//===- llvm/Analysis/AliasAnalysis.h - Alias Analysis Interface -*- C++ -*-===//
//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
// 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. Mod/Ref information is
#define LLVM_ANALYSIS_ALIAS_ANALYSIS_H
#include "llvm/Support/CallSite.h"
+#include "llvm/System/IncludeFile.h"
+#include <vector>
+
+namespace llvm {
+
class LoadInst;
class StoreInst;
+class VAArgInst;
class TargetData;
-class AnalysisUsage;
class Pass;
+class AnalysisUsage;
class AliasAnalysis {
- const TargetData *TD;
protected:
+ const TargetData *TD;
+ AliasAnalysis *AA; // Previous Alias Analysis to chain to.
+
/// 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) {}
+ AliasAnalysis() : TD(0), AA(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; }
//===--------------------------------------------------------------------===//
/// analysis implementations.
///
virtual AliasResult alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size) {
- return MayAlias;
- }
+ const Value *V2, unsigned V2Size);
/// getMustAliases - If there are any pointers known that must alias this
/// pointer, return them now. This allows alias-set based alias analyses to
/// alias analysis supports this, it should ADD any must aliased pointers to
/// the specified vector.
///
- virtual void getMustAliases(Value *P, std::vector<Value*> &RetVals) {}
+ virtual void getMustAliases(Value *P, std::vector<Value*> &RetVals);
+ /// pointsToConstantMemory - If the specified pointer is known to point into
+ /// constant global memory, return true. This allows disambiguation of store
+ /// instructions from constant pointers.
+ ///
+ virtual bool pointsToConstantMemory(const Value *P);
//===--------------------------------------------------------------------===//
/// Simple mod/ref information...
///
enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 };
+
+ /// ModRefBehavior - Summary of how a function affects memory in the program.
+ /// Loads from constant globals are not considered memory accesses for this
+ /// interface. Also, functions may freely modify stack space local to their
+ /// invocation without having to report it through these interfaces.
+ enum ModRefBehavior {
+ // DoesNotAccessMemory - This function does not perform any non-local loads
+ // or stores to memory.
+ //
+ // This property corresponds to the GCC 'const' attribute.
+ DoesNotAccessMemory,
+
+ // AccessesArguments - This function accesses function arguments in
+ // non-volatile and well known ways, but does not access any other memory.
+ //
+ // Clients may call getArgumentAccesses to get specific information about
+ // how pointer arguments are used.
+ AccessesArguments,
+
+ // AccessesArgumentsAndGlobals - This function has accesses function
+ // arguments and global variables in non-volatile and well-known ways, but
+ // does not access any other memory.
+ //
+ // Clients may call getArgumentAccesses to get specific information about
+ // how pointer arguments and globals are used.
+ AccessesArgumentsAndGlobals,
+
+ // OnlyReadsMemory - This function does not perform any non-local stores or
+ // volatile loads, but may read from any memory location.
+ //
+ // This property corresponds to the GCC 'pure' attribute.
+ OnlyReadsMemory,
+
+ // UnknownModRefBehavior - This indicates that the function could not be
+ // classified into one of the behaviors above.
+ UnknownModRefBehavior
+ };
+
+ /// PointerAccessInfo - This struct is used to return results for pointers,
+ /// globals, and the return value of a function.
+ struct PointerAccessInfo {
+ /// V - The value this record corresponds to. This may be an Argument for
+ /// the function, a GlobalVariable, or null, corresponding to the return
+ /// value for the function.
+ Value *V;
+
+ /// ModRefInfo - Whether the pointer is loaded or stored to/from.
+ ///
+ ModRefResult ModRefInfo;
+
+ /// AccessType - Specific fine-grained access information for the argument.
+ /// If none of these classifications is general enough, the
+ /// getModRefBehavior method should not return AccessesArguments*. If a
+ /// record is not returned for a particular argument, the argument is never
+ /// dead and never dereferenced.
+ enum AccessType {
+ /// ScalarAccess - The pointer is dereferenced.
+ ///
+ ScalarAccess,
+
+ /// ArrayAccess - The pointer is indexed through as an array of elements.
+ ///
+ ArrayAccess,
+
+ /// ElementAccess ?? P->F only?
+
+ /// CallsThrough - Indirect calls are made through the specified function
+ /// pointer.
+ CallsThrough
+ };
+ };
+
+ /// getModRefBehavior - Return the behavior of the specified function if
+ /// called from the specified call site. The call site may be null in which
+ /// case the most generic behavior of this function should be returned.
+ virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS,
+ std::vector<PointerAccessInfo> *Info = 0);
+
+ /// doesNotAccessMemory - If the specified function is known to never read or
+ /// write memory, return true. If the function only reads from known-constant
+ /// memory, it is also legal to return true. Functions that unwind the stack
+ /// are not legal for this predicate.
+ ///
+ /// Many optimizations (such as CSE and LICM) can be performed on calls to it,
+ /// without worrying about aliasing properties, and many functions have this
+ /// property (e.g. 'sin' and 'cos').
+ ///
+ /// This property corresponds to the GCC 'const' attribute.
+ ///
+ bool doesNotAccessMemory(Function *F) {
+ return getModRefBehavior(F, CallSite()) == DoesNotAccessMemory;
+ }
+
+ /// onlyReadsMemory - If the specified function is known to only read from
+ /// non-volatile memory (or not access memory at all), return true. Functions
+ /// that unwind the stack are not legal for this predicate.
+ ///
+ /// This property allows many common optimizations to be performed in the
+ /// absence of interfering store instructions, such as CSE of strlen calls.
+ ///
+ /// This property corresponds to the GCC 'pure' attribute.
+ ///
+ bool onlyReadsMemory(Function *F) {
+ /// FIXME: If the analysis returns more precise info, we can reduce it to
+ /// this.
+ ModRefBehavior MRB = getModRefBehavior(F, CallSite());
+ return MRB == DoesNotAccessMemory || MRB == OnlyReadsMemory;
+ }
+
+
/// 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.
/// a particular call site modifies or reads the memory specified by the
/// pointer.
///
- virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size) {
- return ModRef;
- }
+ virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
/// 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.
+ /// the two calls refer to disjoint memory locations, Ref if CS1 reads memory
+ /// written by CS2, Mod if CS1 writes to memory read or written by CS2, or
+ /// ModRef if CS1 might read or write memory accessed by CS2.
///
- virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
- return ModRef;
- }
+ virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
+
+ /// hasNoModRefInfoForCalls - Return true if the analysis has no mod/ref
+ /// information for pairs of function calls (other than "pure" and "const"
+ /// functions). This can be used by clients to avoid many pointless queries.
+ /// Remember that if you override this and chain to another analysis, you must
+ /// make sure that it doesn't have mod/ref info either.
+ ///
+ virtual bool hasNoModRefInfoForCalls() const;
/// 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) {
+ 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) {
+ ModRefResult getModRefInfo(InvokeInst *I, Value *P, unsigned Size) {
return getModRefInfo(CallSite(I), P, Size);
}
+ ModRefResult getModRefInfo(VAArgInst* I, Value* P, unsigned Size) {
+ return AliasAnalysis::Mod;
+ }
ModRefResult getModRefInfo(Instruction *I, Value *P, unsigned Size) {
switch (I->getOpcode()) {
+ case Instruction::VAArg: return getModRefInfo((VAArgInst*)I, P, Size);
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);
}
}
+ //===--------------------------------------------------------------------===//
+ /// Higher level methods for querying mod/ref information.
+ ///
+
/// canBasicBlockModify - Return true if it is possible for execution of the
/// specified basic block to modify the value pointed to by Ptr.
///
///
bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
const Value *Ptr, unsigned Size);
+
+ //===--------------------------------------------------------------------===//
+ /// Methods that clients should call when they transform the program to allow
+ /// alias analyses to update their internal data structures. Note that these
+ /// methods may be called on any instruction, regardless of whether or not
+ /// they have pointer-analysis implications.
+ ///
+
+ /// deleteValue - This method should be called whenever an LLVM Value is
+ /// deleted from the program, for example when an instruction is found to be
+ /// redundant and is eliminated.
+ ///
+ virtual void deleteValue(Value *V);
+
+ /// copyValue - This method should be used whenever a preexisting value in the
+ /// program is copied or cloned, introducing a new value. Note that analysis
+ /// implementations should tolerate clients that use this method to introduce
+ /// the same value multiple times: if the analysis already knows about a
+ /// value, it should ignore the request.
+ ///
+ virtual void copyValue(Value *From, Value *To);
+
+ /// replaceWithNewValue - This method is the obvious combination of the two
+ /// above, and it provided as a helper to simplify client code.
+ ///
+ void replaceWithNewValue(Value *Old, Value *New) {
+ copyValue(Old, New);
+ deleteValue(Old);
+ }
};
+} // End llvm namespace
+
+// Because of the way .a files work, we must force the BasicAA implementation to
+// be pulled in if the AliasAnalysis header is included. Otherwise we run
+// the risk of AliasAnalysis being used, but the default implementation not
+// being linked into the tool that uses it.
+FORCE_DEFINING_FILE_TO_BE_LINKED(AliasAnalysis)
+FORCE_DEFINING_FILE_TO_BE_LINKED(BasicAliasAnalysis)
+
#endif
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