1 //===- Loads.h - Local load analysis --------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares simple local analyses for load instructions.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ANALYSIS_LOADS_H
15 #define LLVM_ANALYSIS_LOADS_H
17 #include "llvm/IR/BasicBlock.h"
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,
31 const DataLayout *TD = nullptr);
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.
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
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.
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);