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 19 namespace llvm { 20 21 class AliasAnalysis; 22 class DataLayout; 23 class 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. 29 bool 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. 50 Value *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
