[lld] [lld-macho] Implement ObjC category merging (-objc_category_merging) (PR #82928)
Kyungwoo Lee via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 29 07:56:13 PST 2024
================
@@ -320,3 +342,1007 @@ void objc::checkCategories() {
}
}
}
+
+namespace {
+
+class ObjcCategoryMerger {
+ // Information about an input category
+ struct InfoInputCategory {
+ ConcatInputSection *catBodyIsec;
+ ConcatInputSection *catListIsec;
+ uint32_t offCatListIsec = 0;
+
+ bool wasMerged = false;
+ };
+
+ // To write new (merged) categories or classes, we will try make limited
+ // assumptions about the alignment and the sections the various class/category
+ // info are stored in and . So we'll just reuse the same sections and
+ // alignment as already used in existing (input) categories. To do this we
+ // have InfoCategoryWriter which contains the various sections that the
+ // generated categories will be written to.
+ template <typename T> struct InfroWriteSection {
+ bool valid = false; // Data has been successfully collected from input
+ uint32_t align = 0;
+ const Section *inputSection;
+ Reloc relocTemplate;
+ T *outputSection;
+ };
+
+ struct InfoCategoryWriter {
+ InfroWriteSection<ConcatOutputSection> catListInfo;
+ InfroWriteSection<CStringSection> catNameInfo;
+ InfroWriteSection<ConcatOutputSection> catBodyInfo;
+ InfroWriteSection<ConcatOutputSection> catPtrListInfo;
+ };
+
+ // Information about a pointer list in the original categories (method lists,
+ // protocol lists, etc)
+ struct PointerListInfo {
+ PointerListInfo(const char *pszSymNamePrefix)
+ : namePrefix(pszSymNamePrefix) {}
+ const char *namePrefix;
+
+ uint32_t structSize = 0;
+ uint32_t structCount = 0;
+
+ std::vector<Symbol *> allPtrs;
+ };
+
+ // Full information about all the categories that are extending a class. This
+ // will have all the additional methods, protocols, proprieties that are
+ // contained in all the categories that extend a particular class.
+ struct ClassExtensionInfo {
+ // Merged names of containers. Ex: base|firstCategory|secondCategory|...
+ std::string mergedContainerName;
+ std::string baseClassName;
+ Symbol *baseClass = nullptr;
+ // In case we generate new data, mark the new data as belonging to this file
+ ObjFile *objFileForMergeData = nullptr;
+
+ PointerListInfo instanceMethods = "__OBJC_$_CATEGORY_INSTANCE_METHODS_";
+ PointerListInfo classMethods = "__OBJC_$_CATEGORY_CLASS_METHODS_";
+ PointerListInfo protocols = "__OBJC_CATEGORY_PROTOCOLS_$_";
+ PointerListInfo instanceProps = "__OBJC_$_PROP_LIST_";
+ PointerListInfo classProps = "__OBJC_$_CLASS_PROP_LIST_";
+ };
+
+public:
+ ObjcCategoryMerger(std::vector<ConcatInputSection *> &_allInputSections);
+ bool doMerge();
+
+private:
+ // This returns bool and always false for easy 'return false;' statements
+ bool registerError(const char *msg);
+
+ bool collectAndValidateCategoriesData();
+ bool
+ mergeCategoriesIntoSingleCategory(std::vector<InfoInputCategory> &categories);
+ bool eraseMergedCategories();
+
+ bool generateCatListForNonErasedCategories(
+ std::map<ConcatInputSection *, std::set<uint64_t>>
+ catListToErasedOffsets);
+ template <typename T>
+ bool collectSectionWriteInfoFromIsec(InputSection *isec,
+ InfroWriteSection<T> &catWriteInfo);
+ bool collectCategoryWriterInfoFromCategory(InfoInputCategory &catInfo);
+ bool parseCatInfoToExtInfo(InfoInputCategory &catInfo,
+ ClassExtensionInfo &extInfo);
+
+ bool tryParseProtocolListInfo(ConcatInputSection *isec,
+ uint32_t symbolsPerStruct,
+ PointerListInfo &ptrList);
+
+ bool parsePointerListInfo(ConcatInputSection *isec, uint32_t secOffset,
+ uint32_t symbolsPerStruct,
+ PointerListInfo &ptrList);
+
+ bool emitAndLinkPointerList(Defined *parentSym, uint32_t linkAtOffset,
+ ClassExtensionInfo &extInfo,
+ PointerListInfo &ptrList);
+
+ bool emitAndLinkProtocolList(Defined *parentSym, uint32_t linkAtOffset,
+ ClassExtensionInfo &extInfo,
+ PointerListInfo &ptrList);
+
+ bool emitCategory(ClassExtensionInfo &extInfo, Defined *&catBodySym);
+ bool emitCatListEntrySec(std::string &forCateogryName,
+ std::string &forBaseClassName, ObjFile *objFile,
+ Defined *&catListSym);
+ bool emitCategoryBody(std::string &name, Defined *nameSym,
+ Symbol *baseClassSym, std::string &baseClassName,
+ ObjFile *objFile, Defined *&catBodySym);
+ bool emitCategoryName(std::string &name, ObjFile *objFile,
+ Defined *&catNameSym);
+ bool createSymbolReference(Defined *refFrom, Symbol *refTo, uint32_t offset,
+ Reloc &relocTemplate);
+ bool tryGetSymbolAtIsecOffset(ConcatInputSection *isec, uint32_t offset,
+ Symbol *&sym);
+ bool tryGetDefinedAtIsecOffset(ConcatInputSection *isec, uint32_t offset,
+ Defined *&defined);
+ bool tryEraseDefinedAtIsecOffset(ConcatInputSection *isec, uint32_t offset,
+ bool stringOnly = false);
+
+ CategoryLayout catLayout;
+ ClassLayout classLayout;
+ ROClassLayout roClassLayout;
+ ListHeaderLayout listHeaderLayout;
+ MethodLayout methodLayout;
+ ProtocolListHeaderLayout protocolListHeaderLayout;
+
+ InfoCategoryWriter infoCategoryWriter;
+ std::vector<ConcatInputSection *> &allInputSections;
+ // Map of base class Symbol to list of InfoInputCategory's for it
+ std::map<const Symbol *, std::vector<InfoInputCategory>> categoryMap;
+
+ // Normally, the binary data comes from the input files, but since we're
+ // generating binary data ourselves, we use the below arrays to store it in.
+ // Need this to be 'static' so the data survives past the ObjcCategoryMerger
+ // object, as the data will be read by the Writer when the final binary is
+ // generated.
+ static SmallVector<SmallString<0>> generatedNames;
+ static SmallVector<SmallVector<uint8_t>> generatedSectionData;
+};
+
+SmallVector<SmallString<0>> ObjcCategoryMerger::generatedNames;
+SmallVector<SmallVector<uint8_t>> ObjcCategoryMerger::generatedSectionData;
+
+ObjcCategoryMerger::ObjcCategoryMerger(
+ std::vector<ConcatInputSection *> &_allInputSections)
+ : catLayout(target->wordSize), classLayout(target->wordSize),
+ roClassLayout(target->wordSize), listHeaderLayout(target->wordSize),
+ methodLayout(target->wordSize),
+ protocolListHeaderLayout(target->wordSize),
+ allInputSections(_allInputSections) {}
+
+bool ObjcCategoryMerger::registerError(const char *msg) {
+ std::string err = "ObjC category merging error[-merge-objc-categories]: ";
+ err += msg;
+ error(err);
+ return false; // Always return false for easy 'return registerError()' syntax.
+}
+
+// This is a template so that it can be used both for CStringSection and
+// ConcatOutputSection
+template <typename T>
+bool ObjcCategoryMerger::collectSectionWriteInfoFromIsec(
+ InputSection *isec, InfroWriteSection<T> &catWriteInfo) {
+ if (catWriteInfo.valid)
+ return true;
+
+ catWriteInfo.inputSection = &isec->section;
+ catWriteInfo.align = isec->align;
+ catWriteInfo.outputSection = dyn_cast_or_null<T>(isec->parent);
+
+ if (isec->relocs.size())
+ catWriteInfo.relocTemplate = isec->relocs[0];
+
+ if (!catWriteInfo.outputSection) {
+ std::string message =
+ "Unexpected output section type for" + isec->getName().str();
+ return registerError(message.c_str());
+ }
+
+ catWriteInfo.valid = true;
+
+ return true;
+}
+
+bool ObjcCategoryMerger::tryGetSymbolAtIsecOffset(ConcatInputSection *isec,
+ uint32_t offset,
+ Symbol *&sym) {
+ const Reloc *reloc = isec->getRelocAt(offset);
+
+ if (!reloc)
+ return false;
+
+ sym = reloc->referent.get<Symbol *>();
+ return sym != nullptr;
+}
+
+bool ObjcCategoryMerger::tryGetDefinedAtIsecOffset(ConcatInputSection *isec,
+ uint32_t offset,
+ Defined *&defined) {
+ Symbol *sym;
+ if (!tryGetSymbolAtIsecOffset(isec, offset, sym))
+ return false;
+
+ defined = dyn_cast_or_null<Defined>(sym);
+ return defined != nullptr;
+}
+
+// Given an ConcatInputSection and an offset, if there is a symbol(Defined) at
+// that offset, then erase the symbol (mark it not live) from the final output.
+// Used for easely erasing already merged strings, method lists, etc ...
+bool ObjcCategoryMerger::tryEraseDefinedAtIsecOffset(ConcatInputSection *isec,
+ uint32_t offset,
+ bool stringOnly) {
+ const Reloc *reloc = isec->getRelocAt(offset);
+
+ if (!reloc)
+ return false;
+
+ Defined *sym = dyn_cast_or_null<Defined>(reloc->referent.get<Symbol *>());
+
+ if (!sym)
+ return false;
+
+ auto *cisec = dyn_cast_or_null<ConcatInputSection>(sym->isec);
+ if (!stringOnly && cisec) {
+ cisec->linkerOptimizeReason = LinkerOptReason::CategoryMerging;
+ return true;
+ }
+
+ if (auto *cisec = dyn_cast_or_null<CStringInputSection>(sym->isec)) {
+ uint32_t totalOffset = sym->value + reloc->addend;
+ StringPiece &piece = cisec->getStringPiece(totalOffset);
+ piece.linkerOptimizeReason = LinkerOptReason::CategoryMerging;
+ return true;
+ }
+
+ return false;
+}
+
+bool ObjcCategoryMerger::collectCategoryWriterInfoFromCategory(
+ InfoInputCategory &catInfo) {
+
+ if (!collectSectionWriteInfoFromIsec<ConcatOutputSection>(
----------------
kyulee-com wrote:
Yeah, it appears we shouldn't run `fatal()` per https://github.com/llvm/llvm-project/blob/main/lld/include/lld/Common/ErrorHandler.h#L32
But I still think there are many ways to simplify the logic with default value without checking boolean for each case. Eventually, `errorCount()` can be used in `Driver.cpp`.
https://github.com/llvm/llvm-project/pull/82928
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