bf1239e78c
This is a PR for thumbv6-none-eabi (bere-metal Armv6k in Thumb mode) which proposed to be added by https://github.com/rust-lang/rust/pull/150138. Armv6k supports atomic instructions, but they are unavailable in Thumb mode unless Thumb-2 instructions available (v6t2). Using Thumb interworking (can be used via `#[instruction_set]`) allows us to use these instructions even from Thumb mode without Thumb-2 instructions, but LLVM does not implement that processing (as of LLVM 21), so this PR implements it in compiler-builtins. The code around `__sync` builtins is basically copied from `arm_linux.rs` which uses kernel_user_helpers for atomic implementation. The atomic implementation is a port of my [atomic-maybe-uninit inline assembly code]. This PR has been tested on QEMU 10.2.0 using patched compiler-builtins and core that applied the changes in this PR and https://github.com/rust-lang/rust/pull/150138 and the [portable-atomic no-std test suite] (can be run with `./tools/no-std.sh thumbv6-none-eabi` on that repo) which tests wrappers around `core::sync::atomic`. (Note that the target-spec used in test sets max-atomic-width to 32 and atomic_cas to true, unlike the current https://github.com/rust-lang/rust/pull/150138.) The original atomic-maybe-uninit implementation has been tested on real Arm hardware. (Note that Armv6k also supports 64-bit atomic instructions, but they are skipped here. This is because there is no corresponding code in `arm_linux.rs` (since the kernel requirements increased in 1.64, it may be possible to implement 64-bit atomics there as well. see also https://github.com/taiki-e/portable-atomic/pull/82), the code becomes more complex than for 32-bit and smaller atomics.) [atomic-maybe-uninit inline assembly code]: https://github.com/taiki-e/atomic-maybe-uninit/blob/HEAD/src/arch/arm.rs [portable-atomic no-std test suite]: https://github.com/taiki-e/portable-atomic/tree/HEAD/tests/no-std-qemu |
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| .. | ||
| function-definitions.json | ||
| function-list.txt | ||
| thumbv6-none-eabi.json | ||
| thumbv7em-none-eabi-renamed.json | ||
| update-api-list.py | ||