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

[Vedant Kumar via llvm-commits]

Hans, I'd be more comfortable with you merging this in.

I'm not sure how to specify release_38 as the target branch to utils/release/merge.sh.

thanks
vedant

p.s: My officemates aren't sure how to do this either. Could you add a note about this to HowToReleaseLLVM.rst?


> On Jan 25, 2016, at 1:15 PM, Hans Wennborg <hans at chromium.org> wrote:
> 
> 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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