FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
CmpInst &ICI, ConstantInt *AndCst) {
// We need TD information to know the pointer size unless this is inbounds.
- if (!GEP->isInBounds() && TD == 0) return 0;
+ if (!GEP->isInBounds() && TD == 0)
+ return 0;
Constant *Init = GV->getInitializer();
if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
}
}
+
+
// Okay, we know we have a single variable index, which must be a
// pointer/array/vector index. If there is no offset, life is simple, return
// the index.
- unsigned IntPtrWidth = TD.getPointerSizeInBits();
+ Type *IntPtrTy = TD.getIntPtrType(GEP->getOperand(0)->getType());
+ unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
if (Offset == 0) {
// Cast to intptrty in case a truncation occurs. If an extension is needed,
// we don't need to bother extending: the extension won't affect where the
// computation crosses zero.
if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
- Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext());
VariableIdx = IC.Builder->CreateTrunc(VariableIdx, IntPtrTy);
}
return VariableIdx;
return 0;
// Okay, we can do this evaluation. Start by converting the index to intptr.
- Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext());
if (VariableIdx->getType() != IntPtrTy)
VariableIdx = IC.Builder->CreateIntCast(VariableIdx, IntPtrTy,
true /*Signed*/);
// If all indices are the same, just compare the base pointers.
if (IndicesTheSame)
- return new ICmpInst(ICmpInst::getSignedPredicate(Cond),
- GEPLHS->getOperand(0), GEPRHS->getOperand(0));
+ return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
// If we're comparing GEPs with two base pointers that only differ in type
// and both GEPs have only constant indices or just one use, then fold
}
if (AllZeros)
return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
- ICmpInst::getSwappedPredicate(Cond), I);
+ ICmpInst::getSwappedPredicate(Cond), I);
// If the other GEP has all zero indices, recurse.
AllZeros = true;
}
/// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X".
-Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI,
+Instruction *InstCombiner::FoldICmpAddOpCst(Instruction &ICI,
Value *X, ConstantInt *CI,
- ICmpInst::Predicate Pred,
- Value *TheAdd) {
+ ICmpInst::Predicate Pred) {
// If we have X+0, exit early (simplifying logic below) and let it get folded
// elsewhere. icmp X+0, X -> icmp X, X
if (CI->isZero()) {
Builder->getInt(RHSV ^ NotSignBit));
}
}
+
+ // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
+ // iff -C is a power of 2
+ if (ICI.getPredicate() == ICmpInst::ICMP_UGT &&
+ XorCST->getValue() == ~RHSV && (RHSV + 1).isPowerOf2())
+ return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), XorCST);
+
+ // (icmp ult (xor X, C), -C) -> (icmp uge X, C)
+ // iff -C is a power of 2
+ if (ICI.getPredicate() == ICmpInst::ICMP_ULT &&
+ XorCST->getValue() == -RHSV && RHSV.isPowerOf2())
+ return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), XorCST);
}
break;
case Instruction::And: // (icmp pred (and X, AndCST), RHS)
return Res;
}
}
+
+ // X & -C == -C -> X > u ~C
+ // X & -C != -C -> X <= u ~C
+ // iff C is a power of 2
+ if (ICI.isEquality() && RHS == LHSI->getOperand(1) && (-RHSV).isPowerOf2())
+ return new ICmpInst(
+ ICI.getPredicate() == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_UGT
+ : ICmpInst::ICMP_ULE,
+ LHSI->getOperand(0), SubOne(RHS));
break;
case Instruction::Or: {
}
case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI)
+ uint32_t TypeBits = RHSV.getBitWidth();
ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
- if (!ShAmt) break;
+ if (!ShAmt) {
+ Value *X;
+ // (1 << X) pred P2 -> X pred Log2(P2)
+ if (match(LHSI, m_Shl(m_One(), m_Value(X)))) {
+ bool RHSVIsPowerOf2 = RHSV.isPowerOf2();
+ ICmpInst::Predicate Pred = ICI.getPredicate();
+ if (ICI.isUnsigned()) {
+ if (!RHSVIsPowerOf2) {
+ // (1 << X) < 30 -> X <= 4
+ // (1 << X) <= 30 -> X <= 4
+ // (1 << X) >= 30 -> X > 4
+ // (1 << X) > 30 -> X > 4
+ if (Pred == ICmpInst::ICMP_ULT)
+ Pred = ICmpInst::ICMP_ULE;
+ else if (Pred == ICmpInst::ICMP_UGE)
+ Pred = ICmpInst::ICMP_UGT;
+ }
+ unsigned RHSLog2 = RHSV.logBase2();
+
+ // (1 << X) >= 2147483648 -> X >= 31 -> X == 31
+ // (1 << X) > 2147483648 -> X > 31 -> false
+ // (1 << X) <= 2147483648 -> X <= 31 -> true
+ // (1 << X) < 2147483648 -> X < 31 -> X != 31
+ if (RHSLog2 == TypeBits-1) {
+ if (Pred == ICmpInst::ICMP_UGE)
+ Pred = ICmpInst::ICMP_EQ;
+ else if (Pred == ICmpInst::ICMP_UGT)
+ return ReplaceInstUsesWith(ICI, Builder->getFalse());
+ else if (Pred == ICmpInst::ICMP_ULE)
+ return ReplaceInstUsesWith(ICI, Builder->getTrue());
+ else if (Pred == ICmpInst::ICMP_ULT)
+ Pred = ICmpInst::ICMP_NE;
+ }
- uint32_t TypeBits = RHSV.getBitWidth();
+ return new ICmpInst(Pred, X,
+ ConstantInt::get(RHS->getType(), RHSLog2));
+ } else if (ICI.isSigned()) {
+ if (RHSV.isAllOnesValue()) {
+ // (1 << X) <= -1 -> X == 31
+ if (Pred == ICmpInst::ICMP_SLE)
+ return new ICmpInst(ICmpInst::ICMP_EQ, X,
+ ConstantInt::get(RHS->getType(), TypeBits-1));
+
+ // (1 << X) > -1 -> X != 31
+ if (Pred == ICmpInst::ICMP_SGT)
+ return new ICmpInst(ICmpInst::ICMP_NE, X,
+ ConstantInt::get(RHS->getType(), TypeBits-1));
+ } else if (!RHSV) {
+ // (1 << X) < 0 -> X == 31
+ // (1 << X) <= 0 -> X == 31
+ if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
+ return new ICmpInst(ICmpInst::ICMP_EQ, X,
+ ConstantInt::get(RHS->getType(), TypeBits-1));
+
+ // (1 << X) >= 0 -> X != 31
+ // (1 << X) > 0 -> X != 31
+ if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
+ return new ICmpInst(ICmpInst::ICMP_NE, X,
+ ConstantInt::get(RHS->getType(), TypeBits-1));
+ }
+ } else if (ICI.isEquality()) {
+ if (RHSVIsPowerOf2)
+ return new ICmpInst(
+ Pred, X, ConstantInt::get(RHS->getType(), RHSV.logBase2()));
+
+ return ReplaceInstUsesWith(
+ ICI, Pred == ICmpInst::ICMP_EQ ? Builder->getFalse()
+ : Builder->getTrue());
+ }
+ }
+ break;
+ }
// Check that the shift amount is in range. If not, don't perform
// undefined shifts. When the shift is visited it will be
return R;
break;
+ case Instruction::Sub: {
+ ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(0));
+ if (!LHSC) break;
+ const APInt &LHSV = LHSC->getValue();
+
+ // C1-X <u C2 -> (X|(C2-1)) == C1
+ // iff C1 & (C2-1) == C2-1
+ // C2 is a power of 2
+ if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() &&
+ RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == (RHSV - 1))
+ return new ICmpInst(ICmpInst::ICMP_EQ,
+ Builder->CreateOr(LHSI->getOperand(1), RHSV - 1),
+ LHSC);
+
+ // C1-X >u C2 -> (X|C2) != C1
+ // iff C1 & C2 == C2
+ // C2+1 is a power of 2
+ if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() &&
+ (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == RHSV)
+ return new ICmpInst(ICmpInst::ICMP_NE,
+ Builder->CreateOr(LHSI->getOperand(1), RHSV), LHSC);
+ break;
+ }
+
case Instruction::Add:
// Fold: icmp pred (add X, C1), C2
if (!ICI.isEquality()) {
Builder->getInt(CR.getLower()));
}
}
+
+ // X-C1 <u C2 -> (X & -C2) == C1
+ // iff C1 & (C2-1) == 0
+ // C2 is a power of 2
+ if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() &&
+ RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == 0)
+ return new ICmpInst(ICmpInst::ICMP_EQ,
+ Builder->CreateAnd(LHSI->getOperand(0), -RHSV),
+ ConstantExpr::getNeg(LHSC));
+
+ // X-C1 >u C2 -> (X & ~C2) != C1
+ // iff C1 & C2 == 0
+ // C2+1 is a power of 2
+ if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() &&
+ (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == 0)
+ return new ICmpInst(ICmpInst::ICMP_NE,
+ Builder->CreateAnd(LHSI->getOperand(0), ~RHSV),
+ ConstantExpr::getNeg(LHSC));
}
break;
}
}
+/// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst
+/// should be swapped.
+/// The descision is based on how many times these two operands are reused
+/// as subtract operands and their positions in those instructions.
+/// The rational is that several architectures use the same instruction for
+/// both subtract and cmp, thus it is better if the order of those operands
+/// match.
+/// \return true if Op0 and Op1 should be swapped.
+static bool swapMayExposeCSEOpportunities(const Value * Op0,
+ const Value * Op1) {
+ // Filter out pointer value as those cannot appears directly in subtract.
+ // FIXME: we may want to go through inttoptrs or bitcasts.
+ if (Op0->getType()->isPointerTy())
+ return false;
+ // Count every uses of both Op0 and Op1 in a subtract.
+ // Each time Op0 is the first operand, count -1: swapping is bad, the
+ // subtract has already the same layout as the compare.
+ // Each time Op0 is the second operand, count +1: swapping is good, the
+ // subtract has a diffrent layout as the compare.
+ // At the end, if the benefit is greater than 0, Op0 should come second to
+ // expose more CSE opportunities.
+ int GlobalSwapBenefits = 0;
+ for (Value::const_use_iterator UI = Op0->use_begin(), UIEnd = Op0->use_end(); UI != UIEnd; ++UI) {
+ const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(*UI);
+ if (!BinOp || BinOp->getOpcode() != Instruction::Sub)
+ continue;
+ // If Op0 is the first argument, this is not beneficial to swap the
+ // arguments.
+ int LocalSwapBenefits = -1;
+ unsigned Op1Idx = 1;
+ if (BinOp->getOperand(Op1Idx) == Op0) {
+ Op1Idx = 0;
+ LocalSwapBenefits = 1;
+ }
+ if (BinOp->getOperand(Op1Idx) != Op1)
+ continue;
+ GlobalSwapBenefits += LocalSwapBenefits;
+ }
+ return GlobalSwapBenefits > 0;
+}
+
Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
bool Changed = false;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+ unsigned Op0Cplxity = getComplexity(Op0);
+ unsigned Op1Cplxity = getComplexity(Op1);
/// Orders the operands of the compare so that they are listed from most
/// complex to least complex. This puts constants before unary operators,
/// before binary operators.
- if (getComplexity(Op0) < getComplexity(Op1)) {
+ if (Op0Cplxity < Op1Cplxity ||
+ (Op0Cplxity == Op1Cplxity &&
+ swapMayExposeCSEOpportunities(Op0, Op1))) {
I.swapOperands();
std::swap(Op0, Op1);
Changed = true;
case Instruction::IntToPtr:
// icmp pred inttoptr(X), null -> icmp pred X, 0
if (RHSC->isNullValue() && TD &&
- TD->getIntPtrType(RHSC->getContext()) ==
+ TD->getIntPtrType(RHSC->getType()) ==
LHSI->getOperand(0)->getType())
return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
Constant::getNullValue(LHSI->getOperand(0)->getType()));
Value *X; ConstantInt *Cst;
// icmp X+Cst, X
if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
- return FoldICmpAddOpCst(I, X, Cst, I.getPredicate(), Op0);
+ return FoldICmpAddOpCst(I, X, Cst, I.getPredicate());
// icmp X, X+Cst
if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
- return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate(), Op1);
+ return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate());
}
return Changed ? &I : 0;
}
-
-
-
-
-
/// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible.
///
Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
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