Loads.h revision 210006 
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/BasicBlock.h"
18
19namespace llvm {
20
21class AliasAnalysis;
22class TargetData;
23
24/// isSafeToLoadUnconditionally - Return true if we know that executing a load
25/// from this value cannot trap.  If it is not obviously safe to load from the
26/// specified pointer, we do a quick local scan of the basic block containing
27/// ScanFrom, to determine if the address is already accessed.
28bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
29                                 unsigned Align, const TargetData *TD = 0);
30
31/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at
32/// the instruction before ScanFrom) checking to see if we have the value at
33/// the memory address *Ptr locally available within a small number of
34///  instructions. If the value is available, return it.
35///
36/// If not, return the iterator for the last validated instruction that the
37/// value would be live through.  If we scanned the entire block and didn't
38/// find something that invalidates *Ptr or provides it, ScanFrom would be
39/// left at begin() and this returns null.  ScanFrom could also be left
40///
41/// MaxInstsToScan specifies the maximum instructions to scan in the block.
42/// If it is set to 0, it will scan the whole block. You can also optionally
43/// specify an alias analysis implementation, which makes this more precise.
44Value *FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
45                                BasicBlock::iterator &ScanFrom,
46                                unsigned MaxInstsToScan = 6,
47                                AliasAnalysis *AA = 0);
48
49}
50
51#endif
52