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c51f300513
No in-tree alias analysis used this facility, and it was not called in any particularly rigorous way, so it seems unlikely to be correct. Note that one of the only stateful AA implementations in-tree, GlobalsModRef is completely broken currently (and any AA passes like it are equally broken) because Module AA passes are not effectively invalidated when a function pass that fails to update the AA stack runs. Ultimately, it doesn't seem like we know how we want to build stateful AA, and until then trying to support and maintain correctness for an untested API is essentially impossible. To that end, I'm planning to rip out all of the update API. It can return if and when we need it and know how to build it on top of the new pass manager and as part of *tested* stateful AA implementations in the tree. Differential Revision: http://reviews.llvm.org/D10889 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241975 91177308-0d34-0410-b5e6-96231b3b80d8
96 lines
3.3 KiB
C++
96 lines
3.3 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/Passes.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.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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void getAnalysisUsage(AnalysisUsage &AU) const override {}
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bool doInitialization(Module &M) override {
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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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DL = &M.getDataLayout();
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return true;
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}
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AliasResult alias(const MemoryLocation &LocA,
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const MemoryLocation &LocB) override {
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return MayAlias;
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}
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ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override {
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return UnknownModRefBehavior;
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}
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ModRefBehavior getModRefBehavior(const Function *F) override {
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return UnknownModRefBehavior;
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}
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bool pointsToConstantMemory(const MemoryLocation &Loc,
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bool OrLocal) override {
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return false;
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}
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ModRefResult getArgModRefInfo(ImmutableCallSite CS,
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unsigned ArgIdx) override {
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return ModRef;
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}
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ModRefResult getModRefInfo(ImmutableCallSite CS,
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const MemoryLocation &Loc) override {
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return ModRef;
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}
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ModRefResult getModRefInfo(ImmutableCallSite CS1,
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ImmutableCallSite CS2) override {
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return ModRef;
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}
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void deleteValue(Value *V) override {}
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void addEscapingUse(Use &U) override {}
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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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void *getAdjustedAnalysisPointer(const void *ID) override {
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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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