[llvm-commits] [PATCH] Reduce number of stubs used in 64bit code

Chris Lattner clattner at apple.com
Tue Sep 22 16:43:45 CDT 2009


On Sep 22, 2009, at 2:36 PM, Evan Phoenix wrote:

> Anyone have a comment on this? If not, it would be great to make it
> into 2.6 if possible.

I don't have an opinion, but it is too late for 2.6, sorry.

-Chris

>
> Thanks!
>
>  - Evan
>
> On Sep 1, 2009, at 2:34 PM, Evan Phoenix wrote:
>
>> Currently the JIT running on a x86_64 platform can only call an
>> external function through a stub. This is because of a conservative
>> decision about how the encoding of a pc-relative address would
>> should up in the machine code stream. These stubs incur a penalty,
>> so any stubs that can be eliminated should be.
>>
>> The attached patch allows the JITEmitter to override the CodeGen's
>> decision to use a stub by validating if a stub is actually needed.
>> Thus any calling functions who's pc-relative offset fits directly in
>> a call instruction are used the same as they would on a 32bit
>> platform.
>>
>> "Long" calls are still done via the stub mechanism.
>>
>> This only effects the calling of externally defined functions. It
>> changes nothing with regard to lazy/future JIT'd LLVM functions.
>>
>> Thanks,
>>
>> - Evan Phoenix
>>
>>
>> <llvm-64bit-
>> stubs5.diff>_______________________________________________
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