//===- ValueMapper.h - Remapping for constants and metadata -----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the MapValue interface which is used by various parts of
// the Transforms/Utils library to implement cloning and linking facilities.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
#define LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/IR/ValueMap.h"
namespace llvm {
class Constant;
class Function;
class GlobalVariable;
class Instruction;
class MDNode;
class Metadata;
class Type;
class Value;
using ValueToValueMapTy = ValueMap<const Value *, WeakTrackingVH>;
/// This is a class that can be implemented by clients to remap types when
/// cloning constants and instructions.
class ValueMapTypeRemapper {
virtual void anchor(); // Out of line method.
public:
virtual ~ValueMapTypeRemapper() = default;
/// The client should implement this method if they want to remap types while
/// mapping values.
virtual Type *remapType(Type *SrcTy) = 0;
};
/// This is a class that can be implemented by clients to materialize Values on
/// demand.
class ValueMaterializer {
virtual void anchor(); // Out of line method.
protected:
ValueMaterializer() = default;
ValueMaterializer(const ValueMaterializer &) = default;
ValueMaterializer &operator=(const ValueMaterializer &) = default;
~ValueMaterializer() = default;
public:
/// This method can be implemented to generate a mapped Value on demand. For
/// example, if linking lazily. Returns null if the value is not materialized.
virtual Value *materialize(Value *V) = 0;
};
/// These are flags that the value mapping APIs allow.
enum RemapFlags {
RF_None = 0,
/// If this flag is set, the remapper knows that only local values within a
/// function (such as an instruction or argument) are mapped, not global
/// values like functions and global metadata.
RF_NoModuleLevelChanges = 1,
/// If this flag is set, the remapper ignores missing function-local entries
/// (Argument, Instruction, BasicBlock) that are not in the value map. If it
/// is unset, it aborts if an operand is asked to be remapped which doesn't
/// exist in the mapping.
///
/// There are no such assertions in MapValue(), whose results are almost
/// unchanged by this flag. This flag mainly changes the assertion behaviour
/// in RemapInstruction().
///
/// Since an Instruction's metadata operands (even that point to SSA values)
/// aren't guaranteed to be dominated by their definitions, MapMetadata will
/// return "!{}" instead of "null" for \a LocalAsMetadata instances whose SSA
/// values are unmapped when this flag is set. Otherwise, \a MapValue()
/// completely ignores this flag.
///
/// \a MapMetadata() always ignores this flag.
RF_IgnoreMissingLocals = 2,
/// Instruct the remapper to reuse and mutate distinct metadata (remapping
/// them in place) instead of cloning remapped copies. This flag has no
/// effect when when RF_NoModuleLevelChanges, since that implies an identity
/// mapping.
RF_ReuseAndMutateDistinctMDs = 4,
/// Any global values not in value map are mapped to null instead of mapping
/// to self. Illegal if RF_IgnoreMissingLocals is also set.
RF_NullMapMissingGlobalValues = 8,
};
inline RemapFlags operator|(RemapFlags LHS, RemapFlags RHS) {
return RemapFlags(unsigned(LHS) | unsigned(RHS));
}
/// Context for (re-)mapping values (and metadata).
///
/// A shared context used for mapping and remapping of Value and Metadata
/// instances using \a ValueToValueMapTy, \a RemapFlags, \a
/// ValueMapTypeRemapper, and \a ValueMaterializer.
///
/// There are a number of top-level entry points:
/// - \a mapValue() (and \a mapConstant());
/// - \a mapMetadata() (and \a mapMDNode());
/// - \a remapInstruction(); and
/// - \a remapFunction().
///
/// The \a ValueMaterializer can be used as a callback, but cannot invoke any
/// of these top-level functions recursively. Instead, callbacks should use
/// one of the following to schedule work lazily in the \a ValueMapper
/// instance:
/// - \a scheduleMapGlobalInitializer()
/// - \a scheduleMapAppendingVariable()
/// - \a scheduleMapGlobalAlias()
/// - \a scheduleMapGlobalIFunc()
/// - \a scheduleRemapFunction()
///
/// Sometimes a callback needs a different mapping context. Such a context can
/// be registered using \a registerAlternateMappingContext(), which takes an
/// alternate \a ValueToValueMapTy and \a ValueMaterializer and returns a ID to
/// pass into the schedule*() functions.
///
/// TODO: lib/Linker really doesn't need the \a ValueHandle in the \a
/// ValueToValueMapTy. We should template \a ValueMapper (and its
/// implementation classes), and explicitly instantiate on two concrete
/// instances of \a ValueMap (one as \a ValueToValueMap, and one with raw \a
/// Value pointers). It may be viable to do away with \a TrackingMDRef in the
/// \a Metadata side map for the lib/Linker case as well, in which case we'll
/// need a new template parameter on \a ValueMap.
///
/// TODO: Update callers of \a RemapInstruction() and \a MapValue() (etc.) to
/// use \a ValueMapper directly.
class ValueMapper {
void *pImpl;
public:
ValueMapper(ValueToValueMapTy &VM, RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr);
ValueMapper(ValueMapper &&) = delete;
ValueMapper(const ValueMapper &) = delete;
ValueMapper &operator=(ValueMapper &&) = delete;
ValueMapper &operator=(const ValueMapper &) = delete;
~ValueMapper();
/// Register an alternate mapping context.
///
/// Returns a MappingContextID that can be used with the various schedule*()
/// API to switch in a different value map on-the-fly.
unsigned
registerAlternateMappingContext(ValueToValueMapTy &VM,
ValueMaterializer *Materializer = nullptr);
/// Add to the current \a RemapFlags.
///
/// \note Like the top-level mapping functions, \a addFlags() must be called
/// at the top level, not during a callback in a \a ValueMaterializer.
void addFlags(RemapFlags Flags);
Metadata *mapMetadata(const Metadata &MD);
MDNode *mapMDNode(const MDNode &N);
Value *mapValue(const Value &V);
Constant *mapConstant(const Constant &C);
void remapInstruction(Instruction &I);
void remapFunction(Function &F);
void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
unsigned MappingContextID = 0);
void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
bool IsOldCtorDtor,
ArrayRef<Constant *> NewMembers,
unsigned MappingContextID = 0);
void scheduleMapGlobalAlias(GlobalAlias &GA, Constant &Aliasee,
unsigned MappingContextID = 0);
void scheduleMapGlobalIFunc(GlobalIFunc &GI, Constant &Resolver,
unsigned MappingContextID = 0);
void scheduleRemapFunction(Function &F, unsigned MappingContextID = 0);
};
/// Look up or compute a value in the value map.
///
/// Return a mapped value for a function-local value (Argument, Instruction,
/// BasicBlock), or compute and memoize a value for a Constant.
///
/// 1. If \c V is in VM, return the result.
/// 2. Else if \c V can be materialized with \c Materializer, do so, memoize
/// it in \c VM, and return it.
/// 3. Else if \c V is a function-local value, return nullptr.
/// 4. Else if \c V is a \a GlobalValue, return \c nullptr or \c V depending
/// on \a RF_NullMapMissingGlobalValues.
/// 5. Else if \c V is a \a MetadataAsValue wrapping a LocalAsMetadata,
/// recurse on the local SSA value, and return nullptr or "metadata !{}" on
/// missing depending on RF_IgnoreMissingValues.
/// 6. Else if \c V is a \a MetadataAsValue, rewrap the return of \a
/// MapMetadata().
/// 7. Else, compute the equivalent constant, and return it.
inline Value *MapValue(const Value *V, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr) {
return ValueMapper(VM, Flags, TypeMapper, Materializer).mapValue(*V);
}
/// Lookup or compute a mapping for a piece of metadata.
///
/// Compute and memoize a mapping for \c MD.
///
/// 1. If \c MD is mapped, return it.
/// 2. Else if \a RF_NoModuleLevelChanges or \c MD is an \a MDString, return
/// \c MD.
/// 3. Else if \c MD is a \a ConstantAsMetadata, call \a MapValue() and
/// re-wrap its return (returning nullptr on nullptr).
/// 4. Else, \c MD is an \a MDNode. These are remapped, along with their
/// transitive operands. Distinct nodes are duplicated or moved depending
/// on \a RF_MoveDistinctNodes. Uniqued nodes are remapped like constants.
///
/// \note \a LocalAsMetadata is completely unsupported by \a MapMetadata.
/// Instead, use \a MapValue() with its wrapping \a MetadataAsValue instance.
inline Metadata *MapMetadata(const Metadata *MD, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr) {
return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMetadata(*MD);
}
/// Version of MapMetadata with type safety for MDNode.
inline MDNode *MapMetadata(const MDNode *MD, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr) {
return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMDNode(*MD);
}
/// Convert the instruction operands from referencing the current values into
/// those specified by VM.
///
/// If \a RF_IgnoreMissingLocals is set and an operand can't be found via \a
/// MapValue(), use the old value. Otherwise assert that this doesn't happen.
///
/// Note that \a MapValue() only returns \c nullptr for SSA values missing from
/// \c VM.
inline void RemapInstruction(Instruction *I, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr) {
ValueMapper(VM, Flags, TypeMapper, Materializer).remapInstruction(*I);
}
/// Remap the operands, metadata, arguments, and instructions of a function.
///
/// Calls \a MapValue() on prefix data, prologue data, and personality
/// function; calls \a MapMetadata() on each attached MDNode; remaps the
/// argument types using the provided \c TypeMapper; and calls \a
/// RemapInstruction() on every instruction.
inline void RemapFunction(Function &F, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr) {
ValueMapper(VM, Flags, TypeMapper, Materializer).remapFunction(F);
}
/// Version of MapValue with type safety for Constant.
inline Constant *MapValue(const Constant *V, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr) {
return ValueMapper(VM, Flags, TypeMapper, Materializer).mapConstant(*V);
}
} // end namespace llvm
#endif // LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H