[llvm] r217325 - [MCJIT] Fix a bug RuntimeDyldImpl's read/writeBytesUnaligned methods.

[David Blaikie]

On Mon, Sep 8, 2014 at 10:56 AM, Lang Hames <lhames at gmail.com> wrote:

> I'm not sure I'd add a function for that, though you could use an
> "increment" variable to merge the loops if you like. I don't think it's
> really worth it though.
>
> The commit message could have been clearer, but this is certainly
> testable: It's is an attempt to get the RuntimeDyld regression tests
> working on PPC.
>

Can those tests be run on other platforms with a fixed triple? (the verify
mode you added doesn't actually have to execute the code, right? So you can
run PPC tests on any platform?)


>
> - Lang.
>
> On Sun, Sep 7, 2014 at 9:10 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>>
>>
>> On Sat, Sep 6, 2014 at 7:05 PM, Lang Hames <lhames at gmail.com> wrote:
>>
>>> Author: lhames
>>> Date: Sat Sep  6 21:05:26 2014
>>> New Revision: 217325
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=217325&view=rev
>>> Log:
>>> [MCJIT] Fix a bug RuntimeDyldImpl's read/writeBytesUnaligned methods.
>>>
>>> The previous implementation was writing to the high-bytes of integers on
>>> BE
>>> targets (when run on LE hosts).
>>>
>>
>> Not testable? (curious what limitations of your new test infrastructure
>> (or curiosities of this issue) make it not applicable to testing this bug)
>>
>> & any nice way to factor the (admittedly minor) duplication in each of
>> these codepaths? (could have a function that takes the increment (1 or -1),
>> non-type template parameter if necessary, but it looks simple/inlinable?)
>>
>>
>>>
>>> http://llvm.org/PR20640
>>>
>>>
>>> Modified:
>>>     llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
>>>
>>> Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=217325&r1=217324&r2=217325&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)
>>> +++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Sat Sep
>>> 6 21:05:26 2014
>>> @@ -398,32 +398,30 @@ unsigned RuntimeDyldImpl::computeSection
>>>  uint64_t RuntimeDyldImpl::readBytesUnaligned(uint8_t *Src,
>>>                                               unsigned Size) const {
>>>    uint64_t Result = 0;
>>> -  uint8_t *Dst = reinterpret_cast<uint8_t*>(&Result);
>>> -
>>> -  if (IsTargetLittleEndian == sys::IsLittleEndianHost) {
>>> -    if (!sys::IsLittleEndianHost)
>>> -      Dst += sizeof(Result) - Size;
>>> -    memcpy(Dst, Src, Size);
>>> -  } else {
>>> -    Dst += Size - 1;
>>> -    for (unsigned i = 0; i < Size; ++i)
>>> -      *Dst-- = *Src++;
>>> -  }
>>> +  if (IsTargetLittleEndian) {
>>> +    Src += Size - 1;
>>> +    while (Size--)
>>> +      Result = (Result << 8) | *Src--;
>>
>> +  } else
>>> +    while (Size--)
>>> +      Result = (Result << 8) | *Src++;
>>
>>
>>>    return Result;
>>>  }
>>>
>>>  void RuntimeDyldImpl::writeBytesUnaligned(uint64_t Value, uint8_t *Dst,
>>>                                            unsigned Size) const {
>>> -  uint8_t *Src = reinterpret_cast<uint8_t*>(&Value);
>>> -  if (IsTargetLittleEndian == sys::IsLittleEndianHost) {
>>> -    if (!sys::IsLittleEndianHost)
>>> -      Src += sizeof(Value) - Size;
>>> -    memcpy(Dst, Src, Size);
>>> +  if (IsTargetLittleEndian) {
>>> +    while (Size--) {
>>> +      *Dst++ = Value & 0xFF;
>>> +      Value >>= 8;
>>> +    }
>>>    } else {
>>> -    Src += Size - 1;
>>> -    for (unsigned i = 0; i < Size; ++i)
>>> -      *Dst++ = *Src--;
>>> +    Dst += Size - 1;
>>> +    while (Size--) {
>>> +      *Dst-- = Value & 0xFF;
>>> +      Value >>= 8;
>>> +    }
>>>    }
>>>  }
>>>
>>>
>>>
>>> _______________________________________________
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>>>
>>
>>
>
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