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add some comments on how this is *supposed* to work. We don't 

need the PreferredEHDataFormat hook, but I have yet-more refactoring to
do before I can zap it.

llvm-svn: 77742
This commit is contained in:
Chris Lattner 2009-07-31 22:18:14 +00:00
parent 47fc2351c0
commit f4b92a8a00
1 changed files with 27 additions and 0 deletions
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27
llvm/lib/CodeGen/AsmPrinter/DwarfException.cpp
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@ -539,6 +539,9 @@ void DwarfException::EmitExceptionTable() {
unsigned SizeAlign = (4 - TotalSize) & 3;
// Begin the exception table.
//MCSection *LSDASection = TAI->getLSDASection();
//Asm->SwitchToSection(LSDASection);
Asm->SwitchToDataSection(TAI->getDwarfExceptionSection());
Asm->EmitAlignment(2, 0, 0, false);
O << "GCC_except_table" << SubprogramCount << ":\n";
@ -560,8 +563,32 @@ void DwarfException::EmitExceptionTable() {
Asm->EmitInt8(dwarf::DW_EH_PE_omit);
Asm->EOL("TType format (DW_EH_PE_omit)");
} else {
// FIXME: Instead of using "PreferredEHDataFormat", we should use a simple
// approach to determine what needs to happen. Basically, if the target
// wants the LSDA to be emitted into a read-only segment (like .text) then
// (unless in static mode) it can't output direct pointers to the typeinfo
// objects, which may be in an arbitrary locations. Instead, it has to use
// and indirect stub pointer to get to the typeinfo.
//
// If the target wants to dump the LSDA's into a segment writable by the
// dynamic linker, then it can just use a normal pointer, and the dynamic
// linker will fix it up.
// TODO: Replace the getDwarfExceptionSection() callback on TAI with a new
// getLSDASection() method on TLOF. Merge and sanitize the implementations,
// and figure out what the ".gcc_except_table" directive expands to on elf
// systems.
//
//if (LSDASection->isWritable()) {
//Asm->EmitInt8(DW_EH_PE_absptr);
//} else {
//Asm->EmitInt8(DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4);
//}
Asm->EmitInt8(TAI->PreferredEHDataFormat());
// FIXME: The comment here should correspond with what PreferredEHDataFormat
// returned.
Asm->EOL("TType format (DW_EH_PE_xxxxx)");