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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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68
gen/modules.cpp
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@ -101,9 +101,9 @@ enum class RegistryStyle {
/// global.
legacyLinkedList,
/// Module references are emitted into the .minfo section, bracketed with
/// extra sections to access the .minfo range. Global constructors/
/// destructors make sure _d_dso_registry is invoked once per ELF object.
/// Module references are emitted into the .minfo section. Global
/// constructors/destructors make sure _d_dso_registry is invoked once per ELF
/// object.
sectionELF,
/// Module references are emitted into the .minfo section. Global
@ -353,34 +353,17 @@ void emitModuleRefToSection(RegistryStyle style, std::string moduleMangle,
assert(style == RegistryStyle::sectionELF ||
style == RegistryStyle::sectionDarwin);
// 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
// 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).
// create the global ctors/dtors. The magic linker symbols used to get the
// start and end of the .minfo section also only need to be emitted for the
// first D module.
// 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");
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$.minfo");
} else {
minfoBeg =
new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
llvm::GlobalValue::LinkOnceODRLinkage,
getNullPtr(moduleInfoPtrTy), "_minfo_beg");
minfoBeg->setSection(".minfo_beg");
minfoBeg->setVisibility(llvm::GlobalValue::HiddenVisibility);
}
}
std::string thismrefname = "_D";
thismrefname += moduleMangle;
thismrefname += "11__moduleRefZ";
@ -390,7 +373,7 @@ void emitModuleRefToSection(RegistryStyle style, std::string moduleMangle,
llvm::GlobalValue::LinkOnceODRLinkage,
DtoBitCast(thisModuleInfo, moduleInfoPtrTy), thismrefname);
thismref->setSection((style == RegistryStyle::sectionDarwin) ? "__DATA,.minfo"
: ".minfo");
: "__minfo");
gIR->usedArray.push_back(thismref);
if (!isFirst) {
@ -398,19 +381,22 @@ void emitModuleRefToSection(RegistryStyle style, std::string moduleMangle,
return;
}
llvm::GlobalVariable *minfoEnd;
if (style == RegistryStyle::sectionDarwin) {
minfoEnd = new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
llvm::GlobalValue::ExternalLinkage,
nullptr, "\1section$end$__DATA$.minfo");
} else {
minfoEnd =
new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
llvm::GlobalValue::LinkOnceODRLinkage,
getNullPtr(moduleInfoPtrTy), "_minfo_end");
minfoEnd->setSection(".minfo_end");
minfoEnd->setVisibility(llvm::GlobalValue::HiddenVisibility);
}
// Use magic linker symbol names to obtain the begin and end of the .minfo
// section.
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,
nullptr, magicBeginSymbolName);
auto minfoEnd = new llvm::GlobalVariable(gIR->module, moduleInfoPtrTy, false,
llvm::GlobalValue::ExternalLinkage,
nullptr, magicEndSymbolName);
minfoBeg->setVisibility(llvm::GlobalValue::HiddenVisibility);
minfoEnd->setVisibility(llvm::GlobalValue::HiddenVisibility);
// Build the ctor to invoke _d_dso_registry.