[llvm] r258406 - [GCOV] Avoid emitting profile arcs for module and skeleton CUs

[Hans Wennborg via llvm-commits]

On Mon, Jan 25, 2016 at 12:01 PM, David Blaikie <dblaikie at gmail.com> wrote:
> This is more in Adrian's territory (he reviewed it & it's the modules debug
> info stuff which he's worked on that this is a fix for), but yes - the
> change seems reasonable enough & the bug seems problematic/annoying enough
> that it'd be worth taking for 3.8

Thanks!

Vedant, please go ahead and merge this with utils/release/merge.sh (or
let me know if you'd prefer me to do it).

Cheers,
Hans


> On Mon, Jan 25, 2016 at 11:55 AM, Hans Wennborg via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>>
>> I'm not sure who's the code owner here, and I'm not qualified to
>> review it myself because I don't know what arc and note files are :-)
>>
>> Just for a second opinion; David, does this look reasonable to you?
>>
>> On Mon, Jan 25, 2016 at 10:14 AM, Vedant Kumar <vsk at apple.com> wrote:
>> > Hi,
>> >
>> > I'd like to propose taking this commit for the 3.8 branch.
>> >
>> > It stops the compiler from writing out gcov-style arc and note files for
>> > module CU's.
>> >
>> > thanks
>> > vedant
>> >
>> >> On Jan 21, 2016, at 9:04 AM, Vedant Kumar via llvm-commits
>> >> <llvm-commits at lists.llvm.org> wrote:
>> >>
>> >> Author: vedantk
>> >> Date: Thu Jan 21 11:04:42 2016
>> >> New Revision: 258406
>> >>
>> >> URL: http://llvm.org/viewvc/llvm-project?rev=258406&view=rev
>> >> Log:
>> >> [GCOV] Avoid emitting profile arcs for module and skeleton CUs
>> >>
>> >> Do not emit profile arc files and note files for module and skeleton
>> >> CU's.
>> >>
>> >> Our users report seeing unexpected *.gcda and *.gcno files in their
>> >> projects when using gcov-style profiling with modules or frameworks.
>> >> The unwanted files come from these modules. This is not very helpful
>> >> for end-users. Further, we've seen reports of instrumented programs
>> >> crashing while writing these files out (due to I/O failures).
>> >
>> > ^ We've also seen crashes because the gcda is not meant to be
>> > backwards-compatible. This results in "cannot merge previous GCDA" errors.
>> >
>> >>
>> >> rdar://problem/22838296
>> >>
>> >> Reviewed-by: aprantl
>> >>
>> >> Differential Revision: http://reviews.llvm.org/D15997
>> >>
>> >> Added:
>> >>    llvm/trunk/test/Transforms/GCOVProfiling/modules.ll
>> >> Modified:
>> >>    llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
>> >>
>> >> Modified: llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
>> >> URL:
>> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp?rev=258406&r1=258405&r2=258406&view=diff
>> >>
>> >> ==============================================================================
>> >> --- llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
>> >> (original)
>> >> +++ llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp Thu Jan
>> >> 21 11:04:42 2016
>> >> @@ -494,6 +494,11 @@ void GCOVProfiler::emitProfileNotes() {
>> >>     // LTO, we'll generate the same .gcno files.
>> >>
>> >>     auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
>> >> +
>> >> +    // Skip module skeleton (and module) CUs.
>> >> +    if (CU->getDWOId())
>> >> +      continue;
>> >> +
>> >>     std::error_code EC;
>> >>     raw_fd_ostream out(mangleName(CU, "gcno"), EC, sys::fs::F_None);
>> >>     std::string EdgeDestinations;
>> >> @@ -853,6 +858,11 @@ Function *GCOVProfiler::insertCounterWri
>> >>   if (CU_Nodes) {
>> >>     for (unsigned i = 0, e = CU_Nodes->getNumOperands(); i != e; ++i) {
>> >>       auto *CU = cast<DICompileUnit>(CU_Nodes->getOperand(i));
>> >> +
>> >> +      // Skip module skeleton (and module) CUs.
>> >> +      if (CU->getDWOId())
>> >> +        continue;
>> >> +
>> >>       std::string FilenameGcda = mangleName(CU, "gcda");
>> >>       uint32_t CfgChecksum = FileChecksums.empty() ? 0 :
>> >> FileChecksums[i];
>> >>       Builder.CreateCall(StartFile,
>> >>
>> >> Added: llvm/trunk/test/Transforms/GCOVProfiling/modules.ll
>> >> URL:
>> >> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GCOVProfiling/modules.ll?rev=258406&view=auto
>> >>
>> >> ==============================================================================
>> >> --- llvm/trunk/test/Transforms/GCOVProfiling/modules.ll (added)
>> >> +++ llvm/trunk/test/Transforms/GCOVProfiling/modules.ll Thu Jan 21
>> >> 11:04:42 2016
>> >> @@ -0,0 +1,12 @@
>> >> +; RUN: opt -insert-gcov-profiling -o - < %s | llvm-dis | FileCheck
>> >> -check-prefix=EMIT-ARCS %s
>> >> +
>> >> +; EMIT-ARCS-NOT: call void @llvm_gcda_start_file
>> >> +
>> >> +!llvm.dbg.cu = !{!0}
>> >> +!llvm.module.flags = !{!3, !4}
>> >> +
>> >> +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1,
>> >> producer: "LLVM", isOptimized: false, runtimeVersion: 2, splitDebugFilename:
>> >> "my.dwo", emissionKind: 1, enums: !2, retainedTypes: !2, subprograms: !2,
>> >> globals: !2, imports: !2, dwoId: 43981)
>> >> +!1 = !DIFile(filename: "<stdin>", directory: "/")
>> >> +!2 = !{}
>> >> +!3 = !{i32 2, !"Dwarf Version", i32 4}
>> >> +!4 = !{i32 2, !"Debug Info Version", i32 3}
>> >>
>> >>
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