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[Utils] Consolidate LockstepReverseIterator into own header (NFC)
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Merged
dwblaikie
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antoniofrighetto:feature/move-lri-in-utils
Feb 21, 2025
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155 changes: 155 additions & 0 deletions
155
llvm/include/llvm/Transforms/Utils/LockstepReverseIterator.h
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,155 @@ | ||
| //===- LockstepReverseIterator.h ------------------------------*- C++ -*---===// | ||
| // | ||
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||
| // See https://llvm.org/LICENSE.txt for license information. | ||
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #ifndef LLVM_TRANSFORMS_UTILS_LOCKSTEPREVERSEITERATOR_H | ||
| #define LLVM_TRANSFORMS_UTILS_LOCKSTEPREVERSEITERATOR_H | ||
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| #include "llvm/ADT/ArrayRef.h" | ||
| #include "llvm/ADT/SetVector.h" | ||
| #include "llvm/ADT/SmallVector.h" | ||
| #include "llvm/IR/BasicBlock.h" | ||
| #include "llvm/IR/Instruction.h" | ||
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| namespace llvm { | ||
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| struct NoActiveBlocksOption {}; | ||
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| struct ActiveBlocksOption { | ||
| SmallSetVector<BasicBlock *, 4> ActiveBlocks; | ||
| SmallSetVector<BasicBlock *, 4> &getActiveBlocks() { return ActiveBlocks; } | ||
| ActiveBlocksOption() = default; | ||
| }; | ||
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| /// Iterates through instructions in a set of blocks in reverse order from the | ||
| /// first non-terminator. For example (assume all blocks have size n): | ||
| /// LockstepReverseIterator I([B1, B2, B3]); | ||
| /// *I-- = [B1[n], B2[n], B3[n]]; | ||
| /// *I-- = [B1[n-1], B2[n-1], B3[n-1]]; | ||
| /// *I-- = [B1[n-2], B2[n-2], B3[n-2]]; | ||
| /// ... | ||
| /// | ||
| /// The iterator continues processing until all blocks have been exhausted if \p | ||
| /// EarlyFailure is explicitly set to \c false. Use \c getActiveBlocks() to | ||
| /// determine which blocks are still going and the order they appear in the list | ||
| /// returned by operator*. | ||
| template <bool EarlyFailure = true> | ||
| class LockstepReverseIterator | ||
| : private std::conditional_t<EarlyFailure, NoActiveBlocksOption, | ||
| ActiveBlocksOption> { | ||
| private: | ||
| using Base = std::conditional_t<EarlyFailure, NoActiveBlocksOption, | ||
| ActiveBlocksOption>; | ||
| ArrayRef<BasicBlock *> Blocks; | ||
| SmallVector<Instruction *, 4> Insts; | ||
| bool Fail; | ||
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| public: | ||
| LockstepReverseIterator(ArrayRef<BasicBlock *> Blocks) : Blocks(Blocks) { | ||
| reset(); | ||
| } | ||
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| void reset() { | ||
| Fail = false; | ||
| if constexpr (!EarlyFailure) { | ||
| this->ActiveBlocks.clear(); | ||
| for (BasicBlock *BB : Blocks) | ||
| this->ActiveBlocks.insert(BB); | ||
| } | ||
| Insts.clear(); | ||
| for (BasicBlock *BB : Blocks) { | ||
| Instruction *Prev = BB->getTerminator()->getPrevNonDebugInstruction(); | ||
| if (!Prev) { | ||
| // Block wasn't big enough - only contained a terminator. | ||
| if constexpr (EarlyFailure) { | ||
| Fail = true; | ||
| return; | ||
| } else { | ||
| this->ActiveBlocks.remove(BB); | ||
| continue; | ||
| } | ||
| } | ||
| Insts.push_back(Prev); | ||
| } | ||
| if (Insts.empty()) | ||
| Fail = true; | ||
| } | ||
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| bool isValid() const { return !Fail; } | ||
| ArrayRef<Instruction *> operator*() const { return Insts; } | ||
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| // Note: This needs to return a SmallSetVector as the elements of | ||
| // ActiveBlocks will be later copied to Blocks using std::copy. The | ||
| // resultant order of elements in Blocks needs to be deterministic. | ||
| // Using SmallPtrSet instead causes non-deterministic order while | ||
| // copying. And we cannot simply sort Blocks as they need to match the | ||
| // corresponding Values. | ||
| SmallSetVector<BasicBlock *, 4> &getActiveBlocks() { | ||
| return Base::getActiveBlocks(); | ||
| } | ||
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| void restrictToBlocks(SmallSetVector<BasicBlock *, 4> &Blocks) { | ||
| static_assert(!EarlyFailure, "Unknown method"); | ||
| for (auto It = Insts.begin(); It != Insts.end();) { | ||
| if (!Blocks.contains((*It)->getParent())) { | ||
| this->ActiveBlocks.remove((*It)->getParent()); | ||
| It = Insts.erase(It); | ||
| } else { | ||
| ++It; | ||
| } | ||
| } | ||
| } | ||
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| LockstepReverseIterator &operator--() { | ||
| if (Fail) | ||
| return *this; | ||
| SmallVector<Instruction *, 4> NewInsts; | ||
| for (Instruction *Inst : Insts) { | ||
| Instruction *Prev = Inst->getPrevNonDebugInstruction(); | ||
| if (!Prev) { | ||
| if constexpr (!EarlyFailure) { | ||
| this->ActiveBlocks.remove(Inst->getParent()); | ||
| } else { | ||
| Fail = true; | ||
| return *this; | ||
| } | ||
| } else { | ||
| NewInsts.push_back(Prev); | ||
| } | ||
| } | ||
| if (NewInsts.empty()) | ||
| Fail = true; | ||
| else | ||
| Insts = NewInsts; | ||
| return *this; | ||
| } | ||
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| LockstepReverseIterator &operator++() { | ||
| static_assert(EarlyFailure, "Unknown method"); | ||
| if (Fail) | ||
| return *this; | ||
| SmallVector<Instruction *, 4> NewInsts; | ||
| for (Instruction *Inst : Insts) { | ||
| Instruction *Next = Inst->getNextNonDebugInstruction(); | ||
| // Already at end of block. | ||
| if (!Next) { | ||
| Fail = true; | ||
| return *this; | ||
| } | ||
| NewInsts.push_back(Next); | ||
| } | ||
| if (NewInsts.empty()) | ||
| Fail = true; | ||
| else | ||
| Insts = NewInsts; | ||
| return *this; | ||
| } | ||
| }; | ||
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| } // end namespace llvm | ||
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| #endif // LLVM_TRANSFORMS_UTILS_LOCKSTEPREVERSEITERATOR_H | ||
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Use
class.Uh oh!
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I'd rather favour
structfor consistency, as we keep the default constructor private forNoActiveBlocksOption, unless it's a strong concern.There was a problem hiding this comment.
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FWIW https://llvm.org/docs/CodingStandards.html#use-of-class-and-struct-keywords says to use struct when all members are public, which isn't the case here