Support C-SKY (experimental)

.github/.cspell/project-dictionary.txt

@@ -1,3 +1,4 @@
+abiv
 amocas
 amoswap
 amswap
@@ -18,10 +19,12 @@ ccmp
 cdsg
 CDSY
 clrex
+cmpne
 cmpw
 cmpxchg
 csel
 cset
+cskyv
 dbar
 distro
 DWCAS
@@ -44,6 +47,7 @@ ldar
 ldarx
 ldaxp
 ldclrp
+ldex
 ldiapp
 ldrex
 ldrexd
@@ -83,6 +87,7 @@ opensbi
 orrs
 partword
 pstq
+pthread
 qbsp
 quadword
 rcpc
@@ -106,6 +111,7 @@ sreg
 srlv
 stbar
 stdcx
+stex
 stilp
 stlxp
 stpq

.github/workflows/ci.yml

@@ -290,6 +290,29 @@ jobs:
             target: armeb-unknown-linux-gnueabi
             os: ubuntu-22.04
           # ------------------------------------------------------------
+          # csky-unknown-linux-gnuabiv2
+          - rust: nightly-2025-02-14 # Rust 1.86, LLVM 19 (oldest version we can use asm_experimental_arch on this target)
+            target: csky-unknown-linux-gnuabiv2
+            # +crt-static: Workaround for C-SKY QEMU issue
+            # ldex/stex requires ck860*
+            flags: -C target-feature=+crt-static -C target-cpu=ck860
+          - rust: nightly
+            target: csky-unknown-linux-gnuabiv2
+            # +crt-static: Workaround for C-SKY QEMU issue
+            # ldex/stex requires ck860*
+            flags: -C target-feature=+crt-static -C target-cpu=ck860
+          # ------------------------------------------------------------
+          # csky-unknown-linux-gnuabiv2hf
+          # TODO: relocations in generic ELF (EM: 252)
+          # - rust: nightly-2025-02-14 # Rust 1.86, LLVM 19 (oldest version we can use asm_experimental_arch on this target)
+          #   target: csky-unknown-linux-gnuabiv2hf
+          #   # +crt-static: Workaround for C-SKY QEMU issue
+          #   flags: -C target-feature=+crt-static
+          # - rust: nightly
+          #   target: csky-unknown-linux-gnuabiv2hf
+          #   # +crt-static: Workaround for C-SKY QEMU issue
+          #   flags: -C target-feature=+crt-static
+          # ------------------------------------------------------------
           # hexagon-unknown-linux-musl
           - rust: nightly-2024-11-29 # Rust 1.85, LLVM 19 (oldest version we can use asm_experimental_arch on this target)
             target: hexagon-unknown-linux-musl
@@ -510,7 +533,34 @@ jobs:
       - uses: taiki-e/setup-cross-toolchain-action@v1
         with:
           target: ${{ matrix.target }}
-        if: steps.prepare.outputs.target-not-host == 'true'
+        if: steps.prepare.outputs.target-not-host == 'true' && !startsWith(matrix.target, 'csky-')
+      # TODO: not yet supported in setup-cross-toolchain-action
+      - run: |
+          retry() {
+            for i in {1..10}; do
+              if "$@"; then
+                return 0
+              else
+                sleep "${i}"
+              fi
+            done
+            "$@"
+          }
+          target="${{ matrix.target }}"
+          # https://github.com/taiki-e/rust-cross-toolchain/pkgs/container/rust-cross-toolchain
+          retry docker create --name gcc-csky-linux-gnuabiv2 "ghcr.io/taiki-e/rust-cross-toolchain:${target}-dev-amd64"
+          docker cp -- "gcc-csky-linux-gnuabiv2:/${target}" "${HOME}"/gcc-csky-linux-gnuabiv2
+          docker rm -f -- gcc-csky-linux-gnuabiv2 >/dev/null
+          printf '%s\n' "${HOME}"/gcc-csky-linux-gnuabiv2/bin >>"${GITHUB_PATH}"
+          printf '%s\n' "CARGO_TARGET_CSKY_UNKNOWN_LINUX_GNUABIV2_LINKER=csky-abiv2-linux-gcc" >>"${GITHUB_ENV}"
+          case "${target}" in
+            *hf) qemu_cpu=ck860fv ;;
+            # https://github.com/taiki-e/atomic-maybe-uninit/pull/32#issuecomment-3341287749
+            *) qemu_cpu=ck860 ;;
+          esac
+          printf '%s\n' "CARGO_TARGET_CSKY_UNKNOWN_LINUX_GNUABIV2_RUNNER=qemu-cskyv2 -cpu ${qemu_cpu}" >>"${GITHUB_ENV}"
+          printf 'BUILD_STD=-Z''build-std\n' >>"${GITHUB_ENV}"
+        if: startsWith(matrix.target, 'csky-')
       - run: |
           target="${{ matrix.target }}"
           target_lower="${target//-/_}"
@@ -525,7 +575,8 @@ jobs:
         if: matrix.flags != ''
       - run: printf '%s\n' "RUSTFLAGS=${RUSTFLAGS} -D linker_messages" >>"${GITHUB_ENV}"
         # TODO(macos): error: linker stderr: ld: ignoring duplicate libraries: '-lc', '-lm'
-        if: matrix.rust == 'nightly' && !contains(matrix.target, '-darwin')
+        # TODO(csky): error: linker stderr: /home/runner/gcc-csky-linux-gnuabiv2/bin/../lib/gcc/csky-linux-gnuabiv2/6.3.0/../../../../csky-linux-gnuabiv2/bin/ld: file ....o's arch flag ck860 conflict with target ck810,set target arch flag to ck860
+        if: matrix.rust == 'nightly' && !(contains(matrix.target, '-darwin') || matrix.target == 'csky-unknown-linux-gnuabiv2')
       # Old LLVM bug: Undefined temporary symbol error when building std.
       - name: Workaround for old LLVM bug about MIPS32
         run: printf 'RELEASE=--release\n' >>"${GITHUB_ENV}"

Cargo.toml

@@ -33,7 +33,7 @@ doc-scrape-examples = false
 [dev-dependencies]
 fastrand = "2"
 paste = "1"
-quickcheck = { version = "1", default-features = false, git = "https://github.com/taiki-e/quickcheck.git", rev = "83b1d59" } # https://github.com/BurntSushi/quickcheck/pull/304 + https://github.com/BurntSushi/quickcheck/pull/282 + https://github.com/BurntSushi/quickcheck/pull/296 + f16/f128 support + lower MSRV
+quickcheck = { version = "1", default-features = false, git = "https://github.com/taiki-e/quickcheck.git", rev = "f0c7237" } # https://github.com/BurntSushi/quickcheck/pull/304 + https://github.com/BurntSushi/quickcheck/pull/282 + https://github.com/BurntSushi/quickcheck/pull/296 + rand -> fastrand + lower MSRV
 
 [target.'cfg(valgrind)'.dev-dependencies]
 crabgrind = "0.1"

README.md

@@ -19,7 +19,7 @@ This crate provides a way to soundly perform such operations.
 
 ## Platform Support
 
-Currently, x86, x86_64, Arm, AArch64, RISC-V, LoongArch, Arm64EC, s390x, MIPS, PowerPC, MSP430, AVR, SPARC, Hexagon, M68k, and Xtensa are supported.
+Currently, x86, x86_64, Arm, AArch64, RISC-V, LoongArch, Arm64EC, s390x, MIPS, PowerPC, MSP430, AVR, SPARC, Hexagon, M68k, C-SKY, and Xtensa are supported.
 (You can use `cfg_{has,no}_*` macros to write code based on whether or not which size of primitives is available.)
 
 | target_arch                     | primitives                                          | load/store | swap/CAS |
@@ -50,9 +50,10 @@ Currently, x86, x86_64, Arm, AArch64, RISC-V, LoongArch, Arm64EC, s390x, MIPS, P
 | hexagon \[9] (experimental)     | isize,usize,i8,u8,i16,u16,i32,u32,i64,u64           | ✓          | ✓        |
 | m68k \[9] (experimental)        | isize,usize,i8,u8,i16,u16,i32,u32                   | ✓          | ✓\[1]    |
 | m68k (+isa-68020) \[9] \[10] (experimental) | i64,u64                                 | ✓          | ✓        |
+| csky \[9] (experimental)        | isize,usize,i8,u8,i16,u16,i32,u32                   | ✓          | ✓\[1]    |
 | xtensa \[9] (experimental)      | isize,usize,i8,u8,i16,u16,i32,u32                   | ✓          | ✓\[1]    |
 
-\[1] Arm's atomic RMW operations are not available on Armv6-M (thumbv6m). RISC-V's atomic RMW operations are not available on targets without the A (or G which means IMAFD) or Zalrsc or Zacas extension, such as riscv32i, riscv32imc, etc. M68k's atomic RMW operations requires target-cpu M68020+ (enabled by default on Linux). Xtensa's atomic RMW operations are not available on esp32s2.<br>
+\[1] Arm's atomic RMW operations are not available on Armv6-M (thumbv6m). RISC-V's atomic RMW operations are not available on targets without the A (or G which means IMAFD) or Zalrsc or Zacas extension, such as riscv32i, riscv32imc, etc. M68k's atomic RMW operations requires target-cpu M68020+ (enabled by default on Linux). C-SKY's atomic RMW operations requires target-cpu ck860\* (enabled by default on the hard-float target). Xtensa's atomic RMW operations are not available on esp32s2.<br>
 \[2] Requires `cmpxchg16b` target feature (enabled by default on Apple, Windows (except Windows 7), and Fuchsia targets).<br>
 \[3] Armv6+ or Linux/Android, except for M-profile architecture such as thumbv6m, thumbv7m, etc.<br>
 \[4] Requires `zacas` target feature.<br>

build.rs

@@ -39,7 +39,7 @@ fn main() {
         // Custom cfgs set by build script. Not public API.
         // grep -F 'cargo:rustc-cfg=' build.rs | grep -Ev '^ *//' | sed -E 's/^.*cargo:rustc-cfg=//; s/(=\\)?".*$//' | LC_ALL=C sort -u | tr '\n' ',' | sed -E 's/,$/\n/'
         println!(
-            "cargo:rustc-check-cfg=cfg(atomic_maybe_uninit_no_asm,atomic_maybe_uninit_no_cmpxchg,atomic_maybe_uninit_no_cmpxchg8b,atomic_maybe_uninit_no_const_mut_refs,atomic_maybe_uninit_no_diagnostic_namespace,atomic_maybe_uninit_no_strict_provenance,atomic_maybe_uninit_no_sync,atomic_maybe_uninit_pre_llvm_20,atomic_maybe_uninit_target_feature,atomic_maybe_uninit_unstable_asm_experimental_arch)"
+            "cargo:rustc-check-cfg=cfg(atomic_maybe_uninit_no_asm,atomic_maybe_uninit_no_cmpxchg,atomic_maybe_uninit_no_cmpxchg8b,atomic_maybe_uninit_no_const_mut_refs,atomic_maybe_uninit_no_diagnostic_namespace,atomic_maybe_uninit_no_ldex_stex,atomic_maybe_uninit_no_strict_provenance,atomic_maybe_uninit_no_sync,atomic_maybe_uninit_pre_llvm_20,atomic_maybe_uninit_target_feature,atomic_maybe_uninit_unstable_asm_experimental_arch)"
         );
         // TODO: handle multi-line target_feature_fallback
         // grep -F 'target_feature_fallback("' build.rs | grep -Ev '^ *//' | sed -E 's/^.*target_feature_fallback\(//; s/",.*$/"/' | LC_ALL=C sort -u | tr '\n' ',' | sed -E 's/,$/\n/'
@@ -118,6 +118,15 @@ fn main() {
                 println!("cargo:rustc-cfg=atomic_maybe_uninit_unstable_asm_experimental_arch");
             }
         }
+        "csky" => {
+            // https://github.com/rust-lang/rust/pull/136217 merged in Rust 1.86 (nightly-2025-02-14).
+            if version.nightly
+                && version.probe(86, 2025, 2, 13)
+                && is_allowed_feature("asm_experimental_arch")
+            {
+                println!("cargo:rustc-cfg=atomic_maybe_uninit_unstable_asm_experimental_arch");
+            }
+        }
         "hexagon" => {
             // https://github.com/rust-lang/rust/pull/133452 merged in Rust 1.85 (nightly-2024-11-29).
             if version.nightly
@@ -501,6 +510,23 @@ fn main() {
             }
             target_feature_fallback("rmw", xmegau);
         }
+        "csky" => {
+            let mut no_ldex_stex = true;
+            if let Some(cpu) = target_cpu() {
+                // https://github.com/llvm/llvm-project/blob/llvmorg-21.1.0/llvm/lib/Target/CSKY/CSKY.td#L373
+                if cpu.starts_with("ck860") {
+                    no_ldex_stex = false;
+                }
+            } else {
+                // https://github.com/rust-lang/rust/blob/1.90.0/compiler/rustc_target/src/spec/targets/csky_unknown_linux_gnuabiv2hf.rs#L20
+                if target == "csky-unknown-linux-gnuabiv2hf" {
+                    no_ldex_stex = false;
+                }
+            }
+            if no_ldex_stex {
+                println!("cargo:rustc-cfg=atomic_maybe_uninit_no_ldex_stex");
+            }
+        }
         _ => {}
     }
 }

src/arch/README.md

@@ -8,6 +8,7 @@ This document describes the operations that are considered atomic by architectur
 - [AArch64](#aarch64)
 - [Arm](#arm)
 - [AVR](#avr)
+- [C-SKY](#c-sky)
 - [Hexagon](#hexagon)
 - [LoongArch](#loongarch)
 - [M68k](#m68k)
@@ -61,6 +62,13 @@ This architecture is always single-core and the following operations are atomic:
   disabling and restoring implementation must imply compiler fences, e.g., asm without nomem/readonly)
   may be moved out of the critical section by compiler optimizations.
 
+## C-SKY
+
+target_arch: csky<br>
+Implementation: [csky.rs](csky.rs)<br>
+
+TODO: reference and overview
+
 ## Hexagon
 
 target_arch: hexagon<br>