using namespace llvm;
using namespace PatternMatch;
+
+/// simplifyValueKnownNonZero - The specific integer value is used in a context
+/// where it is known to be non-zero. If this allows us to simplify the
+/// computation, do so and return the new operand, otherwise return null.
+static Value *simplifyValueKnownNonZero(Value *V, InstCombiner &IC) {
+ // If V has multiple uses, then we would have to do more analysis to determine
+ // if this is safe. For example, the use could be in dynamically unreached
+ // code.
+ if (!V->hasOneUse()) return 0;
+
+ bool MadeChange = false;
+
+ // ((1 << A) >>u B) --> (1 << (A-B))
+ // Because V cannot be zero, we know that B is less than A.
+ Value *A = 0, *B = 0, *PowerOf2 = 0;
+ if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(PowerOf2), m_Value(A))),
+ m_Value(B))) &&
+ // The "1" can be any value known to be a power of 2.
+ isPowerOfTwo(PowerOf2, IC.getTargetData())) {
+ A = IC.Builder->CreateSub(A, B, "tmp");
+ return IC.Builder->CreateShl(PowerOf2, A);
+ }
+
+ // (PowerOfTwo >>u B) --> isExact since shifting out the result would make it
+ // inexact. Similarly for <<.
+ if (BinaryOperator *I = dyn_cast<BinaryOperator>(V))
+ if (I->isLogicalShift() &&
+ isPowerOfTwo(I->getOperand(0), IC.getTargetData())) {
+ // We know that this is an exact/nuw shift and that the input is a
+ // non-zero context as well.
+ if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC)) {
+ I->setOperand(0, V2);
+ MadeChange = true;
+ }
+
+ if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
+ I->setIsExact();
+ MadeChange = true;
+ }
+
+ if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
+ I->setHasNoUnsignedWrap();
+ MadeChange = true;
+ }
+ }
+
+ // TODO: Lots more we could do here:
+ // If V is a phi node, we can call this on each of its operands.
+ // "select cond, X, 0" can simplify to "X".
+
+ return MadeChange ? V : 0;
+}
+
+
/// MultiplyOverflows - True if the multiply can not be expressed in an int
/// this size.
static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) {
return BinaryOperator::CreateAdd(Add, Builder->CreateMul(C1, CI));
}
}
+
+ // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
+ // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
+ // The "* (2**n)" thus becomes a potential shifting opportunity.
+ {
+ const APInt & Val = CI->getValue();
+ const APInt &PosVal = Val.abs();
+ if (Val.isNegative() && PosVal.isPowerOf2()) {
+ Value *X = 0, *Y = 0;
+ if (Op0->hasOneUse()) {
+ ConstantInt *C1;
+ Value *Sub = 0;
+ if (match(Op0, m_Sub(m_Value(Y), m_Value(X))))
+ Sub = Builder->CreateSub(X, Y, "suba");
+ else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))
+ Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
+ if (Sub)
+ return
+ BinaryOperator::CreateMul(Sub,
+ ConstantInt::get(Y->getType(), PosVal));
+ }
+ }
+ }
}
// Simplify mul instructions with a constant RHS.
Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ // The RHS is known non-zero.
+ if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
+ I.setOperand(1, V);
+ return &I;
+ }
+
// Handle cases involving: [su]div X, (select Cond, Y, Z)
// This does not apply for fdiv.
if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
}
}
+ // See if we can fold away this div instruction.
+ if (SimplifyDemandedInstructionBits(I))
+ return &I;
+
// (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
Value *X = 0, *Z = 0;
if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
return 0;
}
+/// dyn_castZExtVal - Checks if V is a zext or constant that can
+/// be truncated to Ty without losing bits.
+static Value *dyn_castZExtVal(Value *V, const Type *Ty) {
+ if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) {
+ if (Z->getSrcTy() == Ty)
+ return Z->getOperand(0);
+ } else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) {
+ if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth())
+ return ConstantExpr::getTrunc(C, Ty);
+ }
+ return 0;
+}
+
Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
return SelectInst::Create(Cond, TSI, FSI);
}
}
+
+ // (zext A) udiv (zext B) --> zext (A udiv B)
+ if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
+ if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
+ return new ZExtInst(Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div",
+ I.isExact()),
+ I.getType());
+
return 0;
}
if (Value *V = SimplifyFDivInst(Op0, Op1, TD))
return ReplaceInstUsesWith(I, V);
- return 0;
-}
-
-/// This function implements the transforms on rem instructions that work
-/// regardless of the kind of rem instruction it is (urem, srem, or frem). It
-/// is used by the visitors to those instructions.
-/// @brief Transforms common to all three rem instructions
-Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
- Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
+ const APFloat &Op1F = Op1C->getValueAPF();
- if (isa<UndefValue>(Op0)) { // undef % X -> 0
- if (I.getType()->isFPOrFPVectorTy())
- return ReplaceInstUsesWith(I, Op0); // X % undef -> undef (could be SNaN)
- return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+ // If the divisor has an exact multiplicative inverse we can turn the fdiv
+ // into a cheaper fmul.
+ APFloat Reciprocal(Op1F.getSemantics());
+ if (Op1F.getExactInverse(&Reciprocal)) {
+ ConstantFP *RFP = ConstantFP::get(Builder->getContext(), Reciprocal);
+ return BinaryOperator::CreateFMul(Op0, RFP);
+ }
}
- if (isa<UndefValue>(Op1))
- return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
-
- // Handle cases involving: rem X, (select Cond, Y, Z)
- if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
- return &I;
return 0;
}
Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
- if (Instruction *common = commonRemTransforms(I))
- return common;
-
- // X % X == 0
- if (Op0 == Op1)
- return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
-
- // 0 % X == 0 for integer, we don't need to preserve faults!
- if (Constant *LHS = dyn_cast<Constant>(Op0))
- if (LHS->isNullValue())
- return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+ // The RHS is known non-zero.
+ if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
+ I.setOperand(1, V);
+ return &I;
+ }
- if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
- // X % 0 == undef, we don't need to preserve faults!
- if (RHS->equalsInt(0))
- return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
-
- if (RHS->equalsInt(1)) // X % 1 == 0
- return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+ // Handle cases involving: rem X, (select Cond, Y, Z)
+ if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
+ return &I;
+ if (isa<ConstantInt>(Op1)) {
if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
if (Instruction *R = FoldOpIntoSelect(I, SI))
Instruction *InstCombiner::visitURem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ if (Value *V = SimplifyURemInst(Op0, Op1, TD))
+ return ReplaceInstUsesWith(I, V);
+
if (Instruction *common = commonIRemTransforms(I))
return common;
return SelectInst::Create(Cond, TrueAnd, FalseAnd);
}
}
-
+
+ // (zext A) urem (zext B) --> zext (A urem B)
+ if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
+ if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
+ return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
+ I.getType());
+
return 0;
}
Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ if (Value *V = SimplifySRemInst(Op0, Op1, TD))
+ return ReplaceInstUsesWith(I, V);
+
// Handle the integer rem common cases
if (Instruction *Common = commonIRemTransforms(I))
return Common;
}
Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
- return commonRemTransforms(I);
-}
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ if (Value *V = SimplifyFRemInst(Op0, Op1, TD))
+ return ReplaceInstUsesWith(I, V);
+
+ // Handle cases involving: rem X, (select Cond, Y, Z)
+ if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
+ return &I;
+
+ return 0;
+}
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