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

[Bruce Hoult via llvm-dev]

For some definition of "starts" :-)

Looks like X86DAGToDAGISel::MatchAddressRecursively is the actual thing to
hack up.

On Mon, Oct 17, 2016 at 6:13 PM, Craig Topper via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> 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> 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> 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
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>>
>>>
>>
>
> --
> ~Craig
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20161017/86856fb3/attachment-0001.html>