diff options
Diffstat (limited to 'contrib/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp | 294 |
1 files changed, 203 insertions, 91 deletions
diff --git a/contrib/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/contrib/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp index c44fe9d..97abc76 100644 --- a/contrib/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/contrib/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -24,14 +24,14 @@ static SelectPatternFlavor MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) { SelectInst *SI = dyn_cast<SelectInst>(V); if (SI == 0) return SPF_UNKNOWN; - + ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition()); if (ICI == 0) return SPF_UNKNOWN; - + LHS = ICI->getOperand(0); RHS = ICI->getOperand(1); - - // (icmp X, Y) ? X : Y + + // (icmp X, Y) ? X : Y if (SI->getTrueValue() == ICI->getOperand(0) && SI->getFalseValue() == ICI->getOperand(1)) { switch (ICI->getPredicate()) { @@ -46,8 +46,8 @@ MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) { case ICmpInst::ICMP_SLE: return SPF_SMIN; } } - - // (icmp X, Y) ? Y : X + + // (icmp X, Y) ? Y : X if (SI->getTrueValue() == ICI->getOperand(1) && SI->getFalseValue() == ICI->getOperand(0)) { switch (ICI->getPredicate()) { @@ -62,9 +62,9 @@ MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) { case ICmpInst::ICMP_SLE: return SPF_SMAX; } } - + // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5) - + return SPF_UNKNOWN; } @@ -136,7 +136,7 @@ Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI, SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0), FI->getOperand(0), SI.getName()+".v"); InsertNewInstBefore(NewSI, SI); - return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI, + return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI, TI->getType()); } @@ -195,7 +195,10 @@ static bool isSelect01(Constant *C1, Constant *C2) { 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 @@ -219,7 +222,7 @@ Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal, 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); @@ -248,7 +251,7 @@ Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal, 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); @@ -278,52 +281,95 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI, Value *FalseVal = SI.getFalseValue(); // Check cases where the comparison is with a constant that - // can be adjusted to fit the min/max idiom. We may edit ICI in - // place here, so make sure the select is the only user. + // can be adjusted to fit the min/max idiom. We may move or edit ICI + // here, so make sure the select is the only user. if (ICI->hasOneUse()) if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) { + // X < MIN ? T : F --> F + if ((Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_ULT) + && CI->isMinValue(Pred == ICmpInst::ICMP_SLT)) + return ReplaceInstUsesWith(SI, FalseVal); + // X > MAX ? T : F --> F + else if ((Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_UGT) + && CI->isMaxValue(Pred == ICmpInst::ICMP_SGT)) + return ReplaceInstUsesWith(SI, FalseVal); switch (Pred) { default: break; case ICmpInst::ICMP_ULT: - case ICmpInst::ICMP_SLT: { - // X < MIN ? T : F --> F - if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT)) - return ReplaceInstUsesWith(SI, FalseVal); - // X < C ? X : C-1 --> X > C-1 ? C-1 : X - Constant *AdjustedRHS = - ConstantInt::get(CI->getContext(), CI->getValue()-1); - if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || - (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) { - Pred = ICmpInst::getSwappedPredicate(Pred); - CmpRHS = AdjustedRHS; - std::swap(FalseVal, TrueVal); - ICI->setPredicate(Pred); - ICI->setOperand(1, CmpRHS); - SI.setOperand(1, TrueVal); - SI.setOperand(2, FalseVal); - Changed = true; - } - break; - } + case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_SGT: { - // X > MAX ? T : F --> F - if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT)) - return ReplaceInstUsesWith(SI, FalseVal); + // These transformations only work for selects over integers. + const IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType()); + if (!SelectTy) + break; + + Constant *AdjustedRHS; + if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT) + AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1); + else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT) + AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1); + // X > C ? X : C+1 --> X < C+1 ? C+1 : X - Constant *AdjustedRHS = - ConstantInt::get(CI->getContext(), CI->getValue()+1); + // X < C ? X : C-1 --> X > C-1 ? C-1 : X if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || - (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) { - Pred = ICmpInst::getSwappedPredicate(Pred); - CmpRHS = AdjustedRHS; - std::swap(FalseVal, TrueVal); - ICI->setPredicate(Pred); - ICI->setOperand(1, CmpRHS); - SI.setOperand(1, TrueVal); - SI.setOperand(2, FalseVal); - Changed = true; - } + (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) + ; // Nothing to do here. Values match without any sign/zero extension. + + // Types do not match. Instead of calculating this with mixed types + // promote all to the larger type. This enables scalar evolution to + // analyze this expression. + else if (CmpRHS->getType()->getScalarSizeInBits() + < SelectTy->getBitWidth()) { + Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy); + + // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X + // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X + // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X + // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X + if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) && + sextRHS == FalseVal) { + CmpLHS = TrueVal; + AdjustedRHS = sextRHS; + } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) && + sextRHS == TrueVal) { + CmpLHS = FalseVal; + AdjustedRHS = sextRHS; + } else if (ICI->isUnsigned()) { + Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy); + // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X + // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X + // zext + signed compare cannot be changed: + // 0xff <s 0x00, but 0x00ff >s 0x0000 + if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) && + zextRHS == FalseVal) { + CmpLHS = TrueVal; + AdjustedRHS = zextRHS; + } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) && + zextRHS == TrueVal) { + CmpLHS = FalseVal; + AdjustedRHS = zextRHS; + } else + break; + } else + break; + } else + break; + + Pred = ICmpInst::getSwappedPredicate(Pred); + CmpRHS = AdjustedRHS; + std::swap(FalseVal, TrueVal); + ICI->setPredicate(Pred); + ICI->setOperand(0, CmpLHS); + ICI->setOperand(1, CmpRHS); + SI.setOperand(1, TrueVal); + SI.setOperand(2, FalseVal); + + // Move ICI instruction right before the select instruction. Otherwise + // the sext/zext value may be defined after the ICI instruction uses it. + ICI->moveBefore(&SI); + + Changed = true; break; } } @@ -399,28 +445,28 @@ static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V, // can always be mapped. const Instruction *I = dyn_cast<Instruction>(V); if (I == 0) return true; - + // If V is a PHI node defined in the same block as the condition PHI, we can // map the arguments. const PHINode *CondPHI = cast<PHINode>(SI.getCondition()); - + if (const PHINode *VP = dyn_cast<PHINode>(I)) if (VP->getParent() == CondPHI->getParent()) return true; - + // Otherwise, if the PHI and select are defined in the same block and if V is // defined in a different block, then we can transform it. if (SI.getParent() == CondPHI->getParent() && I->getParent() != CondPHI->getParent()) return true; - + // Otherwise we have a 'hard' case and we can't tell without doing more // detailed dominator based analysis, punt. return false; } /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form: -/// SPF2(SPF1(A, B), C) +/// SPF2(SPF1(A, B), C) Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1, Value *A, Value *B, @@ -431,7 +477,7 @@ Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner, // MIN(MIN(a, b), a) -> MIN(a, b) if (SPF1 == SPF2) return ReplaceInstUsesWith(Outer, Inner); - + // MAX(MIN(a, b), a) -> a // MIN(MAX(a, b), a) -> a if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) || @@ -440,13 +486,82 @@ Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner, (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN)) return ReplaceInstUsesWith(Outer, C); } - + // TODO: MIN(MIN(A, 23), 97) return 0; } +/// 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(); @@ -478,7 +593,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { "not."+CondVal->getName()), SI); return BinaryOperator::CreateOr(NotCond, TrueVal); } - + // select a, b, a -> a&b // select a, a, b -> a|b if (CondVal == TrueVal) @@ -497,7 +612,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { // 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()); @@ -509,32 +624,9 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { 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 - // 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 = Builder->CreateXor(V, ICA->getOperand(1)); - return ReplaceInstUsesWith(SI, V); - } - } + + 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. @@ -542,7 +634,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) { // Transform (X == Y) ? X : Y -> Y if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { - // This is not safe in general for floating point: + // 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; @@ -554,7 +646,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { } // Transform (X une Y) ? X : Y -> X if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { - // This is not safe in general for floating point: + // 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; @@ -569,7 +661,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ // Transform (X == Y) ? Y : X -> X if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { - // This is not safe in general for floating point: + // 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; @@ -581,7 +673,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { } // Transform (X une Y) ? Y : X -> Y if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { - // This is not safe in general for floating point: + // 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; @@ -639,6 +731,10 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { 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), @@ -654,7 +750,10 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { 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); } } } @@ -663,7 +762,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { if (SI.getType()->isIntegerTy()) { if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal)) return FoldI; - + // MAX(MAX(a, b), a) -> MAX(a, b) // MIN(MIN(a, b), a) -> MIN(a, b) // MAX(MIN(a, b), a) -> a @@ -686,13 +785,26 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { } // See if we can fold the select into a phi node if the condition is a select. - if (isa<PHINode>(SI.getCondition())) + if (isa<PHINode>(SI.getCondition())) // The true/false values have to be live in the PHI predecessor's blocks. if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) && CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI)) if (Instruction *NV = FoldOpIntoPhi(SI)) return NV; + if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) { + if (TrueSI->getCondition() == CondVal) { + SI.setOperand(1, TrueSI->getTrueValue()); + return &SI; + } + } + if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) { + if (FalseSI->getCondition() == CondVal) { + SI.setOperand(2, FalseSI->getFalseValue()); + return &SI; + } + } + if (BinaryOperator::isNot(CondVal)) { SI.setOperand(0, BinaryOperator::getNotArgument(CondVal)); SI.setOperand(1, FalseVal); |
