[PATCH] Support DWARF discriminators in object streamer.
David Blaikie
dblaikie at gmail.com
Fri Feb 14 08:34:06 PST 2014
On Fri, Feb 14, 2014 at 7:37 AM, Rafael Espíndola <
rafael.espindola at gmail.com> wrote:
> We really shouldn't be mixing debug information *in* the .s and debug
> information generated *for* a .s.
>
> It might be that dwarfdump has a bug and needs more information to
> work. In which case that information should be in the .s or we should
> fix dwarfdump.
>
It sort of does. I poked around with this yesterday.
llvm-dwarfdump can't/won't dump debug_line tables if there's no compile
unit that refers to that debug_lines section.
One reason is that you can't actually parse the debug_line tables if you
don't know the size of an address for the compile unit. So llvm-dwarfdump
just reads all the compile units and prints out their respective line
tables.
This is both redundant (it'll print multiple line tables even if all the
compile units share a single one, I think) and needlessly
confusing/incorrect (even if we can't print the guts of the line table, we
should still be able to read the length of the table (maybe print the whole
table header - but I think it has one address field, which can vary
depending on the CU) and skip over its contents).
So what would be nice to see would be: parse all the CUs, sort their
debug_line offsets, then walk the debug_types section in order, printing a
terse summary ("length, unknown data") for each entry/table/thing we didn't
have a CU/address size for, and printing the full dump for each one we do
have the CU/address size for.
The short answer here, without fixing/improving llvm-dwarfdump, would be to
just include a minimal debug_info section with a single compile_unit with
the necessary DW_AT_stmt_list entry that points to the debug_lines section,
then dumping will print it out.
>
> Give me a sec. I am applying you patch and will debug it a bit to see
> what is the issue.
>
> On 14 February 2014 10:28, Diego Novillo <dnovillo at google.com> wrote:
> > I still haven't woken up. I need -g in *both* cases:
> >
> > 1- llvm-dwarfdump needs a -g .o or it will not generate its report.
> > 2- If I do not use -g, I need to write a .file directive so .loc won't
> > get confused.
> > 3- I cannot write a .file directive if I'm using -g.
> >
> > So, the only way to get both tests here is to always run llvm-mc with
> > -g.
> >
> > Hi echristo,
> >
> > http://llvm-reviews.chandlerc.com/D2794
> >
> > CHANGE SINCE LAST DIFF
> > http://llvm-reviews.chandlerc.com/D2794?vs=7129&id=7131#toc
> >
> > Files:
> > lib/DebugInfo/DWARFDebugLine.cpp
> > lib/DebugInfo/DWARFDebugLine.h
> > lib/MC/MCDwarf.cpp
> > test/DebugInfo/X86/ending-run.ll
> > test/DebugInfo/X86/line-info.ll
> > test/MC/ELF/discriminator.s
> > test/MC/MachO/gen-dwarf-cpp.s
> > test/MC/MachO/gen-dwarf.s
> >
> > Index: lib/DebugInfo/DWARFDebugLine.cpp
> > ===================================================================
> > --- lib/DebugInfo/DWARFDebugLine.cpp
> > +++ lib/DebugInfo/DWARFDebugLine.cpp
> > @@ -62,6 +62,7 @@
> > Column = 0;
> > File = 1;
> > Isa = 0;
> > + Discriminator = 0;
> > IsStmt = default_is_stmt;
> > BasicBlock = false;
> > EndSequence = false;
> > @@ -71,7 +72,7 @@
> >
> > void DWARFDebugLine::Row::dump(raw_ostream &OS) const {
> > OS << format("0x%16.16" PRIx64 " %6u %6u", Address, Line, Column)
> > - << format(" %6u %3u ", File, Isa)
> > + << format(" %6u %3u %13u ", File, Isa, Discriminator)
> > << (IsStmt ? " is_stmt" : "")
> > << (BasicBlock ? " basic_block" : "")
> > << (PrologueEnd ? " prologue_end" : "")
> > @@ -85,8 +86,9 @@
> > OS << '\n';
> >
> > if (!Rows.empty()) {
> > - OS << "Address Line Column File ISA Flags\n"
> > - << "------------------ ------ ------ ------ --- -------------\n";
> > + OS << "Address Line Column File ISA Discriminator
> Flags\n"
> > + << "------------------ ------ ------ ------ --- ------------- "
> > + "-------------\n";
> > for (std::vector<Row>::const_iterator pos = Rows.begin(),
> > end = Rows.end(); pos != end; ++pos)
> > pos->dump(OS);
> > @@ -311,6 +313,10 @@
> > }
> > break;
> >
> > + case DW_LNE_set_discriminator:
> > + state.Discriminator = debug_line_data.getULEB128(offset_ptr);
> > + break;
> > +
> > default:
> > // Length doesn't include the zero opcode byte or the length
> itself, but
> > // it does include the sub_opcode, so we have to adjust for
> that below
> > Index: lib/DebugInfo/DWARFDebugLine.h
> > ===================================================================
> > --- lib/DebugInfo/DWARFDebugLine.h
> > +++ lib/DebugInfo/DWARFDebugLine.h
> > @@ -112,6 +112,9 @@
> > // An unsigned integer whose value encodes the applicable
> instruction set
> > // architecture for the current instruction.
> > uint8_t Isa;
> > + // An unsigned integer representing the DWARF path discriminator
> value
> > + // for this location.
> > + uint32_t Discriminator;
> > // A boolean indicating that the current instruction is the
> beginning of a
> > // statement.
> > uint8_t IsStmt:1,
> > Index: lib/MC/MCDwarf.cpp
> > ===================================================================
> > --- lib/MC/MCDwarf.cpp
> > +++ lib/MC/MCDwarf.cpp
> > @@ -137,6 +137,7 @@
> > unsigned Column = 0;
> > unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT :
> 0;
> > unsigned Isa = 0;
> > + unsigned Discriminator = 0;
> > MCSymbol *LastLabel = NULL;
> >
> > // Loop through each MCLineEntry and encode the dwarf line number
> table.
> > @@ -154,6 +155,15 @@
> > MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
> > MCOS->EmitULEB128IntValue(Column);
> > }
> > + if (Discriminator != it->getDiscriminator()) {
> > + Discriminator = it->getDiscriminator();
> > + unsigned Size =
> > +
> MCOS->getContext().getAsmInfo()->getULEB128Size(Discriminator);
> > + MCOS->EmitIntValue(dwarf::DW_LNS_extended_op, 1);
> > + MCOS->EmitULEB128IntValue(Size + 1);
> > + MCOS->EmitIntValue(dwarf::DW_LNE_set_discriminator, 1);
> > + MCOS->EmitULEB128IntValue(Discriminator);
> > + }
> > if (Isa != it->getIsa()) {
> > Isa = it->getIsa();
> > MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
> > Index: test/DebugInfo/X86/ending-run.ll
> > ===================================================================
> > --- test/DebugInfo/X86/ending-run.ll
> > +++ test/DebugInfo/X86/ending-run.ll
> > @@ -4,9 +4,9 @@
> > ; Check that the line table starts at 7, not 4, but that the first
> > ; statement isn't until line 8.
> >
> > -; CHECK-NOT: 0x0000000000000000 7 0 1 0 is_stmt
> > +; CHECK-NOT: 0x0000000000000000 7 0 1 0 0 is_stmt
> > ; CHECK: 0x0000000000000000 7 0 1 0
> > -; CHECK: 0x0000000000000004 8 18 1 0 is_stmt
> prologue_end
> > +; CHECK: 0x0000000000000004 8 18 1 0 0 is_stmt
> prologue_end
> >
> > define i32 @callee(i32 %x) nounwind uwtable ssp {
> > entry:
> > Index: test/DebugInfo/X86/line-info.ll
> > ===================================================================
> > --- test/DebugInfo/X86/line-info.ll
> > +++ test/DebugInfo/X86/line-info.ll
> > @@ -2,7 +2,7 @@
> > ; RUN: llvm-dwarfdump %t | FileCheck %s
> >
> > ; CHECK: [[FILEID:[0-9]+]]]{{.*}}list0.h
> > -; CHECK: [[FILEID]] 0 1 0 is_stmt{{$}}
> > +; CHECK: [[FILEID]] 0 1 0 0 is_stmt{{$}}
> >
> > ; IR generated from clang -g -emit-llvm with the following source:
> > ; list0.h:
> > Index: test/MC/ELF/discriminator.s
> > ===================================================================
> > --- /dev/null
> > +++ test/MC/ELF/discriminator.s
> > @@ -0,0 +1,20 @@
> > +# RUN: llvm-mc -g -triple i386-unknown-unknown %s -filetype=obj -o - |
> llvm-readobj -r | FileCheck %s
> > +# RUN: llvm-mc -g -triple i386-unknown-unknown %s -filetype=obj -o - |
> llvm-dwarfdump -debug-dump=line - | FileCheck %s -check-prefix=DWARF-DUMP
> > +
> > + .text
> > + .globl foo
> > + .type foo, @function
> > + .align 4
> > +foo:
> > + .loc 1 2 discriminator 1
> > + ret
> > + .size foo, .-foo
> > +
> > +# CHECK: Relocations [
> > +# CHECK: Section ({{[^ ]+}}) .rel.debug_line {
> > +# CHECK-NEXT: 0x5B R_386_32 .text 0x0
> > +# CHECK-NEXT: }
> > +
> > +# DWARF-DUMP: Address Line Column File ISA Discriminator
> Flags
> > +# DWARF-DUMP: ------------------ ------ ------ ------ --- -------------
> -------------
> > +# DWARF-DUMP: 0x0000000000000000 2 0 1 0 1
> is_stmt
> > Index: test/MC/MachO/gen-dwarf-cpp.s
> > ===================================================================
> > --- test/MC/MachO/gen-dwarf-cpp.s
> > +++ test/MC/MachO/gen-dwarf-cpp.s
> > @@ -17,6 +17,6 @@
> > // CHECK: file_names[ 2] 0 0x00000000 0x00000000 t.s
> >
> > // We check that the source line number 100 is picked up before the
> "movl"
> > -// CHECK: Address Line Column File ISA Flags
> > -// CHECK: ------------------ ------ ------ ------ --- -------------
> > -// CHECK: 0x0000000000000000 102 0 2 0 is_stmt
> > +// CHECK: Address Line Column File ISA Discriminator
> Flags
> > +// CHECK: ------------------ ------ ------ ------ --- -------------
> -------------
> > +// CHECK: 0x0000000000000000 102 0 2 0 0
> is_stmt
> > Index: test/MC/MachO/gen-dwarf.s
> > ===================================================================
> > --- test/MC/MachO/gen-dwarf.s
> > +++ test/MC/MachO/gen-dwarf.s
> > @@ -113,10 +113,10 @@
> > // CHECK: ---- ---------- ----------
> ---------------------------
> > // CHECK: file_names[ 1] 1 0x00000000 0x00000000 gen-dwarf.s
> >
> > -// CHECK: Address Line Column File ISA Flags
> > -// CHECK: ------------------ ------ ------ ------ --- -------------
> > -// CHECK: 0x0000000000000000 6 0 1 0 is_stmt
> > -// CHECK: 0x0000000000000005 7 0 1 0 is_stmt
> > -// CHECK: 0x0000000000000006 8 0 1 0 is_stmt
> > -// CHECK: 0x0000000000000007 11 0 1 0 is_stmt
> > -// CHECK: 0x0000000000000008 11 0 1 0 is_stmt
> end_sequence
> > +// CHECK: Address Line Column File ISA Discriminator
> Flags
> > +// CHECK: ------------------ ------ ------ ------ --- -------------
> -------------
> > +// CHECK: 0x0000000000000000 6 0 1 0 0
> is_stmt
> > +// CHECK: 0x0000000000000005 7 0 1 0 0
> is_stmt
> > +// CHECK: 0x0000000000000006 8 0 1 0 0
> is_stmt
> > +// CHECK: 0x0000000000000007 11 0 1 0 0
> is_stmt
> > +// CHECK: 0x0000000000000008 11 0 1 0 0
> is_stmt end_sequence
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