#include "InstCombine.h"
#include "llvm/Support/PatternMatch.h"
+#include "llvm/Analysis/InstructionSimplify.h"
using namespace llvm;
using namespace PatternMatch;
ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
if (!C2I)
return false;
- return (C1I->isZero() || C1I->isOne()) && (C2I->isZero() || C2I->isOne());
+ if (!C1I->isZero() && !C2I->isZero()) // One side must be zero.
+ return false;
+ return C1I->isOne() || C1I->isAllOnesValue() ||
+ C2I->isOne() || C2I->isAllOnesValue();
}
/// FoldSelectIntoOp - Try fold the select into one of the operands to
Constant *C = GetSelectFoldableConstant(TVI);
Value *OOp = TVI->getOperand(2-OpToFold);
// Avoid creating select between 2 constants unless it's selecting
- // between 0 and 1.
+ // between 0, 1 and -1.
if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C);
InsertNewInstBefore(NewSel, SI);
Constant *C = GetSelectFoldableConstant(FVI);
Value *OOp = FVI->getOperand(2-OpToFold);
// Avoid creating select between 2 constants unless it's selecting
- // between 0 and 1.
+ // between 0, 1 and -1.
if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp);
InsertNewInstBefore(NewSel, SI);
break;
}
}
+ }
- // (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed
- // (x >s -1) ? -1 : 0 -> ashr x, 31 -> all ones if not signed
- CmpInst::Predicate Pred = CmpInst::BAD_ICMP_PREDICATE;
- if (match(TrueVal, m_ConstantInt<-1>()) &&
- match(FalseVal, m_ConstantInt<0>()))
- Pred = ICI->getPredicate();
- else if (match(TrueVal, m_ConstantInt<0>()) &&
- match(FalseVal, m_ConstantInt<-1>()))
- Pred = CmpInst::getInversePredicate(ICI->getPredicate());
-
- if (Pred != CmpInst::BAD_ICMP_PREDICATE) {
- // If we are just checking for a icmp eq of a single bit and zext'ing it
- // to an integer, then shift the bit to the appropriate place and then
- // cast to integer to avoid the comparison.
- const APInt &Op1CV = CI->getValue();
-
- // sext (x <s 0) to i32 --> x>>s31 true if signbit set.
- // sext (x >s -1) to i32 --> (x>>s31)^-1 true if signbit clear.
- if ((Pred == ICmpInst::ICMP_SLT && Op1CV == 0) ||
- (Pred == ICmpInst::ICMP_SGT && Op1CV.isAllOnesValue())) {
- Value *In = ICI->getOperand(0);
- Value *Sh = ConstantInt::get(In->getType(),
- In->getType()->getScalarSizeInBits()-1);
- In = InsertNewInstBefore(BinaryOperator::CreateAShr(In, Sh,
- In->getName()+".lobit"),
- *ICI);
- if (In->getType() != SI.getType())
- In = CastInst::CreateIntegerCast(In, SI.getType(),
- true/*SExt*/, "tmp", ICI);
-
- if (Pred == ICmpInst::ICMP_SGT)
- In = InsertNewInstBefore(BinaryOperator::CreateNot(In,
- In->getName()+".not"), *ICI);
-
- return ReplaceInstUsesWith(SI, In);
+ // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
+ // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
+ // FIXME: Type and constness constraints could be lifted, but we have to
+ // watch code size carefully. We should consider xor instead of
+ // sub/add when we decide to do that.
+ if (const IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
+ if (TrueVal->getType() == Ty) {
+ if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
+ ConstantInt *C1 = NULL, *C2 = NULL;
+ if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
+ C1 = dyn_cast<ConstantInt>(TrueVal);
+ C2 = dyn_cast<ConstantInt>(FalseVal);
+ } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
+ C1 = dyn_cast<ConstantInt>(FalseVal);
+ C2 = dyn_cast<ConstantInt>(TrueVal);
+ }
+ if (C1 && C2) {
+ // This shift results in either -1 or 0.
+ Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
+
+ // Check if we can express the operation with a single or.
+ if (C2->isAllOnesValue())
+ return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
+
+ Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
+ return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
}
}
}
+ }
if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
// Transform (X == Y) ? X : Y -> Y
}
+/// foldSelectICmpAnd - If one of the constants is zero (we know they can't
+/// both be) and we have an icmp instruction with zero, and we have an 'and'
+/// with the non-constant value and a power of two we can turn the select
+/// into a shift on the result of the 'and'.
+static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
+ ConstantInt *FalseVal,
+ InstCombiner::BuilderTy *Builder) {
+ const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
+ if (!IC || !IC->isEquality())
+ return 0;
+
+ if (ConstantInt *C = dyn_cast<ConstantInt>(IC->getOperand(1)))
+ if (!C->isZero())
+ return 0;
+ ConstantInt *AndRHS;
+ Value *LHS = IC->getOperand(0);
+ if (LHS->getType() != SI.getType() ||
+ !match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
+ return 0;
+
+ // If both select arms are non-zero see if we have a select of the form
+ // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
+ // for 'x ? 2^n : 0' and fix the thing up at the end.
+ ConstantInt *Offset = 0;
+ if (!TrueVal->isZero() && !FalseVal->isZero()) {
+ if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
+ Offset = FalseVal;
+ else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
+ Offset = TrueVal;
+ else
+ return 0;
+
+ // Adjust TrueVal and FalseVal to the offset.
+ TrueVal = ConstantInt::get(Builder->getContext(),
+ TrueVal->getValue() - Offset->getValue());
+ FalseVal = ConstantInt::get(Builder->getContext(),
+ FalseVal->getValue() - Offset->getValue());
+ }
+
+ // Make sure the mask in the 'and' and one of the select arms is a power of 2.
+ if (!AndRHS->getValue().isPowerOf2() ||
+ (!TrueVal->getValue().isPowerOf2() &&
+ !FalseVal->getValue().isPowerOf2()))
+ return 0;
+
+ // Determine which shift is needed to transform result of the 'and' into the
+ // desired result.
+ ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
+ unsigned ValZeros = ValC->getValue().logBase2();
+ unsigned AndZeros = AndRHS->getValue().logBase2();
+
+ Value *V = LHS;
+ if (ValZeros > AndZeros)
+ V = Builder->CreateShl(V, ValZeros - AndZeros);
+ else if (ValZeros < AndZeros)
+ V = Builder->CreateLShr(V, AndZeros - ValZeros);
+
+ // Okay, now we know that everything is set up, we just don't know whether we
+ // have a icmp_ne or icmp_eq and whether the true or false val is the zero.
+ bool ShouldNotVal = !TrueVal->isZero();
+ ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
+ if (ShouldNotVal)
+ V = Builder->CreateXor(V, ValC);
+
+ // Apply an offset if needed.
+ if (Offset)
+ V = Builder->CreateAdd(V, Offset);
+ return V;
+}
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
- // select true, X, Y -> X
- // select false, X, Y -> Y
- if (ConstantInt *C = dyn_cast<ConstantInt>(CondVal))
- return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal);
-
- // select C, X, X -> X
- if (TrueVal == FalseVal)
- return ReplaceInstUsesWith(SI, TrueVal);
-
- if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
- return ReplaceInstUsesWith(SI, FalseVal);
- if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
- return ReplaceInstUsesWith(SI, TrueVal);
- if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
- if (isa<Constant>(TrueVal))
- return ReplaceInstUsesWith(SI, TrueVal);
- else
- return ReplaceInstUsesWith(SI, FalseVal);
- }
+ if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, TD))
+ return ReplaceInstUsesWith(SI, V);
- if (SI.getType() == Type::getInt1Ty(SI.getContext())) {
+ if (SI.getType()->isIntegerTy(1)) {
if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
if (C->getZExtValue()) {
// Change: A = select B, true, C --> A = or B, C
return BinaryOperator::CreateOr(CondVal, FalseVal);
- } else {
- // Change: A = select B, false, C --> A = and !B, C
- Value *NotCond =
- InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
- "not."+CondVal->getName()), SI);
- return BinaryOperator::CreateAnd(NotCond, FalseVal);
}
+ // Change: A = select B, false, C --> A = and !B, C
+ Value *NotCond =
+ InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
+ "not."+CondVal->getName()), SI);
+ return BinaryOperator::CreateAnd(NotCond, FalseVal);
} else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
if (C->getZExtValue() == false) {
// Change: A = select B, C, false --> A = and B, C
return BinaryOperator::CreateAnd(CondVal, TrueVal);
- } else {
- // Change: A = select B, C, true --> A = or !B, C
- Value *NotCond =
- InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
- "not."+CondVal->getName()), SI);
- return BinaryOperator::CreateOr(NotCond, TrueVal);
}
+ // Change: A = select B, C, true --> A = or !B, C
+ Value *NotCond =
+ InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
+ "not."+CondVal->getName()), SI);
+ return BinaryOperator::CreateOr(NotCond, TrueVal);
}
// select a, b, a -> a&b
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
// select C, 1, 0 -> zext C to int
- if (FalseValC->isZero() && TrueValC->getValue() == 1) {
- return CastInst::Create(Instruction::ZExt, CondVal, SI.getType());
- } else if (TrueValC->isZero() && FalseValC->getValue() == 1) {
- // select C, 0, 1 -> zext !C to int
- Value *NotCond =
- InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
- "not."+CondVal->getName()), SI);
- return CastInst::Create(Instruction::ZExt, NotCond, SI.getType());
+ if (FalseValC->isZero() && TrueValC->getValue() == 1)
+ return new ZExtInst(CondVal, SI.getType());
+
+ // select C, -1, 0 -> sext C to int
+ if (FalseValC->isZero() && TrueValC->isAllOnesValue())
+ return new SExtInst(CondVal, SI.getType());
+
+ // select C, 0, 1 -> zext !C to int
+ if (TrueValC->isZero() && FalseValC->getValue() == 1) {
+ Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
+ return new ZExtInst(NotCond, SI.getType());
}
- if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) {
- // If one of the constants is zero (we know they can't both be) and we
- // have an icmp instruction with zero, and we have an 'and' with the
- // non-constant value, eliminate this whole mess. This corresponds to
- // cases like this: ((X & 27) ? 27 : 0)
- if (TrueValC->isZero() || FalseValC->isZero())
- if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) &&
- cast<Constant>(IC->getOperand(1))->isNullValue())
- if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
- if (ICA->getOpcode() == Instruction::And &&
- isa<ConstantInt>(ICA->getOperand(1)) &&
- (ICA->getOperand(1) == TrueValC ||
- ICA->getOperand(1) == FalseValC) &&
- cast<ConstantInt>(ICA->getOperand(1))->getValue().isPowerOf2()) {
- // Okay, now we know that everything is set up, we just don't
- // know whether we have a icmp_ne or icmp_eq and whether the
- // true or false val is the zero.
- bool ShouldNotVal = !TrueValC->isZero();
- ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
- Value *V = ICA;
- if (ShouldNotVal)
- V = InsertNewInstBefore(BinaryOperator::Create(
- Instruction::Xor, V, ICA->getOperand(1)), SI);
- return ReplaceInstUsesWith(SI, V);
- }
+ // select C, 0, -1 -> sext !C to int
+ if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
+ Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
+ return new SExtInst(NotCond, SI.getType());
}
+
+ if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
+ return ReplaceInstUsesWith(SI, V);
}
// See if we are selecting two values based on a comparison of the two values.
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal);
}
- // Transform (X != Y) ? X : Y -> X
- if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
+ // Transform (X une Y) ? X : Y -> X
+ if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
+ // This is not safe in general for floating point:
+ // consider X== -0, Y== +0.
+ // It becomes safe if either operand is a nonzero constant.
+ ConstantFP *CFPt, *CFPf;
+ if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
+ !CFPt->getValueAPF().isZero()) ||
+ ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
+ !CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, TrueVal);
+ }
// NOTE: if we wanted to, this is where to detect MIN/MAX
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal);
}
- // Transform (X != Y) ? Y : X -> Y
- if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
- return ReplaceInstUsesWith(SI, TrueVal);
+ // Transform (X une Y) ? Y : X -> Y
+ if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
+ // This is not safe in general for floating point:
+ // consider X== -0, Y== +0.
+ // It becomes safe if either operand is a nonzero constant.
+ ConstantFP *CFPt, *CFPf;
+ if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
+ !CFPt->getValueAPF().isZero()) ||
+ ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
+ !CFPf->getValueAPF().isZero()))
+ return ReplaceInstUsesWith(SI, TrueVal);
+ }
// NOTE: if we wanted to, this is where to detect MIN/MAX
}
// NOTE: if we wanted to, this is where to detect ABS
Value *NegVal; // Compute -Z
if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
NegVal = ConstantExpr::getNeg(C);
+ } else if (SI.getType()->isFloatingPointTy()) {
+ NegVal = InsertNewInstBefore(
+ BinaryOperator::CreateFNeg(SubOp->getOperand(1),
+ "tmp"), SI);
} else {
NegVal = InsertNewInstBefore(
BinaryOperator::CreateNeg(SubOp->getOperand(1),
NewFalseOp, SI.getName() + ".p");
NewSel = InsertNewInstBefore(NewSel, SI);
- return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
+ if (SI.getType()->isFloatingPointTy())
+ return BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
+ else
+ return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
}
}
}
// See if we can fold the select into one of our operands.
- if (SI.getType()->isInteger()) {
+ if (SI.getType()->isIntegerTy()) {
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
return FoldI;
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