Dummy atomic support #92
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make some crates(like bytes, log) work on ckb-vm
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First of all, the feature name atomic is far too generic, dummy-atomic or single-core-atomic might be better. To me it makes sense to be clear that we are not building an atomic solution, but a placeholder for single core environment.
And I recommend making atomic a riscv-only feature, either by tweaking Cargo file, or adding some guards in build.rs. It really does not make sense to enable atomic for other architectures. Or we can simply make atomic a no-op for other architectures.
Finally, by restricting this feature to riscv only, we don't need to do read_unaligned / write_unaligned, we can just use the aligned version(which would make no different in ckb-vm's implementation) for less cycle consumption.
* feature name changed to `dummy-atomic` * feature `dummy-atomic` can't be used on non risc-v target * use read/write instead of read_unaligned/write_unaligned
README.md
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| @@ -15,7 +15,7 @@ This library contains several modules that help you write CKB contract with Rust | |||
| * `debug!` macro: a `println!` like macro helps debugging | |||
| * `entry!` macro: defines contract entry point | |||
| * `default_alloc!` macro: defines global allocator for no-std rust | |||
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| * `atomic` module: atomic operations | |||
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Some Rust code can be compiled into atomic instructions for the RISC-V
target. However, these atomic instructions are not supported on ckb-vm. To
address this issue, this module has been introduced.
This module provides a Rust dummy atomic implementation inspired by
xxuejie/lib-dummy-atomics.
When the RISC-V atomic extension is disabled by specifying the
target-feature=-aflag, LLVM will attempt to link the atomic operations tofunctions prefixed with
__atomicin this module. For more details, referto the LLVM Atomics Documentation.
On the CKB-VM, only a single thread is present, making dummy atomic
operations sufficient for its purposes.