
return new ShiftInst(Instruction::Shl, Op0,
ConstantUInt::get(Type::UByteTy, C));
return CS->getValue() == Val+1;
}
+/// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
+/// are carefully arranged to allow folding of expressions such as:
+///
+/// (A < B) | (A > B) --> (A != B)
+///
+/// Bit value '4' represents that the comparison is true if A > B, bit value '2'
+/// represents that the comparison is true if A == B, and bit value '1' is true
+/// if A < B.
+///
+static unsigned getSetCondCode(const SetCondInst *SCI) {
+ switch (SCI->getOpcode()) {
+ // False -> 0
+ case Instruction::SetGT: return 1;
+ case Instruction::SetEQ: return 2;
+ case Instruction::SetGE: return 3;
+ case Instruction::SetLT: return 4;
+ case Instruction::SetNE: return 5;
+ case Instruction::SetLE: return 6;
+ // True -> 7
+ default:
+ assert(0 && "Invalid SetCC opcode!");
+ return 0;
+ }
+}
+
+/// getSetCCValue - This is the complement of getSetCondCode, which turns an
+/// opcode and two operands into either a constant true or false, or a brand new
+/// SetCC instruction.
+static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
+ switch (Opcode) {
+ case 0: return ConstantBool::False;
+ case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
+ case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
+ case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
+ case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
+ case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
+ case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
+ case 7: return ConstantBool::True;
+ default: assert(0 && "Illegal SetCCCode!"); return 0;
+ }
+}
+
+// FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
+struct FoldSetCCLogical {
+ InstCombiner &IC;
+ Value *LHS, *RHS;
+ FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
+ : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
+ bool shouldApply(Value *V) const {
+ if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
+ return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
+ SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
+ return false;
+ }
+ Instruction *apply(BinaryOperator &Log) const {
+ SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
+ if (SCI->getOperand(0) != LHS) {
+ assert(SCI->getOperand(1) == LHS);
+ SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
+ }
+
+ unsigned LHSCode = getSetCondCode(SCI);
+ unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
+ unsigned Code;
+ switch (Log.getOpcode()) {
+ case Instruction::And: Code = LHSCode & RHSCode; break;
+ case Instruction::Or: Code = LHSCode | RHSCode; break;
+ case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
+ default: assert(0 && "Illegal logical opcode!"); return 0;
+ }
+
+ Value *RV = getSetCCValue(Code, LHS, RHS);
+ if (Instruction *I = dyn_cast<Instruction>(RV))
+ return I;
+ // Otherwise, it's a constant boolean value...
+ return IC.ReplaceInstUsesWith(Log, RV);
+ }
+};
+
+
+// OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
+// the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
+// guaranteed to be either a shift instruction or a binary operator.
+Instruction *InstCombiner::OptAndOp(Instruction *Op,
+ ConstantIntegral *OpRHS,
+ ConstantIntegral *AndRHS,
+ BinaryOperator &TheAnd) {
+ Value *X = Op->getOperand(0);
+ switch (Op->getOpcode()) {
+ case Instruction::Xor:
+ if ((*AndRHS & *OpRHS)->isNullValue()) {
+ // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
+ return BinaryOperator::create(Instruction::And, X, AndRHS);
+ } else if (Op->hasOneUse()) {
+ // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
+ std::string OpName = Op->getName(); Op->setName("");
+ Instruction *And = BinaryOperator::create(Instruction::And,
+ X, AndRHS, OpName);
+ InsertNewInstBefore(And, TheAnd);
+ return BinaryOperator::create(Instruction::Xor, And, *AndRHS & *OpRHS);
+ }
+ break;
+ case Instruction::Or:
+ // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
+ if ((*AndRHS & *OpRHS)->isNullValue())
+ return BinaryOperator::create(Instruction::And, X, AndRHS);
+ else {
+ Constant *Together = *AndRHS & *OpRHS;
+ if (Together == AndRHS) // (X | C) & C --> C
+ return ReplaceInstUsesWith(TheAnd, AndRHS);
+
+ if (Op->hasOneUse() && Together != OpRHS) {
+ // (X | C1) & C2 --> (X | (C1&C2)) & C2
+ std::string Op0Name = Op->getName(); Op->setName("");
+ Instruction *Or = BinaryOperator::create(Instruction::Or, X,
+ Together, Op0Name);
+ InsertNewInstBefore(Or, TheAnd);
+ return BinaryOperator::create(Instruction::And, Or, AndRHS);
+ }
+ }
+ break;
+ case Instruction::Add:
+ if (Op->hasOneUse()) {
+ // Adding a one to a single bit bit-field should be turned into an XOR
+ // of the bit. First thing to check is to see if this AND is with a
+ // single bit constant.
+ unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
+
+ // Clear bits that are not part of the constant.
+ AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
+
+ // If there is only one bit set...
+ if ((AndRHSV & (AndRHSV-1)) == 0) {
+ // Ok, at this point, we know that we are masking the result of the
+ // ADD down to exactly one bit. If the constant we are adding has
+ // no bits set below this bit, then we can eliminate the ADD.
+ unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
+
+ // Check to see if any bits below the one bit set in AndRHSV are set.
+ if ((AddRHS & (AndRHSV-1)) == 0) {
+ // If not, the only thing that can effect the output of the AND is
+ // the bit specified by AndRHSV. If that bit is set, the effect of
+ // the XOR is to toggle the bit. If it is clear, then the ADD has
+ // no effect.
+ if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
+ TheAnd.setOperand(0, X);
+ return &TheAnd;
+ } else {
+ std::string Name = Op->getName(); Op->setName("");
+ // Pull the XOR out of the AND.
+ Instruction *NewAnd =
+ BinaryOperator::create(Instruction::And, X, AndRHS, Name);
+ InsertNewInstBefore(NewAnd, TheAnd);
+ return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
+ }
+ }
+ }
+ }
+ break;
+
+ case Instruction::Shl: {
+ // We know that the AND will not produce any of the bits shifted in, so if
+ // the anded constant includes them, clear them now!
+ //
+ Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
+ Constant *CI = *AndRHS & *(*AllOne << *OpRHS);
+ if (CI != AndRHS) {
+ TheAnd.setOperand(1, CI);
+ return &TheAnd;
+ }
+ break;
+ }
+ case Instruction::Shr:
+ // We know that the AND will not produce any of the bits shifted in, so if
+ // the anded constant includes them, clear them now! This only applies to
+ // unsigned shifts, because a signed shr may bring in set bits!
+ //
+ if (AndRHS->getType()->isUnsigned()) {
+ Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
+ Constant *CI = *AndRHS & *(*AllOne >> *OpRHS);
+ if (CI != AndRHS) {
+ TheAnd.setOperand(1, CI);
+ return &TheAnd;
+ }
+ }
+ break;
+ }
+ return 0;
+}
+
Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
bool Changed = SimplifyCommutative(I);
if (RHS->isAllOnesValue())
return ReplaceInstUsesWith(I, Op0);
- if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
+ // Optimize a variety of ((val OP C1) & C2) combinations...
+ if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
+ Instruction *Op0I = cast<Instruction>(Op0);
Value *X = Op0I->getOperand(0);
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
- if (Op0I->getOpcode() == Instruction::Xor) {
- if ((*RHS & *Op0CI)->isNullValue()) {
- // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
- return BinaryOperator::create(Instruction::And, X, RHS);
- } else if (isOnlyUse(Op0)) {
- // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
- std::string Op0Name = Op0I->getName(); Op0I->setName("");
- Instruction *And = BinaryOperator::create(Instruction::And,
- X, RHS, Op0Name);
- InsertNewInstBefore(And, I);
- return BinaryOperator::create(Instruction::Xor, And, *RHS & *Op0CI);
- }
- } else if (Op0I->getOpcode() == Instruction::Or) {
- // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
- if ((*RHS & *Op0CI)->isNullValue())
- return BinaryOperator::create(Instruction::And, X, RHS);
-
- Constant *Together = *RHS & *Op0CI;
- if (Together == RHS) // (X | C) & C --> C
- return ReplaceInstUsesWith(I, RHS);
-
- if (isOnlyUse(Op0)) {
- if (Together != Op0CI) {
- // (X | C1) & C2 --> (X | (C1&C2)) & C2
- std::string Op0Name = Op0I->getName(); Op0I->setName("");
- Instruction *Or = BinaryOperator::create(Instruction::Or, X,
- Together, Op0Name);
- InsertNewInstBefore(Or, I);
- return BinaryOperator::create(Instruction::And, Or, RHS);
- }
- }
- }
+ if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
+ return Res;
}
}
if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+ // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
+ if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
+ if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
+ return R;
+
return Changed ? &I : 0;
}
}
}
+ // (A & C1)|(A & C2) == A & (C1|C2)
+ if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
+ if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
+ if (LHS->getOperand(0) == RHS->getOperand(0))
+ if (Constant *C0 = dyn_castMaskingAnd(LHS))
+ if (Constant *C1 = dyn_castMaskingAnd(RHS))
+ return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
+ *C0 | *C1);
+
Value *Op0NotVal = dyn_castNotVal(Op0);
Value *Op1NotVal = dyn_castNotVal(Op1);
return BinaryOperator::createNot(And);
}
+ // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
+ if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
+ if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
+ return R;
+
return Changed ? &I : 0;
}
if (Op0 == Op1)
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
- if (ConstantIntegral *Op1C = dyn_cast<ConstantIntegral>(Op1)) {
+ if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
// xor X, 0 == X
- if (Op1C->isNullValue())
+ if (RHS->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);
-
+ if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
// xor (setcc A, B), true = not (setcc A, B) = setncc A, B
- if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0))
- if (SCI->use_size() == 1)
+ if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
+ if (RHS == ConstantBool::True && SCI->hasOneUse())
return new SetCondInst(SCI->getInverseCondition(),
SCI->getOperand(0), SCI->getOperand(1));
+
+ // ~(c-X) == X-c-1 == X+(-c-1)
+ if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue() &&
+ isa<Constant>(Op0I->getOperand(0))) {
+ Constant *ConstantRHS = *-*cast<Constant>(Op0I->getOperand(0)) -
+ *ConstantInt::get(I.getType(), 1);
+ return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
+ ConstantRHS);
+ }
+
+ if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
+ switch (Op0I->getOpcode()) {
+ case Instruction::Add:
+ // ~(X-c) --> (-c-1)-X
+ if (RHS->isAllOnesValue())
+ return BinaryOperator::create(Instruction::Sub,
+ *-*Op0CI -
+ *ConstantInt::get(I.getType(), 1),
+ Op0I->getOperand(0));
+ break;
+ case Instruction::And:
+ // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
+ if ((*RHS & *Op0CI)->isNullValue())
+ return BinaryOperator::create(Instruction::Or, Op0, RHS);
+ break;
+ case Instruction::Or:
+ // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
+ if ((*RHS & *Op0CI) == RHS)
+ return BinaryOperator::create(Instruction::And, Op0, ~*RHS);
+ break;
+ default: break;
+ }
}
}
}
if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
- if (Op0I->getOpcode() == Instruction::Or && Op0I->use_size() == 1) {
+ if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
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
if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
return BinaryOperator::create(Instruction::Or, Op0, Op1);
+ // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
+ if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
+ if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
+ return R;
+
return Changed ? &I : 0;
}
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))
+ // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
+ if (isa<ConstantPointerNull>(Op1) &&
+ (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
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());
+ return BinaryOperator::create(Instruction::Xor, Op0, Op1);
// Otherwise we need to make a temporary intermediate instruction and insert
// it into the instruction stream. This is what we are after:
Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
I.getName()+"tmp");
InsertNewInstBefore(Xor, I);
- return BinaryOperator::createNot(Xor, I.getName());
+ return BinaryOperator::createNot(Xor);
}
// Handle the setXe cases...
// 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 BinaryOperator::create(Instruction::Or, Not, Op1);
}
// Check to see if we are doing one of many comparisons against constant
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 (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
+ switch (BO->getOpcode()) {
+ case Instruction::Add:
+ if (CI->isNullValue()) {
+ // Replace ((add A, B) != 0) with (A != -B) if A or B is
+ // efficiently invertible, or if the add has just this one use.
+ Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
+ if (Value *NegVal = dyn_castNegVal(BOp1))
+ return new SetCondInst(I.getOpcode(), BOp0, NegVal);
+ else if (Value *NegVal = dyn_castNegVal(BOp0))
+ return new SetCondInst(I.getOpcode(), NegVal, BOp1);
+ else if (BO->hasOneUse()) {
+ Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
+ BO->setName("");
+ InsertNewInstBefore(Neg, I);
+ return new SetCondInst(I.getOpcode(), BOp0, Neg);
+ }
+ }
+ break;
+ case Instruction::Xor:
+ // For the xor case, we can xor two constants together, eliminating
+ // the explicit xor.
+ if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
+ return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
+ *CI ^ *BOC);
+
+ // FALLTHROUGH
+ case Instruction::Sub:
+ // Replace (([sub|xor] A, B) != 0) with (A != B)
+ if (CI->isNullValue())
+ return new SetCondInst(I.getOpcode(), BO->getOperand(0),
+ BO->getOperand(1));
+ break;
+
+ case 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 (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
if (!(*BOC & *~*CI)->isNullValue())
return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
- } else if (BO->getOpcode() == Instruction::And) {
+ break;
+
+ case Instruction::And:
+ if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
// 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);
+
+ // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
+ // to be a signed value as appropriate.
+ if (isSignBit(BOC)) {
+ Value *X = BO->getOperand(0);
+ // If 'X' is not signed, insert a cast now...
+ if (!BOC->getType()->isSigned()) {
+ const Type *DestTy;
+ switch (BOC->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(X,DestTy,X->getName()+".signed");
+ InsertNewInstBefore(NewCI, I);
+ X = NewCI;
+ }
+ return new SetCondInst(isSetNE ? Instruction::SetLT :
+ Instruction::SetGE, X,
+ Constant::getNullValue(X->getType()));
+ }
}
+ default: break;
+ }
+ }
}
// Check to see if we are comparing against the minimum or maximum value...
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());
+ return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
- return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
+ return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
} else if (CI->isMaxValue()) {
if (I.getOpcode() == Instruction::SetGT) // A > MAX -> 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());
+ return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
- return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
+ return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
// 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());
+ return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
- return BinaryOperator::create(Instruction::SetNE, Op0,
- SubOne(CI), I.getName());
+ return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
} else if (isMaxValueMinusOne(CI)) {
if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
- return BinaryOperator::create(Instruction::SetEQ, Op0,
- AddOne(CI), I.getName());
+ return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
- return BinaryOperator::create(Instruction::SetNE, Op0,
- AddOne(CI), I.getName());
+ return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
}
}
+ // Test to see if the operands of the setcc are casted versions of other
+ // values. If the cast can be stripped off both arguments, we do so now.
+ if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
+ Value *CastOp0 = CI->getOperand(0);
+ if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
+ !isa<Argument>(Op1) &&
+ (I.getOpcode() == Instruction::SetEQ ||
+ I.getOpcode() == Instruction::SetNE)) {
+ // We keep moving the cast from the left operand over to the right
+ // operand, where it can often be eliminated completely.
+ Op0 = CastOp0;
+
+ // If operand #1 is a cast instruction, see if we can eliminate it as
+ // well.
+ if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
+ if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
+ Op0->getType()))
+ Op1 = CI2->getOperand(0);
+
+ // If Op1 is a constant, we can fold the cast into the constant.
+ if (Op1->getType() != Op0->getType())
+ if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
+ Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
+ } else {
+ // Otherwise, cast the RHS right before the setcc
+ Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
+ InsertNewInstBefore(cast<Instruction>(Op1), I);
+ }
+ return BinaryOperator::create(I.getOpcode(), Op0, Op1);
+ }
+
+ // Handle the special case of: setcc (cast bool to X), <cst>
+ // This comes up when you have code like
+ // int X = A < B;
+ // if (X) ...
+ // For generality, we handle any zero-extension of any operand comparison
+ // with a constant.
+ if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
+ const Type *SrcTy = CastOp0->getType();
+ const Type *DestTy = Op0->getType();
+ if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
+ (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
+ // Ok, we have an expansion of operand 0 into a new type. Get the
+ // constant value, masink off bits which are not set in the RHS. These
+ // could be set if the destination value is signed.
+ uint64_t ConstVal = ConstantRHS->getRawValue();
+ ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
+
+ // If the constant we are comparing it with has high bits set, which
+ // don't exist in the original value, the values could never be equal,
+ // because the source would be zero extended.
+ unsigned SrcBits =
+ SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
+ bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
+ if (ConstVal & ~((1ULL << SrcBits)-1)) {
+ switch (I.getOpcode()) {
+ default: assert(0 && "Unknown comparison type!");
+ case Instruction::SetEQ:
+ return ReplaceInstUsesWith(I, ConstantBool::False);
+ case Instruction::SetNE:
+ return ReplaceInstUsesWith(I, ConstantBool::True);
+ case Instruction::SetLT:
+ case Instruction::SetLE:
+ if (DestTy->isSigned() && HasSignBit)
+ return ReplaceInstUsesWith(I, ConstantBool::False);
+ return ReplaceInstUsesWith(I, ConstantBool::True);
+ case Instruction::SetGT:
+ case Instruction::SetGE:
+ if (DestTy->isSigned() && HasSignBit)
+ return ReplaceInstUsesWith(I, ConstantBool::True);
+ return ReplaceInstUsesWith(I, ConstantBool::False);
+ }
+ }
+
+ // Otherwise, we can replace the setcc with a setcc of the smaller
+ // operand value.
+ Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
+ return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
+ }
+ }
+ }
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
assert(I.getOperand(1)->getType() == Type::UByteTy);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ bool isLeftShift = I.getOpcode() == Instruction::Shl;
// shl X, 0 == X and shr X, 0 == X
// shl 0, X == 0 and shr 0, X == 0
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));
- }
- }
- }
- }
+ // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
+ if (!isLeftShift)
+ if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
+ if (CSI->isAllOnesValue())
+ return ReplaceInstUsesWith(I, CSI);
- // 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)) {
+ // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
+ // of a signed value.
+ //
unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
if (CUI->getValue() >= TypeBits &&
- (!Op0->getType()->isSigned() || I.getOpcode() == Instruction::Shl))
+ (!Op0->getType()->isSigned() || isLeftShift))
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());
+ // ((X*C1) << C2) == (X * (C1 << C2))
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
+ if (BO->getOpcode() == Instruction::Mul && isLeftShift)
+ if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
+ return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
+ *BOOp << *CUI);
+
+ // If the operand is an bitwise operator with a constant RHS, and the
+ // shift is the only use, we can pull it out of the shift.
+ if (Op0->hasOneUse())
+ if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
+ if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
+ bool isValid = true; // Valid only for And, Or, Xor
+ bool highBitSet = false; // Transform if high bit of constant set?
+
+ switch (Op0BO->getOpcode()) {
+ default: isValid = false; break; // Do not perform transform!
+ case Instruction::Or:
+ case Instruction::Xor:
+ highBitSet = false;
+ break;
+ case Instruction::And:
+ highBitSet = true;
+ break;
+ }
+
+ // If this is a signed shift right, and the high bit is modified
+ // by the logical operation, do not perform the transformation.
+ // The highBitSet boolean indicates the value of the high bit of
+ // the constant which would cause it to be modified for this
+ // operation.
+ //
+ if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
+ uint64_t Val = Op0C->getRawValue();
+ isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
+ }
+
+ if (isValid) {
+ Constant *NewRHS =
+ ConstantFoldShiftInstruction(I.getOpcode(), Op0C, CUI);
+
+ Instruction *NewShift =
+ new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
+ Op0BO->getName());
+ Op0BO->setName("");
+ InsertNewInstBefore(NewShift, I);
+
+ return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
+ NewRHS);
+ }
+ }
+
+ // If this is a shift of a shift, see if we can fold the two together...
+ if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
+ if (ConstantUInt *ShiftAmt1C =
+ dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
+ unsigned ShiftAmt1 = ShiftAmt1C->getValue();
+ unsigned ShiftAmt2 = CUI->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));
+ }
+
+ // Check for (A << c1) >> c2 or visaversa. If we are dealing with
+ // signed types, we can only support the (A >> c1) << c2 configuration,
+ // because it can not turn an arbitrary bit of A into a sign bit.
+ if (I.getType()->isUnsigned() || isLeftShift) {
+ // Calculate bitmask for what gets shifted off the edge...
+ Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
+ if (isLeftShift)
+ C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
+ else
+ C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
+
+ Instruction *Mask =
+ BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
+ C, Op0SI->getOperand(0)->getName()+".mask");
+ InsertNewInstBefore(Mask, I);
+
+ // 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));
+ }
+ }
+ }
}
- // 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;
}
// isEliminableCastOfCast - Return true if it is valid to eliminate the CI
// instruction.
//
-static inline bool isEliminableCastOfCast(const CastInst &CI,
- const CastInst *CSrc) {
- assert(CI.getOperand(0) == CSrc);
- const Type *SrcTy = CSrc->getOperand(0)->getType();
- const Type *MidTy = CSrc->getType();
- const Type *DstTy = CI.getType();
+static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
+ const Type *DstTy) {
// 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
return false;
}
+static bool ValueRequiresCast(const Value *V, const Type *Ty) {
+ if (V->getType() == Ty || isa<Constant>(V)) return false;
+ if (const CastInst *CI = dyn_cast<CastInst>(V))
+ if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
+ return false;
+ return true;
+}
+
+/// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
+/// InsertBefore instruction. This is specialized a bit to avoid inserting
+/// casts that are known to not do anything...
+///
+Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
+ Instruction *InsertBefore) {
+ if (V->getType() == DestTy) return V;
+ if (Constant *C = dyn_cast<Constant>(V))
+ return ConstantExpr::getCast(C, DestTy);
+
+ CastInst *CI = new CastInst(V, DestTy, V->getName());
+ InsertNewInstBefore(CI, *InsertBefore);
+ return CI;
+}
// CastInst simplification
//
// one!
//
if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
- if (isEliminableCastOfCast(CI, CSrc)) {
+ if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
+ CSrc->getType(), CI.getType())) {
// 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));
}
}
- // If this is a cast to bool (which is effectively a "!=0" test), then we can
- // perform a few optimizations...
+ // If we are casting a malloc or alloca to a pointer to a type of the same
+ // size, rewrite the allocation instruction to allocate the "right" type.
//
- if (CI.getType() == Type::BoolTy) {
- if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Src)) {
- Value *Op0 = BO->getOperand(0), *Op1 = BO->getOperand(1);
+ if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
+ if (AI->hasOneUse() && !AI->isArrayAllocation())
+ if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
+ // Get the type really allocated and the type casted to...
+ const Type *AllocElTy = AI->getAllocatedType();
+ unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
+ const Type *CastElTy = PTy->getElementType();
+ unsigned CastElTySize = TD->getTypeSize(CastElTy);
+
+ // If the allocation is for an even multiple of the cast type size
+ if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
+ Value *Amt = ConstantUInt::get(Type::UIntTy,
+ AllocElTySize/CastElTySize);
+ std::string Name = AI->getName(); AI->setName("");
+ AllocationInst *New;
+ if (isa<MallocInst>(AI))
+ New = new MallocInst(CastElTy, Amt, Name);
+ else
+ New = new AllocaInst(CastElTy, Amt, Name);
+ InsertNewInstBefore(New, CI);
+ return ReplaceInstUsesWith(CI, New);
+ }
+ }
- 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);
+ // If the source value is an instruction with only this use, we can attempt to
+ // propagate the cast into the instruction. Also, only handle integral types
+ // for now.
+ if (Instruction *SrcI = dyn_cast<Instruction>(Src))
+ if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
+ CI.getType()->isInteger()) { // Don't mess with casts to bool here
+ const Type *DestTy = CI.getType();
+ unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
+ unsigned DestBitSize = getTypeSizeInBits(DestTy);
- // 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;
+ Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
+ Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
+ switch (SrcI->getOpcode()) {
+ case Instruction::Add:
+ case Instruction::Mul:
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()));
+ case Instruction::Or:
+ case Instruction::Xor:
+ // If we are discarding information, or just changing the sign, rewrite.
+ if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
+ // Don't insert two casts if they cannot be eliminated. We allow two
+ // casts to be inserted if the sizes are the same. This could only be
+ // converting signedness, which is a noop.
+ if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
+ !ValueRequiresCast(Op0, DestTy)) {
+ Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
+ Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
+ return BinaryOperator::create(cast<BinaryOperator>(SrcI)
+ ->getOpcode(), Op0c, Op1c);
}
+ }
+ break;
+ case Instruction::Shl:
+ // Allow changing the sign of the source operand. Do not allow changing
+ // the size of the shift, UNLESS the shift amount is a constant. We
+ // mush not change variable sized shifts to a smaller size, because it
+ // is undefined to shift more bits out than exist in the value.
+ if (DestBitSize == SrcBitSize ||
+ (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
+ Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
+ return new ShiftInst(Instruction::Shl, Op0c, Op1);
+ }
break;
- default: break;
}
}
- }
-
+
return 0;
}
// CallInst simplification
//
Instruction *InstCombiner::visitCallInst(CallInst &CI) {
- if (transformConstExprCastCall(&CI)) return 0;
- return 0;
+ return visitCallSite(&CI);
}
// InvokeInst simplification
//
Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
- if (transformConstExprCastCall(&II)) return 0;
- return 0;
+ return visitCallSite(&II);
}
// getPromotedType - Return the specified type promoted as it would be to pass
}
}
+// visitCallSite - Improvements for call and invoke instructions.
+//
+Instruction *InstCombiner::visitCallSite(CallSite CS) {
+ bool Changed = false;
+
+ // If the callee is a constexpr cast of a function, attempt to move the cast
+ // to the arguments of the call/invoke.
+ if (transformConstExprCastCall(CS)) return 0;
+
+ Value *Callee = CS.getCalledValue();
+ const PointerType *PTy = cast<PointerType>(Callee->getType());
+ const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
+ if (FTy->isVarArg()) {
+ // See if we can optimize any arguments passed through the varargs area of
+ // the call.
+ for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
+ E = CS.arg_end(); I != E; ++I)
+ if (CastInst *CI = dyn_cast<CastInst>(*I)) {
+ // If this cast does not effect the value passed through the varargs
+ // area, we can eliminate the use of the cast.
+ Value *Op = CI->getOperand(0);
+ if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
+ *I = Op;
+ Changed = true;
+ }
+ }
+ }
+
+ return Changed ? CS.getInstruction() : 0;
+}
+
// transformConstExprCastCall - If the callee is a constexpr cast of a function,
// attempt to move the cast to the arguments of the call/invoke.
//
const Type *OldRetTy = Caller->getType();
if (Callee->isExternal() &&
- !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
+ !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
+ !Caller->use_empty())
return false; // Cannot transform this return value...
unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
if (NV->getType() != Type::VoidTy) {
NV = NC = new CastInst(NC, Caller->getType(), "tmp");
- InsertNewInstBefore(NC, *Caller);
+
+ // If this is an invoke instruction, we should insert it after the first
+ // non-phi, instruction in the normal successor block.
+ if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
+ BasicBlock::iterator I = II->getNormalDest()->begin();
+ while (isa<PHINode>(I)) ++I;
+ InsertNewInstBefore(NC, *I);
+ } else {
+ // Otherwise, it's a call, just insert cast right after the call instr
+ InsertNewInstBefore(NC, *Caller);
+ }
AddUsesToWorkList(*Caller);
} else {
NV = Constant::getNullValue(Caller->getType());
// PHINode simplification
//
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
- // If the PHI node only has one incoming value, eliminate the PHI node...
- 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());
-
- // All of the incoming values are the same, replace the PHI node now.
- return ReplaceInstUsesWith(PN, InVal);
+ if (Value *V = hasConstantValue(&PN))
+ return ReplaceInstUsesWith(PN, V);
+ return 0;
}
return 0;
}
+Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
+ Value *Op = FI.getOperand(0);
+
+ // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
+ if (CastInst *CI = dyn_cast<CastInst>(Op))
+ if (isa<PointerType>(CI->getOperand(0)->getType())) {
+ FI.setOperand(0, CI->getOperand(0));
+ return &FI;
+ }
+
+ return 0;
+}
+
+
/// GetGEPGlobalInitializer - Given a constant, and a getelementptr
/// constantexpr, return the constant value being addressed by the constant
/// expression, or null if something is funny.
bool InstCombiner::runOnFunction(Function &F) {
bool Changed = false;
+ TD = &getAnalysis<TargetData>();
WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
// 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);
-
+ if (I->getNumOperands() < 4)
+ 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;
- }
- }
+
+ I->getParent()->getInstList().erase(I);
+ removeFromWorkList(I);
+ continue;
+ }
// Instruction isn't dead, see if we can constant propagate it...
if (Constant *C = ConstantFoldInstruction(I)) {
ReplaceInstUsesWith(*I, C);
++NumConstProp;
- BasicBlock::iterator BBI = I;
- if (dceInstruction(BBI)) {
- removeFromWorkList(I);
- continue;
- }
+ I->getParent()->getInstList().erase(I);
+ removeFromWorkList(I);
+ continue;
}
-
+
// Now that we have an instruction, try combining it to simplify it...
if (Instruction *Result = visit(*I)) {
++NumCombined;
// 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);
+
+ // Move the name to the new instruction first...
+ std::string OldName = I->getName(); I->setName("");
+ Result->setName(OldName);
+
+ // Insert the new instruction into the basic block...
+ BasicBlock *InstParent = I->getParent();
+ InstParent->getInstList().insert(I, Result);
+
+ // Everything uses the new instruction now...
+ I->replaceAllUsesWith(Result);
+
+ // Erase the old instruction.
+ InstParent->getInstList().erase(I);
} else {
BasicBlock::iterator II = I;
return Changed;
}
-Pass *createInstructionCombiningPass() {
+Pass *llvm::createInstructionCombiningPass() {
return new InstCombiner();
}
+
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