[llvm] r218702 - Disable the -gmlt optimization implemented in r218129 under Darwin due to issues with dsymutil.
David Blaikie
dblaikie at gmail.com
Tue Sep 30 21:15:10 PDT 2014
On Sep 30, 2014 9:09 PM, "Justin Bogner" <mail at justinbogner.com> wrote:
>
> David Blaikie <dblaikie at gmail.com> writes:
> > Author: dblaikie
> > Date: Tue Sep 30 16:28:32 2014
> > New Revision: 218702
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=218702&view=rev
> > Log:
> > Disable the -gmlt optimization implemented in r218129 under Darwin due
> > to issues with dsymutil.
>
> This is causing a test failure on darwin:
>
>
http://lab.llvm.org:8013/builders/clang-x86_64-darwin11-nobootstrap-RAincremental/builds/4936/steps/run.llvm.tests/logs/LLVM%3A%3Agmlt.test
>
> I'll revert in a bit if you're not around.
If you can make that test xfail on Darwin (or just not run there - since
there's a specific Darwin variant of the test) that'd be swell. It'll be
easier for you to verify that that works than me (since I don't Dev on a
Mac)
>
> > r218129 omits DW_TAG_subprograms which have no inlined subroutines when
> > emitting -gmlt data. This makes -gmlt very low cost for -O0 builds.
> >
> > Darwin's dsymutil reasonably considers a CU empty if it has no
> > subprograms (which occurs with the above optimization in -O0 programs
> > without any force_inline function calls) and drops the line table, CU,
> > and everything in this situation, making backtraces impossible.
> >
> > Until dsymutil is modified to account for this, disable this
> > optimization on Darwin to preserve the desired functionality.
> > (see r218545, which should be reverted after this patch, for other
> > discussion/details)
> >
> > Footnote:
> > In the long term, it doesn't look like this scheme (of simplified debug
> > info to describe inlining to enable backtracing) is tenable, it is far
> > too size inefficient for optimized code (the DW_TAG_inlined_subprograms,
> > even once compressed, are nearly twice as large as the line table
> > itself (also compressed)) and we'll be considering things like Cary's
> > two level line table proposal to encode all this information directly in
> > the line table.
> >
> > Modified:
> > llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> > llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h
> > llvm/trunk/test/DebugInfo/gmlt.ll
> >
> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> > URL:
> >
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=218702&r1=218701&r2=218702&view=diff
> >
==============================================================================
> > --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Tue Sep 30
16:28:32 2014
> > @@ -171,6 +171,7 @@ DwarfDebug::DwarfDebug(AsmPrinter *A, Mo
> > GlobalRangeCount(0), InfoHolder(A, "info_string",
DIEValueAllocator),
> > UsedNonDefaultText(false),
> > SkeletonHolder(A, "skel_string", DIEValueAllocator),
> > + IsDarwin(Triple(A->getTargetTriple()).isOSDarwin()),
> > AccelNames(DwarfAccelTable::Atom(dwarf::DW_ATOM_die_offset,
> > dwarf::DW_FORM_data4)),
> > AccelObjC(DwarfAccelTable::Atom(dwarf::DW_ATOM_die_offset,
> > @@ -190,8 +191,6 @@ DwarfDebug::DwarfDebug(AsmPrinter *A, Mo
> >
> > // Turn on accelerator tables for Darwin by default, pubnames by
> > // default for non-Darwin, and handle split dwarf.
> > - bool IsDarwin = Triple(A->getTargetTriple()).isOSDarwin();
> > -
> > if (DwarfAccelTables == Default)
> > HasDwarfAccelTables = IsDarwin;
> > else
> > @@ -1698,7 +1697,7 @@ void DwarfDebug::endFunction(const Machi
> > // Under -gmlt, skip building the subprogram if there are no inlined
> > // subroutines inside it.
> > if (TheCU.getCUNode().getEmissionKind() == DIBuilder::LineTablesOnly
&&
> > - LScopes.getAbstractScopesList().empty()) {
> > + LScopes.getAbstractScopesList().empty() && !IsDarwin) {
> > assert(ScopeVariables.empty());
> > assert(CurrentFnArguments.empty());
> > assert(DbgValues.empty());
> >
> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h
> > URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h?rev=218702&r1=218701&r2=218702&view=diff
> >
==============================================================================
> > --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h (original)
> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.h Tue Sep 30 16:28:32
2014
> > @@ -319,6 +319,7 @@ class DwarfDebug : public AsmPrinterHand
> >
> > // True iff there are multiple CUs in this module.
> > bool SingleCU;
> > + bool IsDarwin;
> >
> > AddressPool AddrPool;
> >
> >
> > Modified: llvm/trunk/test/DebugInfo/gmlt.ll
> > URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/gmlt.ll?rev=218702&r1=218701&r2=218702&view=diff
> >
==============================================================================
> > --- llvm/trunk/test/DebugInfo/gmlt.ll (original)
> > +++ llvm/trunk/test/DebugInfo/gmlt.ll Tue Sep 30 16:28:32 2014
> > @@ -1,5 +1,7 @@
> > ; REQUIRES: object-emission
> > ; RUN: %llc_dwarf -O0 -filetype=obj < %s | llvm-dwarfdump - |
FileCheck %s
> > +; RUN: %llc_dwarf -O0 -filetype=obj < %s -mtriple x86_64-apple-darwin
| llvm-dwarfdump - \
> > +; RUN: | FileCheck --check-prefix=CHECK --check-prefix=DARWIN %s
> >
> > ; Generated from the following source compiled with clang++ -gmlt:
> > ; void f1() {}
> > @@ -17,6 +19,25 @@
> > ; CHECK: DW_AT_ranges [DW_FORM_sec_offset] (0x00000000)
> > ; CHECK-NOT: {{DW_TAG|NULL}}
> >
> > +; Omitting the subprograms without inlined subroutines is not possible
> > +; currently on Darwin as dsymutil will drop the whole CU if it has no
subprograms
> > +; (which happens with this optimization if there are no inlined
subroutines).
> > +
> > +; DARWIN: DW_TAG_subprogram
> > +; DARWIN-NOT: DW_TAG
> > +; DARWIN: DW_AT_name {{.*}} "f1"
> > +; DARWIN-NOT: {{DW_TAG|NULL}}
> > +; DARWIN: DW_TAG_subprogram
> > +; DARWIN-NOT: DW_TAG
> > +; DARWIN: DW_AT_name {{.*}} "f2"
> > +; DARWIN-NOT: {{DW_TAG|NULL}}
> > +; DARWIN: DW_TAG_subprogram
> > +; DARWIN-NOT: DW_TAG
> > +; Can't check the abstract_origin value across the DARWIN/CHECK
checking and
> > +; ordering, so don't bother - just trust me, it refers to f3 down
there.
> > +; DARWIN: DW_AT_abstract_origin
> > +; DARWIN-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
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
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