1//===- Loads.h - Local load analysis --------------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file declares simple local analyses for load instructions. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_ANALYSIS_LOADS_H 15#define LLVM_ANALYSIS_LOADS_H 16 17#include "llvm/IR/BasicBlock.h" 18 19namespace llvm { 20 21class AliasAnalysis; 22class DataLayout; 23class MDNode; 24 25/// isSafeToLoadUnconditionally - Return true if we know that executing a load 26/// from this value cannot trap. If it is not obviously safe to load from the 27/// specified pointer, we do a quick local scan of the basic block containing 28/// ScanFrom, to determine if the address is already accessed. 29bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom, 30 unsigned Align, 31 const DataLayout *TD = nullptr); 32 33/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at 34/// the instruction before ScanFrom) checking to see if we have the value at 35/// the memory address *Ptr locally available within a small number of 36/// instructions. If the value is available, return it. 37/// 38/// If not, return the iterator for the last validated instruction that the 39/// value would be live through. If we scanned the entire block and didn't 40/// find something that invalidates *Ptr or provides it, ScanFrom would be 41/// left at begin() and this returns null. ScanFrom could also be left 42/// 43/// MaxInstsToScan specifies the maximum instructions to scan in the block. 44/// If it is set to 0, it will scan the whole block. You can also optionally 45/// specify an alias analysis implementation, which makes this more precise. 46/// 47/// If TBAATag is non-null and a load or store is found, the TBAA tag from the 48/// load or store is recorded there. If there is no TBAA tag or if no access 49/// is found, it is left unmodified. 50Value *FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB, 51 BasicBlock::iterator &ScanFrom, 52 unsigned MaxInstsToScan = 6, 53 AliasAnalysis *AA = nullptr, 54 MDNode **TBAATag = nullptr); 55 56} 57 58#endif 59