[PATCH] D109372: [RISCV][RFC] Add Clang support for RISC-V overlay system

Tue Sep 7 11:05:01 PDT 2021

jrtc27 added a comment.

In D109372#2987405 <https://reviews.llvm.org/D109372#2987405>, @MaskRay wrote:

> The name "overlay" is ambiguous. Even after I ruled out Gentoo Overlay and overlayfs, I am thinking whether this has anything to do with `OVERLAY` description in a linker script: https://sourceware.org/binutils/docs/ld/Overlay-Description.html#Overlay-Description
>
>> which are used to mark functions or global data as only accessible through the overlay engine
>
> Can you give more descriptions for folks who don't follow the RISC-V side proposal but need to review your changes? :)

Basically hardware-assisted code+rodata banking (I guess either by actually banking ROMs or just paging stuff in and out) that's mostly transparent to software. Functions at the boundary of components (don't know what the granularity is) use a weird indirect calling convention where you instead call into some magic runtime with a unique ID for the callee, it ensures everything's loaded and then tail calls it for you.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D109372/new/

https://reviews.llvm.org/D109372