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ELF: Use magic linker symbol names for begin/end of .minfo.

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This commit is contained in:
Johan Engelen 2016-10-16 19:48:18 +02:00
parent 9dad1609db
commit eb0f97aaf1
1 changed files with 27 additions and 41 deletions
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64
gen/modules.cpp
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@ -101,9 +101,9 @@ enum class RegistryStyle {
/// global. /// global.
legacyLinkedList, legacyLinkedList,
/// Module references are emitted into the .minfo section, bracketed with /// Module references are emitted into the .minfo section. Global
/// extra sections to access the .minfo range. Global constructors/ /// constructors/destructors make sure _d_dso_registry is invoked once per ELF
/// destructors make sure _d_dso_registry is invoked once per ELF object. /// object.
sectionELF, sectionELF,
/// Module references are emitted into the .minfo section. Global /// Module references are emitted into the .minfo section. Global
@ -353,34 +353,17 @@ void emitModuleRefToSection(RegistryStyle style, std::string moduleMangle,
assert(style == RegistryStyle::sectionELF || assert(style == RegistryStyle::sectionELF ||
style == RegistryStyle::sectionDarwin); style == RegistryStyle::sectionDarwin);
// Only for the first D module to be emitted into this llvm::Module we need to // Only for the first D module to be emitted into this llvm::Module we need to
// create the _minfo_beg/_minfo_end symbols and the global ctors/dtors. For // create the global ctors/dtors. The magic linker symbols used to get the
// all subsequent ones, we just need to emit an additional reference into the // start and end of the .minfo section also only need to be emitted for the
// .minfo section (even with --gc-sections, the section is already kept alive // first D module.
// by the first module's reference being used in the ctor/dtor functions). // For all subsequent ones, we just need to emit an additional reference into
// the .minfo section (even with --gc-sections, the section is already kept
// alive by the first module's reference being used in the ctor/dtor
// functions).
const bool isFirst = !gIR->module.getGlobalVariable("ldc.dso_slot"); const bool isFirst = !gIR->module.getGlobalVariable("ldc.dso_slot");
llvm::Type *const moduleInfoPtrTy = DtoPtrToType(Module::moduleinfo->type); llvm::Type *const moduleInfoPtrTy = DtoPtrToType(Module::moduleinfo->type);
// Order is important here: For ELF, we must create the symbols in the
// bracketing sections right before/after the ModuleInfo reference
// so that they end up in the correct order in the object file.
llvm::GlobalVariable *minfoBeg;
if (isFirst) {
if (style == RegistryStyle::sectionDarwin) {
minfoBeg =
new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
llvm::GlobalValue::ExternalLinkage, nullptr,
"\1section$start$__DATA$.minfo");
} else {
minfoBeg =
new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
llvm::GlobalValue::LinkOnceODRLinkage,
getNullPtr(moduleInfoPtrTy), "_minfo_beg");
minfoBeg->setSection(".minfo_beg");
minfoBeg->setVisibility(llvm::GlobalValue::HiddenVisibility);
}
}
std::string thismrefname = "_D"; std::string thismrefname = "_D";
thismrefname += moduleMangle; thismrefname += moduleMangle;
thismrefname += "11__moduleRefZ"; thismrefname += "11__moduleRefZ";
@ -390,7 +373,7 @@ void emitModuleRefToSection(RegistryStyle style, std::string moduleMangle,
llvm::GlobalValue::LinkOnceODRLinkage, llvm::GlobalValue::LinkOnceODRLinkage,
DtoBitCast(thisModuleInfo, moduleInfoPtrTy), thismrefname); DtoBitCast(thisModuleInfo, moduleInfoPtrTy), thismrefname);
thismref->setSection((style == RegistryStyle::sectionDarwin) ? "__DATA,.minfo" thismref->setSection((style == RegistryStyle::sectionDarwin) ? "__DATA,.minfo"
: ".minfo"); : "__minfo");
gIR->usedArray.push_back(thismref); gIR->usedArray.push_back(thismref);
if (!isFirst) { if (!isFirst) {
@ -398,19 +381,22 @@ void emitModuleRefToSection(RegistryStyle style, std::string moduleMangle,
return; return;
} }
llvm::GlobalVariable *minfoEnd; // Use magic linker symbol names to obtain the begin and end of the .minfo
if (style == RegistryStyle::sectionDarwin) { // section.
minfoEnd = new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false, const auto magicBeginSymbolName = (style == RegistryStyle::sectionDarwin)
? "\1section$start$__DATA$.minfo"
: "__start___minfo";
const auto magicEndSymbolName = (style == RegistryStyle::sectionDarwin)
? "\1section$end$__DATA$.minfo"
: "__stop___minfo";
auto minfoBeg = new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
llvm::GlobalValue::ExternalLinkage, llvm::GlobalValue::ExternalLinkage,
nullptr, "\1section$end$__DATA$.minfo"); nullptr, magicBeginSymbolName);
} else { auto minfoEnd = new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
minfoEnd = llvm::GlobalValue::ExternalLinkage,
new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false, nullptr, magicEndSymbolName);
llvm::GlobalValue::LinkOnceODRLinkage, minfoBeg->setVisibility(llvm::GlobalValue::HiddenVisibility);
getNullPtr(moduleInfoPtrTy), "_minfo_end");
minfoEnd->setSection(".minfo_end");
minfoEnd->setVisibility(llvm::GlobalValue::HiddenVisibility); minfoEnd->setVisibility(llvm::GlobalValue::HiddenVisibility);
}
// Build the ctor to invoke _d_dso_registry. // Build the ctor to invoke _d_dso_registry.