[llvm-dev] LLVM backend -- Avoid base+index address mode for X86

[Craig Topper via llvm-dev]

I think the code your looking for starts at X86DAGtoDAGISel::selectAddr in
X86ISelDAGtoDAG.cpp.

On Monday, October 17, 2016, Hong Hu via llvm-dev <llvm-dev at lists.llvm.org>
wrote:

> Hi Bruce,
>
> Thanks for you reply.
>
> I check the *.td files under the lib/Target/X86 folder, but have not got
> interesting findings. It requires some knowledge of LLVM backend to fully
> understand the *.td files. I will get some background and keep searching.
>
> Of course I appreciate if anyone with such experience can point the
> concrete locations.
>
> Regards,
> Hu Hong
>
> On 17 October 2016 at 22:20, Bruce Hoult <bruce at hoult.org
> <javascript:_e(%7B%7D,'cvml','bruce at hoult.org');>> wrote:
>
>> For experimental purposes, you should be able to just go
>> into lib/Target/X86 and remove the patterns in .td files (or maybe some
>> .cpp .. I'm not familiar with the X86 mechanisms) that map to base+index
>> addressing modes.
>>
>> Then the compiler will automatically use some extra temporary register to
>> calculate intermediate addresses.
>>
>> On Mon, Oct 17, 2016 at 5:51 AM, Hong Hu via llvm-dev <
>> llvm-dev at lists.llvm.org
>> <javascript:_e(%7B%7D,'cvml','llvm-dev at lists.llvm.org');>> wrote:
>>
>>> Hi All,
>>>
>>> I have a question regarding LLVM backend. I appreciate a lot if anyone
>>> can provide some hints.
>>>
>>> My work here is to avoid base+index address mode for X86 target, to
>>> allow base-register only or index-register only address mode. For example,
>>> "mov (%rsi), %rbx" is allowed, but "mov (%rsi, %rax), %rbx" is not
>>> allowed.
>>>
>>> I understand LLVM backend is a complex system. Can any one help point
>>> out which subsystem I should look into to solve my question?
>>>
>>> Regards,
>>> Hu Hong
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> <javascript:_e(%7B%7D,'cvml','llvm-dev at lists.llvm.org');>
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
>>
>

-- 
~Craig
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