It's inefficient to have place the exception tables (which contain the LSDA)

into the __DATA section. At launch time, dyld has to update most of the section
to fix up the type info pointers. It's better to place it into the __TEXT
section and use pc-rel indirect pointer encodings. Similar to the personality
routine.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82274 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2009-09-18 21:14:36 +00:00
parent fb2e752e41
commit 296ab7e544
2 changed files with 43 additions and 8 deletions

View File

@ -893,14 +893,49 @@ void DwarfException::EmitExceptionTable() {
// of the catch clauses as they appear in the source code, and must be kept in
// the same order. As a result, changing the order of the catch clause would
// change the semantics of the program.
for (std::vector<GlobalVariable *>::const_reverse_iterator
I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
const GlobalVariable *GV = *I;
PrintRelDirective();
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned Index = 1;
if (GV) {
O << Asm->Mang->getMangledName(GV);
for (std::vector<GlobalVariable *>::const_reverse_iterator
I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I, ++Index) {
const GlobalVariable *TI = *I;
if (TI) {
if (TTypeFormat == dwarf::DW_EH_PE_absptr) {
// Print out the unadorned name of the type info.
PrintRelDirective();
O << Asm->Mang->getMangledName(TI);
} else {
bool IsTypeInfoIndirect = false, IsTypeInfoPCRel = false;
const MCExpr *TypeInfoRef =
TLOF.getSymbolForDwarfGlobalReference(TI, Asm->Mang, Asm->MMI,
IsTypeInfoIndirect,
IsTypeInfoPCRel);
if (!IsTypeInfoPCRel) {
// If the reference to the type info symbol is not already
// pc-relative, then we need to subtract our current address from it.
// Do this by emitting a label and subtracting it from the expression
// we already have. This is equivalent to emitting "foo - .", but we
// have to emit the label for "." directly.
SmallString<64> Name;
raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
<< "typeinforef_addr" << Asm->getFunctionNumber() << "_" << Index;
MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
Asm->OutStreamer.EmitLabel(DotSym);
TypeInfoRef =
MCBinaryExpr::CreateSub(TypeInfoRef,
MCSymbolRefExpr::Create(DotSym,
Asm->OutContext),
Asm->OutContext);
}
O << MAI->getData32bitsDirective();
TypeInfoRef->print(O, MAI);
}
} else {
PrintRelDirective();
O << "0x0";
}

View File

@ -782,8 +782,8 @@ void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
}
// Exception Handling.
LSDASection = getMachOSection("__DATA", "__gcc_except_tab", 0,
SectionKind::getDataRel());
LSDASection = getMachOSection("__TEXT", "__gcc_except_tab", 0,
SectionKind::getReadOnly());
EHFrameSection =
getMachOSection("__TEXT", "__eh_frame",
MCSectionMachO::S_COALESCED |