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valuenum.h
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valuenum.h
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// Defines the class "ValueNumStore", which maintains value numbers for a compilation.
// Recall that "value numbering" assigns an integer value number to each expression. The "value
// number property" is that two expressions with the same value number will evaluate to the same value
// at runtime. Expressions with different value numbers may or may not be equivalent. This property
// of value numbers has obvious applications in redundancy-elimination optimizations.
//
// Since value numbers give us a way of talking about the (immutable) values to which expressions
// evaluate, they provide a good "handle" to use for attributing properties to values. For example,
// we might note that some value number represents some particular integer constant -- which has obvious
// application to constant propagation. Or that we know the exact type of some object reference,
// which might be used in devirtualization.
//
// Finally, we will also use value numbers to express control-flow-dependent assertions. Some test may
// imply that after the test, something new is known about a value: that an object reference is non-null
// after a dereference (since control flow continued because no exception was thrown); that an integer
// value is restricted to some subrange in after a comparison test; etc.
// In addition to classical numbering, this implementation also performs disambiguation of heap writes,
// using memory SSA and the following aliasing model:
//
// 1. Arrays of different types do not alias - taking into account the array compatibility rules, i. e.
// "int[] <-> uint[]" and such being allowed.
// 2. Different static fields do not alias (meaning mutable overlapping RVA statics are not supported).
// 3. Different class fields do not alias. Struct fields are allowed to alias - this supports code that
// does reinterpretation of structs (e. g. "Unsafe.As<StructOne, StructTwo>(...)"), but makes it UB
// to alias reference types in the same manner (including via explicit layout).
//
// The no aliasing rule for fields should be interpreted to mean that "ld[s]fld[a] FieldOne" cannot refer
// to the same location as "ld[s]fld[a] FieldTwo". The aliasing model above reflects the fact type safety
// rules in .NET largely only apply to reference types, while struct locations can be and often are treated
// by user code (and, importantly, the compiler itself) as simple blobs of bytes.
//
// Abstractly, numbering maintains states of memory in "maps", which are indexed into with various "selectors",
// loads reading from said maps and stores recording new states for them (note that as with everything VN,
// the "maps" are immutable, thus an update is performed via deriving a new map from an existing one).
//
// Due to the fact we allow struct field access to alias, but still want to optimize it, our model has two
// types of maps and selectors: precise and physical. Precise maps allow arbitrary selectors, and if those
// are known to be distinct values (e. g. different constants), the values they select are also presumed to
// represent distinct locations. Physical maps, on the other hand, can only have one type of selector: "the
// physical selector", representing offset of the location and its size (in bytes), where both must be known
// at compile time. Naturally, different physical selectors can refer to overlapping locations.
//
// The following "VNFunc"s are relevant when it comes to map numbering:
//
// 1. "MapSelect" - represents a "value" taken from another map at a given index: "map[index] => value". It is
// the "VNForMapSelect[Work]" method that represents the core of the selection infrastructure: it performs
// various reductions based on the maps (listed below) being selected from, before "giving up" and creating
// a new "MapSelect" VN. "MapSelect"s are used for both precise and physical maps.
// 2. "Phi[Memory]Def" - the PHI function applied to multiple reaching definitions for a given block. PHIs can
// be reduced by the selection process: "Phi(d:1, d:2, ...)[index]" is evaluated as "Phi(d:1[index], ...)",
// so if all the inner selections ("d:n[index]") agree, that value is returned as the selected one.
// 3. "MapStore" - this is the precise "update" map, it represents a map after a "set" operation at some index.
// MapStore VNs naturally "chain" together, the next map representing an update of the previous, and will be
// traversed by the selection process as long as the store indices are constant, and different from the one
// being selected (meaning they represent distinct locations): "map[F0 := V0][F1 := V1][F0]" => "V0".
// 4. "MapPhysicalStore" - the physical equivalent to "MapStore", can only be indexed with physical selectors,
// with the selection rules taking into account aliasability of physical locations.
// 5. "BitCast" - the physical map representing "identity" selection ("map[0:sizeof(map) - 1]"). Exists because
// physical maps themselves do not have a strong type identity (the physical selector only cares about size).
// but the VN/IR at large do. Is a no-op in the selection process. One can notice that we could have chosen
// to represent this concept with an identity "MapPhysicalStore", however, a different "VNFunc" was ultimately
// chosen due to it being easier to reason about and a little cheaper, with the expectation that "BitCast"s
// would be reasonably common - the scenario they are meant to handle are stores/loads to/from structs with
// one field, where the location can be referenced from the IR as both TYP_STRUCT and the field's type.
//
// We give "placeholder" types (TYP_UNDEF and TYP_UNKNOWN as TYP_MEM and TYP_HEAP) to maps that do not represent
// values found in IR, which are currently all precise (though that is not a requirement of the model).
//
// We choose to maintain the following invariants with regards to types of physical locations:
//
// 1. Tree VNs are always "normalized on load" - their types are made to match (via bitcasts). We presume this
// makes the rest of the compiler code simpler, as it will not have to reason about "TYP_INT" trees having
// "TYP_FLOAT" value numbers. This normalization is currently not always done; that should be fixed.
// 2. Types of locals are "normalized on store" - this is different from the rest of physical locations, as not
// only VN looks at these value numbers (stored in SSA descriptors), and similar to the tree case, we presume
// it is simpler to reason about matching types.
// 3. Types of all other locations (array elements and fields) are not normalized - these only appear in the VN
// itself as physical maps / values.
//
// Note as well how we handle type identity for structs: we canonicalize on their size. This has the significant
// consequence that any two equally-sized structs can be given the same value number, even if they have different
// ABI characteristics or GC layout. The primary motivations for this are throughout and simplicity, however, we
// would also like the compiler at large to treat structs with compatible layouts as equivalent, so that we can
// propagate copies between them freely.
//
//
// Let's review the following snippet to demonstrate how the MapSelect/MapStore machinery works. Say we have this
// snippet of (C#) code:
//
// int Procedure(OneClass obj, AnotherClass subj, int objVal, int subjVal)
// {
// obj.StructField.ScalarField = objVal;
// subj.OtherScalarField = subjVal;
//
// return obj.StructField.ScalarField + subj.OtherScalarField;
// }
//
// On entry, we assign some VN to the GcHeap (VN mostly only cares about GcHeap, so from now on the term "heap"
// will be used to mean GcHeap), $Heap.
//
// A store to the ScalarField is seen. Now, the value numbering of fields is done in the following pattern for
// maps that it builds: [$Heap][$FirstField][$Object][offset:offset + size of the store]. It may seem odd that
// the indexing is done first for the field, and only then for the object, but the reason for that is the fact
// that it enables MapStores to $Heap to refer to distinct selectors, thus enabling the traversal through the
// map updates when looking for the values that were stored. Were $Object VNs used for this, the traversal could
// not be performed, as two numerically different VNs can, obviously, refer to the same object.
//
// With that in mind, the following maps are first built for the store ("field VNs" - VNs for handles):
//
// $StructFieldMap = MapSelect($Heap, $StructField)
// $StructFieldForObjMap = MapSelect($StructFieldMap, $Obj)
//
// Now that we know where to store, the store maps are built:
//
// $ScalarFieldSelector = PhysicalSelector(offsetof(ScalarField), sizeof(ScalarField))
// $NewStructFieldForObjMap = MapPhysicalStore($StructFieldForObjMap, $ScalarFieldSelector, $ObjVal)
// $NewStructFieldMap = MapStore($StructFieldMap, $Obj, $NewStructFieldForObjMap)
// $NewHeap = MapStore($Heap, $StructField, $NewStructFieldMap)
//
// Notice that the maps are built in the opposite order, as we must first know the value of the "narrower" map to
// store into the "wider" map.
//
// Similarly, the numbering is performed for "subj.OtherScalarField = subjVal", and the heap state updated (say to
// $NewHeapWithSubj). Now when we call "VNForMapSelect" to find out the stored values when numbering the reads, the
// following traversal is performed:
//
// $obj.StructField.AnotherStructField.ScalarField
// = $NewHeapWithSubj[$StructField][$Obj][$ScalarFieldSelector]:
// "$NewHeapWithSubj.Index == $StructField" => false (not the needed map).
// "IsConst($NewHeapWithSubj.Index) && IsConst($StructField)" => true (can continue, non-aliasing indices).
// "$NewHeap.Index == $StructField" => true, Value is $NewStructFieldMap.
// "$NewStructFieldMap.Index == $Obj" => true, Value is $NewStructFieldForObjMap.
// "$NewStructFieldForObjMap.Index == $ScalarFieldSelector" => true, Value is $ObjVal (found it!).
//
// And similarly for the $SubjVal - we end up with a nice $Add($ObjVal, $SubjVal) feeding the return.
//
// While the above example focuses on fields, the idea is universal to all supported location types. Statics are
// modeled as straight indices into the heap (MapSelect($Heap, $Field) returns the value of the field for them),
// arrays - like fields, but with the primiary selector being not the first field, but the "equivalence class" of
// an array, i. e. the type of its elements, taking into account things like "int[]" being legally aliasable as
// "uint[]". Physical maps are used to number local fields.
/*****************************************************************************/
#ifndef _VALUENUM_H_
#define _VALUENUM_H_
/*****************************************************************************/
#include "vartype.h"
// For "GT_COUNT"
#include "gentree.h"
// Defines the type ValueNum.
#include "valuenumtype.h"
// Defines the type SmallHashTable.
#include "smallhash.h"
// A "ValueNumStore" represents the "universe" of value numbers used in a single
// compilation.
// All members of the enumeration genTreeOps are also members of VNFunc.
// (Though some of these may be labeled "illegal").
enum VNFunc
{
// Implicitly, elements of genTreeOps here.
VNF_Boundary = GT_COUNT,
#define ValueNumFuncDef(nm, arity, commute, knownNonNull, sharedStatic, extra) VNF_##nm,
#include "valuenumfuncs.h"
VNF_COUNT
};
// Given a GenTree node return the VNFunc that should be used when value numbering
//
VNFunc GetVNFuncForNode(GenTree* node);
// An instance of this struct represents an application of the function symbol
// "m_func" to the first "m_arity" (<= 4) argument values in "m_args."
struct VNFuncApp
{
VNFunc m_func;
unsigned m_arity;
ValueNum* m_args;
bool Equals(const VNFuncApp& funcApp)
{
if (m_func != funcApp.m_func)
{
return false;
}
if (m_arity != funcApp.m_arity)
{
return false;
}
for (unsigned i = 0; i < m_arity; i++)
{
if (m_args[i] != funcApp.m_args[i])
{
return false;
}
}
return true;
}
};
// We use a unique prefix character when printing value numbers in dumps: i.e. $1c0
// This define is used with string concatenation to put this in printf format strings
#define FMT_VN "$%x"
// We will use this placeholder type for memory maps that do not represent IR values ("field maps", etc).
static const var_types TYP_MEM = TYP_UNDEF;
// We will use this placeholder type for memory maps representing "the heap" (GcHeap/ByrefExposed).
static const var_types TYP_HEAP = TYP_UNKNOWN;
class ValueNumStore
{
public:
// We will reserve "max unsigned" to represent "not a value number", for maps that might start uninitialized.
static const ValueNum NoVN = UINT32_MAX;
// A second special value, used to indicate that a function evaluation would cause infinite recursion.
static const ValueNum RecursiveVN = UINT32_MAX - 1;
// Special value used to represent something that isn't in a loop for VN functions that take loop parameters.
static const unsigned NoLoop = UINT32_MAX;
// Special value used to represent something that may or may not be in a loop, so needs to be handled
// conservatively.
static const unsigned UnknownLoop = UINT32_MAX - 1;
// ==================================================================================================
// VNMap - map from something to ValueNum, where something is typically a constant value or a VNFunc
// This class has two purposes - to abstract the implementation and to validate the ValueNums
// being stored or retrieved.
template <class fromType, class keyfuncs = JitLargePrimitiveKeyFuncs<fromType>>
class VNMap : public JitHashTable<fromType, keyfuncs, ValueNum>
{
public:
VNMap(CompAllocator alloc)
: JitHashTable<fromType, keyfuncs, ValueNum>(alloc)
{
}
bool Set(fromType k, ValueNum val)
{
assert(val != RecursiveVN);
return JitHashTable<fromType, keyfuncs, ValueNum>::Set(k, val);
}
bool Lookup(fromType k, ValueNum* pVal = nullptr) const
{
bool result = JitHashTable<fromType, keyfuncs, ValueNum>::Lookup(k, pVal);
assert(!result || *pVal != RecursiveVN);
return result;
}
};
private:
Compiler* m_pComp;
// For allocations. (Other things?)
CompAllocator m_alloc;
// TODO-Cleanup: should transform "attribs" into a struct with bit fields. That would be simpler...
enum VNFOpAttrib
{
VNFOA_IllegalGenTreeOp = 0x1, // corresponds to a genTreeOps value that is not a legal VN func.
VNFOA_Commutative = 0x2, // 1 iff the function is commutative.
VNFOA_Arity1 = 0x4, // Bits 2,3,4 encode the arity.
VNFOA_Arity2 = 0x8, // Bits 2,3,4 encode the arity.
VNFOA_Arity4 = 0x10, // Bits 2,3,4 encode the arity.
VNFOA_KnownNonNull = 0x20, // 1 iff the result is known to be non-null.
VNFOA_SharedStatic = 0x40, // 1 iff this VNF is represent one of the shared static jit helpers
};
static const unsigned VNFOA_IllegalGenTreeOpShift = 0;
static const unsigned VNFOA_CommutativeShift = 1;
static const unsigned VNFOA_ArityShift = 2;
static const unsigned VNFOA_ArityBits = 3;
static const unsigned VNFOA_MaxArity = (1 << VNFOA_ArityBits) - 1; // Max arity we can represent.
static const unsigned VNFOA_ArityMask = (VNFOA_Arity4 | VNFOA_Arity2 | VNFOA_Arity1);
static const unsigned VNFOA_KnownNonNullShift = 5;
static const unsigned VNFOA_SharedStaticShift = 6;
static_assert_no_msg(unsigned(VNFOA_IllegalGenTreeOp) == (1 << VNFOA_IllegalGenTreeOpShift));
static_assert_no_msg(unsigned(VNFOA_Commutative) == (1 << VNFOA_CommutativeShift));
static_assert_no_msg(unsigned(VNFOA_Arity1) == (1 << VNFOA_ArityShift));
static_assert_no_msg(VNFOA_ArityMask == (VNFOA_MaxArity << VNFOA_ArityShift));
static_assert_no_msg(unsigned(VNFOA_KnownNonNull) == (1 << VNFOA_KnownNonNullShift));
static_assert_no_msg(unsigned(VNFOA_SharedStatic) == (1 << VNFOA_SharedStaticShift));
// These enum constants are used to encode the cast operation in the lowest bits by VNForCastOper
enum VNFCastAttrib
{
VCA_UnsignedSrc = 0x01,
VCA_BitCount = 1, // the number of reserved bits
VCA_ReservedBits = 0x01, // i.e. (VCA_UnsignedSrc)
};
// Helpers and an array of length GT_COUNT, mapping genTreeOp values to their VNFOpAttrib.
static constexpr uint8_t GetOpAttribsForArity(genTreeOps oper, GenTreeOperKind kind);
static constexpr uint8_t GetOpAttribsForGenTree(genTreeOps oper,
bool commute,
bool illegalAsVNFunc,
GenTreeOperKind kind);
static constexpr uint8_t GetOpAttribsForFunc(int arity, bool commute, bool knownNonNull, bool sharedStatic);
static const uint8_t s_vnfOpAttribs[];
// Returns "true" iff gtOper is a legal value number function.
// (Requires InitValueNumStoreStatics to have been run.)
static bool GenTreeOpIsLegalVNFunc(genTreeOps gtOper);
// Returns "true" iff "vnf" is a commutative (and thus binary) operator.
// (Requires InitValueNumStoreStatics to have been run.)
static bool VNFuncIsCommutative(VNFunc vnf);
bool VNEvalCanFoldBinaryFunc(var_types type, VNFunc func, ValueNum arg0VN, ValueNum arg1VN);
bool VNEvalCanFoldUnaryFunc(var_types type, VNFunc func, ValueNum arg0VN);
// Returns "true" iff "vnf" should be folded by evaluating the func with constant arguments.
bool VNEvalShouldFold(var_types typ, VNFunc func, ValueNum arg0VN, ValueNum arg1VN);
// Value number a type comparison
ValueNum VNEvalFoldTypeCompare(var_types type, VNFunc func, ValueNum arg0VN, ValueNum arg1VN);
// return vnf(v0)
template <typename T>
static T EvalOp(VNFunc vnf, T v0);
// returns vnf(v0, v1).
template <typename T>
T EvalOp(VNFunc vnf, T v0, T v1);
// return vnf(v0) or vnf(v0, v1), respectively (must, of course be unary/binary ops, respectively.)
template <typename T>
static T EvalOpSpecialized(VNFunc vnf, T v0);
template <typename T>
T EvalOpSpecialized(VNFunc vnf, T v0, T v1);
template <typename T>
static int EvalComparison(VNFunc vnf, T v0, T v1);
// Should only instantiate (in a non-trivial way) for "int" and "INT64". Returns true iff dividing "v0" by "v1"
// would produce integer overflow (an ArithmeticException -- *not* division by zero, which is separate.)
template <typename T>
static bool IsOverflowIntDiv(T v0, T v1);
// Should only instantiate (in a non-trivial way) for integral types (signed/unsigned int32/int64).
// Returns true iff v is the zero of the appropriate type.
template <typename T>
static bool IsIntZero(T v);
public:
// Given an constant value number return its value.
int GetConstantInt32(ValueNum argVN);
INT64 GetConstantInt64(ValueNum argVN);
double GetConstantDouble(ValueNum argVN);
float GetConstantSingle(ValueNum argVN);
#if defined(FEATURE_SIMD)
simd8_t GetConstantSimd8(ValueNum argVN);
simd12_t GetConstantSimd12(ValueNum argVN);
simd16_t GetConstantSimd16(ValueNum argVN);
#if defined(TARGET_XARCH)
simd32_t GetConstantSimd32(ValueNum argVN);
simd64_t GetConstantSimd64(ValueNum argVN);
simdmask_t GetConstantSimdMask(ValueNum argVN);
#endif // TARGET_XARCH
#endif // FEATURE_SIMD
private:
// Assumes that all the ValueNum arguments of each of these functions have been shown to represent constants.
// Assumes that "vnf" is a operator of the appropriate arity (unary for the first, binary for the second).
// Assume that "CanEvalForConstantArgs(vnf)" is true.
// Returns the result of evaluating the function with those constant arguments.
ValueNum EvalFuncForConstantArgs(var_types typ, VNFunc vnf, ValueNum vn0);
ValueNum EvalFuncForConstantArgs(var_types typ, VNFunc vnf, ValueNum vn0, ValueNum vn1);
ValueNum EvalFuncForConstantFPArgs(var_types typ, VNFunc vnf, ValueNum vn0, ValueNum vn1);
ValueNum EvalCastForConstantArgs(var_types typ, VNFunc vnf, ValueNum vn0, ValueNum vn1);
ValueNum EvalBitCastForConstantArgs(var_types dstType, ValueNum arg0VN);
ValueNum EvalUsingMathIdentity(var_types typ, VNFunc vnf, ValueNum vn0, ValueNum vn1);
// This is the constant value used for the default value of m_mapSelectBudget
#define DEFAULT_MAP_SELECT_BUDGET 100 // used by JitVNMapSelBudget
// This is the maximum number of MapSelect terms that can be "considered" as part of evaluation of a top-level
// MapSelect application.
int m_mapSelectBudget;
template <typename T, typename NumMap>
inline ValueNum VnForConst(T cnsVal, NumMap* numMap, var_types varType);
// returns true iff vn is known to be a constant int32 that is > 0
bool IsVNPositiveInt32Constant(ValueNum vn);
public:
// Validate that the new initializer for s_vnfOpAttribs matches the old code.
static void ValidateValueNumStoreStatics();
// Initialize an empty ValueNumStore.
ValueNumStore(Compiler* comp, CompAllocator allocator);
// Returns "true" iff "vnf" (which may have been created by a cast from an integral value) represents
// a legal value number function.
// (Requires InitValueNumStoreStatics to have been run.)
static bool VNFuncIsLegal(VNFunc vnf)
{
return unsigned(vnf) > VNF_Boundary || GenTreeOpIsLegalVNFunc(static_cast<genTreeOps>(vnf));
}
// Returns "true" iff "vnf" is one of:
// VNF_ADD_OVF, VNF_SUB_OVF, VNF_MUL_OVF,
// VNF_ADD_UN_OVF, VNF_SUB_UN_OVF, VNF_MUL_UN_OVF.
static bool VNFuncIsOverflowArithmetic(VNFunc vnf);
// Returns "true" iff "vnf" is VNF_Cast or VNF_CastOvf.
static bool VNFuncIsNumericCast(VNFunc vnf);
// Returns the arity of "vnf".
static unsigned VNFuncArity(VNFunc vnf);
// Requires "gtOper" to be a genTreeOps legally representing a VNFunc, and returns that
// VNFunc.
// (Requires InitValueNumStoreStatics to have been run.)
static VNFunc GenTreeOpToVNFunc(genTreeOps gtOper)
{
assert(GenTreeOpIsLegalVNFunc(gtOper));
return static_cast<VNFunc>(gtOper);
}
#ifdef DEBUG
static void RunTests(Compiler* comp);
#endif // DEBUG
// This block of methods gets value numbers for constants of primitive types.
ValueNum VNForIntCon(INT32 cnsVal);
ValueNum VNForIntPtrCon(ssize_t cnsVal);
ValueNum VNForLongCon(INT64 cnsVal);
ValueNum VNForFloatCon(float cnsVal);
ValueNum VNForDoubleCon(double cnsVal);
ValueNum VNForByrefCon(target_size_t byrefVal);
#if defined(FEATURE_SIMD)
ValueNum VNForSimd8Con(simd8_t cnsVal);
ValueNum VNForSimd12Con(simd12_t cnsVal);
ValueNum VNForSimd16Con(simd16_t cnsVal);
#if defined(TARGET_XARCH)
ValueNum VNForSimd32Con(simd32_t cnsVal);
ValueNum VNForSimd64Con(simd64_t cnsVal);
ValueNum VNForSimdMaskCon(simdmask_t cnsVal);
#endif // TARGET_XARCH
#endif // FEATURE_SIMD
ValueNum VNForGenericCon(var_types typ, uint8_t* cnsVal);
#ifdef TARGET_64BIT
ValueNum VNForPtrSizeIntCon(INT64 cnsVal)
{
return VNForLongCon(cnsVal);
}
#else
ValueNum VNForPtrSizeIntCon(INT32 cnsVal)
{
return VNForIntCon(cnsVal);
}
#endif
// Packs information about the cast into an integer constant represented by the returned value number,
// to be used as the second operand of VNF_Cast & VNF_CastOvf.
ValueNum VNForCastOper(var_types castToType, bool srcIsUnsigned);
// Unpacks the information stored by VNForCastOper in the constant represented by the value number.
void GetCastOperFromVN(ValueNum vn, var_types* pCastToType, bool* pSrcIsUnsigned);
// We keep handle values in a separate pool, so we don't confuse a handle with an int constant
// that happens to be the same...
ValueNum VNForHandle(ssize_t cnsVal, GenTreeFlags iconFlags);
void AddToEmbeddedHandleMap(ssize_t embeddedHandle, ssize_t compileTimeHandle)
{
m_embeddedToCompileTimeHandleMap.AddOrUpdate(embeddedHandle, compileTimeHandle);
}
bool EmbeddedHandleMapLookup(ssize_t embeddedHandle, ssize_t* compileTimeHandle)
{
return m_embeddedToCompileTimeHandleMap.TryGetValue(embeddedHandle, compileTimeHandle);
}
void AddToFieldAddressToFieldSeqMap(ValueNum fldAddr, FieldSeq* fldSeq)
{
m_fieldAddressToFieldSeqMap.AddOrUpdate(fldAddr, fldSeq);
}
FieldSeq* GetFieldSeqFromAddress(ValueNum fldAddr)
{
FieldSeq* fldSeq;
if (m_fieldAddressToFieldSeqMap.TryGetValue(fldAddr, &fldSeq))
{
return fldSeq;
}
return nullptr;
}
CORINFO_CLASS_HANDLE GetObjectType(ValueNum vn, bool* pIsExact, bool* pIsNonNull);
// And the single constant for an object reference type.
static ValueNum VNForNull()
{
return ValueNum(SRC_Null);
}
// A special value number for "void" -- sometimes a type-void thing is an argument,
// and we want the args to be non-NoVN.
static ValueNum VNForVoid()
{
return ValueNum(SRC_Void);
}
static ValueNumPair VNPForVoid()
{
return ValueNumPair(VNForVoid(), VNForVoid());
}
// A special value number for the empty set of exceptions.
static ValueNum VNForEmptyExcSet()
{
return ValueNum(SRC_EmptyExcSet);
}
static ValueNumPair VNPForEmptyExcSet()
{
return ValueNumPair(VNForEmptyExcSet(), VNForEmptyExcSet());
}
// Returns the value number for zero of the given "typ".
// It has an unreached() for a "typ" that has no zero value, such as TYP_VOID.
ValueNum VNZeroForType(var_types typ);
// Returns the value number for a zero-initialized struct.
ValueNum VNForZeroObj(ClassLayout* layout);
// Returns the value number for one of the given "typ".
// It returns NoVN for a "typ" that has no one value, such as TYP_REF.
ValueNum VNOneForType(var_types typ);
// Returns the value number for AllBitsSet of the given "typ".
// It has an unreached() for a "typ" that has no all bits set value, such as TYP_VOID.
ValueNum VNAllBitsForType(var_types typ);
#ifdef FEATURE_SIMD
// Returns the value number for one of the given "simdType" and "simdBaseType".
ValueNum VNOneForSimdType(var_types simdType, var_types simdBaseType);
// A helper function for constructing VNF_SimdType VNs.
ValueNum VNForSimdType(unsigned simdSize, CorInfoType simdBaseJitType);
#endif // FEATURE_SIMD
// Create or return the existimg value number representing a singleton exception set
// for the exception value "x".
ValueNum VNExcSetSingleton(ValueNum x);
ValueNumPair VNPExcSetSingleton(ValueNumPair x);
// Returns true if the current pair of items are in ascending order and they are not duplicates.
// Used to verify that exception sets are in ascending order when processing them.
bool VNCheckAscending(ValueNum item, ValueNum xs1);
// Returns the VN representing the union of the two exception sets "xs0" and "xs1".
// These must be VNForEmptyExcSet() or applications of VNF_ExcSetCons, obeying
// the ascending order invariant. (which is preserved in the result)
ValueNum VNExcSetUnion(ValueNum xs0, ValueNum xs1);
ValueNumPair VNPExcSetUnion(ValueNumPair xs0vnp, ValueNumPair xs1vnp);
// Returns the VN representing the intersection of the two exception sets "xs0" and "xs1".
// These must be applications of VNF_ExcSetCons or the empty set. (i.e VNForEmptyExcSet())
// and also must be in ascending order.
ValueNum VNExcSetIntersection(ValueNum xs0, ValueNum xs1);
ValueNumPair VNPExcSetIntersection(ValueNumPair xs0vnp, ValueNumPair xs1vnp);
// Returns true if every exception singleton in the vnCandidateSet is also present
// in the vnFullSet.
// Both arguments must be either VNForEmptyExcSet() or applications of VNF_ExcSetCons.
bool VNExcIsSubset(ValueNum vnFullSet, ValueNum vnCandidateSet);
bool VNPExcIsSubset(ValueNumPair vnpFullSet, ValueNumPair vnpCandidateSet);
// Returns "true" iff "vn" is an application of "VNF_ValWithExc".
bool VNHasExc(ValueNum vn)
{
VNFuncApp funcApp;
return GetVNFunc(vn, &funcApp) && funcApp.m_func == VNF_ValWithExc;
}
// If vn "excSet" is "VNForEmptyExcSet()" we just return "vn"
// otherwise we use VNExcSetUnion to combine the exception sets of both "vn" and "excSet"
// and return that ValueNum
ValueNum VNWithExc(ValueNum vn, ValueNum excSet);
ValueNumPair VNPWithExc(ValueNumPair vnp, ValueNumPair excSetVNP);
// This sets "*pvn" to the Normal value and sets "*pvnx" to Exception set value.
// "pvnx" represents the set of all exceptions that can happen for the expression
void VNUnpackExc(ValueNum vnWx, ValueNum* pvn, ValueNum* pvnx);
void VNPUnpackExc(ValueNumPair vnWx, ValueNumPair* pvn, ValueNumPair* pvnx);
// This returns the Union of exceptions from vnWx and vnExcSet
ValueNum VNUnionExcSet(ValueNum vnWx, ValueNum vnExcSet);
// This returns the Union of exceptions from vnpWx and vnpExcSet
ValueNumPair VNPUnionExcSet(ValueNumPair vnpWx, ValueNumPair vnpExcSet);
// Sets the normal value to a new unique ValueNum
// Keeps any Exception set values
ValueNum VNMakeNormalUnique(ValueNum vn);
// Sets the liberal & conservative
// Keeps any Exception set values
ValueNumPair VNPMakeNormalUniquePair(ValueNumPair vnp);
// A new unique value with the given exception set.
ValueNum VNUniqueWithExc(var_types type, ValueNum vnExcSet);
// A new unique VN pair with the given exception set pair.
ValueNumPair VNPUniqueWithExc(var_types type, ValueNumPair vnpExcSet);
// If "vn" is a "VNF_ValWithExc(norm, excSet)" value, returns the "norm" argument; otherwise,
// just returns "vn".
// The Normal value is the value number of the expression when no exceptions occurred
ValueNum VNNormalValue(ValueNum vn);
// Given a "vnp", get the ValueNum kind based upon vnk,
// then call VNNormalValue on that ValueNum
// The Normal value is the value number of the expression when no exceptions occurred
ValueNum VNNormalValue(ValueNumPair vnp, ValueNumKind vnk);
// Given a "vnp", get the NormalValuew for the VNK_Liberal part of that ValueNum
// The Normal value is the value number of the expression when no exceptions occurred
inline ValueNum VNLiberalNormalValue(ValueNumPair vnp)
{
return VNNormalValue(vnp, VNK_Liberal);
}
// Given a "vnp", get the NormalValuew for the VNK_Conservative part of that ValueNum
// The Normal value is the value number of the expression when no exceptions occurred
inline ValueNum VNConservativeNormalValue(ValueNumPair vnp)
{
return VNNormalValue(vnp, VNK_Conservative);
}
// Given a "vnp", get the Normal values for both the liberal and conservative parts of "vnp"
// The Normal value is the value number of the expression when no exceptions occurred
ValueNumPair VNPNormalPair(ValueNumPair vnp);
// If "vn" is a "VNF_ValWithExc(norm, excSet)" value, returns the "excSet" argument; otherwise,
// we return a special Value Number representing the empty exception set.
// The exception set value is the value number of the set of possible exceptions.
ValueNum VNExceptionSet(ValueNum vn);
ValueNumPair VNPExceptionSet(ValueNumPair vn);
// True "iff" vn is a value known to be non-null. (For example, the result of an allocation...)
bool IsKnownNonNull(ValueNum vn);
// True "iff" vn is a value returned by a call to a shared static helper.
bool IsSharedStatic(ValueNum vn);
// VNForFunc: We have five overloads, for arities 0, 1, 2, 3 and 4
ValueNum VNForFunc(var_types typ, VNFunc func);
ValueNum VNForFunc(var_types typ, VNFunc func, ValueNum opVNwx);
// This must not be used for VNF_MapSelect applications; instead use VNForMapSelect, below.
ValueNum VNForFunc(var_types typ, VNFunc func, ValueNum op1VNwx, ValueNum op2VNwx);
ValueNum VNForFunc(var_types typ, VNFunc func, ValueNum op1VNwx, ValueNum op2VNwx, ValueNum op3VNwx);
// The following four-op VNForFunc is used for VNF_PtrToArrElem, elemTypeEqVN, arrVN, inxVN, fldSeqVN
ValueNum VNForFunc(
var_types typ, VNFunc func, ValueNum op1VNwx, ValueNum op2VNwx, ValueNum op3VNwx, ValueNum op4VNwx);
// Skip all folding checks.
ValueNum VNForFuncNoFolding(var_types typ, VNFunc func, ValueNum op1VNwx, ValueNum op2VNwx);
ValueNum VNForCast(VNFunc func, ValueNum castToVN, ValueNum objVN);
ValueNum VNForMapSelect(ValueNumKind vnk, var_types type, ValueNum map, ValueNum index);
ValueNum VNForMapPhysicalSelect(ValueNumKind vnk, var_types type, ValueNum map, unsigned offset, unsigned size);
ValueNum VNForMapSelectInner(ValueNumKind vnk, var_types type, ValueNum map, ValueNum index);
// A method that does the work for VNForMapSelect and may call itself recursively.
ValueNum VNForMapSelectWork(ValueNumKind vnk,
var_types type,
ValueNum map,
ValueNum index,
int* pBudget,
bool* pUsedRecursiveVN,
class SmallValueNumSet& loopMemoryDependencies);
// A specialized version of VNForFunc that is used for VNF_MapStore and provides some logging when verbose is set
ValueNum VNForMapStore(ValueNum map, ValueNum index, ValueNum value);
ValueNum VNForMapPhysicalStore(ValueNum map, unsigned offset, unsigned size, ValueNum value);
bool MapIsPrecise(ValueNum map) const
{
return (TypeOfVN(map) == TYP_HEAP) || (TypeOfVN(map) == TYP_MEM);
}
bool MapIsPhysical(ValueNum map) const
{
return !MapIsPrecise(map);
}
ValueNum EncodePhysicalSelector(unsigned offset, unsigned size);
unsigned DecodePhysicalSelector(ValueNum selector, unsigned* pSize);
ValueNum VNForFieldSelector(CORINFO_FIELD_HANDLE fieldHnd, var_types* pFieldType, unsigned* pSize);
// These functions parallel the ones above, except that they take liberal/conservative VN pairs
// as arguments, and return such a pair (the pair of the function applied to the liberal args, and
// the function applied to the conservative args).
ValueNumPair VNPairForFunc(var_types typ, VNFunc func)
{
ValueNumPair res;
res.SetBoth(VNForFunc(typ, func));
return res;
}
ValueNumPair VNPairForFunc(var_types typ, VNFunc func, ValueNumPair opVN)
{
ValueNum liberalFuncVN = VNForFunc(typ, func, opVN.GetLiberal());
ValueNum conservativeFuncVN;
if (opVN.BothEqual())
{
conservativeFuncVN = liberalFuncVN;
}
else
{
conservativeFuncVN = VNForFunc(typ, func, opVN.GetConservative());
}
return ValueNumPair(liberalFuncVN, conservativeFuncVN);
}
ValueNumPair VNPairForFunc(var_types typ, VNFunc func, ValueNumPair op1VN, ValueNumPair op2VN)
{
ValueNum liberalFuncVN = VNForFunc(typ, func, op1VN.GetLiberal(), op2VN.GetLiberal());
ValueNum conservativeFuncVN;
if (op1VN.BothEqual() && op2VN.BothEqual())
{
conservativeFuncVN = liberalFuncVN;
}
else
{
conservativeFuncVN = VNForFunc(typ, func, op1VN.GetConservative(), op2VN.GetConservative());
}
return ValueNumPair(liberalFuncVN, conservativeFuncVN);
}
ValueNumPair VNPairForFuncNoFolding(var_types typ, VNFunc func, ValueNumPair op1VN, ValueNumPair op2VN)
{
ValueNum liberalFuncVN = VNForFuncNoFolding(typ, func, op1VN.GetLiberal(), op2VN.GetLiberal());
ValueNum conservativeFuncVN;
if (op1VN.BothEqual() && op2VN.BothEqual())
{
conservativeFuncVN = liberalFuncVN;
}
else
{
conservativeFuncVN = VNForFuncNoFolding(typ, func, op1VN.GetConservative(), op2VN.GetConservative());
}
return ValueNumPair(liberalFuncVN, conservativeFuncVN);
}
ValueNumPair VNPairForFunc(var_types typ, VNFunc func, ValueNumPair op1VN, ValueNumPair op2VN, ValueNumPair op3VN)
{
ValueNum liberalFuncVN = VNForFunc(typ, func, op1VN.GetLiberal(), op2VN.GetLiberal(), op3VN.GetLiberal());
ValueNum conservativeFuncVN;
if (op1VN.BothEqual() && op2VN.BothEqual() && op3VN.BothEqual())
{
conservativeFuncVN = liberalFuncVN;
}
else
{
conservativeFuncVN =
VNForFunc(typ, func, op1VN.GetConservative(), op2VN.GetConservative(), op3VN.GetConservative());
}
return ValueNumPair(liberalFuncVN, conservativeFuncVN);
}
ValueNumPair VNPairForFunc(
var_types typ, VNFunc func, ValueNumPair op1VN, ValueNumPair op2VN, ValueNumPair op3VN, ValueNumPair op4VN)
{
ValueNum liberalFuncVN =
VNForFunc(typ, func, op1VN.GetLiberal(), op2VN.GetLiberal(), op3VN.GetLiberal(), op4VN.GetLiberal());
ValueNum conservativeFuncVN;
if (op1VN.BothEqual() && op2VN.BothEqual() && op3VN.BothEqual() && op4VN.BothEqual())
{
conservativeFuncVN = liberalFuncVN;
}
else
{
conservativeFuncVN = VNForFunc(typ, func, op1VN.GetConservative(), op2VN.GetConservative(),
op3VN.GetConservative(), op4VN.GetConservative());
}
return ValueNumPair(liberalFuncVN, conservativeFuncVN);
}
ValueNum VNForExpr(BasicBlock* block, var_types type = TYP_UNKNOWN);
ValueNumPair VNPairForExpr(BasicBlock* block, var_types type);
// This controls extra tracing of the "evaluation" of "VNF_MapSelect" functions.
#define FEATURE_VN_TRACE_APPLY_SELECTORS 1
ValueNum VNForLoad(ValueNumKind vnk,
ValueNum locationValue,
unsigned locationSize,
var_types loadType,
ssize_t offset,
unsigned loadSize);
ValueNumPair VNPairForLoad(
ValueNumPair locationValue, unsigned locationSize, var_types loadType, ssize_t offset, unsigned loadSize);
ValueNum VNForStore(
ValueNum locationValue, unsigned locationSize, ssize_t offset, unsigned storeSize, ValueNum value);
ValueNumPair VNPairForStore(
ValueNumPair locationValue, unsigned locationSize, ssize_t offset, unsigned storeSize, ValueNumPair value);
static bool LoadStoreIsEntire(unsigned locationSize, ssize_t offset, unsigned indSize)
{
return (offset == 0) && (locationSize == indSize);
}
ValueNum VNForLoadStoreBitCast(ValueNum value, var_types indType, unsigned indSize);
ValueNumPair VNPairForLoadStoreBitCast(ValueNumPair value, var_types indType, unsigned indSize);
// Compute the ValueNumber for a cast
ValueNum VNForCast(ValueNum srcVN,
var_types castToType,
var_types castFromType,
bool srcIsUnsigned = false,
bool hasOverflowCheck = false);
// Compute the ValueNumberPair for a cast
ValueNumPair VNPairForCast(ValueNumPair srcVNPair,
var_types castToType,
var_types castFromType,
bool srcIsUnsigned = false,
bool hasOverflowCheck = false);
ValueNum EncodeBitCastType(var_types castToType, unsigned size);
var_types DecodeBitCastType(ValueNum castToTypeVN, unsigned* pSize);
ValueNum VNForBitCast(ValueNum srcVN, var_types castToType, unsigned size);
ValueNumPair VNPairForBitCast(ValueNumPair srcVNPair, var_types castToType, unsigned size);
ValueNum VNForFieldSeq(FieldSeq* fieldSeq);
FieldSeq* FieldSeqVNToFieldSeq(ValueNum vn);
ValueNum ExtendPtrVN(GenTree* opA, GenTree* opB);
ValueNum ExtendPtrVN(GenTree* opA, FieldSeq* fieldSeq, ssize_t offset);
// Queries on value numbers.
// All queries taking value numbers require that those value numbers are valid, that is, that
// they have been returned by previous "VNFor..." operations. They can assert false if this is
// not true.
// Returns TYP_UNKNOWN if the given value number has not been given a type.
var_types TypeOfVN(ValueNum vn) const;
// Returns nullptr if the given value number is not dependent on memory defined in a loop.
class FlowGraphNaturalLoop* LoopOfVN(ValueNum vn);
// Returns true iff the VN represents a constant.
bool IsVNConstant(ValueNum vn);
// Returns true iff the VN represents a (non-handle) constant.
bool IsVNConstantNonHandle(ValueNum vn);
// Returns true iff the VN represents an integer constant.
bool IsVNInt32Constant(ValueNum vn);
// Returns true if the VN represents a node that is never negative.
bool IsVNNeverNegative(ValueNum vn);
typedef SmallHashTable<ValueNum, bool, 8U> CheckedBoundVNSet;
// Returns true if the VN is known or likely to appear as the conservative value number
// of the length argument to a GT_BOUNDS_CHECK node.
bool IsVNCheckedBound(ValueNum vn);
// Record that a VN is known to appear as the conservative value number of the length
// argument to a GT_BOUNDS_CHECK node.
void SetVNIsCheckedBound(ValueNum vn);
// Information about the individual components of a value number representing an unsigned
// comparison of some value against a checked bound VN.
struct UnsignedCompareCheckedBoundInfo
{
unsigned cmpOper;
ValueNum vnIdx;
ValueNum vnBound;
UnsignedCompareCheckedBoundInfo()
: cmpOper(GT_NONE)
, vnIdx(NoVN)
, vnBound(NoVN)
{
}
};
struct CompareCheckedBoundArithInfo
{
// (vnBound - 1) > vnOp
// (vnBound arrOper arrOp) cmpOper cmpOp
ValueNum vnBound;
unsigned arrOper;
ValueNum arrOp;
bool arrOpLHS; // arrOp is on the left side of cmpOp expression
unsigned cmpOper;
ValueNum cmpOp;
CompareCheckedBoundArithInfo()
: vnBound(NoVN)
, arrOper(GT_NONE)
, arrOp(NoVN)
, arrOpLHS(false)
, cmpOper(GT_NONE)
, cmpOp(NoVN)
{
}
#ifdef DEBUG
void dump(ValueNumStore* vnStore)
{
vnStore->vnDump(vnStore->m_pComp, cmpOp);
printf(" ");
printf(vnStore->VNFuncName((VNFunc)cmpOper));
printf(" ");
vnStore->vnDump(vnStore->m_pComp, vnBound);
if (arrOper != GT_NONE)
{
printf(vnStore->VNFuncName((VNFunc)arrOper));
vnStore->vnDump(vnStore->m_pComp, arrOp);
}
}
#endif
};
struct ConstantBoundInfo
{
// 100 > vnOp
int constVal;
unsigned cmpOper;
ValueNum cmpOpVN;
bool isUnsigned;
ConstantBoundInfo()
: constVal(0)
, cmpOper(GT_NONE)
, cmpOpVN(NoVN)
, isUnsigned(false)
{
}
#ifdef DEBUG
void dump(ValueNumStore* vnStore)
{
vnStore->vnDump(vnStore->m_pComp, cmpOpVN);
printf(" ");
printf(vnStore->VNFuncName((VNFunc)cmpOper));
printf(" ");
printf("%d", constVal);
}
#endif
};
// Check if "vn" is "new [] (type handle, size)"
bool IsVNNewArr(ValueNum vn, VNFuncApp* funcApp);
// Check if "vn" IsVNNewArr and return false if arr size cannot be determined.
bool TryGetNewArrSize(ValueNum vn, int* size);
// Check if "vn" is "a.Length" or "a.GetLength(n)"
bool IsVNArrLen(ValueNum vn);