[LLVMdev] question on instruction selection
nunoplopes at sapo.pt
Wed Jan 27 16:07:21 PST 2010
> On Jan 26, 2010, at 3:16 PM, Nuno Lopes wrote:
>> For now, I'm just trying to understand what's the main contribution of
>> paper towards simplifying the retargeting of a compiler. Don't get me
>> I do not want to bash the paper; I just feel that something is escaping
>> The approach proposed seems to be fairly similar to what gcc and LLVM do.
>> What makes me wondering is why their algorithm needs heavy reasoning to
>> semantic equivalence checking, while gcc & LLVM only need simple pattern
>> matching. That's why I've been scratching my head the whole day :)
>> Do you have any insight that can enlighten me, please?
> I took a very quick look at the paper. I think the idea is to
> declaratively specify
> the semantics of each IR operation and each machine instruction, and then
> automatically figure out how to select the IR operations to machine
> GCC and LLVM require that mapping to be specified manually.
I believe it is not that automated. The IR->RTL pass is not automated at
I think I'll just talk with the author once again (now more knowledgeable
about llvm) :)
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