Move NoAA out of BasicAliasAnalysis.cpp into its own file, now that

it doesn't have a special relationship with BasicAliasAnalysis
anymore.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116876 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/NoAliasAnalysis.cpp

@@ -0,0 +1,84 @@
+//===- NoAliasAnalysis.cpp - Minimal Alias Analysis Impl ------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the default implementation of the Alias Analysis interface
+// that simply returns "I don't know" for all queries.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Pass.h"
+#include "llvm/Target/TargetData.h"
+using namespace llvm;
+
+namespace {
+  /// NoAA - This class implements the -no-aa pass, which always returns "I
+  /// don't know" for alias queries.  NoAA is unlike other alias analysis
+  /// implementations, in that it does not chain to a previous analysis.  As
+  /// such it doesn't follow many of the rules that other alias analyses must.
+  ///
+  struct NoAA : public ImmutablePass, public AliasAnalysis {
+    static char ID; // Class identification, replacement for typeinfo
+    NoAA() : ImmutablePass(ID) {
+      initializeNoAAPass(*PassRegistry::getPassRegistry());
+    }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    }
+
+    virtual void initializePass() {
+      // Note: NoAA does not call InitializeAliasAnalysis because it's
+      // special and does not support chaining.
+      TD = getAnalysisIfAvailable<TargetData>();
+    }
+
+    virtual AliasResult alias(const Location &LocA, const Location &LocB) {
+      return MayAlias;
+    }
+
+    virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
+      return UnknownModRefBehavior;
+    }
+    virtual ModRefBehavior getModRefBehavior(const Function *F) {
+      return UnknownModRefBehavior;
+    }
+
+    virtual bool pointsToConstantMemory(const Location &Loc) { return false; }
+    virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+                                       const Location &Loc) {
+      return ModRef;
+    }
+    virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+                                       ImmutableCallSite CS2) {
+      return ModRef;
+    }
+
+    virtual void deleteValue(Value *V) {}
+    virtual void copyValue(Value *From, Value *To) {}
+    
+    /// getAdjustedAnalysisPointer - This method is used when a pass implements
+    /// an analysis interface through multiple inheritance.  If needed, it
+    /// should override this to adjust the this pointer as needed for the
+    /// specified pass info.
+    virtual void *getAdjustedAnalysisPointer(const void *ID) {
+      if (ID == &AliasAnalysis::ID)
+        return (AliasAnalysis*)this;
+      return this;
+    }
+  };
+}  // End of anonymous namespace
+
+// Register this pass...
+char NoAA::ID = 0;
+INITIALIZE_AG_PASS(NoAA, AliasAnalysis, "no-aa",
+                   "No Alias Analysis (always returns 'may' alias)",
+                   true, true, true)
+
+ImmutablePass *llvm::createNoAAPass() { return new NoAA(); }