Last good:
https://build.chromium.org/p/chromium.fyi/builders/ClangToTAndroid%20%28dbg%29/builds/1968
clang 313392

First bad:
https://build.chromium.org/p/chromium.fyi/builders/ClangToTAndroid%20%28dbg%29/builds/1969
clang 313442


Some suspects:

------------------------------------------------------------------------
r313399 | rnk | 2017-09-15 14:49:56 -0700 (Fri, 15 Sep 2017) | 25 lines

[DebugInfo] Add missing DW_OP_deref when an NRVO pointer is spilled

Summary:
Fixes PR34513.

Indirect DBG_VALUEs typically come from dbg.declares of non-trivially
copyable C++ objects that must be passed by address. We were already
handling the case where the virtual register gets allocated to a
physical register and is later spilled. That's what usually happens for
normal parameters that aren't NRVO variables: they usually appear in
physical register parameters, and are spilled later in the function,
which would correctly add deref.

NRVO variables are different because the dbg.declare can come much later
after earlier instructions cause the incoming virtual register to be
spilled.

Also, clean up this code. We only need to look at the first operand of a
DBG_VALUE, which eliminates the operand loop.

Reviewers: aprantl, dblaikie, probinson

Subscribers: MatzeB, qcolombet, llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D37929
------------------------------------------------------------------------

------------------------------------------------------------------------
r313400 | rnk | 2017-09-15 14:54:38 -0700 (Fri, 15 Sep 2017) | 18 lines

[DebugInfo] Insert DW_OP_deref when spilling indirect DBG_VALUEs

Summary:
This comes up in optimized debug info for C++ programs that pass and
return objects indirectly by address. In these programs,
llvm.dbg.declare survives optimization, which causes us to emit indirect
DBG_VALUE instructions. The fast register allocator knows to insert
DW_OP_deref when spilling indirect DBG_VALUE instructions, but the
LiveDebugVariables did not until this change.

This fixes part of PR34513. I need to look into why this doesn't work at
-O0 and I'll send follow up patches to handle that.

Reviewers: aprantl, dblaikie, probinson

Subscribers: qcolombet, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D37911
------------------------------------------------------------------------

Attaching reproducer.

Deleted: decode-958617.c 3.2 MB

decode-958617.c 3.2 MB View Download

Deleted: decode-958617.sh 7.4 KB

decode-958617.sh 7.4 KB View Download

The assert started with r313400.

Reid, maybe you can take a look. This seems to be part of a series of patches, so maybe it's easier for you to fix than for me to revert?

We should be able to safely revert just that patch. One patch changed fast regalloc and the other changed greedy regalloc. Let's take a look though.

Reverted with r313589 in the meantime

Reid re-landed with a fix in r313640, but now iOS is sad (I'm guessing it's a similar problem).

From https://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device/builds/262881:

FAILED: obj/third_party/libvpx/libvpx/idct32x32_34_add_neon.o 
export DEVELOPER_DIR=/b/build/slave/ios-device/build/src/build/ios_files/Xcode.app;  /b/build/slave/cache/goma_client/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang -MMD -MF obj/third_party/libvpx/libvpx/idct32x32_34_add_neon.o.d -DV8_DEPRECATION_WARNINGS -DNO_TCMALLOC -DCHROMIUM_BUILD -DFIELDTRIAL_TESTING_ENABLED -DCR_CLANG_REVISION=\"313640-1\" -DCR_XCODE_VERSION=0900 -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DNS_BLOCK_ASSERTIONS=1 -I../.. -Igen -I../../third_party/libvpx/source/config -I../../third_party/libvpx/source/config/ios/arm-neon -I../../third_party/libvpx/source/libvpx -Igen/third_party/libvpx -I../../third_party/libvpx/source/libvpx -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -fcolor-diagnostics -arch armv7 -Oz -fno-omit-frame-pointer -gdwarf-2 -isysroot /b/build/slave/ios-device/build/src/build/ios_files/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS11.0.sdk -stdlib=libc++ -miphoneos-version-min=9.0 -fvisibility=hidden -Xclang -load -Xclang ../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.dylib -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang check-auto-raw-pointer -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Werror -Wall -Wno-unused-variable -Wundeclared-selector -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-covered-switch-default -Wno-unneeded-internal-declaration -Wno-inconsistent-missing-override -Wno-undefined-var-template -Wno-nonportable-include-path -Wno-address-of-packed-member -Wno-unused-lambda-capture -Wno-user-defined-warnings -Wno-enum-compare-switch -Wno-tautological-unsigned-zero-compare -Wno-conversion -Wno-parentheses-equality -Wno-unused-function -std=c11 -c ../../third_party/libvpx/source/libvpx/vpx_dsp/arm/idct32x32_34_add_neon.c -o obj/third_party/libvpx/libvpx/idct32x32_34_add_neon.o
Assertion failed: (DwarfRegs.size() == 1), function addMachineRegExpression, file /b/build/slave/mac_upload_clang/build/src/third_party/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp, line 245.
0  clang                    0x0000000109b83558 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  clang                    0x0000000109b83c46 llvm::sys::PrintStackTraceOnErrorSignal(llvm::StringRef, bool) + 886
2  libsystem_platform.dylib 0x00007fffe0299b3a _sigtramp + 26
3  libsystem_platform.dylib 0x00000003ffffffff _sigtramp + 534144223
4  libsystem_c.dylib        0x00007fffe011e420 abort + 129
5  libsystem_c.dylib        0x00007fffe00e5893 basename_r + 0
6  clang                    0x000000010a2ae8a3 llvm::DwarfExpression::addMachineRegExpression(llvm::TargetRegisterInfo const&, llvm::DIExpressionCursor&, unsigned int, unsigned int) + 1171
7  clang                    0x000000010a29b8d9 llvm::DwarfDebug::emitDebugLocEntry(llvm::ByteStreamer&, llvm::DebugLocStream::Entry const&) + 1049
8  clang                    0x000000010a299bb0 llvm::DebugLocEntry::finalize(llvm::AsmPrinter const&, llvm::DebugLocStream::ListBuilder&, llvm::DIBasicType const*) + 608
9  clang                    0x000000010a298e42 llvm::DwarfDebug::collectVariableInfo(llvm::DwarfCompileUnit&, llvm::DISubprogram const*, llvm::DenseSet<std::__1::pair<llvm::DILocalVariable const*, llvm::DILocation const*>, llvm::DenseMapInfo<std::__1::pair<llvm::DILocalVariable const*, llvm::DILocation const*> > >&) + 498
10 clang                    0x000000010a29a616 llvm::DwarfDebug::endFunctionImpl(llvm::MachineFunction const*) + 358
11 clang                    0x000000010a27b556 llvm::DebugHandlerBase::endFunction(llvm::MachineFunction const*) + 102
12 clang                    0x000000010a26ac52 llvm::AsmPrinter::EmitFunctionBody() + 8098
13 clang                    0x00000001086ea3a0 llvm::createA15SDOptimizerPass() + 16512
14 clang                    0x000000010931f3a8 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) + 184
15 clang                    0x0000000109612d5d llvm::FPPassManager::runOnFunction(llvm::Function&) + 541
16 clang                    0x0000000109613043 llvm::FPPassManager::runOnModule(llvm::Module&) + 67
17 clang                    0x000000010961358b llvm::legacy::PassManagerImpl::run(llvm::Module&) + 955
18 clang                    0x0000000109d66333 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::DataLayout const&, llvm::Module*, clang::BackendAction, std::__1::unique_ptr<llvm::raw_pwrite_stream, std::__1::default_delete<llvm::raw_pwrite_stream> >) + 15379
19 clang                    0x0000000109f60fb6 clang::EmitObjAction::EmitObjAction(llvm::LLVMContext*) + 2198
20 clang                    0x000000010a212c3c clang::MultiplexConsumer::HandleTranslationUnit(clang::ASTContext&) + 44
21 clang                    0x000000010a959232 clang::ParseAST(clang::Sema&, bool, bool) + 466
22 clang                    0x000000010a1e8e29 clang::FrontendAction::Execute() + 137
23 clang                    0x000000010a18bfc1 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 801
24 clang                    0x000000010a237a12 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 4482
25 clang                    0x000000010839b26a cc1_main(llvm::ArrayRef<char const*>, char const*, void*) + 1418
26 clang                    0x0000000108398f4f main + 11519
27 clang                    0x0000000108395fa4 start + 52
Stack dump:
0.	Program arguments: /b/build/slave/ios-device/build/src/third_party/llvm-build/Release+Asserts/bin/clang -cc1 -triple thumbv7-apple-ios9.0.0 -emit-obj -disable-free -main-file-name idct32x32_34_add_neon.c -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -relaxed-aliasing -masm-verbose -faligned-alloc-unavailable -target-cpu generic -target-feature +soft-float-abi -target-abi apcs-gnu -mfloat-abi soft -fallow-half-arguments-and-returns -dwarf-column-info -debug-info-kind=standalone -dwarf-version=2 -debugger-tuning=lldb -target-linker-version 274.1 -coverage-notes-file /b/build/slave/ios-device/build/src/out/Release-iphoneos/obj/third_party/libvpx/libvpx/idct32x32_34_add_neon.gcno -resource-dir /b/build/slave/ios-device/build/src/third_party/llvm-build/Release+Asserts/lib/clang/6.0.0 -dependency-file obj/third_party/libvpx/libvpx/idct32x32_34_add_neon.o.d -MT obj/third_party/libvpx/libvpx/idct32x32_34_add_neon.o -isysroot /b/build/slave/ios-device/build/src/build/ios_files/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS11.0.sdk -D V8_DEPRECATION_WARNINGS -D NO_TCMALLOC -D CHROMIUM_BUILD -D FIELDTRIAL_TESTING_ENABLED -D CR_CLANG_REVISION="313640-1" -D CR_XCODE_VERSION=0900 -D NDEBUG -D NVALGRIND -D DYNAMIC_ANNOTATIONS_ENABLED=0 -D NS_BLOCK_ASSERTIONS=1 -I ../.. -I gen -I ../../third_party/libvpx/source/config -I ../../third_party/libvpx/source/config/ios/arm-neon -I ../../third_party/libvpx/source/libvpx -I gen/third_party/libvpx -I ../../third_party/libvpx/source/libvpx -D __DATE__= -D __TIME__= -D __TIMESTAMP__= -Oz -Wno-builtin-macro-redefined -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Werror -Wall -Wno-unused-variable -Wundeclared-selector -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-covered-switch-default -Wno-unneeded-internal-declaration -Wno-inconsistent-missing-override -Wno-undefined-var-template -Wno-nonportable-include-path -Wno-address-of-packed-member -Wno-unused-lambda-capture -Wno-user-defined-warnings -Wno-enum-compare-switch -Wno-tautological-unsigned-zero-compare -Wno-conversion -Wno-parentheses-equality -Wno-unused-function -std=c11 -fdebug-compilation-dir /b/build/slave/ios-device/build/src/out/Release-iphoneos -ferror-limit 19 -fmessage-length 0 -fvisibility hidden -stack-protector 1 -stack-protector-buffer-size 4 -fblocks -fencode-extended-block-signature -fobjc-runtime=ios-9.0.0 -fsjlj-exceptions -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -vectorize-slp -load ../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.dylib -add-plugin find-bad-constructs -plugin-arg-find-bad-constructs check-auto-raw-pointer -o obj/third_party/libvpx/libvpx/idct32x32_34_add_neon.o -x c ../../third_party/libvpx/source/libvpx/vpx_dsp/arm/idct32x32_34_add_neon.c 
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module '../../third_party/libvpx/source/libvpx/vpx_dsp/arm/idct32x32_34_add_neon.c'.
4.	Running pass 'ARM Assembly Printer' on function '@vpx_idct32_6_neon'
clang: error: unable to execute command: Abort trap: 6
clang: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 6.0.0 (trunk 313640)
Target: arm-apple-darwin16.7.0
Thread model: posix
InstalledDir: /b/build/slave/ios-device/build/src/out/Release-iphoneos/../../third_party/llvm-build/Release+Asserts/bin
clang: note: diagnostic msg: PLEASE submit a bug report to http://llvm.org/bugs/ and include the crash backtrace, preprocessed source, and associated run script.

Deleted: idct32x32_34_add_neon-6ec7a8.c 6.7 MB

idct32x32_34_add_neon-6ec7a8.c 6.7 MB View Download

Deleted: idct32x32_34_add_neon-6ec7a8.sh 7.2 KB

idct32x32_34_add_neon-6ec7a8.sh 7.2 KB View Download

Reid reverted in r313679 and relanded with r313775+r313786, so hopefully it's fixed.