[PATCH] Minor cleanup for GNU TLS support
David Blaikie
dblaikie at gmail.com
Mon Oct 7 10:00:16 PDT 2013
On Mon, Oct 7, 2013 at 9:53 AM, Eric Christopher <echristo at gmail.com> wrote:
> On Sat, Oct 5, 2013 at 6:07 PM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> >
> > On Sat, Oct 5, 2013 at 5:45 PM, Richard Mitton <richard at codersnotes.com>
> > wrote:
> >>
> >> It's better without the *user in the switch, as the code that calls it
> >> will then just print 'invalid opcode %x' or whatever, as opposed to
> right
> >> now, where it knows about DW_OP_lo_user+0, but not any other user OPs
> >> (DW_OP_lo_user+N), which is silly.
> >>
> >> I don't think there's anything that really uses this much already, but
> >> I'll see if I can figure something out to test it with and the update
> the
> >> patch
> >
> >
> > When we print assembly (rather than the usual debug info of emitting an
> > object file and then using llvm-dwarfdump) we annotate the assembly with
> > comments - but thinking about it, I don't think we annotate DWARF
> > expressions/operators/etc, so this probably isn't visible. I wonder if we
> > call the OperationEncodingString at all.
> >
>
> We may not, but it'll be nice to do so. It's handy to use when debugging
> anyhow.
>
Guessing: I suspect we can't really do it easily at the moment because the
dumping code would have to get a lot smarter. The form doesn't imply
whether or not the bytes are a DWARF expression or not, does it? (ie: data1
may or may not be a DWARF expression, it might instead be a file/line
number, etc... ) so we might end up annotating things that aren't DWARF
expressions as though they are. I guess maybe we could have a table of
attribute kind + form to decide whether to annotate the bytes as DWARF
expressions or not.
>
> -eric
>
> >>
> >> .
> >>
> >>
> >> Eric Christopher wrote:
> >>>
> >>> Should dump differently I'd have thought. Also don't want to delete
> >>> the DW_OP_*_user text I'd think.
> >>>
> >>> -eric
> >>>
> >>> On Sat, Oct 5, 2013 at 2:33 PM, Richard Mitton<richard at codersnotes.com
> >
> >>> wrote:
> >>>
> >>>>>
> >>>>> No functionality change.
> >>>>>
> >>>>
> >>>> Nothing to test! :)
> >>>>
> >>>>
> >>>>
> >>>> Eric Christopher wrote:
> >>>>
> >>>>>
> >>>>> Testcase? :)
> >>>>>
> >>>>> -eric
> >>>>>
> >>>>> On Sat, Oct 5, 2013 at 11:19 AM, Richard
> >>>>> Mitton<richard at codersnotes.com>
> >>>>> wrote:
> >>>>>
> >>>>>
> >>>>>>
> >>>>>> Formally added an explicit enum for DWARF TLS support. No
> >>>>>> functionality
> >>>>>> change.
> >>>>>>
> >>>>>>
> >>>>>> http://llvm-reviews.chandlerc.com/D1845
> >>>>>>
> >>>>>> Files:
> >>>>>> include/llvm/Support/Dwarf.h
> >>>>>> lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> >>>>>> lib/Support/Dwarf.cpp
> >>>>>>
> >>>>>> Index: include/llvm/Support/Dwarf.h
> >>>>>> ===================================================================
> >>>>>> --- include/llvm/Support/Dwarf.h
> >>>>>> +++ include/llvm/Support/Dwarf.h
> >>>>>> @@ -486,6 +486,9 @@
> >>>>>> DW_OP_lo_user = 0xe0,
> >>>>>> DW_OP_hi_user = 0xff,
> >>>>>>
> >>>>>> + // Extensions for GNU-style thread-local storage.
> >>>>>> + DW_OP_GNU_push_tls_address = 0xe0,
> >>>>>> +
> >>>>>> // Extensions for Fission proposal.
> >>>>>> DW_OP_GNU_addr_index = 0xfb,
> >>>>>> DW_OP_GNU_const_index = 0xfc,
> >>>>>> Index: lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> >>>>>> ===================================================================
> >>>>>> --- lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> >>>>>> +++ lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> >>>>>> @@ -1513,14 +1513,15 @@
> >>>>>> // 1) Start with a constNu of the appropriate pointer
> size
> >>>>>> addUInt(Block, 0, dwarf::DW_FORM_data1,
> >>>>>> PointerSize == 4 ? dwarf::DW_OP_const4u :
> >>>>>> dwarf::DW_OP_const8u);
> >>>>>> - // 2) containing the (relocated) address of the TLS
> variable
> >>>>>> + // 2) containing the (relocated) offset of the TLS variable
> >>>>>> + // within the module's TLS block.
> >>>>>> addExpr(Block, 0, dwarf::DW_FORM_udata, Expr);
> >>>>>> } else {
> >>>>>> addUInt(Block, 0, dwarf::DW_FORM_data1,
> >>>>>> dwarf::DW_OP_GNU_const_index);
> >>>>>> addUInt(Block, 0, dwarf::DW_FORM_udata,
> >>>>>> DU->getAddrPoolIndex(Expr));
> >>>>>> }
> >>>>>> - // 3) followed by a custom OP to tell the debugger about TLS
> >>>>>> (presumably)
> >>>>>> - addUInt(Block, 0, dwarf::DW_FORM_data1,
> dwarf::DW_OP_lo_user);
> >>>>>> + // 3) followed by a custom OP to make the debugger do a TLS
> >>>>>> lookup.
> >>>>>> + addUInt(Block, 0, dwarf::DW_FORM_data1,
> >>>>>> dwarf::DW_OP_GNU_push_tls_address);
> >>>>>> } else
> >>>>>> addOpAddress(Block, Sym);
> >>>>>> // Do not create specification DIE if context is either
> compile
> >>>>>> unit
> >>>>>> Index: lib/Support/Dwarf.cpp
> >>>>>> ===================================================================
> >>>>>> --- lib/Support/Dwarf.cpp
> >>>>>> +++ lib/Support/Dwarf.cpp
> >>>>>> @@ -456,10 +456,11 @@
> >>>>>> case DW_OP_bit_piece: return
> "DW_OP_bit_piece";
> >>>>>> case DW_OP_implicit_value: return
> >>>>>> "DW_OP_implicit_value";
> >>>>>> case DW_OP_stack_value: return
> >>>>>> "DW_OP_stack_value";
> >>>>>> - case DW_OP_lo_user: return "DW_OP_lo_user";
> >>>>>> - case DW_OP_hi_user: return "DW_OP_hi_user";
> >>>>>>
> >>>>>> - // DWARF5 Fission Proposal Op Extensions
> >>>>>> + // GNU thread-local storage
> >>>>>> + case DW_OP_GNU_push_tls_address: return
> >>>>>> "DW_OP_GNU_push_tls_address";
> >>>>>> +
> >>>>>> + // DWARF5 Fission Proposal Op Extensions
> >>>>>> case DW_OP_GNU_addr_index: return
> >>>>>> "DW_OP_GNU_addr_index";
> >>>>>> case DW_OP_GNU_const_index: return
> >>>>>> "DW_OP_GNU_const_index";
> >>>>>> }
> >>>>>>
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> >>>>>>
> >>>>>>
> >>>>>>
> >>>>
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> >>
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