[PATCH] D120327: compiler-rt: Add udivmodei5 to builtins and add bitint library

Tue Mar 22 05:52:19 PDT 2022

erichkeane added a comment.

In D120327#3398754 <https://reviews.llvm.org/D120327#3398754>, @FreddyYe wrote:

> To be honest, I'm not familiar in compiler-rt component. And my experience before was mainly to find out the feasibility to support arbitrary-bits-division for _BitInt(). Fortunately, my proposal was basically same as this one: emit a new libcall in backend; add library support; use malloc()... And I even used a more simple division algorithm model: sub-shift, which has been shared in the RFC link. So my experience before may not be very helpful here. Anyway I can try my best. So everyone is OK with use malloc(), right? That was my biggest concern. BTW FYI the largest _BitInt() support is 8,388,608 . Hi @mgehre-amd Will you upload another patch to set the bitint.a as a default link library of clang when this patch gets landed in? I believe FE will reopen _BitInt() > 128 bit unless division is supported by default but not by option `--rtlib=compiler-rt`. @erichkeane @aaron.ballman

Yes, that is correct, we cannot enable _BitInt>128 unless we have the library support 'compiled in'.  I believe we need to make bitint.a be a default library that gets linked in.

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https://reviews.llvm.org/D120327