forked from OSchip/llvm-project
89 lines
3.1 KiB
C++
89 lines
3.1 KiB
C++
//===- NoAliasAnalysis.cpp - Minimal Alias Analysis Impl ------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the default implementation of the Alias Analysis interface
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// that simply returns "I don't know" for all queries.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/Passes.h"
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#include "llvm/Pass.h"
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#include "llvm/Target/TargetData.h"
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using namespace llvm;
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namespace {
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/// NoAA - This class implements the -no-aa pass, which always returns "I
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/// don't know" for alias queries. NoAA is unlike other alias analysis
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/// implementations, in that it does not chain to a previous analysis. As
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/// such it doesn't follow many of the rules that other alias analyses must.
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///
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struct NoAA : public ImmutablePass, public AliasAnalysis {
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static char ID; // Class identification, replacement for typeinfo
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NoAA() : ImmutablePass(ID) {
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initializeNoAAPass(*PassRegistry::getPassRegistry());
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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}
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virtual void initializePass() {
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// Note: NoAA does not call InitializeAliasAnalysis because it's
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// special and does not support chaining.
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TD = getAnalysisIfAvailable<TargetData>();
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}
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virtual AliasResult alias(const Location &LocA, const Location &LocB) {
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return MayAlias;
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}
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virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
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return UnknownModRefBehavior;
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}
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virtual ModRefBehavior getModRefBehavior(const Function *F) {
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return UnknownModRefBehavior;
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}
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virtual bool pointsToConstantMemory(const Location &Loc,
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bool OrLocal) {
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return false;
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}
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virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
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const Location &Loc) {
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return ModRef;
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}
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virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
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ImmutableCallSite CS2) {
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return ModRef;
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}
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virtual void deleteValue(Value *V) {}
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virtual void copyValue(Value *From, Value *To) {}
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virtual void addEscapingUse(Use &U) {}
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/// getAdjustedAnalysisPointer - This method is used when a pass implements
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/// an analysis interface through multiple inheritance. If needed, it
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/// should override this to adjust the this pointer as needed for the
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/// specified pass info.
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virtual void *getAdjustedAnalysisPointer(const void *ID) {
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if (ID == &AliasAnalysis::ID)
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return (AliasAnalysis*)this;
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return this;
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}
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};
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} // End of anonymous namespace
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// Register this pass...
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char NoAA::ID = 0;
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INITIALIZE_AG_PASS(NoAA, AliasAnalysis, "no-aa",
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"No Alias Analysis (always returns 'may' alias)",
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true, true, true)
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ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }
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