diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/CodeGen/CodeGenPrepare.cpp | 29 | ||||
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 187 | ||||
| -rw-r--r-- | llvm/lib/Transforms/Utils/Local.cpp | 202 |
3 files changed, 239 insertions, 179 deletions
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp index 03e57787307..4326ba99538 100644 --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp @@ -5211,6 +5211,24 @@ bool CodeGenPrepare::optimizeInst(Instruction *I, bool& ModifiedDT) { return false; } +/// Given an OR instruction, check to see if this is a bitreverse +/// idiom. If so, insert the new intrinsic and return true. +static bool makeBitReverse(Instruction &I, const DataLayout &DL, + const TargetLowering &TLI) { + if (!I.getType()->isIntegerTy() || + !TLI.isOperationLegalOrCustom(ISD::BITREVERSE, + TLI.getValueType(DL, I.getType(), true))) + return false; + + SmallVector<Instruction*, 4> Insts; + if (!recognizeBitReverseOrBSwapIdiom(&I, false, true, Insts)) + return false; + Instruction *LastInst = Insts.back(); + I.replaceAllUsesWith(LastInst); + RecursivelyDeleteTriviallyDeadInstructions(&I); + return true; +} + // In this pass we look for GEP and cast instructions that are used // across basic blocks and rewrite them to improve basic-block-at-a-time // selection. @@ -5226,6 +5244,17 @@ bool CodeGenPrepare::optimizeBlock(BasicBlock &BB, bool& ModifiedDT) { } MadeChange |= dupRetToEnableTailCallOpts(&BB); + bool MadeBitReverse = true; + while (TLI && MadeBitReverse) { + MadeBitReverse = false; + for (auto &I : reverse(BB)) { + if (makeBitReverse(I, *DL, *TLI)) { + MadeBitReverse = MadeChange = true; + break; + } + } + } + return MadeChange; } diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 95c50d32c82..76cefd97cd8 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -17,6 +17,7 @@ #include "llvm/IR/Intrinsics.h" #include "llvm/IR/PatternMatch.h" #include "llvm/Transforms/Utils/CmpInstAnalysis.h" +#include "llvm/Transforms/Utils/Local.h" using namespace llvm; using namespace PatternMatch; @@ -1565,190 +1566,18 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) { return Changed ? &I : nullptr; } - -/// Analyze the specified subexpression and see if it is capable of providing -/// pieces of a bswap or bitreverse. The subexpression provides a potential -/// piece of a bswap or bitreverse if it can be proven that each non-zero bit in -/// the output of the expression came from a corresponding bit in some other -/// value. This function is recursive, and the end result is a mapping of -/// (value, bitnumber) to bitnumber. It is the caller's responsibility to -/// validate that all `value`s are identical and that the bitnumber to bitnumber -/// mapping is correct for a bswap or bitreverse. -/// -/// For example, if the current subexpression if "(shl i32 %X, 24)" then we know -/// that the expression deposits the low byte of %X into the high byte of the -/// result and that all other bits are zero. This expression is accepted, -/// BitValues[24-31] are set to %X and BitProvenance[24-31] are set to [0-7]. -/// -/// This function returns true if the match was unsuccessful and false if so. -/// On entry to the function the "OverallLeftShift" is a signed integer value -/// indicating the number of bits that the subexpression is later shifted. For -/// example, if the expression is later right shifted by 16 bits, the -/// OverallLeftShift value would be -16 on entry. This is used to specify which -/// bits of BitValues are actually being set. -/// -/// Similarly, BitMask is a bitmask where a bit is clear if its corresponding -/// bit is masked to zero by a user. For example, in (X & 255), X will be -/// processed with a bytemask of 255. BitMask is always in the local -/// (OverallLeftShift) coordinate space. -/// -static bool CollectBitParts(Value *V, int OverallLeftShift, APInt BitMask, - SmallVectorImpl<Value *> &BitValues, - SmallVectorImpl<int> &BitProvenance) { - if (Instruction *I = dyn_cast<Instruction>(V)) { - // If this is an or instruction, it may be an inner node of the bswap. - if (I->getOpcode() == Instruction::Or) - return CollectBitParts(I->getOperand(0), OverallLeftShift, BitMask, - BitValues, BitProvenance) || - CollectBitParts(I->getOperand(1), OverallLeftShift, BitMask, - BitValues, BitProvenance); - - // If this is a logical shift by a constant, recurse with OverallLeftShift - // and BitMask adjusted. - if (I->isLogicalShift() && isa<ConstantInt>(I->getOperand(1))) { - unsigned ShAmt = - cast<ConstantInt>(I->getOperand(1))->getLimitedValue(~0U); - // Ensure the shift amount is defined. - if (ShAmt > BitValues.size()) - return true; - - unsigned BitShift = ShAmt; - if (I->getOpcode() == Instruction::Shl) { - // X << C -> collect(X, +C) - OverallLeftShift += BitShift; - BitMask = BitMask.lshr(BitShift); - } else { - // X >>u C -> collect(X, -C) - OverallLeftShift -= BitShift; - BitMask = BitMask.shl(BitShift); - } - - if (OverallLeftShift >= (int)BitValues.size()) - return true; - if (OverallLeftShift <= -(int)BitValues.size()) - return true; - - return CollectBitParts(I->getOperand(0), OverallLeftShift, BitMask, - BitValues, BitProvenance); - } - - // If this is a logical 'and' with a mask that clears bits, clear the - // corresponding bits in BitMask. - if (I->getOpcode() == Instruction::And && - isa<ConstantInt>(I->getOperand(1))) { - unsigned NumBits = BitValues.size(); - APInt Bit(I->getType()->getPrimitiveSizeInBits(), 1); - const APInt &AndMask = cast<ConstantInt>(I->getOperand(1))->getValue(); - - for (unsigned i = 0; i != NumBits; ++i, Bit <<= 1) { - // If this bit is masked out by a later operation, we don't care what - // the and mask is. - if (BitMask[i] == 0) - continue; - - // If the AndMask is zero for this bit, clear the bit. - APInt MaskB = AndMask & Bit; - if (MaskB == 0) { - BitMask.clearBit(i); - continue; - } - - // Otherwise, this bit is kept. - } - - return CollectBitParts(I->getOperand(0), OverallLeftShift, BitMask, - BitValues, BitProvenance); - } - } - - // Okay, we got to something that isn't a shift, 'or' or 'and'. This must be - // the input value to the bswap/bitreverse. To be part of a bswap or - // bitreverse we must be demanding a contiguous range of bits from it. - unsigned InputBitLen = BitMask.countPopulation(); - unsigned InputBitNo = BitMask.countTrailingZeros(); - if (BitMask.getBitWidth() - BitMask.countLeadingZeros() - InputBitNo != - InputBitLen) - // Not a contiguous set range of bits! - return true; - - // We know we're moving a contiguous range of bits from the input to the - // output. Record which bits in the output came from which bits in the input. - unsigned DestBitNo = InputBitNo + OverallLeftShift; - for (unsigned I = 0; I < InputBitLen; ++I) - BitProvenance[DestBitNo + I] = InputBitNo + I; - - // If the destination bit value is already defined, the values are or'd - // together, which isn't a bswap/bitreverse (unless it's an or of the same - // bits). - if (BitValues[DestBitNo] && BitValues[DestBitNo] != V) - return true; - for (unsigned I = 0; I < InputBitLen; ++I) - BitValues[DestBitNo + I] = V; - - return false; -} - -static bool bitTransformIsCorrectForBSwap(unsigned From, unsigned To, - unsigned BitWidth) { - if (From % 8 != To % 8) - return false; - // Convert from bit indices to byte indices and check for a byte reversal. - From >>= 3; - To >>= 3; - BitWidth >>= 3; - return From == BitWidth - To - 1; -} - -static bool bitTransformIsCorrectForBitReverse(unsigned From, unsigned To, - unsigned BitWidth) { - return From == BitWidth - To - 1; -} - /// Given an OR instruction, check to see if this is a bswap or bitreverse /// idiom. If so, insert the new intrinsic and return it. Instruction *InstCombiner::MatchBSwapOrBitReverse(BinaryOperator &I) { - IntegerType *ITy = dyn_cast<IntegerType>(I.getType()); - if (!ITy) - return nullptr; // Can't do vectors. - unsigned BW = ITy->getBitWidth(); - - /// We keep track of which bit (BitProvenance) inside which value (BitValues) - /// defines each bit in the result. - SmallVector<Value *, 8> BitValues(BW, nullptr); - SmallVector<int, 8> BitProvenance(BW, -1); - - // Try to find all the pieces corresponding to the bswap. - APInt BitMask = APInt::getAllOnesValue(BitValues.size()); - if (CollectBitParts(&I, 0, BitMask, BitValues, BitProvenance)) - return nullptr; - - // Check to see if all of the bits come from the same value. - Value *V = BitValues[0]; - if (!V) return nullptr; // Didn't find a bit? Must be zero. - - if (!std::all_of(BitValues.begin(), BitValues.end(), - [&](const Value *X) { return X == V; })) - return nullptr; - - // Now, is the bit permutation correct for a bswap or a bitreverse? We can - // only byteswap values with an even number of bytes. - bool OKForBSwap = BW % 16 == 0, OKForBitReverse = true;; - for (unsigned i = 0, e = BitValues.size(); i != e; ++i) { - OKForBSwap &= bitTransformIsCorrectForBSwap(BitProvenance[i], i, BW); - OKForBitReverse &= - bitTransformIsCorrectForBitReverse(BitProvenance[i], i, BW); - } - - Intrinsic::ID Intrin; - if (OKForBSwap) - Intrin = Intrinsic::bswap; - else if (OKForBitReverse) - Intrin = Intrinsic::bitreverse; - else + SmallVector<Instruction*, 4> Insts; + if (!recognizeBitReverseOrBSwapIdiom(&I, true, false, Insts)) return nullptr; + Instruction *LastInst = Insts.pop_back_val(); + LastInst->removeFromParent(); - Function *F = Intrinsic::getDeclaration(I.getModule(), Intrin, ITy); - return CallInst::Create(F, V); + for (auto *Inst : Insts) + Worklist.Add(Inst); + return LastInst; } /// We have an expression of the form (A&C)|(B&D). Check if A is (cond?-1:0) diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp index e28232c4201..92e3a6b118b 100644 --- a/llvm/lib/Transforms/Utils/Local.cpp +++ b/llvm/lib/Transforms/Utils/Local.cpp @@ -1588,3 +1588,205 @@ bool llvm::callsGCLeafFunction(ImmutableCallSite CS) { return false; } + +/// A potential constituent of a bitreverse or bswap expression. See +/// collectBitParts for a fuller explanation. +struct BitPart { + BitPart(Value *P, unsigned BW) : Provider(P) { + Provenance.resize(BW); + } + + /// The Value that this is a bitreverse/bswap of. + Value *Provider; + /// The "provenance" of each bit. Provenance[A] = B means that bit A + /// in Provider becomes bit B in the result of this expression. + SmallVector<int8_t, 32> Provenance; // int8_t means max size is i128. + + enum { Unset = -1 }; +}; + +/// Analyze the specified subexpression and see if it is capable of providing +/// pieces of a bswap or bitreverse. The subexpression provides a potential +/// piece of a bswap or bitreverse if it can be proven that each non-zero bit in +/// the output of the expression came from a corresponding bit in some other +/// value. This function is recursive, and the end result is a mapping of +/// bitnumber to bitnumber. It is the caller's responsibility to validate that +/// the bitnumber to bitnumber mapping is correct for a bswap or bitreverse. +/// +/// For example, if the current subexpression if "(shl i32 %X, 24)" then we know +/// that the expression deposits the low byte of %X into the high byte of the +/// result and that all other bits are zero. This expression is accepted and a +/// BitPart is returned with Provider set to %X and Provenance[24-31] set to +/// [0-7]. +/// +/// To avoid revisiting values, the BitPart results are memoized into the +/// provided map. To avoid unnecessary copying of BitParts, BitParts are +/// constructed in-place in the \c BPS map. Because of this \c BPS needs to +/// store BitParts objects, not pointers. As we need the concept of a nullptr +/// BitParts (Value has been analyzed and the analysis failed), we an Optional +/// type instead to provide the same functionality. +/// +/// Because we pass around references into \c BPS, we must use a container that +/// does not invalidate internal references (std::map instead of DenseMap). +/// +static const Optional<BitPart> & +collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals, + std::map<Value *, Optional<BitPart>> &BPS) { + auto I = BPS.find(V); + if (I != BPS.end()) + return I->second; + + auto &Result = BPS[V] = None; + auto BitWidth = cast<IntegerType>(V->getType())->getBitWidth(); + + if (Instruction *I = dyn_cast<Instruction>(V)) { + // If this is an or instruction, it may be an inner node of the bswap. + if (I->getOpcode() == Instruction::Or) { + auto &A = collectBitParts(I->getOperand(0), MatchBSwaps, + MatchBitReversals, BPS); + auto &B = collectBitParts(I->getOperand(1), MatchBSwaps, + MatchBitReversals, BPS); + if (!A || !B) + return Result; + + // Try and merge the two together. + if (!A->Provider || A->Provider != B->Provider) + return Result; + + Result = BitPart(A->Provider, BitWidth); + for (unsigned i = 0; i < A->Provenance.size(); ++i) { + if (A->Provenance[i] != BitPart::Unset && + B->Provenance[i] != BitPart::Unset && + A->Provenance[i] != B->Provenance[i]) + return Result = None; + + if (A->Provenance[i] == BitPart::Unset) + Result->Provenance[i] = B->Provenance[i]; + else + Result->Provenance[i] = A->Provenance[i]; + } + + return Result; + } + + // If this is a logical shift by a constant, recurse then shift the result. + if (I->isLogicalShift() && isa<ConstantInt>(I->getOperand(1))) { + unsigned BitShift = + cast<ConstantInt>(I->getOperand(1))->getLimitedValue(~0U); + // Ensure the shift amount is defined. + if (BitShift > BitWidth) + return Result; + + auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps, + MatchBitReversals, BPS); + if (!Res) + return Result; + Result = Res; + + // Perform the "shift" on BitProvenance. + auto &P = Result->Provenance; + if (I->getOpcode() == Instruction::Shl) { + P.erase(std::prev(P.end(), BitShift), P.end()); + P.insert(P.begin(), BitShift, BitPart::Unset); + } else { + P.erase(P.begin(), std::next(P.begin(), BitShift)); + P.insert(P.end(), BitShift, BitPart::Unset); + } + + return Result; + } + + // If this is a logical 'and' with a mask that clears bits, recurse then + // unset the appropriate bits. + if (I->getOpcode() == Instruction::And && + isa<ConstantInt>(I->getOperand(1))) { + APInt Bit(I->getType()->getPrimitiveSizeInBits(), 1); + const APInt &AndMask = cast<ConstantInt>(I->getOperand(1))->getValue(); + + // Check that the mask allows a multiple of 8 bits for a bswap, for an + // early exit. + unsigned NumMaskedBits = AndMask.countPopulation(); + if (!MatchBitReversals && NumMaskedBits % 8 != 0) + return Result; + + auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps, + MatchBitReversals, BPS); + if (!Res) + return Result; + Result = Res; + + for (unsigned i = 0; i < BitWidth; ++i, Bit <<= 1) + // If the AndMask is zero for this bit, clear the bit. + if ((AndMask & Bit) == 0) + Result->Provenance[i] = BitPart::Unset; + + return Result; + } + } + + // Okay, we got to something that isn't a shift, 'or' or 'and'. This must be + // the input value to the bswap/bitreverse. + Result = BitPart(V, BitWidth); + for (unsigned i = 0; i < BitWidth; ++i) + Result->Provenance[i] = i; + return Result; +} + +static bool bitTransformIsCorrectForBSwap(unsigned From, unsigned To, + unsigned BitWidth) { + if (From % 8 != To % 8) + return false; + // Convert from bit indices to byte indices and check for a byte reversal. + From >>= 3; + To >>= 3; + BitWidth >>= 3; + return From == BitWidth - To - 1; +} + +static bool bitTransformIsCorrectForBitReverse(unsigned From, unsigned To, + unsigned BitWidth) { + return From == BitWidth - To - 1; +} + +/// Given an OR instruction, check to see if this is a bitreverse +/// idiom. If so, insert the new intrinsic and return true. +bool llvm::recognizeBitReverseOrBSwapIdiom( + Instruction *I, bool MatchBSwaps, bool MatchBitReversals, + SmallVectorImpl<Instruction *> &InsertedInsts) { + if (Operator::getOpcode(I) != Instruction::Or) + return false; + if (!MatchBSwaps && !MatchBitReversals) + return false; + IntegerType *ITy = dyn_cast<IntegerType>(I->getType()); + if (!ITy || ITy->getBitWidth() > 128) + return false; // Can't do vectors or integers > 128 bits. + unsigned BW = ITy->getBitWidth(); + + // Try to find all the pieces corresponding to the bswap. + std::map<Value *, Optional<BitPart>> BPS; + auto Res = collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS); + if (!Res) + return false; + auto &BitProvenance = Res->Provenance; + + // Now, is the bit permutation correct for a bswap or a bitreverse? We can + // only byteswap values with an even number of bytes. + bool OKForBSwap = BW % 16 == 0, OKForBitReverse = true; + for (unsigned i = 0; i < BW; ++i) { + OKForBSwap &= bitTransformIsCorrectForBSwap(BitProvenance[i], i, BW); + OKForBitReverse &= + bitTransformIsCorrectForBitReverse(BitProvenance[i], i, BW); + } + + Intrinsic::ID Intrin; + if (OKForBSwap && MatchBSwaps) + Intrin = Intrinsic::bswap; + else if (OKForBitReverse && MatchBitReversals) + Intrin = Intrinsic::bitreverse; + else + return false; + + Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, ITy); + InsertedInsts.push_back(CallInst::Create(F, Res->Provider, "rev", I)); + return true; +} |
