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c413330c99
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120405 91177308-0d34-0410-b5e6-96231b3b80d8
486 lines
20 KiB
C++
486 lines
20 KiB
C++
//===- llvm/Analysis/AliasAnalysis.h - Alias Analysis Interface -*- C++ -*-===//
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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 generic AliasAnalysis interface, which is used as the
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// common interface used by all clients of alias analysis information, and
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// implemented by all alias analysis implementations. Mod/Ref information is
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// also captured by this interface.
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//
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// Implementations of this interface must implement the various virtual methods,
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// which automatically provides functionality for the entire suite of client
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// APIs.
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//
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// This API identifies memory regions with the Location class. The pointer
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// component specifies the base memory address of the region. The Size specifies
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// the maximum size (in address units) of the memory region, or UnknownSize if
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// the size is not known. The TBAA tag identifies the "type" of the memory
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// reference; see the TypeBasedAliasAnalysis class for details.
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//
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// Some non-obvious details include:
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// - Pointers that point to two completely different objects in memory never
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// alias, regardless of the value of the Size component.
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// - NoAlias doesn't imply inequal pointers. The most obvious example of this
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// is two pointers to constant memory. Even if they are equal, constant
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// memory is never stored to, so there will never be any dependencies.
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// In this and other situations, the pointers may be both NoAlias and
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// MustAlias at the same time. The current API can only return one result,
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// though this is rarely a problem in practice.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_ALIAS_ANALYSIS_H
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#define LLVM_ANALYSIS_ALIAS_ANALYSIS_H
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#include "llvm/Support/CallSite.h"
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#include <vector>
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namespace llvm {
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class LoadInst;
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class StoreInst;
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class VAArgInst;
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class TargetData;
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class Pass;
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class AnalysisUsage;
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class MemTransferInst;
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class MemIntrinsic;
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class AliasAnalysis {
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protected:
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const TargetData *TD;
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private:
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AliasAnalysis *AA; // Previous Alias Analysis to chain to.
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protected:
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/// InitializeAliasAnalysis - Subclasses must call this method to initialize
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/// the AliasAnalysis interface before any other methods are called. This is
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/// typically called by the run* methods of these subclasses. This may be
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/// called multiple times.
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///
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void InitializeAliasAnalysis(Pass *P);
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/// getAnalysisUsage - All alias analysis implementations should invoke this
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/// directly (using AliasAnalysis::getAnalysisUsage(AU)).
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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public:
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static char ID; // Class identification, replacement for typeinfo
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AliasAnalysis() : TD(0), AA(0) {}
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virtual ~AliasAnalysis(); // We want to be subclassed
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/// UnknownSize - This is a special value which can be used with the
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/// size arguments in alias queries to indicate that the caller does not
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/// know the sizes of the potential memory references.
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static uint64_t const UnknownSize = ~UINT64_C(0);
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/// getTargetData - Return a pointer to the current TargetData object, or
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/// null if no TargetData object is available.
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///
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const TargetData *getTargetData() const { return TD; }
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/// getTypeStoreSize - Return the TargetData store size for the given type,
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/// if known, or a conservative value otherwise.
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///
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uint64_t getTypeStoreSize(const Type *Ty);
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//===--------------------------------------------------------------------===//
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/// Alias Queries...
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///
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/// Location - A description of a memory location.
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struct Location {
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/// Ptr - The address of the start of the location.
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const Value *Ptr;
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/// Size - The maximum size of the location, in address-units, or
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/// UnknownSize if the size is not known. Note that an unknown size does
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/// not mean the pointer aliases the entire virtual address space, because
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/// there are restrictions on stepping out of one object and into another.
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/// See http://llvm.org/docs/LangRef.html#pointeraliasing
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uint64_t Size;
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/// TBAATag - The metadata node which describes the TBAA type of
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/// the location, or null if there is no known unique tag.
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const MDNode *TBAATag;
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explicit Location(const Value *P = 0, uint64_t S = UnknownSize,
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const MDNode *N = 0)
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: Ptr(P), Size(S), TBAATag(N) {}
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Location getWithNewPtr(const Value *NewPtr) const {
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Location Copy(*this);
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Copy.Ptr = NewPtr;
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return Copy;
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}
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Location getWithNewSize(uint64_t NewSize) const {
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Location Copy(*this);
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Copy.Size = NewSize;
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return Copy;
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}
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Location getWithoutTBAATag() const {
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Location Copy(*this);
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Copy.TBAATag = 0;
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return Copy;
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}
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};
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/// getLocation - Fill in Loc with information about the memory reference by
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/// the given instruction.
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Location getLocation(const LoadInst *LI);
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Location getLocation(const StoreInst *SI);
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Location getLocation(const VAArgInst *VI);
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static Location getLocationForSource(const MemTransferInst *MTI);
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static Location getLocationForDest(const MemIntrinsic *MI);
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/// Alias analysis result - Either we know for sure that it does not alias, we
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/// know for sure it must alias, or we don't know anything: The two pointers
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/// _might_ alias. This enum is designed so you can do things like:
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/// if (AA.alias(P1, P2)) { ... }
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/// to check to see if two pointers might alias.
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///
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/// See docs/AliasAnalysis.html for more information on the specific meanings
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/// of these values.
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///
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enum AliasResult {
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NoAlias = 0, ///< No dependencies.
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MayAlias = 1, ///< Anything goes.
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MustAlias = 2 ///< Pointers are equal.
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};
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/// alias - The main low level interface to the alias analysis implementation.
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/// Returns an AliasResult indicating whether the two pointers are aliased to
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/// each other. This is the interface that must be implemented by specific
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/// alias analysis implementations.
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virtual AliasResult alias(const Location &LocA, const Location &LocB);
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/// alias - A convenience wrapper.
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AliasResult alias(const Value *V1, uint64_t V1Size,
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const Value *V2, uint64_t V2Size) {
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return alias(Location(V1, V1Size), Location(V2, V2Size));
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}
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/// alias - A convenience wrapper.
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AliasResult alias(const Value *V1, const Value *V2) {
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return alias(V1, UnknownSize, V2, UnknownSize);
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}
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/// isNoAlias - A trivial helper function to check to see if the specified
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/// pointers are no-alias.
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bool isNoAlias(const Location &LocA, const Location &LocB) {
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return alias(LocA, LocB) == NoAlias;
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}
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/// isNoAlias - A convenience wrapper.
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bool isNoAlias(const Value *V1, uint64_t V1Size,
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const Value *V2, uint64_t V2Size) {
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return isNoAlias(Location(V1, V1Size), Location(V2, V2Size));
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}
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/// pointsToConstantMemory - If the specified memory location is
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/// known to be constant, return true. If OrLocal is true and the
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/// specified memory location is known to be "local" (derived from
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/// an alloca), return true. Otherwise return false.
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virtual bool pointsToConstantMemory(const Location &Loc,
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bool OrLocal = false);
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/// pointsToConstantMemory - A convenient wrapper.
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bool pointsToConstantMemory(const Value *P, bool OrLocal = false) {
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return pointsToConstantMemory(Location(P), OrLocal);
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}
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//===--------------------------------------------------------------------===//
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/// Simple mod/ref information...
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///
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/// ModRefResult - Represent the result of a mod/ref query. Mod and Ref are
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/// bits which may be or'd together.
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///
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enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 };
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/// These values define additional bits used to define the
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/// ModRefBehavior values.
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enum { Nowhere = 0, ArgumentPointees = 4, Anywhere = 8 | ArgumentPointees };
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/// ModRefBehavior - Summary of how a function affects memory in the program.
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/// Loads from constant globals are not considered memory accesses for this
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/// interface. Also, functions may freely modify stack space local to their
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/// invocation without having to report it through these interfaces.
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enum ModRefBehavior {
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/// DoesNotAccessMemory - This function does not perform any non-local loads
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/// or stores to memory.
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///
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/// This property corresponds to the GCC 'const' attribute.
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/// This property corresponds to the LLVM IR 'readnone' attribute.
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/// This property corresponds to the IntrNoMem LLVM intrinsic flag.
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DoesNotAccessMemory = Nowhere | NoModRef,
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/// OnlyReadsArgumentPointees - The only memory references in this function
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/// (if it has any) are non-volatile loads from objects pointed to by its
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/// pointer-typed arguments, with arbitrary offsets.
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///
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/// This property corresponds to the IntrReadArgMem LLVM intrinsic flag.
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OnlyReadsArgumentPointees = ArgumentPointees | Ref,
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/// OnlyAccessesArgumentPointees - The only memory references in this
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/// function (if it has any) are non-volatile loads and stores from objects
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/// pointed to by its pointer-typed arguments, with arbitrary offsets.
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///
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/// This property corresponds to the IntrReadWriteArgMem LLVM intrinsic flag.
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OnlyAccessesArgumentPointees = ArgumentPointees | ModRef,
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/// OnlyReadsMemory - This function does not perform any non-local stores or
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/// volatile loads, but may read from any memory location.
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///
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/// This property corresponds to the GCC 'pure' attribute.
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/// This property corresponds to the LLVM IR 'readonly' attribute.
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/// This property corresponds to the IntrReadMem LLVM intrinsic flag.
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OnlyReadsMemory = Anywhere | Ref,
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/// UnknownModRefBehavior - This indicates that the function could not be
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/// classified into one of the behaviors above.
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UnknownModRefBehavior = Anywhere | ModRef
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};
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/// getModRefBehavior - Return the behavior when calling the given call site.
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virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
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/// getModRefBehavior - Return the behavior when calling the given function.
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/// For use when the call site is not known.
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virtual ModRefBehavior getModRefBehavior(const Function *F);
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/// doesNotAccessMemory - If the specified call is known to never read or
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/// write memory, return true. If the call only reads from known-constant
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/// memory, it is also legal to return true. Calls that unwind the stack
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/// are legal for this predicate.
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///
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/// Many optimizations (such as CSE and LICM) can be performed on such calls
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/// without worrying about aliasing properties, and many calls have this
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/// property (e.g. calls to 'sin' and 'cos').
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///
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/// This property corresponds to the GCC 'const' attribute.
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///
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bool doesNotAccessMemory(ImmutableCallSite CS) {
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return getModRefBehavior(CS) == DoesNotAccessMemory;
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}
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/// doesNotAccessMemory - If the specified function is known to never read or
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/// write memory, return true. For use when the call site is not known.
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///
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bool doesNotAccessMemory(const Function *F) {
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return getModRefBehavior(F) == DoesNotAccessMemory;
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}
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/// onlyReadsMemory - If the specified call is known to only read from
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/// non-volatile memory (or not access memory at all), return true. Calls
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/// that unwind the stack are legal for this predicate.
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///
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/// This property allows many common optimizations to be performed in the
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/// absence of interfering store instructions, such as CSE of strlen calls.
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///
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/// This property corresponds to the GCC 'pure' attribute.
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///
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bool onlyReadsMemory(ImmutableCallSite CS) {
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return onlyReadsMemory(getModRefBehavior(CS));
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}
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/// onlyReadsMemory - If the specified function is known to only read from
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/// non-volatile memory (or not access memory at all), return true. For use
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/// when the call site is not known.
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///
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bool onlyReadsMemory(const Function *F) {
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return onlyReadsMemory(getModRefBehavior(F));
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}
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/// onlyReadsMemory - Return true if functions with the specified behavior are
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/// known to only read from non-volatile memory (or not access memory at all).
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///
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static bool onlyReadsMemory(ModRefBehavior MRB) {
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return !(MRB & Mod);
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}
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/// onlyAccessesArgPointees - Return true if functions with the specified
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/// behavior are known to read and write at most from objects pointed to by
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/// their pointer-typed arguments (with arbitrary offsets).
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///
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static bool onlyAccessesArgPointees(ModRefBehavior MRB) {
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return !(MRB & Anywhere & ~ArgumentPointees);
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}
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/// doesAccessArgPointees - Return true if functions with the specified
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/// behavior are known to potentially read or write from objects pointed
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/// to be their pointer-typed arguments (with arbitrary offsets).
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///
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static bool doesAccessArgPointees(ModRefBehavior MRB) {
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return (MRB & ModRef) && (MRB & ArgumentPointees);
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}
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/// getModRefInfo - Return information about whether or not an instruction may
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/// read or write the specified memory location. An instruction
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/// that doesn't read or write memory may be trivially LICM'd for example.
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ModRefResult getModRefInfo(const Instruction *I,
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const Location &Loc) {
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switch (I->getOpcode()) {
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case Instruction::VAArg: return getModRefInfo((const VAArgInst*)I, Loc);
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case Instruction::Load: return getModRefInfo((const LoadInst*)I, Loc);
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case Instruction::Store: return getModRefInfo((const StoreInst*)I, Loc);
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case Instruction::Call: return getModRefInfo((const CallInst*)I, Loc);
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case Instruction::Invoke: return getModRefInfo((const InvokeInst*)I,Loc);
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default: return NoModRef;
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}
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}
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/// getModRefInfo - A convenience wrapper.
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ModRefResult getModRefInfo(const Instruction *I,
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const Value *P, uint64_t Size) {
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return getModRefInfo(I, Location(P, Size));
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}
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/// getModRefInfo (for call sites) - Return whether information about whether
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/// a particular call site modifies or reads the specified memory location.
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virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
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const Location &Loc);
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/// getModRefInfo (for call sites) - A convenience wrapper.
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ModRefResult getModRefInfo(ImmutableCallSite CS,
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const Value *P, uint64_t Size) {
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return getModRefInfo(CS, Location(P, Size));
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}
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/// getModRefInfo (for calls) - Return whether information about whether
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/// a particular call modifies or reads the specified memory location.
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ModRefResult getModRefInfo(const CallInst *C, const Location &Loc) {
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return getModRefInfo(ImmutableCallSite(C), Loc);
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}
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/// getModRefInfo (for calls) - A convenience wrapper.
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ModRefResult getModRefInfo(const CallInst *C, const Value *P, uint64_t Size) {
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return getModRefInfo(C, Location(P, Size));
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}
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/// getModRefInfo (for invokes) - Return whether information about whether
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/// a particular invoke modifies or reads the specified memory location.
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ModRefResult getModRefInfo(const InvokeInst *I,
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const Location &Loc) {
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return getModRefInfo(ImmutableCallSite(I), Loc);
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}
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/// getModRefInfo (for invokes) - A convenience wrapper.
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ModRefResult getModRefInfo(const InvokeInst *I,
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const Value *P, uint64_t Size) {
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return getModRefInfo(I, Location(P, Size));
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}
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/// getModRefInfo (for loads) - Return whether information about whether
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/// a particular load modifies or reads the specified memory location.
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ModRefResult getModRefInfo(const LoadInst *L, const Location &Loc);
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/// getModRefInfo (for loads) - A convenience wrapper.
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ModRefResult getModRefInfo(const LoadInst *L, const Value *P, uint64_t Size) {
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return getModRefInfo(L, Location(P, Size));
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}
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/// getModRefInfo (for stores) - Return whether information about whether
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/// a particular store modifies or reads the specified memory location.
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ModRefResult getModRefInfo(const StoreInst *S, const Location &Loc);
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/// getModRefInfo (for stores) - A convenience wrapper.
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ModRefResult getModRefInfo(const StoreInst *S, const Value *P, uint64_t Size) {
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return getModRefInfo(S, Location(P, Size));
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}
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/// getModRefInfo (for va_args) - Return whether information about whether
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/// a particular va_arg modifies or reads the specified memory location.
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ModRefResult getModRefInfo(const VAArgInst* I, const Location &Loc);
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/// getModRefInfo (for va_args) - A convenience wrapper.
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ModRefResult getModRefInfo(const VAArgInst* I, const Value* P, uint64_t Size) {
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return getModRefInfo(I, Location(P, Size));
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}
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/// getModRefInfo - Return information about whether two call sites may refer
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/// to the same set of memory locations. See
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/// http://llvm.org/docs/AliasAnalysis.html#ModRefInfo
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/// for details.
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virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
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ImmutableCallSite CS2);
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//===--------------------------------------------------------------------===//
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/// Higher level methods for querying mod/ref information.
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///
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/// canBasicBlockModify - Return true if it is possible for execution of the
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/// specified basic block to modify the value pointed to by Ptr.
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bool canBasicBlockModify(const BasicBlock &BB, const Location &Loc);
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/// canBasicBlockModify - A convenience wrapper.
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bool canBasicBlockModify(const BasicBlock &BB, const Value *P, uint64_t Size){
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return canBasicBlockModify(BB, Location(P, Size));
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}
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/// canInstructionRangeModify - Return true if it is possible for the
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/// execution of the specified instructions to modify the value pointed to by
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/// Ptr. The instructions to consider are all of the instructions in the
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/// range of [I1,I2] INCLUSIVE. I1 and I2 must be in the same basic block.
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bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
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const Location &Loc);
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/// canInstructionRangeModify - A convenience wrapper.
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bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
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const Value *Ptr, uint64_t Size) {
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return canInstructionRangeModify(I1, I2, Location(Ptr, Size));
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}
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//===--------------------------------------------------------------------===//
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/// Methods that clients should call when they transform the program to allow
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/// alias analyses to update their internal data structures. Note that these
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/// methods may be called on any instruction, regardless of whether or not
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/// they have pointer-analysis implications.
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///
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/// deleteValue - This method should be called whenever an LLVM Value is
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/// deleted from the program, for example when an instruction is found to be
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/// redundant and is eliminated.
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///
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virtual void deleteValue(Value *V);
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/// copyValue - This method should be used whenever a preexisting value in the
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/// program is copied or cloned, introducing a new value. Note that analysis
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/// implementations should tolerate clients that use this method to introduce
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/// the same value multiple times: if the analysis already knows about a
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/// value, it should ignore the request.
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///
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virtual void copyValue(Value *From, Value *To);
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/// replaceWithNewValue - This method is the obvious combination of the two
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/// above, and it provided as a helper to simplify client code.
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///
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void replaceWithNewValue(Value *Old, Value *New) {
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copyValue(Old, New);
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deleteValue(Old);
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}
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};
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/// isNoAliasCall - Return true if this pointer is returned by a noalias
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/// function.
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bool isNoAliasCall(const Value *V);
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/// isIdentifiedObject - Return true if this pointer refers to a distinct and
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/// identifiable object. This returns true for:
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/// Global Variables and Functions (but not Global Aliases)
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/// Allocas and Mallocs
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|
/// ByVal and NoAlias Arguments
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|
/// NoAlias returns
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|
///
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|
bool isIdentifiedObject(const Value *V);
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} // End llvm namespace
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#endif
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