103 lines
4.5 KiB
C++
103 lines
4.5 KiB
C++
//===- 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/Support/DataTypes.h"
|
|
#include <string>
|
|
|
|
namespace llvm {
|
|
class Value;
|
|
class Instruction;
|
|
class APInt;
|
|
class TargetData;
|
|
class LLVMContext;
|
|
|
|
/// ComputeMaskedBits - Determine which of the bits specified in Mask are
|
|
/// known to be either zero or one and return them in the KnownZero/KnownOne
|
|
/// bit sets. This code only analyzes bits in Mask, in order to short-circuit
|
|
/// processing.
|
|
///
|
|
/// 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.
|
|
void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero,
|
|
APInt &KnownOne, const TargetData *TD = 0,
|
|
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 TargetData *TD = 0, 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 TargetData *TD = 0,
|
|
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);
|
|
|
|
/// FindScalarValue - 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,
|
|
const unsigned *idx_begin,
|
|
const unsigned *idx_end,
|
|
LLVMContext &Context,
|
|
Instruction *InsertBefore = 0);
|
|
|
|
/// This is a convenience wrapper for finding values indexed by a single index
|
|
/// only.
|
|
inline Value *FindInsertedValue(Value *V, const unsigned Idx,
|
|
LLVMContext &Context,
|
|
Instruction *InsertBefore = 0) {
|
|
const unsigned Idxs[1] = { Idx };
|
|
return FindInsertedValue(V, &Idxs[0], &Idxs[1], Context, InsertBefore);
|
|
}
|
|
|
|
/// 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. If
|
|
/// StopAtNul is set to true (the default), the returned string is truncated
|
|
/// by a nul character in the global. If StopAtNul is false, the nul
|
|
/// character is included in the result string.
|
|
bool GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset = 0,
|
|
bool StopAtNul = true);
|
|
} // end namespace llvm
|
|
|
|
#endif
|