[llvm] r218129 - Omit DW_TAG_subprograms for subprograms without inlined subroutines when producing -gmlt data
David Blaikie
dblaikie at gmail.com
Sat Sep 20 07:47:34 PDT 2014
On Sep 19, 2014 6:03 PM, "Alexey Samsonov" <vonosmas at gmail.com> wrote:
>
> Thanks, this is awesome! Note that we might want to keep CU ranges
emission, as it speeds up address symbolizing: it's far quicker to scan CU
ranges and build address->CU relation, than load and parse all the
.debug_line section.
Ah - no doubt. At only 0.5% (uncompressed and in an optimized (-O2) build
(might be worse at -O0_ I'm gathering numbers for my gmlt improvements at
-O0 next)) its probably worth it, but certainly something to weigh up if we
ever go after it.
>
> On Fri, Sep 19, 2014 at 10:03 AM, David Blaikie <dblaikie at gmail.com>
wrote:
>>
>> Author: dblaikie
>> Date: Fri Sep 19 12:03:16 2014
>> New Revision: 218129
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=218129&view=rev
>> Log:
>> Omit DW_TAG_subprograms for subprograms without inlined subroutines when
producing -gmlt data
>>
>> To reduce the size of -gmlt data, skip the subprograms without any
>> inlined subroutines. Since we've now got the ability to make these
>> determinations in the backend (funnily enough - we added the flag so we
>> wouldn't produce ranges under -gmlt, but with this change we use the
>> flag, but go back to producing ranges under -gmlt).
>>
>> Instead, just produce CU ranges to inform the consumer which parts of
>> the code are described by this CU's line table. Tools could inspect the
>> line table directly to compute the range, but the CU ranges only seem to
>> be about 0.5% of object/executable size, so I'm not too worried about
>> teaching llvm-symbolizer that trick just yet - it's certainly a possible
>> piece of future work.
>>
>> Update an llvm-symbolizer test just to demonstrate that this schema is
>> acceptable there (if it wasn't, the compiler-rt tests would catch this,
>> but good to have an in-llvm-tree test for llvm-symbolizer's behavior
>> here)
>>
>> Building the clang binary with -gmlt with this patch reduces the total
>> size of object files by 5.1% (5.56% without ranges) without compression
>> and the executable by 4.37% (4.75% without ranges).
>>
>> Modified:
>> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
>> llvm/trunk/test/DebugInfo/Inputs/dwarfdump-inl-test.elf-x86-64
>> llvm/trunk/test/DebugInfo/gmlt.ll
>> llvm/trunk/test/DebugInfo/llvm-symbolizer.test
>>
>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>> URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=218129&r1=218128&r2=218129&view=diff
>>
==============================================================================
>> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Fri Sep 19 12:03:16
2014
>> @@ -856,12 +856,14 @@ void DwarfDebug::finishSubprogramDefinit
>> // If this subprogram has an abstract definition, reference
that
>> SPCU->addDIEEntry(*D, dwarf::DW_AT_abstract_origin,
*AbsSPDIE);
>> } else {
>> - if (!D)
>> + if (!D && TheCU.getEmissionKind() != DIBuilder::LineTablesOnly)
>> // Lazily construct the subprogram if we didn't see either
concrete or
>> - // inlined versions during codegen.
>> + // inlined versions during codegen. (except in -gmlt ^ where
we want
>> + // to omit these entirely)
>> D = SPCU->getOrCreateSubprogramDIE(SP);
>> - // And attach the attributes
>> - SPCU->applySubprogramAttributesToDefinition(SP, *D);
>> + if (D)
>> + // And attach the attributes
>> + SPCU->applySubprogramAttributesToDefinition(SP, *D);
>> }
>> }
>> }
>> @@ -1690,6 +1692,24 @@ void DwarfDebug::endFunction(const Machi
>> LexicalScope *FnScope = LScopes.getCurrentFunctionScope();
>> DwarfCompileUnit &TheCU = *SPMap.lookup(FnScope->getScopeNode());
>>
>> + // Add the range of this function to the list of ranges for the CU.
>> + TheCU.addRange(RangeSpan(FunctionBeginSym, FunctionEndSym));
>> +
>> + // Under -gmlt, skip building the subprogram if there are no inlined
>> + // subroutines inside it.
>> + if (TheCU.getCUNode().getEmissionKind() == DIBuilder::LineTablesOnly
&&
>> + LScopes.getAbstractScopesList().empty()) {
>> + assert(ScopeVariables.empty());
>> + assert(CurrentFnArguments.empty());
>> + assert(DbgValues.empty());
>> + assert(AbstractVariables.empty());
>> + LabelsBeforeInsn.clear();
>> + LabelsAfterInsn.clear();
>> + PrevLabel = nullptr;
>> + CurFn = nullptr;
>> + return;
>> + }
>> +
>> // Construct abstract scopes.
>> for (LexicalScope *AScope : LScopes.getAbstractScopesList()) {
>> DISubprogram SP(AScope->getScopeNode());
>> @@ -1710,10 +1730,6 @@ void DwarfDebug::endFunction(const Machi
>> if (!CurFn->getTarget().Options.DisableFramePointerElim(*CurFn))
>> TheCU.addFlag(CurFnDIE, dwarf::DW_AT_APPLE_omit_frame_ptr);
>>
>> - // Add the range of this function to the list of ranges for the CU.
>> - RangeSpan Span(FunctionBeginSym, FunctionEndSym);
>> - TheCU.addRange(std::move(Span));
>> -
>> // Clear debug info
>> // Ownership of DbgVariables is a bit subtle - ScopeVariables owns
all the
>> // DbgVariables except those that are also in AbstractVariables
(since they
>>
>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
>> URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp?rev=218129&r1=218128&r2=218129&view=diff
>>
==============================================================================
>> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfUnit.cpp Fri Sep 19 12:03:16
2014
>> @@ -2049,23 +2049,20 @@ void DwarfUnit::emitHeader(const MCSymbo
>> }
>>
>> void DwarfCompileUnit::addRange(RangeSpan Range) {
>> - // Only add a range for this unit if we're emitting full debug.
>> - if (getCUNode().getEmissionKind() == DIBuilder::FullDebug) {
>> - bool SameAsPrevCU = this == DD->getPrevCU();
>> - DD->setPrevCU(this);
>> - // If we have no current ranges just add the range and return,
otherwise,
>> - // check the current section and CU against the previous section
and CU we
>> - // emitted into and the subprogram was contained within. If these
are the
>> - // same then extend our current range, otherwise add this as a new
range.
>> - if (CURanges.empty() || !SameAsPrevCU ||
>> - (&CURanges.back().getEnd()->getSection() !=
>> - &Range.getEnd()->getSection())) {
>> - CURanges.push_back(Range);
>> - return;
>> - }
>> -
>> - CURanges.back().setEnd(Range.getEnd());
>> + bool SameAsPrevCU = this == DD->getPrevCU();
>> + DD->setPrevCU(this);
>> + // If we have no current ranges just add the range and return,
otherwise,
>> + // check the current section and CU against the previous section and
CU we
>> + // emitted into and the subprogram was contained within. If these are
the
>> + // same then extend our current range, otherwise add this as a new
range.
>> + if (CURanges.empty() || !SameAsPrevCU ||
>> + (&CURanges.back().getEnd()->getSection() !=
>> + &Range.getEnd()->getSection())) {
>> + CURanges.push_back(Range);
>> + return;
>> }
>> +
>> + CURanges.back().setEnd(Range.getEnd());
>> }
>>
>> void DwarfCompileUnit::initStmtList(MCSymbol *DwarfLineSectionSym) {
>>
>> Modified: llvm/trunk/test/DebugInfo/Inputs/dwarfdump-inl-test.elf-x86-64
>> URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Inputs/dwarfdump-inl-test.elf-x86-64?rev=218129&r1=218128&r2=218129&view=diff
>>
==============================================================================
>> Binary files - no diff available.
>>
>> Modified: llvm/trunk/test/DebugInfo/gmlt.ll
>> URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/gmlt.ll?rev=218129&r1=218128&r2=218129&view=diff
>>
==============================================================================
>> --- llvm/trunk/test/DebugInfo/gmlt.ll (original)
>> +++ llvm/trunk/test/DebugInfo/gmlt.ll Fri Sep 19 12:03:16 2014
>> @@ -1,33 +1,72 @@
>> ; REQUIRES: object-emission
>> ; RUN: %llc_dwarf -O0 -filetype=obj < %s | llvm-dwarfdump - | FileCheck
%s
>>
>> -; Generated from the following source compiled with clang -gmlt:
>> -; void f1(void) {}
>> -; void f2(void) __attribute__((section("__TEXT,__bar"))) {}
>> +; Generated from the following source compiled with clang++ -gmlt:
>> +; void f1() {}
>> +; void __attribute__((section("__TEXT,__bar"))) f2() {}
>> +; void __attribute__((always_inline)) f3() { f1(); }
>> +; void f4() { f3(); }
>>
>> ; Check that
>> -; * -gmlt ('Emission Kind' of 'LineTablesOnly' in the CU debug info
metadata)
>> -; doesn't produce ranges.
>> -; * if no ranges are produced, no debug_ranges list (not even an empty
one) is
>> -; emitted.
>> -
>> -; -gmlt means no DW_AT_ranges on the CU, even though there are parts of
the CU
>> -; in different sections and this would normally necessitate a
DW_AT_ranges
>> -; attribute on the CU.
>> +; * -gmlt includes no DW_TAG_subprograms for subprograms without
inlined
>> +; subroutines.
>> +; * yet still produces DW_AT_ranges and a range list in debug_ranges
that
>> +; describes those subprograms
>> +
>> ; CHECK: DW_TAG_compile_unit
>> -; CHECK-NOT: DW_AT_ranges
>> +; CHECK: DW_AT_ranges [DW_FORM_sec_offset] (0x00000000)
>> ; CHECK-NOT: {{DW_TAG|NULL}}
>> +
>> +
>> +; FIXME: Emitting separate abstract definitions is inefficient when we
could
>> +; just attach the DW_AT_name to the inlined_subroutine directly. Except
that
>> +; would produce many string relocations. Implement string indexing in
the
>> +; skeleton CU to address the relocation problem, then remove abstract
>> +; definitions from -gmlt here.
>> +
>> +; CHECK: [[F3_ABS_DEF:.*]]: DW_TAG_subprogram
>> +; CHECK-NEXT: DW_AT_name {{.*}} "f3"
>> +
>> +; FIXME: We don't really need DW_AT_inline, consumers can ignore this
due to
>> +; the absence of high_pc/low_pc/ranges and know that they just need it
for
>> +; retrieving the name of a concrete inlined instance
>> +
>> +; CHECK-NEXT: DW_AT_inline
>> +; CHECK-NOT: {{DW_TAG|DW_AT|NULL}}
>> +
>> ; Check that we only provide the minimal attributes on a subprogram to
save space.
>> ; CHECK: DW_TAG_subprogram
>> ; CHECK-NEXT: DW_AT_low_pc
>> ; CHECK-NEXT: DW_AT_high_pc
>> ; CHECK-NEXT: DW_AT_name
>> -; CHECK-NOT: DW_AT
>> -; CHECK: {{DW_TAG|NULL}}
>> +; CHECK-NOT: {{DW_TAG|DW_AT}}
>> +; CHECK: DW_TAG_inlined_subroutine
>> +
>> +; As mentioned above - replace DW_AT_abstract_origin with DW_AT_name to
save
>> +; space once we have support for string indexing in non-dwo sections
>>
>> -; FIXME: We probably want to avoid printing out anything if the section
isn't there.
>> +; CHECK-NEXT: DW_AT_abstract_origin {{.*}} {[[F3_ABS_DEF]]}
>> +; CHECK-NEXT: DW_AT_low_pc
>> +; CHECK-NEXT: DW_AT_high_pc
>> +; CHECK-NEXT: DW_AT_call_file
>> +; CHECK-NEXT: DW_AT_call_line
>> +
>> +; Make sure we don't have any other subprograms here (subprograms with
no
>> +; inlined subroutines are omitted by design to save space)
>> +
>> +; CHECK-NOT: {{DW_TAG|DW_AT}}
>> +; CHECK: NULL
>> +; CHECK-NOT: {{DW_TAG|DW_AT}}
>> +; CHECK: NULL
>> +
>> +
>> +; FIXME: llvm-dwarfdump should detect the relocations here and realize
that the
>> +; first two "end of list" are really just unrelocated values describing
the two
>> +; functions in the CU.
>> ; CHECK: .debug_ranges contents:
>> -; CHECK-NOT: 00000000 <End of list>
>> +; CHECK: 00000000 <End of list>
>> +; CHECK: 00000010 <End of list>
>> +; CHECK: 00000020 <End of list>
>>
>> ; Check that we don't emit any pubnames or pubtypes under -gmlt
>> ; CHECK: .debug_pubnames contents:
>> @@ -37,33 +76,56 @@
>> ; CHECK-NOT: Offset
>>
>> ; Function Attrs: nounwind uwtable
>> -define void @f1() #0 {
>> +define void @_Z2f1v() #0 {
>> +entry:
>> + ret void, !dbg !13
>> +}
>> +
>> +; Function Attrs: nounwind uwtable
>> +define void @_Z2f2v() #0 section "__TEXT,__bar" {
>> +entry:
>> + ret void, !dbg !14
>> +}
>> +
>> +; Function Attrs: alwaysinline nounwind uwtable
>> +define void @_Z2f3v() #1 {
>> entry:
>> - ret void, !dbg !11
>> + call void @_Z2f1v(), !dbg !15
>> + ret void, !dbg !16
>> }
>>
>> ; Function Attrs: nounwind uwtable
>> -define void @f2() #0 section "__TEXT,__bar" {
>> +define void @_Z2f4v() #0 {
>> entry:
>> - ret void, !dbg !12
>> + call void @_Z2f1v() #2, !dbg !17
>> + ret void, !dbg !19
>> }
>>
>> attributes #0 = { nounwind uwtable "less-precise-fpmad"="false"
"no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"
"no-infs-fp-math"="false" "no-nans-fp-math"="false"
"stack-protector-buffer-size"="8" "unsafe-fp-math"="false"
"use-soft-float"="false" }
>> +attributes #1 = { alwaysinline nounwind uwtable
"less-precise-fpmad"="false" "no-frame-pointer-elim"="true"
"no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false"
"no-nans-fp-math"="false" "stack-protector-buffer-size"="8"
"unsafe-fp-math"="false" "use-soft-float"="false" }
>> +attributes #2 = { nounwind }
>>
>> !llvm.dbg.cu = !{!0}
>> -!llvm.module.flags = !{!8, !9}
>> -!llvm.ident = !{!10}
>> +!llvm.module.flags = !{!10, !11}
>> +!llvm.ident = !{!12}
>>
>> -!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang
version 3.6.0 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2,
metadata !3, metadata !2, metadata !2, metadata !"", i32 2} ; [
DW_TAG_compile_unit ] [/tmp/dbginfo/cu-line-tables.c] [DW_LANG_C99]
>> -!1 = metadata !{metadata !"cu-line-tables.c", metadata !"/tmp/dbginfo"}
>> +!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang
version 3.6.0 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2,
metadata !3, metadata !2, metadata !2, metadata !"", i32 2} ; [
DW_TAG_compile_unit ] [/tmp/dbginfo/gmlt.cpp] [DW_LANG_C_plus_plus]
>> +!1 = metadata !{metadata !"gmlt.cpp", metadata !"/tmp/dbginfo"}
>> !2 = metadata !{}
>> -!3 = metadata !{metadata !4, metadata !7}
>> -!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f1",
metadata !"f1", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0,
i32 0, null, i32 256, i1 false, void ()* @f1, null, null, metadata !2, i32
1} ; [ DW_TAG_subprogram ] [line 1] [def] [f1]
>> -!5 = metadata !{i32 786473, metadata !1} ; [ DW_TAG_file_type
] [/tmp/dbginfo/cu-line-tables.c]
>> +!3 = metadata !{metadata !4, metadata !7, metadata !8, metadata !9}
>> +!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f1",
metadata !"f1", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0,
i32 0, null, i32 256, i1 false, void ()* @_Z2f1v, null, null, metadata !2,
i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [f1]
>> +!5 = metadata !{i32 786473, metadata !1} ; [ DW_TAG_file_type
] [/tmp/dbginfo/gmlt.cpp]
>> !6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0,
i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null} ; [
DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
>> -!7 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f2",
metadata !"f2", metadata !"", i32 2, metadata !6, i1 false, i1 true, i32 0,
i32 0, null, i32 256, i1 false, void ()* @f2, null, null, metadata !2, i32
2} ; [ DW_TAG_subprogram ] [line 2] [def] [f2]
>> -!8 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
>> -!9 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
>> -!10 = metadata !{metadata !"clang version 3.6.0 "}
>> -!11 = metadata !{i32 1, i32 16, metadata !4, null}
>> -!12 = metadata !{i32 2, i32 48, metadata !7, null}
>> +!7 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f2",
metadata !"f2", metadata !"", i32 2, metadata !6, i1 false, i1 true, i32 0,
i32 0, null, i32 256, i1 false, void ()* @_Z2f2v, null, null, metadata !2,
i32 2} ; [ DW_TAG_subprogram ] [line 2] [def] [f2]
>> +!8 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f3",
metadata !"f3", metadata !"", i32 3, metadata !6, i1 false, i1 true, i32 0,
i32 0, null, i32 256, i1 false, void ()* @_Z2f3v, null, null, metadata !2,
i32 3} ; [ DW_TAG_subprogram ] [line 3] [def] [f3]
>> +!9 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f4",
metadata !"f4", metadata !"", i32 4, metadata !6, i1 false, i1 true, i32 0,
i32 0, null, i32 256, i1 false, void ()* @_Z2f4v, null, null, metadata !2,
i32 4} ; [ DW_TAG_subprogram ] [line 4] [def] [f4]
>> +!10 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
>> +!11 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
>> +!12 = metadata !{metadata !"clang version 3.6.0 "}
>> +!13 = metadata !{i32 1, i32 12, metadata !4, null}
>> +!14 = metadata !{i32 2, i32 53, metadata !7, null}
>> +!15 = metadata !{i32 3, i32 44, metadata !8, null}
>> +!16 = metadata !{i32 3, i32 50, metadata !8, null}
>> +!17 = metadata !{i32 3, i32 44, metadata !8, metadata !18}
>> +!18 = metadata !{i32 4, i32 13, metadata !9, null}
>> +!19 = metadata !{i32 4, i32 19, metadata !9, null}
>>
>> Modified: llvm/trunk/test/DebugInfo/llvm-symbolizer.test
>> URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/llvm-symbolizer.test?rev=218129&r1=218128&r2=218129&view=diff
>>
==============================================================================
>> --- llvm/trunk/test/DebugInfo/llvm-symbolizer.test (original)
>> +++ llvm/trunk/test/DebugInfo/llvm-symbolizer.test Fri Sep 19 12:03:16
2014
>> @@ -6,9 +6,9 @@ RUN: echo "%p/Inputs/dwarfdump-test.elf-
>> RUN: echo "%p/Inputs/dwarfdump-test2.elf-x86-64 0x4004e8" >> %t.input
>> RUN: echo "%p/Inputs/dwarfdump-test2.elf-x86-64 0x4004f4" >> %t.input
>> RUN: echo "%p/Inputs/dwarfdump-test4.elf-x86-64 0x62c" >> %t.input
>> -RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x710" >> %t.input
>> -RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x7d1" >> %t.input
>> -RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x785" >> %t.input
>> +RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x8dc" >> %t.input
>> +RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0xa05" >> %t.input
>> +RUN: echo "%p/Inputs/dwarfdump-inl-test.elf-x86-64 0x987" >> %t.input
>> RUN: echo "%p/Inputs/dwarfdump-inl-test.high_pc.elf-x86-64 0x568" >>
%t.input
>> RUN: echo "\"%p/Inputs/dwarfdump-test3.elf-x86-64 space\" 0x640" >>
%t.input
>> RUN: echo "\"%p/Inputs/dwarfdump-test3.elf-x86-64 space\" 0x633" >>
%t.input
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
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>
>
>
>
> --
> Alexey Samsonov
> vonosmas at gmail.com
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