granite-rust

History

Yuki Okushi 5af6385f9f Rollup merge of #109860 - zyedidia:riscv-relax, r=petrochenkov Add support for RISC-V relax target feature This adds `relax` as an allowed RISC-V target feature. The relax feature in LLVM enables [linker relaxation](https://www.sifive.com/blog/all-aboard-part-3-linker-relaxation-in-riscv-toolchain), an optimization specific to RISC-V that allows global variable accesses to be resolved by the linker by using the global pointer (`gp`) register (rather than constructing the addresses from scratch for each access). Enabling `relax` will cause LLVM to emit relocations in the object file that support this. The feature can be enabled in rustc with `-C target-feature=+relax`. Currently this feature is disabled by default, but maybe it should be enabled by default since it is an easy performance improvement (but requires the `gp` register to be set up properly). GCC/Clang enable this feature by default (for both hosted/bare-metal targets), and include the `-mno-relax` flag to disable it (see [here](`466d554dca/clang/lib/Driver/ToolChains/Arch/RISCV.cpp (L145)`) for the code that enables it in Clang). I think it would make sense to enable by default, at least for all hosted targets since the `gp` register should be automatically set up by the runtime. For bare-metal targets, `gp` must be set up manually, so it is probably best to leave off by default to avoid breaking existing applications that do not set up `gp`. Leaving it disabled by default for all targets is also reasonable though. Let me know your thoughts. Thanks! Fixes #109426.		2023-04-11 12:18:50 +09:00
..
src	Rollup merge of #109860 - zyedidia:riscv-relax, r=petrochenkov	2023-04-11 12:18:50 +09:00
Cargo.toml	remove unused imports	2023-02-06 17:40:18 +03:00
messages.ftl	Simplify message paths	2023-03-11 22:51:57 +01:00
README.md	mv compiler to compiler/	2020-08-30 18:45:07 +03:00

README.md

Please read the rustc-dev-guide chapter on Backend Agnostic Codegen.