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
24 /// ComputeMaskedBits - Determine which of the bits specified in Mask are
25 /// known to be either zero or one and return them in the KnownZero/KnownOne
26 /// bit sets. This code only analyzes bits in Mask, in order to short-circuit
28 void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero,
29 APInt &KnownOne, TargetData *TD = 0,
32 /// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
33 /// this predicate to simplify operations downstream. Mask is known to be
34 /// zero for bits that V cannot have.
35 bool MaskedValueIsZero(Value *V, const APInt &Mask,
36 TargetData *TD = 0, unsigned Depth = 0);
39 /// ComputeNumSignBits - Return the number of times the sign bit of the
40 /// register is replicated into the other bits. We know that at least 1 bit
41 /// is always equal to the sign bit (itself), but other cases can give us
42 /// information. For example, immediately after an "ashr X, 2", we know that
43 /// the top 3 bits are all equal to each other, so we return 3.
45 /// 'Op' must have a scalar integer type.
47 unsigned ComputeNumSignBits(Value *Op, TargetData *TD = 0,
50 /// CannotBeNegativeZero - Return true if we can prove that the specified FP
51 /// value is never equal to -0.0.
53 bool CannotBeNegativeZero(const Value *V, unsigned Depth = 0);
55 /// FindScalarValue - Given an aggregrate and an sequence of indices, see if
56 /// the scalar value indexed is already around as a register, for example if
57 /// it were inserted directly into the aggregrate.
59 /// If InsertBefore is not null, this function will duplicate (modified)
60 /// insertvalues when a part of a nested struct is extracted.
61 Value *FindInsertedValue(Value *V,
62 const unsigned *idx_begin,
63 const unsigned *idx_end,
64 Instruction *InsertBefore = 0);
66 /// This is a convenience wrapper for finding values indexed by a single index
68 inline Value *FindInsertedValue(Value *V, const unsigned Idx,
69 Instruction *InsertBefore = 0) {
70 const unsigned Idxs[1] = { Idx };
71 return FindInsertedValue(V, &Idxs[0], &Idxs[1], InsertBefore);
73 } // end namespace llvm