Assertion fails in bitcode writer with LLVM 12 RC5+

[llvmbot]

Bugzilla Link	49919
Version	trunk
OS	Windows NT
Blocks	#48246 #48661
Attachments	.ll file
Reporter	LLVM Bugzilla Contributor
CC	@davidbolvansky,@slacka,@tstellar

Extended Description

While testing LLVM 12 RC5+ (fa0971b) with LDC, I've hit a bitcode writer assertion when targeting x86_64-windows-msvc. Creating textual LLVM assembly, textual machine assembly and machine code works fine, just the bitcode fails - pretty bad news for LTO. Switching the triple to x86_64-linux-gnu makes it work as well.

I'm attaching the trivial textual LLVM assembly. The stack trace is:

Assertion failed: Val && "isa<> used on a null pointer", file C:\LDC\llvm-project\llvm\include\llvm/Support/Casting.h, line 104
#​0 0x00007ff6d3c4bfd6 HandleAbort C:\LDC\llvm-project\llvm\lib\Support\Windows\Signals.inc:408:0
#​1 0x00007ff6d4277cd4 raise minkernel\crts\ucrt\src\appcrt\misc\signal.cpp:547:0
#​2 0x00007ff6d4266708 abort minkernel\crts\ucrt\src\appcrt\startup\abort.cpp:71:0
#​3 0x00007ff6d426d518 common_assert_to_stderr<wchar_t> minkernel\crts\ucrt\src\appcrt\startup\assert.cpp:175:0
#​4 0x00007ff6d426d63a _wassert minkernel\crts\ucrt\src\appcrt\startup\assert.cpp:443:0
#​5 0x00007ff6d349bc1f llvm::ValueEnumerator::EnumerateType(class llvm::Type *) C:\LDC\llvm-project\llvm\lib\Bitcode\Writer\ValueEnumerator.cpp:916:0
#​6 0x00007ff6d349fb90 llvm::ValueEnumerator::incorporateFunction(class llvm::Function const &) C:\LDC\llvm-project\llvm\lib\Bitcode\Writer\ValueEnumerator.cpp:1001:0
#​7 0x00007ff6d346f499 llvm::SmallVectorTemplateCommon<unsigned int,void>::getFirstEl C:\LDC\llvm-project\llvm\include\llvm\ADT\SmallVector.h:114:0
#​8 0x00007ff6d346f499 llvm::SmallVectorTemplateCommon<unsigned int,void>::SmallVectorTemplateCommon C:\LDC\llvm-project\llvm\include\llvm\ADT\SmallVector.h:121:0
#​9 0x00007ff6d346f499 llvm::SmallVectorTemplateBase<unsigned int,1>::SmallVectorTemplateBase C:\LDC\llvm-project\llvm\include\llvm\ADT\SmallVector.h:472:0
#​10 0x00007ff6d346f499 llvm::SmallVectorImpl::SmallVectorImpl C:\LDC\llvm-project\llvm\include\llvm\ADT\SmallVector.h:573:0
#​11 0x00007ff6d346f499 llvm::SmallVector<unsigned int,64>::SmallVector C:\LDC\llvm-project\llvm\include\llvm\ADT\SmallVector.h:1171:0
#​12 0x00007ff6d346f499 anonymous namespace'::ModuleBitcodeWriter::writeFunction C:\LDC\llvm-project\llvm\lib\Bitcode\Writer\BitcodeWriter.cpp:3268:0 #​13 0x00007ff6d3460376 llvm::operator!= C:\LDC\llvm-project\llvm\include\llvm\ADT\ilist_iterator.h:148:0 #​14 0x00007ff6d3460376 anonymous namespace'::ModuleBitcodeWriter::write C:\LDC\llvm-project\llvm\lib\Bitcode\Writer\BitcodeWriter.cpp:4396:0
#​15 0x00007ff6d34601e7 `anonymous namespace'::ModuleBitcodeWriterBase::~ModuleBitcodeWriterBase C:\LDC\llvm-project\llvm\lib\Bitcode\Writer\BitcodeWriter.cpp:156:0
#​16 0x00007ff6d34601e7 llvm::BitcodeWriter::writeModule(class llvm::Module const &, bool, class llvm::ModuleSummaryIndex const *, bool, class std::array<unsigned int, 5> *) C:\LDC\llvm-project\llvm\lib\Bitcode\Writer\BitcodeWriter.cpp:4576:0
#​17 0x00007ff6d3460bd7 llvm::WriteBitcodeToFile(class llvm::Module const &, class llvm::raw_ostream &, bool, class llvm::ModuleSummaryIndex const *, bool, class std::array<unsigned int, 5> *) C:\LDC\llvm-project\llvm\lib\Bitcode\Writer\BitcodeWriter.cpp:4603:0
#​18 0x00007ff6d125a498 writeModule(class llvm::Module *, char const *) C:\LDC\ldc\driver\toobj.cpp:390:0
#​19 0x00007ff6d11e55aa std::unique_ptr<llvm::ToolOutputFile,std::default_deletellvm::ToolOutputFile >::operator bool C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.28.29333\include\memory:2672:0
#​20 0x00007ff6d11e55aa ldc::CodeGenerator::writeAndFreeLLModule(char const *) C:\LDC\ldc\driver\codegenerator.cpp:274:0
#​21 0x00007ff6d11e611e Logger::enabled C:\LDC\ldc\gen\logger.h:106:0
#​22 0x00007ff6d11e611e ldc::CodeGenerator::emit(class Module *) C:\LDC\ldc\driver\codegenerator.cpp:282:0
#​23 0x00007ff6d1176592 llvm::timeTraceProfilerEnabled C:\LDC\LLVM-x64\include\llvm\Support\TimeProfiler.h:34:0
#​24 0x00007ff6d1176592 TimeTraceScope::~TimeTraceScope C:\LDC\ldc\driver\timetrace.h:56:0
#​25 0x00007ff6d1176592 codegenModules(struct Array<class Module *> &) C:\LDC\ldc\driver\main.cpp:1197:0
#​26 0x00007ff6d103ebe9 mars_mainBody(struct Param &, struct Array<char const *> &, struct Array<char const *> &) C:\LDC\ldc\dmd\mars.d:882:0
#​27 0x00007ff6d1174975 cppmain(void) C:\LDC\ldc\driver\main.cpp:1141:0
#​28 0x00007ff6d4052cc9 _D2rt6dmain212_d_run_main2UAAamPUQgZiZ6runAllMFZv (C:\LDC\ninja-ldc\bin\ldc2.exe+0x3102cc9)
#​29 0x00007ff6d4052997 _d_run_main2 (C:\LDC\ninja-ldc\bin\ldc2.exe+0x3102997)
#​30 0x00007ff6d4052c53 _d_wrun_main (C:\LDC\ninja-ldc\bin\ldc2.exe+0x3102c53)
#​31 0x00007ff6d11740a3 wmain C:\LDC\ldc\driver\main.cpp:1007:0

[llvmbot]

The reason is that ValueEnumerator::incorporateFunction assumes all sret and byval parameters have associated type information.

[tstellar]

Is there a fix for this?

[slacka]

From separate email from Martin Kinkelin

it was a regression, and the extra type annotations being mandatory
(well, for bitcode generation only) not mentioned in the LLVM 12.0.0
changelog IIRC. I've added them in our frontend in the meantime and
haven't tested any more recent LLVM versions. I've quickly glanced at
the code in LLVM 12.0.1, and it still seems to assume the types are
non-null in
https://github.com/llvm/llvmproject/blob/fed41342a82f5a3a9201819a82bf7a48313e296b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp#L1003-L1006.

Tom,
Would it still make sense to backport Martin's fix to the 12.x line?

[slacka]

corrected mangled URL:

llvm-project/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp

Lines 1003 to 1006 in fed4134

	if (I.hasAttribute(Attribute::ByVal))
	EnumerateType(I.getParamByValType());
	else if (I.hasAttribute(Attribute::StructRet))
	EnumerateType(I.getParamStructRetType());

[tstellar]

It's too late, 12.0.1 has already been released.