detect: Support run-time detection on powerpc64 AIX

.github/.cspell/project-dictionary.txt

@@ -44,6 +44,7 @@ espup
 exynos
 FIQs
 getauxval
+getsystemcfg
 HWCAP
 ifunc
 includepath

src/imp/atomic128/README.md

@@ -46,6 +46,7 @@ Here is the table of targets that support run-time feature detection and the ins
 | aarch64     | fuchsia              | zx_system_get_features | Enabled by default |
 | powerpc64   | linux                | getauxval       | Disabled by default |
 | powerpc64   | freebsd              | elf_aux_info    | Disabled by default |
+| powerpc64   | aix                  | getsystemcfg    | Disabled by default |
 
 Run-time detection is enabled by default on most targets and can be disabled with `--cfg portable_atomic_no_outline_atomics`.
 

src/imp/atomic128/detect/powerpc64_aix.rs

@@ -0,0 +1,68 @@
+// Run-time feature detection on powerpc64 AIX by using getsystemcfg.
+//
+// Refs:
+// - https://github.com/golang/go/blob/master/src/internal/cpu/cpu_ppc64x_aix.go
+
+include!("common.rs");
+
+// core::ffi::c_* (except c_void) requires Rust 1.64, libc will soon require Rust 1.47
+mod ffi {
+    pub(crate) use super::c_types::{c_int, c_ulong};
+
+    // https://github.com/rust-lang/libc/blob/0.2.140/src/unix/aix/mod.rs#L1576
+    // https://github.com/golang/go/blob/master/src/internal/cpu/cpu_ppc64x_aix.go
+    pub(crate) const SC_IMPL: c_int = 2;
+    pub(crate) const POWER_8: c_ulong = 0x10000;
+
+    extern "C" {
+        // https://www.ibm.com/docs/en/aix/7.2?topic=g-getsystemcfg-subroutine
+        // https://github.com/rust-lang/libc/blob/0.2.140/src/unix/aix/powerpc64.rs#L569
+        pub(crate) fn getsystemcfg(name: c_int) -> c_ulong;
+    }
+}
+
+#[cold]
+fn _detect(info: &mut CpuInfo) {
+    // SAFETY: calling getsystemcfg is safe.
+    let impl_ = unsafe { ffi::getsystemcfg(ffi::SC_IMPL) };
+    if impl_ == ffi::c_ulong::MAX {
+        return;
+    }
+    if impl_ & ffi::POWER_8 != 0 {
+        info.set(CpuInfo::HAS_QUADWORD_ATOMICS);
+    }
+}
+
+#[allow(
+    clippy::alloc_instead_of_core,
+    clippy::std_instead_of_alloc,
+    clippy::std_instead_of_core,
+    clippy::undocumented_unsafe_blocks,
+    clippy::wildcard_imports
+)]
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // Static assertions for FFI bindings.
+    // This checks that FFI bindings defined in this crate and FFI bindings defined
+    // in libc compatible signatures (or the same values if constants).
+    // Since this is static assertion, we can detect problems with
+    // `cargo check --tests --target <target>` run in CI (via TESTS=1 build.sh)
+    // without actually running tests on these platforms.
+    // See also tools/codegen/src/ffi.rs.
+    // TODO: auto-generate this test
+    #[allow(
+        clippy::cast_possible_wrap,
+        clippy::cast_sign_loss,
+        clippy::cast_possible_truncation,
+        clippy::no_effect_underscore_binding
+    )]
+    const _: fn() = || {
+        use test_helper::libc;
+        let mut _getsystemcfg: unsafe extern "C" fn(ffi::c_int) -> ffi::c_ulong = ffi::getsystemcfg;
+        _getsystemcfg = libc::getsystemcfg;
+        static_assert!(ffi::SC_IMPL == libc::SC_IMPL);
+        static_assert!(ffi::POWER_8 == libc::POWER_8);
+    };
+}

src/imp/atomic128/powerpc64.rs

@@ -59,6 +59,18 @@ mod fallback;
 ))]
 #[path = "detect/auxv.rs"]
 mod detect;
+#[cfg(not(portable_atomic_no_outline_atomics))]
+#[cfg(any(test, portable_atomic_outline_atomics))] // TODO(powerpc64): currently disabled by default
+#[cfg(any(
+    test,
+    not(any(
+        target_feature = "quadword-atomics",
+        portable_atomic_target_feature = "quadword-atomics",
+    )),
+))]
+#[cfg(target_os = "aix")]
+#[path = "detect/powerpc64_aix.rs"]
+mod detect;
 
 use core::{arch::asm, sync::atomic::Ordering};
 

src/imp/fallback/mod.rs

@@ -36,6 +36,7 @@
                 ),
                 target_os = "android",
                 target_os = "freebsd",
+                target_os = "aix",
             ),
             not(any(miri, portable_atomic_sanitize_thread)),
         ),

src/imp/mod.rs

@@ -87,6 +87,7 @@ mod x86_64;
                 ),
                 target_os = "android",
                 target_os = "freebsd",
+                target_os = "aix",
             ),
             not(any(miri, portable_atomic_sanitize_thread)),
         ),
@@ -369,6 +370,7 @@ items! {
                         ),
                         target_os = "android",
                         target_os = "freebsd",
+                        target_os = "aix",
                     ),
                     not(any(miri, portable_atomic_sanitize_thread)),
                 ),
@@ -442,6 +444,7 @@ pub(crate) use self::x86_64::{AtomicI128, AtomicU128};
                 ),
                 target_os = "android",
                 target_os = "freebsd",
+                target_os = "aix",
             ),
             not(any(miri, portable_atomic_sanitize_thread)),
         ),

src/utils.rs

@@ -513,6 +513,7 @@ mod atomic_64_macros {
                         ),
                         target_os = "android",
                         target_os = "freebsd",
+                        target_os = "aix",
                     ),
                     not(any(miri, portable_atomic_sanitize_thread)),
                 ),
@@ -596,6 +597,7 @@ mod atomic_128_macros {
                         ),
                         target_os = "android",
                         target_os = "freebsd",
+                        target_os = "aix",
                     ),
                     not(any(miri, portable_atomic_sanitize_thread)),
                 ),

tools/build.sh

@@ -99,6 +99,7 @@ default_targets=(
     powerpc64le-unknown-linux-musl
     powerpc64-unknown-freebsd
     powerpc64le-unknown-freebsd
+    powerpc64-ibm-aix
 
     # s390x
     # rustc --print target-list | grep -E '^s390x'
@@ -153,7 +154,8 @@ is_no_std() {
     case "$1" in
         # https://github.com/rust-lang/rust/blob/1.70.0/library/std/build.rs#L41
         # TODO: aarch64-unknown-linux-uclibc is a custom target and libc/std currently doesn't support it.
-        *-none* | *-uefi* | *-psp* | *-psx* | *-cuda* | avr-* | aarch64-unknown-linux-uclibc) return 0 ;;
+        # TODO: std currently doesn't support AIX: https://github.com/rust-lang/rust/pull/109882
+        *-none* | *-uefi* | *-psp* | *-psx* | *-cuda* | avr-* | aarch64-unknown-linux-uclibc | *-aix) return 0 ;;
         *) return 1 ;;
     esac
 }