diff --git a/include/llvm/Analysis/Loads.h b/include/llvm/Analysis/Loads.h index f9700c3a01f..a59c1f88e22 100644 --- a/include/llvm/Analysis/Loads.h +++ b/include/llvm/Analysis/Loads.h @@ -88,6 +88,34 @@ Value *FindAvailableLoadedValue(LoadInst *Load, bool *IsLoadCSE = nullptr, unsigned *NumScanedInst = nullptr); +/// Scan backwards to see if we have the value of the given pointer available +/// locally within a small number of instructions. +/// +/// You can use this function to scan across multiple blocks: after you call +/// this function, if ScanFrom points at the beginning of the block, it's safe +/// to continue scanning the predecessors. +/// +/// \param Ptr The pointer we want the load and store to originate from. +/// \param AccessTy The access type of the pointer. +/// \param AtLeastAtomic Are we looking for at-least an atomic load/store ? In +/// case it is false, we can return an atomic or non-atomic load or store. In +/// case it is true, we need to return an atomic load or store. +/// \param ScanBB The basic block to scan. +/// \param [in,out] ScanFrom The location to start scanning from. When this +/// function returns, it points at the last instruction scanned. +/// \param MaxInstsToScan The maximum number of instructions to scan. If this +/// is zero, the whole block will be scanned. +/// \param AA Optional pointer to alias analysis, to make the scan more +/// precise. +/// \param [out] IsLoad Whether the returned value is a load from the same +/// location in memory, as opposed to the value operand of a store. +/// +/// \returns The found value, or nullptr if no value is found. +Value *FindAvailablePtrLoadStore(Value *Ptr, Type *AccessTy, bool AtLeastAtomic, + BasicBlock *ScanBB, + BasicBlock::iterator &ScanFrom, + unsigned MaxInstsToScan, AliasAnalysis *AA, + bool *IsLoad, unsigned *NumScanedInst); } #endif diff --git a/lib/Analysis/Loads.cpp b/lib/Analysis/Loads.cpp index 5d842db912c..96799a459bf 100644 --- a/lib/Analysis/Loads.cpp +++ b/lib/Analysis/Loads.cpp @@ -312,22 +312,26 @@ Value *llvm::FindAvailableLoadedValue(LoadInst *Load, BasicBlock *ScanBB, BasicBlock::iterator &ScanFrom, unsigned MaxInstsToScan, - AliasAnalysis *AA, bool *IsLoadCSE, + AliasAnalysis *AA, bool *IsLoad, unsigned *NumScanedInst) { - if (MaxInstsToScan == 0) - MaxInstsToScan = ~0U; - - Value *Ptr = Load->getPointerOperand(); - Type *AccessTy = Load->getType(); - - // We can never remove a volatile load - if (Load->isVolatile()) - return nullptr; - - // Anything stronger than unordered is currently unimplemented. + // Don't CSE load that is volatile or anything stronger than unordered. if (!Load->isUnordered()) return nullptr; + return FindAvailablePtrLoadStore( + Load->getPointerOperand(), Load->getType(), Load->isAtomic(), ScanBB, + ScanFrom, MaxInstsToScan, AA, IsLoad, NumScanedInst); +} + +Value *llvm::FindAvailablePtrLoadStore(Value *Ptr, Type *AccessTy, + bool AtLeastAtomic, BasicBlock *ScanBB, + BasicBlock::iterator &ScanFrom, + unsigned MaxInstsToScan, + AliasAnalysis *AA, bool *IsLoadCSE, + unsigned *NumScanedInst) { + if (MaxInstsToScan == 0) + MaxInstsToScan = ~0U; + const DataLayout &DL = ScanBB->getModule()->getDataLayout(); // Try to get the store size for the type. @@ -363,7 +367,7 @@ Value *llvm::FindAvailableLoadedValue(LoadInst *Load, // We can value forward from an atomic to a non-atomic, but not the // other way around. - if (LI->isAtomic() < Load->isAtomic()) + if (LI->isAtomic() < AtLeastAtomic) return nullptr; if (IsLoadCSE) @@ -382,7 +386,7 @@ Value *llvm::FindAvailableLoadedValue(LoadInst *Load, // We can value forward from an atomic to a non-atomic, but not the // other way around. - if (SI->isAtomic() < Load->isAtomic()) + if (SI->isAtomic() < AtLeastAtomic) return nullptr; if (IsLoadCSE)