#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 "llvm/Support/CallSite.h"
Instruction *visitPHINode(PHINode &PN);
Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
Instruction *visitAllocationInst(AllocationInst &AI);
+ Instruction *visitLoadInst(LoadInst &LI);
Instruction *visitBranchInst(BranchInst &BI);
// visitInstruction - Specify what to return for unhandled instructions...
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) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
const Type *Ty = CI->getType();
- uint64_t Val = Ty->isSigned() ?
- (uint64_t)cast<ConstantSInt>(CI)->getValue() :
- cast<ConstantUInt>(CI)->getValue();
+ 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, Op1);
// and X, -1 == X
- if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1))
+ 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",
- &I);
- WorkList.push_back(Or);
+ Op1NotVal,I.getName()+".demorgan");
+ InsertNewInstBefore(Or, I);
return BinaryOperator::createNot(Or);
}
return ReplaceInstUsesWith(I, Op0);
// or X, -1 == -1
- if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1))
+ 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);
// integers at the end of their ranges...
//
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
- if (CI->isNullValue()) {
- if (I.getOpcode() == Instruction::SetNE)
- return new CastInst(Op0, Type::BoolTy, I.getName());
- else if (I.getOpcode() == Instruction::SetEQ) {
+ // 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)
- Instruction *Val = new CastInst(Op0, Type::BoolTy, I.getName()+".not");
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 (BinaryOperator *BO = dyn_cast<BinaryOperator>(Src)) {
Value *Op0 = BO->getOperand(0), *Op1 = BO->getOperand(1);
- // Replace (cast (sub A, B) to bool) with (setne A, B)
- if (BO->getOpcode() == Instruction::Sub)
+ 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.
- if (BO->getOpcode() == Instruction::Add)
+ case Instruction::Add:
if (Value *NegVal = dyn_castNegVal(Op1))
return new SetCondInst(Instruction::SetNE, Op0, NegVal);
else if (Value *NegVal = dyn_castNegVal(Op0))
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;
}
+/// 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;
+}
+
+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()))
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