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103 lines
4.5 KiB
C++
103 lines
4.5 KiB
C++
//===- llvm/Analysis/ValueTracking.h - Walk computations --------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains routines that help analyze properties that chains of
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// computations have.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_VALUETRACKING_H
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#define LLVM_ANALYSIS_VALUETRACKING_H
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#include "llvm/System/DataTypes.h"
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#include <string>
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namespace llvm {
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class Value;
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class Instruction;
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class APInt;
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class TargetData;
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class LLVMContext;
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/// ComputeMaskedBits - Determine which of the bits specified in Mask are
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/// known to be either zero or one and return them in the KnownZero/KnownOne
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/// bit sets. This code only analyzes bits in Mask, in order to short-circuit
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/// processing.
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///
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/// This function is defined on values with integer type, values with pointer
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/// type (but only if TD is non-null), and vectors of integers. In the case
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/// where V is a vector, the mask, known zero, and known one values are the
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/// same width as the vector element, and the bit is set only if it is true
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/// for all of the elements in the vector.
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void ComputeMaskedBits(Value *V, const APInt &Mask, APInt &KnownZero,
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APInt &KnownOne, const TargetData *TD = 0,
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unsigned Depth = 0);
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/// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
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/// this predicate to simplify operations downstream. Mask is known to be
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/// zero for bits that V cannot have.
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///
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/// This function is defined on values with integer type, values with pointer
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/// type (but only if TD is non-null), and vectors of integers. In the case
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/// where V is a vector, the mask, known zero, and known one values are the
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/// same width as the vector element, and the bit is set only if it is true
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/// for all of the elements in the vector.
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bool MaskedValueIsZero(Value *V, const APInt &Mask,
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const TargetData *TD = 0, unsigned Depth = 0);
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/// ComputeNumSignBits - Return the number of times the sign bit of the
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/// register is replicated into the other bits. We know that at least 1 bit
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/// is always equal to the sign bit (itself), but other cases can give us
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/// information. For example, immediately after an "ashr X, 2", we know that
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/// the top 3 bits are all equal to each other, so we return 3.
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///
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/// 'Op' must have a scalar integer type.
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///
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unsigned ComputeNumSignBits(Value *Op, const TargetData *TD = 0,
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unsigned Depth = 0);
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/// CannotBeNegativeZero - Return true if we can prove that the specified FP
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/// value is never equal to -0.0.
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///
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bool CannotBeNegativeZero(const Value *V, unsigned Depth = 0);
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/// FindScalarValue - Given an aggregrate and an sequence of indices, see if
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/// the scalar value indexed is already around as a register, for example if
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/// it were inserted directly into the aggregrate.
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///
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/// If InsertBefore is not null, this function will duplicate (modified)
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/// insertvalues when a part of a nested struct is extracted.
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Value *FindInsertedValue(Value *V,
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const unsigned *idx_begin,
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const unsigned *idx_end,
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LLVMContext &Context,
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Instruction *InsertBefore = 0);
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/// This is a convenience wrapper for finding values indexed by a single index
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/// only.
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inline Value *FindInsertedValue(Value *V, const unsigned Idx,
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LLVMContext &Context,
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Instruction *InsertBefore = 0) {
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const unsigned Idxs[1] = { Idx };
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return FindInsertedValue(V, &Idxs[0], &Idxs[1], Context, InsertBefore);
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}
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/// GetConstantStringInfo - This function computes the length of a
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/// null-terminated C string pointed to by V. If successful, it returns true
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/// and returns the string in Str. If unsuccessful, it returns false. If
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/// StopAtNul is set to true (the default), the returned string is truncated
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/// by a nul character in the global. If StopAtNul is false, the nul
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/// character is included in the result string.
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bool GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset = 0,
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bool StopAtNul = true);
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} // end namespace llvm
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#endif
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