1 //===- llvm/Analysis/ValueTracking.h - Walk computations --------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains routines that help analyze properties that chains of
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ANALYSIS_VALUETRACKING_H
16 #define LLVM_ANALYSIS_VALUETRACKING_H
18 #include "llvm/Support/DataTypes.h"
27 /// ComputeMaskedBits - Determine which of the bits specified in Mask are
28 /// known to be either zero or one and return them in the KnownZero/KnownOne
29 /// bit sets. This code only analyzes bits in Mask, in order to short-circuit
31 void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero,
32 APInt &KnownOne, TargetData *TD = 0,
35 /// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
36 /// this predicate to simplify operations downstream. Mask is known to be
37 /// zero for bits that V cannot have.
38 bool MaskedValueIsZero(Value *V, const APInt &Mask,
39 TargetData *TD = 0, unsigned Depth = 0);
42 /// ComputeNumSignBits - Return the number of times the sign bit of the
43 /// register is replicated into the other bits. We know that at least 1 bit
44 /// is always equal to the sign bit (itself), but other cases can give us
45 /// information. For example, immediately after an "ashr X, 2", we know that
46 /// the top 3 bits are all equal to each other, so we return 3.
48 /// 'Op' must have a scalar integer type.
50 unsigned ComputeNumSignBits(Value *Op, TargetData *TD = 0,
53 /// CannotBeNegativeZero - Return true if we can prove that the specified FP
54 /// value is never equal to -0.0.
56 bool CannotBeNegativeZero(const Value *V, unsigned Depth = 0);
58 /// FindScalarValue - Given an aggregrate and an sequence of indices, see if
59 /// the scalar value indexed is already around as a register, for example if
60 /// it were inserted directly into the aggregrate.
62 /// If InsertBefore is not null, this function will duplicate (modified)
63 /// insertvalues when a part of a nested struct is extracted.
64 Value *FindInsertedValue(Value *V,
65 const unsigned *idx_begin,
66 const unsigned *idx_end,
67 Instruction *InsertBefore = 0);
69 /// This is a convenience wrapper for finding values indexed by a single index
71 inline Value *FindInsertedValue(Value *V, const unsigned Idx,
72 Instruction *InsertBefore = 0) {
73 const unsigned Idxs[1] = { Idx };
74 return FindInsertedValue(V, &Idxs[0], &Idxs[1], InsertBefore);
77 /// GetConstantStringInfo - This function computes the length of a
78 /// null-terminated C string pointed to by V. If successful, it returns true
79 /// and returns the string in Str. If unsuccessful, it returns false. If
80 /// StopAtNul is set to true (the default), the returned string is truncated
81 /// by a nul character in the global. If StopAtNul is false, the nul
82 /// character is included in the result string.
83 bool GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset = 0,
84 bool StopAtNul = true);
85 } // end namespace llvm