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

[Hans Wennborg via llvm-commits]

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}
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>