[llvm-dev] uninitialized values in Attributes.cpp

[Evgenii Stepanov via llvm-dev]

We disable loopunswitch when building with msan here:
https://github.com/llvm-mirror/llvm/blob/93e6e5414ded14bcbb233baaaa5567132fee9a0c/lib/Transforms/Scalar/LoopUnswitch.cpp#L591

You can try making that unconditional to see if it would help valgrind.


On Sun, Nov 20, 2016 at 7:58 AM, regehr via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Hi Sanjoy, I'm building with Clang-3.9.  I'll give MSan a try and see what
> it says.
>
> John
>
>
>
> On 11/20/2016 03:03 AM, Sanjoy Das via llvm-dev wrote:
>>
>> Hi John,
>>
>> This is probably somewhat of a stretch, but since the problem does not
>> happen with a Debug build, could it be due to loop unswitching (or
>> optimizations like that) kicking in when building LLVM?  That is, due
>> to speculating the branch out of loops like
>>
>>   val = *uninitialized_loc
>>   for (; false;) {
>>     if (val)
>>       foo();
>>     else
>>       bar();
>>   }
>>
>> ?
>>
>> What compiler are you building with?
>>
>> -- Sanjoy
>>
>> On Sat, Nov 19, 2016 at 9:00 PM, regehr via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>>>
>>> I did a RelWithDebInfo + asserts build of LLVM just now and, when running
>>> "make check" under Valgrind, am seeing a lot of uses of uninitialized
>>> memory
>>> like the one below.  Anyone know offhand what's likely to be the root
>>> cause?
>>> Unfortunately a Debug build doesn't give these errors.  Thanks,
>>>
>>> John
>>>
>>>
>>> FAIL: LLVM :: Analysis/BasicAA/pr18573.ll (2093 of 18733)
>>> ******************** TEST 'LLVM :: Analysis/BasicAA/pr18573.ll' FAILED
>>> ********************
>>> Script:
>>> --
>>> /home/regehr/llvm/build-vg/./bin/opt
>>> /home/regehr/llvm/test/Analysis/BasicAA/pr18573.ll -O2 -S |
>>> /home/regehr/llvm/build-vg/./bin/FileCheck
>>> /home/regehr/llvm/test/Analysis/BasicAA/pr18573.ll
>>> --
>>> Exit Code: 123
>>>
>>> Command Output (stderr):
>>> --
>>> ==29299== Conditional jump or move depends on uninitialised value(s)
>>> ==29299==    at 0x13FCF12: hasAttribute (Attributes.cpp:421)
>>> ==29299==    by 0x13FCF12: hasAttribute (Attributes.cpp:186)
>>> ==29299==    by 0x13FCF12: operator() (Attributes.cpp:627)
>>> ==29299==    by 0x13FCF12: operator()<const std::pair<unsigned int,
>>> llvm::Attribute> *> (predefined_ops.h:234)
>>> ==29299==    by 0x13FCF12: __find_if<const std::pair<unsigned int,
>>> llvm::Attribute> *, __gnu_cxx::__ops::_Iter_pred<(lambda at
>>> ../lib/IR/Attributes.cpp:627:3)> > (stl_algo.h:140)
>>> ==29299==    by 0x13FCF12: __find_if<const std::pair<unsigned int,
>>> llvm::Attribute> *, __gnu_cxx::__ops::_Iter_pred<(lambda at
>>> ../lib/IR/Attributes.cpp:627:3)> > (stl_algo.h:161)
>>> ==29299==    by 0x13FCF12: find_if<const std::pair<unsigned int,
>>> llvm::Attribute> *, (lambda at ../lib/IR/Attributes.cpp:627:3)>
>>> (stl_algo.h:3815)
>>> ==29299==    by 0x13FCF12: none_of<const std::pair<unsigned int,
>>> llvm::Attribute> *, (lambda at ../lib/IR/Attributes.cpp:627:3)>
>>> (stl_algo.h:526)
>>> ==29299==    by 0x13FCF12: none_of<llvm::ArrayRef<std::pair<unsigned int,
>>> llvm::Attribute> > &, (lambda at ../lib/IR/Attributes.cpp:627:3)>
>>> (STLExtras.h:607)
>>> ==29299==    by 0x13FCF12: llvm::AttributeSet::get(llvm::LLVMContext&,
>>> llvm::ArrayRef<std::pair<unsigned int, llvm::Attribute> >)
>>> (Attributes.cpp:627)
>>> ==29299==    by 0x13FD62B: llvm::AttributeSet::get(llvm::LLVMContext&,
>>> unsigned int, llvm::ArrayRef<llvm::Attribute::AttrKind>)
>>> (Attributes.cpp:712)
>>> ==29299==    by 0x146F9AC:
>>> llvm::Intrinsic::getAttributes(llvm::LLVMContext&, llvm::Intrinsic::ID)
>>> (Intrinsics.gen:20104)
>>> ==29299==    by 0x146F3A0: llvm::Function::Function(llvm::FunctionType*,
>>> llvm::GlobalValue::LinkageTypes, llvm::Twine const&, llvm::Module*)
>>> (Function.cpp:277)
>>> ==29299==    by 0x1CD2B36: Create (Function.h:106)
>>> ==29299==    by 0x1CD2B36:
>>> llvm::LLParser::ParseFunctionHeader(llvm::Function*&, bool)
>>> (LLParser.cpp:4766)
>>> ==29299==    by 0x1CCE2C2: llvm::LLParser::ParseDeclare()
>>> (LLParser.cpp:444)
>>> ==29299==    by 0x1CCC15A: llvm::LLParser::ParseTopLevelEntities()
>>> (LLParser.cpp:276)
>>> ==29299==    by 0x1CCBFBF: llvm::LLParser::Run() (LLParser.cpp:74)
>>> ==29299==    by 0x1CC59D8: llvm::parseAssemblyInto(llvm::MemoryBufferRef,
>>> llvm::Module&, llvm::SMDiagnostic&, llvm::SlotMapping*) (Parser.cpp:31)
>>> ==29299==    by 0x1CC5C16: llvm::parseAssembly(llvm::MemoryBufferRef,
>>> llvm::SMDiagnostic&, llvm::LLVMContext&, llvm::SlotMapping*)
>>> (Parser.cpp:41)
>>> ==29299==    by 0x158C59E: llvm::parseIR(llvm::MemoryBufferRef,
>>> llvm::SMDiagnostic&, llvm::LLVMContext&) (IRReader.cpp:89)
>>> ==29299==    by 0x158CA61: llvm::parseIRFile(llvm::StringRef,
>>> llvm::SMDiagnostic&, llvm::LLVMContext&) (IRReader.cpp:102)
>>> ==29299==
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>>
>>
>>
>>
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