android / platform / prebuilts / clang / darwin-x86 / sdk / 3.5 / 031fad734623c88aa9e66c36bc426c09bff4e7e8 / . / include / llvm / Analysis / ValueTracking.h

//===- llvm/Analysis/ValueTracking.h - Walk computations --------*- C++ -*-===// | |

// | |

// The LLVM Compiler Infrastructure | |

// | |

// This file is distributed under the University of Illinois Open Source | |

// License. See LICENSE.TXT for details. | |

// | |

//===----------------------------------------------------------------------===// | |

// | |

// This file contains routines that help analyze properties that chains of | |

// computations have. | |

// | |

//===----------------------------------------------------------------------===// | |

#ifndef LLVM_ANALYSIS_VALUETRACKING_H | |

#define LLVM_ANALYSIS_VALUETRACKING_H | |

#include "llvm/ADT/ArrayRef.h" | |

#include "llvm/Support/DataTypes.h" | |

namespace llvm { | |

class Value; | |

class Instruction; | |

class APInt; | |

class DataLayout; | |

class StringRef; | |

class MDNode; | |

class TargetLibraryInfo; | |

/// Determine which bits of V are known to be either zero or one and return | |

/// them in the KnownZero/KnownOne bit sets. | |

/// | |

/// This function is defined on values with integer type, values with pointer | |

/// type (but only if TD is non-null), and vectors of integers. In the case | |

/// where V is a vector, the known zero and known one values are the | |

/// same width as the vector element, and the bit is set only if it is true | |

/// for all of the elements in the vector. | |

void computeKnownBits(Value *V, APInt &KnownZero, APInt &KnownOne, | |

const DataLayout *TD = nullptr, unsigned Depth = 0); | |

/// Compute known bits from the range metadata. | |

/// \p KnownZero the set of bits that are known to be zero | |

void computeKnownBitsFromRangeMetadata(const MDNode &Ranges, | |

APInt &KnownZero); | |

/// ComputeSignBit - Determine whether the sign bit is known to be zero or | |

/// one. Convenience wrapper around computeKnownBits. | |

void ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne, | |

const DataLayout *TD = nullptr, unsigned Depth = 0); | |

/// isKnownToBeAPowerOfTwo - Return true if the given value is known to have | |

/// exactly one bit set when defined. For vectors return true if every | |

/// element is known to be a power of two when defined. Supports values with | |

/// integer or pointer type and vectors of integers. If 'OrZero' is set then | |

/// returns true if the given value is either a power of two or zero. | |

bool isKnownToBeAPowerOfTwo(Value *V, bool OrZero = false, unsigned Depth = 0); | |

/// isKnownNonZero - Return true if the given value is known to be non-zero | |

/// when defined. For vectors return true if every element is known to be | |

/// non-zero when defined. Supports values with integer or pointer type and | |

/// vectors of integers. | |

bool isKnownNonZero(Value *V, const DataLayout *TD = nullptr, | |

unsigned Depth = 0); | |

/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use | |

/// this predicate to simplify operations downstream. Mask is known to be | |

/// zero for bits that V cannot have. | |

/// | |

/// This function is defined on values with integer type, values with pointer | |

/// type (but only if TD is non-null), and vectors of integers. In the case | |

/// where V is a vector, the mask, known zero, and known one values are the | |

/// same width as the vector element, and the bit is set only if it is true | |

/// for all of the elements in the vector. | |

bool MaskedValueIsZero(Value *V, const APInt &Mask, | |

const DataLayout *TD = nullptr, unsigned Depth = 0); | |

/// ComputeNumSignBits - Return the number of times the sign bit of the | |

/// register is replicated into the other bits. We know that at least 1 bit | |

/// is always equal to the sign bit (itself), but other cases can give us | |

/// information. For example, immediately after an "ashr X, 2", we know that | |

/// the top 3 bits are all equal to each other, so we return 3. | |

/// | |

/// 'Op' must have a scalar integer type. | |

/// | |

unsigned ComputeNumSignBits(Value *Op, const DataLayout *TD = nullptr, | |

unsigned Depth = 0); | |

/// ComputeMultiple - This function computes the integer multiple of Base that | |

/// equals V. If successful, it returns true and returns the multiple in | |

/// Multiple. If unsuccessful, it returns false. Also, if V can be | |

/// simplified to an integer, then the simplified V is returned in Val. Look | |

/// through sext only if LookThroughSExt=true. | |

bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple, | |

bool LookThroughSExt = false, | |

unsigned Depth = 0); | |

/// CannotBeNegativeZero - Return true if we can prove that the specified FP | |

/// value is never equal to -0.0. | |

/// | |

bool CannotBeNegativeZero(const Value *V, unsigned Depth = 0); | |

/// isBytewiseValue - If the specified value can be set by repeating the same | |

/// byte in memory, return the i8 value that it is represented with. This is | |

/// true for all i8 values obviously, but is also true for i32 0, i32 -1, | |

/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated | |

/// byte store (e.g. i16 0x1234), return null. | |

Value *isBytewiseValue(Value *V); | |

/// FindInsertedValue - Given an aggregrate and an sequence of indices, see if | |

/// the scalar value indexed is already around as a register, for example if | |

/// it were inserted directly into the aggregrate. | |

/// | |

/// If InsertBefore is not null, this function will duplicate (modified) | |

/// insertvalues when a part of a nested struct is extracted. | |

Value *FindInsertedValue(Value *V, | |

ArrayRef<unsigned> idx_range, | |

Instruction *InsertBefore = nullptr); | |

/// GetPointerBaseWithConstantOffset - Analyze the specified pointer to see if | |

/// it can be expressed as a base pointer plus a constant offset. Return the | |

/// base and offset to the caller. | |

Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, | |

const DataLayout *TD); | |

static inline const Value * | |

GetPointerBaseWithConstantOffset(const Value *Ptr, int64_t &Offset, | |

const DataLayout *TD) { | |

return GetPointerBaseWithConstantOffset(const_cast<Value*>(Ptr), Offset,TD); | |

} | |

/// getConstantStringInfo - This function computes the length of a | |

/// null-terminated C string pointed to by V. If successful, it returns true | |

/// 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 *TD = nullptr, | |

unsigned MaxLookup = 6); | |

static inline const Value * | |

GetUnderlyingObject(const Value *V, const DataLayout *TD = nullptr, | |

unsigned MaxLookup = 6) { | |

return GetUnderlyingObject(const_cast<Value *>(V), TD, MaxLookup); | |

} | |

/// GetUnderlyingObjects - This method is similar to GetUnderlyingObject | |

/// except that it can look through phi and select instructions and return | |

/// multiple objects. | |

void GetUnderlyingObjects(Value *V, | |

SmallVectorImpl<Value *> &Objects, | |

const DataLayout *TD = nullptr, | |

unsigned MaxLookup = 6); | |

/// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer | |

/// are lifetime markers. | |

bool onlyUsedByLifetimeMarkers(const Value *V); | |

/// 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. | |

/// | |

/// 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. | |

/// However, 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 DataLayout *TD = 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); | |

} // end namespace llvm | |

#endif |