Checkin of new alias analysis interface:

* Takes into account the size of the memory reference to determine aliasing.
  * Expose mod/ref information in a more consistent way


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5631 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/AliasAnalysis.h

@@ -2,24 +2,61 @@
 //
 // This file defines the generic AliasAnalysis interface, which is used as the
 // common interface used by all clients of alias analysis information, and
-// implemented by all alias analysis implementations.
+// implemented by all alias analysis implementations.  Mod/Ref information is
+// also captured by this interface.
 //
 // Implementations of this interface must implement the various virtual methods,
 // which automatically provides functionality for the entire suite of client
 // APIs.
 //
+// This API represents memory as a (Pointer, Size) pair.  The Pointer component
+// specifies the base memory address of the region, the Size specifies how large
+// of an area is being queried.  If Size is 0, two pointers only alias if they
+// are exactly equal.  If size is greater than zero, but small, the two pointers
+// alias if the areas pointed to overlap.  If the size is very large (ie, ~0U),
+// then the two pointers alias if they may be pointing to components of the same
+// memory object.  Pointers that point to two completely different objects in
+// memory never alias, regardless of the value of the Size component.
+//
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_ANALYSIS_ALIAS_ANALYSIS_H
 #define LLVM_ANALYSIS_ALIAS_ANALYSIS_H
 
-class Value;
+#include "llvm/Support/CallSite.h"
-class CallInst;
+class LoadInst;
-class InvokeInst;
+class StoreInst;
-class BasicBlock;
+class TargetData;
-class Instruction;
+class AnalysisUsage;
+class Pass;
 
-struct AliasAnalysis {
+class AliasAnalysis {
+  const TargetData *TD;
+protected:
+  /// InitializeAliasAnalysis - Subclasses must call this method to initialize
+  /// the AliasAnalysis interface before any other methods are called.  This is
+  /// typically called by the run* methods of these subclasses.  This may be
+  /// called multiple times.
+  ///
+  void InitializeAliasAnalysis(Pass *P);
+  
+  // getAnalysisUsage - All alias analysis implementations should invoke this
+  // directly (using AliasAnalysis::getAnalysisUsage(AU)) to make sure that
+  // TargetData is required by the pass.
+  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+
+public:
+  AliasAnalysis() : TD(0) {}
+  virtual ~AliasAnalysis();  // We want to be subclassed
+
+  /// getTargetData - Every alias analysis implementation depends on the size of
+  /// data items in the current Target.  This provides a uniform way to handle
+  /// it.
+  const TargetData &getTargetData() const { return *TD; }
+
+  //===--------------------------------------------------------------------===//
+  /// Alias Queries...
+  ///
 
   /// Alias analysis result - Either we know for sure that it does not alias, we
   /// know for sure it must alias, or we don't know anything: The two pointers
@@ -27,29 +64,72 @@ struct AliasAnalysis {
   ///     if (AA.alias(P1, P2)) { ... }
   /// to check to see if two pointers might alias.
   ///
-  enum Result { NoAlias = 0, MayAlias = 1, MustAlias = 2 };
+  enum AliasResult { NoAlias = 0, MayAlias = 1, MustAlias = 2 };
 
   /// alias - The main low level interface to the alias analysis implementation.
   /// Returns a Result indicating whether the two pointers are aliased to each
   /// other.  This is the interface that must be implemented by specific alias
   /// analysis implementations.
   ///
-  virtual Result alias(const Value *V1, const Value *V2) = 0;
+  virtual AliasResult alias(const Value *V1, unsigned V1Size,
+                            const Value *V2, unsigned V2Size) {
+    return MayAlias;
+  }
 
-  /// canCallModify - Return a Result that indicates whether the specified
+  //===--------------------------------------------------------------------===//
-  /// function call can modify the memory location pointed to by Ptr.
+  /// Simple mod/ref information...
   ///
-  virtual Result canCallModify(const CallInst &CI, const Value *Ptr) = 0;
 
-  /// canInvokeModify - Return a Result that indicates whether the specified
+  /// ModRefResult - Represent the result of a mod/ref query.  Mod and Ref are
-  /// function invoke can modify the memory location pointed to by Ptr.
+  /// bits which may be or'd together.
   ///
-  virtual Result canInvokeModify(const InvokeInst &I, const Value *Ptr) = 0;
+  enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 };
+
+  /// getModRefInfo - Return information about whether or not an instruction may
+  /// read or write memory specified by the pointer operand.  An instruction
+  /// that doesn't read or write memory may be trivially LICM'd for example.
+
+  /// getModRefInfo (for call sites) - Return whether information about whether
+  /// a particular call site modifies or reads the memory specified by the
+  /// pointer.
+  ///
+  virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+    return ModRef;
+  }
+
+  /// getModRefInfo - Return information about whether two call sites may refer
+  /// to the same set of memory locations.  This function returns NoModRef if
+  /// the two calls refer to disjoint memory locations, Ref if they both read
+  /// some of the same memory, Mod if they both write to some of the same
+  /// memory, and ModRef if they read and write to the same memory.
+  ///
+  virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
+    return ModRef;
+  }
+
+  /// Convenience functions...
+  ModRefResult getModRefInfo(LoadInst *L, Value *P, unsigned Size);
+  ModRefResult getModRefInfo(StoreInst*S, Value *P, unsigned Size);
+  ModRefResult getModRefInfo(CallInst  *C, Value *P, unsigned Size) {
+    return getModRefInfo(CallSite(C), P, Size);
+  }
+  ModRefResult getModRefInfo(InvokeInst*I, Value *P, unsigned Size) {
+    return getModRefInfo(CallSite(I), P, Size);
+  }
+  ModRefResult getModRefInfo(Instruction *I, Value *P, unsigned Size) {
+    switch (I->getOpcode()) {
+    case Instruction::Load:   return getModRefInfo((LoadInst*)I, P, Size);
+    case Instruction::Store:  return getModRefInfo((StoreInst*)I, P, Size);
+    case Instruction::Call:   return getModRefInfo((CallInst*)I, P, Size);
+    case Instruction::Invoke: return getModRefInfo((InvokeInst*)I, P, Size);
+    default:                  return NoModRef;
+    }
+  }
 
   /// canBasicBlockModify - Return true if it is possible for execution of the
   /// specified basic block to modify the value pointed to by Ptr.
   ///
-  bool canBasicBlockModify(const BasicBlock &BB, const Value *Ptr);
+  bool canBasicBlockModify(const BasicBlock &BB, const Value *P, unsigned Size);
 
   /// canInstructionRangeModify - Return true if it is possible for the
   /// execution of the specified instructions to modify the value pointed to by
@@ -57,9 +137,7 @@ struct AliasAnalysis {
   /// range of [I1,I2] INCLUSIVE.  I1 and I2 must be in the same basic block.
   ///
   bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
-                                 const Value *Ptr);
+                                 const Value *Ptr, unsigned Size);
-
-  virtual ~AliasAnalysis();  // We want to be subclassed
 };
 
 #endif