+ /// and returns the string in Str. If unsuccessful, it returns false. This
+ /// does not include the trailing nul character by default. If TrimAtNul is
+ /// set to false, then this returns any trailing nul characters as well as any
+ /// other characters that come after it.
+ bool getConstantStringInfo(const Value *V, StringRef &Str,
+ uint64_t Offset = 0, bool TrimAtNul = true);
+
+ /// GetStringLength - If we can compute the length of the string pointed to by
+ /// the specified pointer, return 'len+1'. If we can't, return 0.
+ uint64_t GetStringLength(Value *V);
+
+ /// GetUnderlyingObject - This method strips off any GEP address adjustments
+ /// and pointer casts from the specified value, returning the original object
+ /// being addressed. Note that the returned value has pointer type if the
+ /// specified value does. If the MaxLookup value is non-zero, it limits the
+ /// number of instructions to be stripped off.
+ Value *GetUnderlyingObject(Value *V, const DataLayout &DL,
+ unsigned MaxLookup = 6);
+ static inline const Value *GetUnderlyingObject(const Value *V,
+ const DataLayout &DL,
+ unsigned MaxLookup = 6) {
+ return GetUnderlyingObject(const_cast<Value *>(V), DL, MaxLookup);
+ }
+
+ /// \brief This method is similar to GetUnderlyingObject except that it can
+ /// look through phi and select instructions and return multiple objects.
+ ///
+ /// If LoopInfo is passed, loop phis are further analyzed. If a pointer
+ /// accesses different objects in each iteration, we don't look through the
+ /// phi node. E.g. consider this loop nest:
+ ///
+ /// int **A;
+ /// for (i)
+ /// for (j) {
+ /// A[i][j] = A[i-1][j] * B[j]
+ /// }
+ ///
+ /// This is transformed by Load-PRE to stash away A[i] for the next iteration
+ /// of the outer loop:
+ ///
+ /// Curr = A[0]; // Prev_0
+ /// for (i: 1..N) {
+ /// Prev = Curr; // Prev = PHI (Prev_0, Curr)
+ /// Curr = A[i];
+ /// for (j: 0..N) {
+ /// Curr[j] = Prev[j] * B[j]
+ /// }
+ /// }
+ ///
+ /// Since A[i] and A[i-1] are independent pointers, getUnderlyingObjects
+ /// should not assume that Curr and Prev share the same underlying object thus
+ /// it shouldn't look through the phi above.
+ void GetUnderlyingObjects(Value *V, SmallVectorImpl<Value *> &Objects,
+ const DataLayout &DL, LoopInfo *LI = nullptr,
+ unsigned MaxLookup = 6);
+
+ /// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer
+ /// are lifetime markers.
+ bool onlyUsedByLifetimeMarkers(const Value *V);
+
+ /// isDereferenceablePointer - Return true if this is always a dereferenceable
+ /// pointer. If the context instruction is specified perform context-sensitive
+ /// analysis and return true if the pointer is dereferenceable at the
+ /// specified instruction.
+ bool isDereferenceablePointer(const Value *V, const DataLayout &DL,
+ const Instruction *CtxI = nullptr,
+ const DominatorTree *DT = nullptr,
+ const TargetLibraryInfo *TLI = nullptr);
+
+ /// isSafeToSpeculativelyExecute - Return true if the instruction does not
+ /// have any effects besides calculating the result and does not have
+ /// undefined behavior.
+ ///
+ /// This method never returns true for an instruction that returns true for
+ /// mayHaveSideEffects; however, this method also does some other checks in
+ /// addition. It checks for undefined behavior, like dividing by zero or
+ /// loading from an invalid pointer (but not for undefined results, like a
+ /// shift with a shift amount larger than the width of the result). It checks
+ /// for malloc and alloca because speculatively executing them might cause a
+ /// memory leak. It also returns false for instructions related to control
+ /// flow, specifically terminators and PHI nodes.
+ ///
+ /// If the CtxI is specified this method performs context-sensitive analysis
+ /// and returns true if it is safe to execute the instruction immediately
+ /// before the CtxI.
+ ///
+ /// If the CtxI is NOT specified this method only looks at the instruction
+ /// itself and its operands, so if this method returns true, it is safe to
+ /// move the instruction as long as the correct dominance relationships for
+ /// the operands and users hold.
+ ///
+ /// This method can return true for instructions that read memory;
+ /// for such instructions, moving them may change the resulting value.
+ bool isSafeToSpeculativelyExecute(const Value *V,
+ const Instruction *CtxI = nullptr,
+ const DominatorTree *DT = nullptr,
+ const TargetLibraryInfo *TLI = nullptr);
+
+ /// isKnownNonNull - Return true if this pointer couldn't possibly be null by
+ /// its definition. This returns true for allocas, non-extern-weak globals
+ /// and byval arguments.
+ bool isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI = nullptr);
+
+ /// isKnownNonNullAt - Return true if this pointer couldn't possibly be null.
+ /// If the context instruction is specified perform context-sensitive analysis
+ /// and return true if the pointer couldn't possibly be null at the specified
+ /// instruction.
+ bool isKnownNonNullAt(const Value *V,
+ const Instruction *CtxI = nullptr,
+ const DominatorTree *DT = nullptr,
+ const TargetLibraryInfo *TLI = nullptr);
+
+ /// Return true if it is valid to use the assumptions provided by an
+ /// assume intrinsic, I, at the point in the control-flow identified by the
+ /// context instruction, CxtI.
+ bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI,
+ const DominatorTree *DT = nullptr);
+
+ enum class OverflowResult { AlwaysOverflows, MayOverflow, NeverOverflows };
+ OverflowResult computeOverflowForUnsignedMul(Value *LHS, Value *RHS,
+ const DataLayout &DL,
+ AssumptionCache *AC,
+ const Instruction *CxtI,
+ const DominatorTree *DT);
+ OverflowResult computeOverflowForUnsignedAdd(Value *LHS, Value *RHS,
+ const DataLayout &DL,
+ AssumptionCache *AC,
+ const Instruction *CxtI,
+ const DominatorTree *DT);
+
+ /// Return true if this function can prove that the instruction I will
+ /// always transfer execution to one of its successors (including the next
+ /// instruction that follows within a basic block). E.g. this is not
+ /// guaranteed for function calls that could loop infinitely.
+ ///
+ /// In other words, this function returns false for instructions that may
+ /// transfer execution or fail to transfer execution in a way that is not
+ /// captured in the CFG nor in the sequence of instructions within a basic
+ /// block.
+ ///
+ /// Undefined behavior is assumed not to happen, so e.g. division is
+ /// guaranteed to transfer execution to the following instruction even
+ /// though division by zero might cause undefined behavior.
+ bool isGuaranteedToTransferExecutionToSuccessor(const Instruction *I);
+
+ /// Return true if this function can prove that the instruction I
+ /// is executed for every iteration of the loop L.
+ ///
+ /// Note that this currently only considers the loop header.
+ bool isGuaranteedToExecuteForEveryIteration(const Instruction *I,
+ const Loop *L);
+
+ /// Return true if this function can prove that I is guaranteed to yield
+ /// full-poison (all bits poison) if at least one of its operands are
+ /// full-poison (all bits poison).
+ ///
+ /// The exact rules for how poison propagates through instructions have
+ /// not been settled as of 2015-07-10, so this function is conservative
+ /// and only considers poison to be propagated in uncontroversial
+ /// cases. There is no attempt to track values that may be only partially
+ /// poison.
+ bool propagatesFullPoison(const Instruction *I);
+
+ /// Return either nullptr or an operand of I such that I will trigger
+ /// undefined behavior if I is executed and that operand has a full-poison
+ /// value (all bits poison).
+ const Value *getGuaranteedNonFullPoisonOp(const Instruction *I);
+
+ /// Return true if this function can prove that if PoisonI is executed
+ /// and yields a full-poison value (all bits poison), then that will
+ /// trigger undefined behavior.
+ ///
+ /// Note that this currently only considers the basic block that is
+ /// the parent of I.
+ bool isKnownNotFullPoison(const Instruction *PoisonI);
+
+ /// \brief Specific patterns of select instructions we can match.
+ enum SelectPatternFlavor {
+ SPF_UNKNOWN = 0,
+ SPF_SMIN, // Signed minimum
+ SPF_UMIN, // Unsigned minimum
+ SPF_SMAX, // Signed maximum
+ SPF_UMAX, // Unsigned maximum
+ SPF_ABS, // Absolute value
+ SPF_NABS // Negated absolute value
+ };
+ /// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind
+ /// and providing the out parameter results if we successfully match.
+ ///
+ /// If CastOp is not nullptr, also match MIN/MAX idioms where the type does
+ /// not match that of the original select. If this is the case, the cast
+ /// operation (one of Trunc,SExt,Zext) that must be done to transform the
+ /// type of LHS and RHS into the type of V is returned in CastOp.
+ ///
+ /// For example:
+ /// %1 = icmp slt i32 %a, i32 4
+ /// %2 = sext i32 %a to i64
+ /// %3 = select i1 %1, i64 %2, i64 4
+ ///
+ /// -> LHS = %a, RHS = i32 4, *CastOp = Instruction::SExt
+ ///
+ SelectPatternFlavor matchSelectPattern(Value *V, Value *&LHS, Value *&RHS,
+ Instruction::CastOps *CastOp = nullptr);
+