Don't SHF_ALLOC the blockmap and LLVM bitcode sections.

It's not clear if it's correct to be SHF_ALLOCing these sections, so we
err on the side of caution and don't.

For more info, see:
ykjit/yk#923

Author: vext01

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -99,8 +99,6 @@ namespace llvm {
 extern FunctionSummary::ForceSummaryHotnessType ForceSummaryEdgesCold;
 }
 
-extern bool YkAllocLLVMBCSection;
-
 namespace {
 
 /// These are manifest constants used by the bitcode writer. They do not need to
@@ -5185,45 +5183,15 @@ void llvm::embedBitcodeInModule(llvm::Module &M, llvm::MemoryBufferRef Buf,
       ModuleData = ArrayRef<uint8_t>((const uint8_t *)Buf.getBufferStart(),
                                      Buf.getBufferSize());
   }
-
-  GlobalValue::LinkageTypes SymLinkage = GlobalValue::PrivateLinkage;
-
-  // For the YK JIT we prepend a header containing the size of the bitcode.
-  // This is required in order to load bitcode from memory.
-  std::vector<uint8_t> YkModuleData;
-  if (YkAllocLLVMBCSection) {
-    // Write length field.
-    uint64_t ModuleDataSize = ModuleData.size();
-    uint8_t *Bytes = reinterpret_cast<uint8_t *>(&ModuleDataSize);
-    for (size_t I = 0; I < sizeof(ModuleDataSize); I++)
-      YkModuleData.push_back(Bytes[I]);
-
-    // Append bitcode.
-    std::move(ModuleData.begin(), ModuleData.end(),
-              std::back_inserter(YkModuleData));
-    ModuleData = YkModuleData;
-
-    // Ensure the symbol is exported in the resulting binary.
-    SymLinkage = GlobalValue::ExternalLinkage;
-  }
-
   llvm::Constant *ModuleConstant =
       llvm::ConstantDataArray::get(M.getContext(), ModuleData);
   llvm::GlobalVariable *GV = new llvm::GlobalVariable(
-      M, ModuleConstant->getType(), true, SymLinkage, ModuleConstant);
+      M, ModuleConstant->getType(), true, llvm::GlobalValue::PrivateLinkage,
+      ModuleConstant);
   GV->setSection(getSectionNameForBitcode(T));
-
-  if (YkAllocLLVMBCSection) {
-    // For Yk there will only ever be one embedded (LTO'd) module. This gives
-    // us the freedom to align the section so that we can read our size header
-    // without issue.
-    GV->setAlignment(Align(sizeof(uint64_t)));
-  } else {
-    // Set alignment to 1 to prevent padding between two contributions from input
-    // sections after linking.
-    GV->setAlignment(Align(1));
-  }
-
+  // Set alignment to 1 to prevent padding between two contributions from input
+  // sections after linking.
+  GV->setAlignment(Align(1));
   UsedArray.push_back(
       ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
   if (llvm::GlobalVariable *Old =

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -138,7 +138,6 @@ static cl::opt<bool>
                       cl::desc("Embed final IR as bitcode after all "
                                "optimisations and transformations have run."));
 
-extern bool YkAllocLLVMBBAddrMapSection;
 extern bool YkExtendedLLVMBBAddrMapSection;
 extern bool YkStackMapOffsetFix;
 extern bool YkEmbedIR;
@@ -1403,18 +1402,6 @@ void AsmPrinter::emitBBAddrMapSection(const MachineFunction &MF) {
 
   OutStreamer->pushSection();
   OutStreamer->switchSection(BBAddrMapSection);
-
-  if (YkAllocLLVMBBAddrMapSection) {
-    if (!YkEmittedFirstBBAddrMap) {
-      // Add the `ykllvm.bbaddrmaps.start` symbol.
-      emitYkBBAddrMapSymbol(MF.getContext(), *OutStreamer, true);
-      YkEmittedFirstBBAddrMap = true;
-    }
-    // We cache the last seen bbaddrmap section fragment so that we can insert
-    // the stop symbol when the asmprinter is finalising.
-    YkLastBBAddrMapSection = BBAddrMapSection;
-  }
-
   OutStreamer->AddComment("version");
   uint8_t BBAddrMapVersion = OutStreamer->getContext().getBBAddrMapVersion();
   OutStreamer->emitInt8(BBAddrMapVersion);
@@ -2513,14 +2500,6 @@ void AsmPrinter::emitRemarksSection(remarks::RemarkStreamer &RS) {
 }
 
 bool AsmPrinter::doFinalization(Module &M) {
-  if (YkAllocLLVMBBAddrMapSection && YkEmittedFirstBBAddrMap) {
-    // Add the `ykllvm.bbaddrmaps.stop` symbol.
-    OutStreamer->pushSection();
-    OutStreamer->switchSection(YkLastBBAddrMapSection);
-    emitYkBBAddrMapSymbol(OutContext, *OutStreamer, false);
-    OutStreamer->popSection();
-  }
-
   // The `embed-bitcode` flag serialises the LLVM IR after only architecture
   // agnostic optimisations have been run, but then proceeds to apply other
   // optimisations and transformations afterwards. Sometimes this final version

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -71,8 +71,6 @@
 using namespace llvm;
 using namespace dwarf;
 
-extern bool YkAllocLLVMBCSection;
-
 static cl::opt<bool> JumpTableInFunctionSection(
     "jumptable-in-function-section", cl::Hidden, cl::init(false),
     cl::desc("Putting Jump Table in function section"));
@@ -810,12 +808,6 @@ static MCSection *selectExplicitSectionGlobal(
       Retain, ForceUnique);
 
   const MCSymbolELF *LinkedToSym = getLinkedToSymbol(GO, TM);
-
-  // The Yk JIT expects to load the IR from its address space. This tells the
-  // loader to load the section.
-  if (YkAllocLLVMBCSection && (SectionName == ".llvmbc"))
-    Flags |= llvm::ELF::SHF_ALLOC;
-
   MCSectionELF *Section = Ctx.getELFSection(
       SectionName, getELFSectionType(SectionName, Kind), Flags, EntrySize,
       Group, IsComdat, UniqueID, LinkedToSym);

llvm/lib/MC/MCObjectFileInfo.cpp

@@ -1131,8 +1131,6 @@ MCObjectFileInfo::getStackSizesSection(const MCSection &TextSec) const {
                             cast<MCSymbolELF>(TextSec.getBeginSymbol()));
 }
 
-extern bool YkAllocLLVMBBAddrMapSection;
-
 MCSection *
 MCObjectFileInfo::getBBAddrMapSection(const MCSection &TextSec) const {
   if (Ctx->getObjectFileType() != MCContext::IsELF)
@@ -1146,9 +1144,6 @@ MCObjectFileInfo::getBBAddrMapSection(const MCSection &TextSec) const {
     Flags |= ELF::SHF_GROUP;
   }
 
-  if (YkAllocLLVMBBAddrMapSection)
-    Flags |= ELF::SHF_ALLOC;
-
   // Use the text section's begin symbol and unique ID to create a separate
   // .llvm_bb_addr_map section associated with every unique text section.
   return Ctx->getELFSection(".llvm_bb_addr_map", ELF::SHT_LLVM_BB_ADDR_MAP,

llvm/lib/Support/Yk.cpp

@@ -4,35 +4,6 @@
 
 using namespace llvm;
 
-bool YkAllocLLVMBCSection;
-namespace {
-struct CreateYkAllocLLVMBCSectionParser {
-  static void *call() {
-    return new cl::opt<bool, true>(
-        "yk-alloc-llvmbc-section",
-        cl::desc("Make the `.llvmbc` section loadable"), cl::NotHidden,
-        cl::location(YkAllocLLVMBCSection));
-  }
-};
-} // namespace
-static ManagedStatic<cl::opt<bool, true>, CreateYkAllocLLVMBCSectionParser>
-    YkAllocLLVMBCSectionParser;
-
-bool YkAllocLLVMBBAddrMapSection;
-namespace {
-struct CreateYkAllocLLVMBBAddrMapSectionParser {
-  static void *call() {
-    return new cl::opt<bool, true>(
-        "yk-alloc-llvmbbaddrmap-section",
-        cl::desc("Make the `.llvmbbaddrmap` section loadable"), cl::NotHidden,
-        cl::location(YkAllocLLVMBBAddrMapSection));
-  }
-};
-} // namespace
-static ManagedStatic<cl::opt<bool, true>,
-                     CreateYkAllocLLVMBBAddrMapSectionParser>
-    YkAllocLLVMBBAddrMapSectionParser;
-
 bool YkExtendedLLVMBBAddrMapSection;
 namespace {
 struct CreateYkExtendedLLVMBBAddrMapSectionParser {
@@ -126,8 +97,6 @@ struct CreateYkEmbedIRParser {
 static ManagedStatic<cl::opt<bool, true>, CreateYkEmbedIRParser> YkEmbedIRParser;
 
 void llvm::initYkOptions() {
-  *YkAllocLLVMBCSectionParser;
-  *YkAllocLLVMBBAddrMapSectionParser;
   *YkExtendedLLVMBBAddrMapSectionParser;
   *YkStackMapOffsetFixParser;
   *YkStackMapAdditionalLocsParser;