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https://github.com/RPCS3/llvm-mirror.git
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1add31cc93
into Analysis as a standalone function, since there's no need for it to be in VMCore. Also, update it to use isKnownNonZero and other goodies available in Analysis, making it more precise, enabling more aggressive optimization. llvm-svn: 146610
183 lines
9.0 KiB
C++
183 lines
9.0 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/ADT/ArrayRef.h"
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#include "llvm/Support/DataTypes.h"
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#include <string>
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namespace llvm {
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template <typename T> class SmallVectorImpl;
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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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/// 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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/// ComputeSignBit - Determine whether the sign bit is known to be zero or
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/// one. Convenience wrapper around ComputeMaskedBits.
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void ComputeSignBit(Value *V, bool &KnownZero, bool &KnownOne,
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const TargetData *TD = 0, unsigned Depth = 0);
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/// isPowerOfTwo - Return true if the given value is known to have exactly one
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/// bit set when defined. For vectors return true if every element is known to
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/// be a power of two when defined. Supports values with integer or pointer
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/// type and vectors of integers. If 'OrZero' is set then returns true if the
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/// given value is either a power of two or zero.
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bool isPowerOfTwo(Value *V, const TargetData *TD = 0, bool OrZero = false,
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unsigned Depth = 0);
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/// isKnownNonZero - Return true if the given value is known to be non-zero
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/// when defined. For vectors return true if every element is known to be
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/// non-zero when defined. Supports values with integer or pointer type and
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/// vectors of integers.
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bool isKnownNonZero(Value *V, const TargetData *TD = 0, 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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/// ComputeMultiple - This function computes the integer multiple of Base that
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/// equals V. If successful, it returns true and returns the multiple in
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/// Multiple. If unsuccessful, it returns false. Also, if V can be
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/// simplified to an integer, then the simplified V is returned in Val. Look
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/// through sext only if LookThroughSExt=true.
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bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
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bool LookThroughSExt = false,
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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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/// isBytewiseValue - If the specified value can be set by repeating the same
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/// byte in memory, return the i8 value that it is represented with. This is
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/// true for all i8 values obviously, but is also true for i32 0, i32 -1,
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/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated
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/// byte store (e.g. i16 0x1234), return null.
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Value *isBytewiseValue(Value *V);
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/// FindInsertedValue - 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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ArrayRef<unsigned> idx_range,
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Instruction *InsertBefore = 0);
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/// GetPointerBaseWithConstantOffset - Analyze the specified pointer to see if
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/// it can be expressed as a base pointer plus a constant offset. Return the
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/// base and offset to the caller.
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Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
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const TargetData &TD);
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static inline const Value *
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GetPointerBaseWithConstantOffset(const Value *Ptr, int64_t &Offset,
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const TargetData &TD) {
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return GetPointerBaseWithConstantOffset(const_cast<Value*>(Ptr), Offset,TD);
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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(const Value *V, std::string &Str,
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uint64_t Offset = 0,
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bool StopAtNul = true);
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/// GetStringLength - If we can compute the length of the string pointed to by
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/// the specified pointer, return 'len+1'. If we can't, return 0.
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uint64_t GetStringLength(Value *V);
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/// GetUnderlyingObject - This method strips off any GEP address adjustments
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/// and pointer casts from the specified value, returning the original object
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/// being addressed. Note that the returned value has pointer type if the
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/// specified value does. If the MaxLookup value is non-zero, it limits the
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/// number of instructions to be stripped off.
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Value *GetUnderlyingObject(Value *V, const TargetData *TD = 0,
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unsigned MaxLookup = 6);
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static inline const Value *
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GetUnderlyingObject(const Value *V, const TargetData *TD = 0,
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unsigned MaxLookup = 6) {
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return GetUnderlyingObject(const_cast<Value *>(V), TD, MaxLookup);
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}
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/// onlyUsedByLifetimeMarkers - Return true if the only users of this pointer
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/// are lifetime markers.
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bool onlyUsedByLifetimeMarkers(const Value *V);
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/// isSafeToSpeculativelyExecute - Return true if the instruction does not
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/// have any effects besides calculating the result and does not have
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/// undefined behavior.
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///
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/// This method never returns true for an instruction that returns true for
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/// mayHaveSideEffects; however, this method also does some other checks in
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/// addition. It checks for undefined behavior, like dividing by zero or
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/// loading from an invalid pointer (but not for undefined results, like a
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/// shift with a shift amount larger than the width of the result). It checks
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/// for malloc and alloca because speculatively executing them might cause a
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/// memory leak. It also returns false for instructions related to control
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/// flow, specifically terminators and PHI nodes.
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///
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/// This method only looks at the instruction itself and its operands, so if
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/// this method returns true, it is safe to move the instruction as long as
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/// the correct dominance relationships for the operands and users hold.
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/// However, this method can return true for instructions that read memory;
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/// for such instructions, moving them may change the resulting value.
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bool isSafeToSpeculativelyExecute(const Instruction *Inst,
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const TargetData *TD = 0);
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} // end namespace llvm
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#endif
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