[PATCH] D137532: [LoongArch] Implement the TargetLowering::getRegisterByName hook

Mon Nov 14 01:58:20 PST 2022

gonglingqin added a comment.

In D137532#3924134 <https://reviews.llvm.org/D137532#3924134>, @xen0n wrote:

> In D137532#3924037 <https://reviews.llvm.org/D137532#3924037>, @gonglingqin wrote:
>
>> In D137532#3923952 <https://reviews.llvm.org/D137532#3923952>, @xen0n wrote:
>>
>>> I'm curious what usage case motivated the change? Not to say it's unnecessary but it's better to have people know a bit more background behind this work.
>>
>> This interface is required by the code in https://github.com/loongson/linux/blob/master/arch/loongarch/include/asm/percpu.h#L12-L18. This patch can avoid crashes when compiling the kernel with llvm in the future.
>
> Very nice to know.
>
> BTW, are the normal GPRs already supported like this too (things like global `register long foo __asm__("$a0")`), even without this change, or are such usages invalid in the first place? Memory is failing me.

As @xry111 said, any local register variables with assigned GPR can be read (the analysis process is completed by clang), but only reserved registers can be read when reading global registers.

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  https://reviews.llvm.org/D137532/new/

https://reviews.llvm.org/D137532