• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 //===- NoAliasAnalysis.cpp - Minimal Alias Analysis Impl ------------------===//
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 defines the default implementation of the Alias Analysis interface
11 // that simply returns "I don't know" for all queries.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Analysis/AliasAnalysis.h"
16 #include "llvm/Analysis/Passes.h"
17 #include "llvm/Pass.h"
18 #include "llvm/Target/TargetData.h"
19 using namespace llvm;
20 
21 namespace {
22   /// NoAA - This class implements the -no-aa pass, which always returns "I
23   /// don't know" for alias queries.  NoAA is unlike other alias analysis
24   /// implementations, in that it does not chain to a previous analysis.  As
25   /// such it doesn't follow many of the rules that other alias analyses must.
26   ///
27   struct NoAA : public ImmutablePass, public AliasAnalysis {
28     static char ID; // Class identification, replacement for typeinfo
NoAA__anona87d49130111::NoAA29     NoAA() : ImmutablePass(ID) {
30       initializeNoAAPass(*PassRegistry::getPassRegistry());
31     }
32 
getAnalysisUsage__anona87d49130111::NoAA33     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
34     }
35 
initializePass__anona87d49130111::NoAA36     virtual void initializePass() {
37       // Note: NoAA does not call InitializeAliasAnalysis because it's
38       // special and does not support chaining.
39       TD = getAnalysisIfAvailable<TargetData>();
40     }
41 
alias__anona87d49130111::NoAA42     virtual AliasResult alias(const Location &LocA, const Location &LocB) {
43       return MayAlias;
44     }
45 
getModRefBehavior__anona87d49130111::NoAA46     virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
47       return UnknownModRefBehavior;
48     }
getModRefBehavior__anona87d49130111::NoAA49     virtual ModRefBehavior getModRefBehavior(const Function *F) {
50       return UnknownModRefBehavior;
51     }
52 
pointsToConstantMemory__anona87d49130111::NoAA53     virtual bool pointsToConstantMemory(const Location &Loc,
54                                         bool OrLocal) {
55       return false;
56     }
getModRefInfo__anona87d49130111::NoAA57     virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
58                                        const Location &Loc) {
59       return ModRef;
60     }
getModRefInfo__anona87d49130111::NoAA61     virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
62                                        ImmutableCallSite CS2) {
63       return ModRef;
64     }
65 
deleteValue__anona87d49130111::NoAA66     virtual void deleteValue(Value *V) {}
copyValue__anona87d49130111::NoAA67     virtual void copyValue(Value *From, Value *To) {}
addEscapingUse__anona87d49130111::NoAA68     virtual void addEscapingUse(Use &U) {}
69 
70     /// getAdjustedAnalysisPointer - This method is used when a pass implements
71     /// an analysis interface through multiple inheritance.  If needed, it
72     /// should override this to adjust the this pointer as needed for the
73     /// specified pass info.
getAdjustedAnalysisPointer__anona87d49130111::NoAA74     virtual void *getAdjustedAnalysisPointer(const void *ID) {
75       if (ID == &AliasAnalysis::ID)
76         return (AliasAnalysis*)this;
77       return this;
78     }
79   };
80 }  // End of anonymous namespace
81 
82 // Register this pass...
83 char NoAA::ID = 0;
84 INITIALIZE_AG_PASS(NoAA, AliasAnalysis, "no-aa",
85                    "No Alias Analysis (always returns 'may' alias)",
86                    true, true, true)
87 
createNoAAPass()88 ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
89