XCore.cpp | Explore in Territory

//===- XCore.cpp ----------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "ABIInfoImpl.h"
#include "TargetInfo.h"

usingnamespaceclang;
usingnamespaceclang::CodeGen;

//===----------------------------------------------------------------------===//
// XCore ABI Implementation
//===----------------------------------------------------------------------===//

namespace {

/// A SmallStringEnc instance is used to build up the TypeString by passing
/// it by reference between functions that append to it.
SmallStringEnc;

/// TypeStringCache caches the meta encodings of Types.
///
/// The reason for caching TypeStrings is two fold:
///   1. To cache a type's encoding for later uses;
///   2. As a means to break recursive member type inclusion.
///
/// A cache Entry can have a Status of:
///   NonRecursive:   The type encoding is not recursive;
///   Recursive:      The type encoding is recursive;
///   Incomplete:     An incomplete TypeString;
///   IncompleteUsed: An incomplete TypeString that has been used in a
///                   Recursive type encoding.
///
/// A NonRecursive entry will have all of its sub-members expanded as fully
/// as possible. Whilst it may contain types which are recursive, the type
/// itself is not recursive and thus its encoding may be safely used whenever
/// the type is encountered.
///
/// A Recursive entry will have all of its sub-members expanded as fully as
/// possible. The type itself is recursive and it may contain other types which
/// are recursive. The Recursive encoding must not be used during the expansion
/// of a recursive type's recursive branch. For simplicity the code uses
/// IncompleteCount to reject all usage of Recursive encodings for member types.
///
/// An Incomplete entry is always a RecordType and only encodes its
/// identifier e.g. "s(S){}". Incomplete 'StubEnc' entries are ephemeral and
/// are placed into the cache during type expansion as a means to identify and
/// handle recursive inclusion of types as sub-members. If there is recursion
/// the entry becomes IncompleteUsed.
///
/// During the expansion of a RecordType's members:
///
///   If the cache contains a NonRecursive encoding for the member type, the
///   cached encoding is used;
///
///   If the cache contains a Recursive encoding for the member type, the
///   cached encoding is 'Swapped' out, as it may be incorrect, and...
///
///   If the member is a RecordType, an Incomplete encoding is placed into the
///   cache to break potential recursive inclusion of itself as a sub-member;
///
///   Once a member RecordType has been expanded, its temporary incomplete
///   entry is removed from the cache. If a Recursive encoding was swapped out
///   it is swapped back in;
///
///   If an incomplete entry is used to expand a sub-member, the incomplete
///   entry is marked as IncompleteUsed. The cache keeps count of how many
///   IncompleteUsed entries it currently contains in IncompleteUsedCount;
///
///   If a member's encoding is found to be a NonRecursive or Recursive viz:
///   IncompleteUsedCount==0, the member's encoding is added to the cache.
///   Else the member is part of a recursive type and thus the recursion has
///   been exited too soon for the encoding to be correct for the member.
///
class TypeStringCache { … };

/// TypeString encodings for enum & union fields must be order.
/// FieldEncoding is a helper for this ordering process.
class FieldEncoding { … };

class XCoreABIInfo : public DefaultABIInfo { … };

class XCoreTargetCodeGenInfo : public TargetCodeGenInfo { … };

} // End anonymous namespace.

// TODO: this implementation is likely now redundant with the default
// EmitVAArg.
RValue XCoreABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
                               QualType Ty, AggValueSlot Slot) const { … }

/// During the expansion of a RecordType, an incomplete TypeString is placed
/// into the cache as a means to identify and break recursion.
/// If there is a Recursive encoding in the cache, it is swapped out and will
/// be reinserted by removeIncomplete().
/// All other types of encoding should have been used rather than arriving here.
void TypeStringCache::addIncomplete(const IdentifierInfo *ID,
                                    std::string StubEnc) { … }

/// Once the RecordType has been expanded, the temporary incomplete TypeString
/// must be removed from the cache.
/// If a Recursive was swapped out by addIncomplete(), it will be replaced.
/// Returns true if the RecordType was defined recursively.
bool TypeStringCache::removeIncomplete(const IdentifierInfo *ID) { … }

/// Add the encoded TypeString to the cache only if it is NonRecursive or
/// Recursive (viz: all sub-members were expanded as fully as possible).
void TypeStringCache::addIfComplete(const IdentifierInfo *ID, StringRef Str,
                                    bool IsRecursive) { … }

/// Return a cached TypeString encoding for the ID. If there isn't one, or we
/// are recursively expanding a type (IncompleteCount != 0) and the cached
/// encoding is Recursive, return an empty StringRef.
StringRef TypeStringCache::lookupStr(const IdentifierInfo *ID) { … }

/// The XCore ABI includes a type information section that communicates symbol
/// type information to the linker. The linker uses this information to verify
/// safety/correctness of things such as array bound and pointers et al.
/// The ABI only requires C (and XC) language modules to emit TypeStrings.
/// This type information (TypeString) is emitted into meta data for all global
/// symbols: definitions, declarations, functions & variables.
///
/// The TypeString carries type, qualifier, name, size & value details.
/// Please see 'Tools Development Guide' section 2.16.2 for format details:
/// https://www.xmos.com/download/public/Tools-Development-Guide%28X9114A%29.pdf
/// The output is tested by test/CodeGen/xcore-stringtype.c.
///
static bool getTypeString(SmallStringEnc &Enc, const Decl *D,
                          const CodeGen::CodeGenModule &CGM,
                          TypeStringCache &TSC);

/// XCore uses emitTargetMD to emit TypeString metadata for global symbols.
void XCoreTargetCodeGenInfo::emitTargetMD(
    const Decl *D, llvm::GlobalValue *GV,
    const CodeGen::CodeGenModule &CGM) const { … }

void XCoreTargetCodeGenInfo::emitTargetMetadata(
    CodeGen::CodeGenModule &CGM,
    const llvm::MapVector<GlobalDecl, StringRef> &MangledDeclNames) const { … }

static bool appendType(SmallStringEnc &Enc, QualType QType,
                       const CodeGen::CodeGenModule &CGM,
                       TypeStringCache &TSC);

/// Helper function for appendRecordType().
/// Builds a SmallVector containing the encoded field types in declaration
/// order.
static bool extractFieldType(SmallVectorImpl<FieldEncoding> &FE,
                             const RecordDecl *RD,
                             const CodeGen::CodeGenModule &CGM,
                             TypeStringCache &TSC) { … }

/// Appends structure and union types to Enc and adds encoding to cache.
/// Recursively calls appendType (via extractFieldType) for each field.
/// Union types have their fields ordered according to the ABI.
static bool appendRecordType(SmallStringEnc &Enc, const RecordType *RT,
                             const CodeGen::CodeGenModule &CGM,
                             TypeStringCache &TSC, const IdentifierInfo *ID) { … }

/// Appends enum types to Enc and adds the encoding to the cache.
static bool appendEnumType(SmallStringEnc &Enc, const EnumType *ET,
                           TypeStringCache &TSC,
                           const IdentifierInfo *ID) { … }

/// Appends type's qualifier to Enc.
/// This is done prior to appending the type's encoding.
static void appendQualifier(SmallStringEnc &Enc, QualType QT) { … }

/// Appends built-in types to Enc.
static bool appendBuiltinType(SmallStringEnc &Enc, const BuiltinType *BT) { … }

/// Appends a pointer encoding to Enc before calling appendType for the pointee.
static bool appendPointerType(SmallStringEnc &Enc, const PointerType *PT,
                              const CodeGen::CodeGenModule &CGM,
                              TypeStringCache &TSC) { … }

/// Appends array encoding to Enc before calling appendType for the element.
static bool appendArrayType(SmallStringEnc &Enc, QualType QT,
                            const ArrayType *AT,
                            const CodeGen::CodeGenModule &CGM,
                            TypeStringCache &TSC, StringRef NoSizeEnc) { … }

/// Appends a function encoding to Enc, calling appendType for the return type
/// and the arguments.
static bool appendFunctionType(SmallStringEnc &Enc, const FunctionType *FT,
                             const CodeGen::CodeGenModule &CGM,
                             TypeStringCache &TSC) { … }

/// Handles the type's qualifier before dispatching a call to handle specific
/// type encodings.
static bool appendType(SmallStringEnc &Enc, QualType QType,
                       const CodeGen::CodeGenModule &CGM,
                       TypeStringCache &TSC) { … }

static bool getTypeString(SmallStringEnc &Enc, const Decl *D,
                          const CodeGen::CodeGenModule &CGM,
                          TypeStringCache &TSC) { … }

std::unique_ptr<TargetCodeGenInfo>
CodeGen::createXCoreTargetCodeGenInfo(CodeGenModule &CGM) { … }
llvm/clang/lib/CodeGen/Targets/XCore.cpp
