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__anon71c4efb90111::NoAA29 NoAA() : ImmutablePass(ID) {
30 initializeNoAAPass(*PassRegistry::getPassRegistry());
31 }
32
getAnalysisUsage__anon71c4efb90111::NoAA33 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
34 }
35
initializePass__anon71c4efb90111::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__anon71c4efb90111::NoAA42 virtual AliasResult alias(const Location &LocA, const Location &LocB) {
43 return MayAlias;
44 }
45
getModRefBehavior__anon71c4efb90111::NoAA46 virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
47 return UnknownModRefBehavior;
48 }
getModRefBehavior__anon71c4efb90111::NoAA49 virtual ModRefBehavior getModRefBehavior(const Function *F) {
50 return UnknownModRefBehavior;
51 }
52
pointsToConstantMemory__anon71c4efb90111::NoAA53 virtual bool pointsToConstantMemory(const Location &Loc,
54 bool OrLocal) {
55 return false;
56 }
getModRefInfo__anon71c4efb90111::NoAA57 virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
58 const Location &Loc) {
59 return ModRef;
60 }
getModRefInfo__anon71c4efb90111::NoAA61 virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
62 ImmutableCallSite CS2) {
63 return ModRef;
64 }
65
deleteValue__anon71c4efb90111::NoAA66 virtual void deleteValue(Value *V) {}
copyValue__anon71c4efb90111::NoAA67 virtual void copyValue(Value *From, Value *To) {}
addEscapingUse__anon71c4efb90111::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__anon71c4efb90111::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