| //===- 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. |
| void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero, |
| APInt &KnownOne, 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. |
| bool MaskedValueIsZero(Value *V, const APInt &Mask, |
| 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, 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 |