[lld] r233088 - [Mips] Suppress "right shift by too large amount" warning

[Aaron Ballman]

On Tue, Mar 24, 2015 at 12:16 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
> On Tue, Mar 24, 2015 at 8:49 AM, Simon Atanasyan <simon at atanasyan.com>
> wrote:
>>
>> Author: atanasyan
>> Date: Tue Mar 24 10:49:59 2015
>> New Revision: 233088
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=233088&view=rev
>> Log:
>> [Mips] Suppress "right shift by too large amount" warning
>>
>> Visual C++ shows the "right shift by too large amount" warning if
>> `MipsELFReference` is instantiated for 32-bit target and
>> `Elf_Rel_Impl::getType`
>> method has `unsigned char` return type. We can freely suppress the warning
>> in
>> that case because MIPS 32-bit ABI does not pack multiple relocation types
>> into
>> the single field `r_type` and the `MipsELFReference::_tag` should be
>> always
>> zero in that case.
>
>
> Can we just disable the MSVC warning if it's wrong, then?

IMO, the MSVC warning was correct (the original code was right
shifting all significant bits away) and should not be disabled.

~Aaron

>
>>
>>
>> No functional changes.
>>
>> Modified:
>>     lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFFile.h
>>
>> Modified: lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFFile.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFFile.h?rev=233088&r1=233087&r2=233088&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFFile.h (original)
>> +++ lld/trunk/lib/ReaderWriter/ELF/Mips/MipsELFFile.h Tue Mar 24 10:49:59
>> 2015
>> @@ -101,13 +101,13 @@ public:
>>        : ELFReference<ELFT>(
>>              &rel, rel.r_offset - symValue, Reference::KindArch::Mips,
>>              rel.getType(_isMips64EL) & 0xff, rel.getSymbol(_isMips64EL)),
>> -        _tag(rel.getType(_isMips64EL) >> 8) {}
>> +        _tag(uint32_t(rel.getType(_isMips64EL)) >> 8) {}
>>
>>    MipsELFReference(uint64_t symValue, const Elf_Rel &rel)
>>        : ELFReference<ELFT>(rel.r_offset - symValue,
>> Reference::KindArch::Mips,
>>                             rel.getType(_isMips64EL) & 0xff,
>>                             rel.getSymbol(_isMips64EL)),
>> -        _tag(rel.getType(_isMips64EL) >> 8) {}
>> +        _tag(uint32_t(rel.getType(_isMips64EL)) >> 8) {}
>>
>>    uint32_t tag() const override { return _tag; }
>>    void setTag(uint32_t tag) { _tag = tag; }
>>
>>
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>
>
>
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