#include "InstCombine.h"
#include "llvm/Support/PatternMatch.h"
+#include "llvm/Analysis/InstructionSimplify.h"
using namespace llvm;
using namespace PatternMatch;
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
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());
}
+ // 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 (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
ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
Value *V = ICA;
if (ShouldNotVal)
- V = InsertNewInstBefore(BinaryOperator::Create(
- Instruction::Xor, V, ICA->getOperand(1)), SI);
+ V = Builder->CreateXor(V, ICA->getOperand(1));
return ReplaceInstUsesWith(SI, V);
}
}
!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
}
// 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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