[LLVMdev] llvm2cpp attributes handling

[Harris BAKIRAS]

Hello,

I saw that the breaking assert was removed.
Anyway, I made a patch to add the target dependent attributes when 
generating the code in CPPBackend.cpp.

As you told me, the new API provides functions for general solution.

Harris Bakiras

On 03/25/2013 05:28 PM, David Blaikie wrote:
> +Bill who worked on the attribute change
>
> On Mon, Mar 25, 2013 at 9:15 AM, Harris BAKIRAS <h.bakiras at gmail.com> wrote:
>> Hi everyone,
>>
>> We are using the llvm2cpp feature of LLVM in the VMKit project and there are
>> some issues that I would like to point out.
>>
>> I made a tiny reproducible example here, to be clear:
>>
>> echo "int main() { return 0; };" > test.c && clang test.c -emit-llvm -c -o -
>> | llc -march=cpp -cppgen=function -cppfor=main -o -
>>
>> This command is supposed to generate the C++ code to construct the main
>> function in LLVM (see main_llvm2cpp.cc joined file).
>> But an error occurs while generating the code (see stack trace below).
>>
>> It appears that an assertion is broken while treating attributes in the file
>> CPPBackend.cpp.
>> So I dumped the main function's attributes before treating them, here is the
>> result:
>>
>> PAL[
>>    { ~0U => nounwind uwtable "less-precise-fpmad"="false"
>> "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="true"
>> "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false"
>> "use-soft-float"="false" }
>> ]
>>
>> The problem is that llvm2cpp code generation supports only the attributes
>> present in the AttrKind enum of the Attribute class.
>> It means that the following attributes are not supported:
>>      - "less-precise-fpmad"
>>      - "no-frame-pointer-elim"
>>      - "no-frame-pointer-elim-non-leaf"
>>      - "no-infs-fp-math"
>>      - "no-nans-fp-math"
>>      - "unsafe-fp-math"
>>      - "use-soft-float"
>>
>> What is extremely strange, is that those attributes are set by clang with no
>> particular option.
>>
>> So, is the assert in CPPBackend.cpp deprecated or should those attributes be
>> handled somehow in C++ code generation (which means that the previous
>> attribute list should be added to the AttrKind enum of the Attribute class)?
> I believe that the C++ code generation should be updated (patches
> welcome - if you're relying on this functionality you may wish to
> contribute to it as I believe it's not much more than a learning tool
> for most other users/developers & is liable to rot fairly easily (if
> it's important to you, a bot/test cases to keep it working might be
> useful)) but probably not by "handling" the new attributes
> specifically. I think with the new attributes API there should be a
> general solution that doesn't require handling specific attributes
> explicitly, though I may be wrong.
>
> - David
>
>> Cheers,
>>
>> --
>>
>> Harris Bakiras
>>
>>     llc: CPPBackend.cpp:521: void
>> {anonymous}::CppWriter::printAttributes(const llvm::AttributeSet&, const
>> string&): Assertion `!attrs.hasAttributes() && "Unhandled attribute!"'
>> failed.
>> 0  llc             0x00000000010edc22 llvm::sys::PrintStackTrace(_IO_FILE*)
>> + 34
>> 1  llc             0x00000000010ed049
>> 2  libpthread.so.0 0x00007f9701addcb0
>> 3  libc.so.6       0x00007f9700d2f425 gsignal + 53
>> 4  libc.so.6       0x00007f9700d32b8b abort + 379
>> 5  libc.so.6       0x00007f9700d280ee
>> 6  libc.so.6       0x00007f9700d28192
>> 7  llc             0x000000000064fed3
>> 8  llc             0x000000000065335b
>> 9  llc             0x0000000000659fed
>> 10 llc             0x000000000065b0dc
>> 11 llc             0x0000000001081230
>> llvm::MPPassManager::runOnModule(llvm::Module&) + 688
>> 12 llc             0x0000000001081405
>> llvm::PassManagerImpl::run(llvm::Module&) + 245
>> 13 llc             0x0000000000565d27
>> 14 llc             0x0000000000551281 main + 353
>> 15 libc.so.6       0x00007f9700d1a76d __libc_start_main + 237
>> 16 llc             0x0000000000561fd5
>> Stack dump:
>> 0.    Program arguments: llc -march=cpp -cppgen=function -cppfor=main -o -
>> 1.    Running pass 'C++ backend' on module '<stdin>'.
>> Aborted (core dumped)
>>
>>
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>>

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