Mark all NuttX targets as tier 3 target and support the standard library

[no1wudi]

The support for standard library added by #130595.

[rustbot]

r? @GuillaumeGomez

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[taiki-e]

Could you update std field in metadata in target specs too? (Otherwise, Cargo will treat the target as not supporting std by default.)

rust/compiler/rustc_target/src/spec/targets/armv7a_nuttx_eabi.rs

Lines 30 to 35 in 814ebca

	metadata: crate::spec::TargetMetadata {
	description: Some("ARMv7-A Cortex-A with NuttX".into()),
	tier: Some(3),
	host_tools: Some(false),
	std: Some(false),
	},

[no1wudi]

Could you update std field in metadata in target specs too? (Otherwise, Cargo will treat the target as not supporting std by default.)

rust/compiler/rustc_target/src/spec/targets/armv7a_nuttx_eabi.rs

Lines 30 to 35 in 814ebca

	metadata: crate::spec::TargetMetadata {
	description: Some("ARMv7-A Cortex-A with NuttX".into()),
	tier: Some(3),
	host_tools: Some(false),
	std: Some(false),
	},

OK, I'll update the metadata later

[rustbot]

These commits modify compiler targets.
(See the Target Tier Policy.)

[no1wudi]

@rustbot review

[taiki-e]

std requires atomic CAS (std uses Arc and Arc requires atomic CAS), but it is disabled in the thumbv6m-nuttx-eabi target spec.

rust/compiler/rustc_target/src/spec/targets/thumbv6m_nuttx_eabi.rs

Lines 23 to 30 in 6edf283

	// The ARMv6-M architecture doesn't support unaligned loads/stores so we disable them
	// with +strict-align.
	// Also force-enable 32-bit atomics, which allows the use of atomic load/store only.
	// The resulting atomics are ABI incompatible with atomics backed by libatomic.
	features: "+strict-align,+atomics-32".into(),
	// There are no atomic CAS instructions available in the instruction set of the ARMv6-M
	// architecture
	atomic_cas: false,

Therefore, std should not actually be supported at thumbv6m-nuttx-eabi at this time.

However, IIUC this platform provide atomic builtins, so this problem should be fixed by just removing +atomics-32 and atomic_cas: false. (as already done in riscv32imc-unknown-nuttx-elf that has no atomic CAS instructions)

(In practice, it would also be necessary to audit whether atomic builtins are implemented correctly (like #115577 (comment) and #115577 (comment)), but that is a separate issue since riscv32imc nuttx already uses it.)

[jieyouxu]

@rustbot author (see review above)

[no1wudi]

Therefore, std should not actually be supported at thumbv6m-nuttx-eabi at this time.

However, IIUC this platform provide atomic builtins, so this problem should be fixed by just removing +atomics-32 and atomic_cas: false. (as already done in riscv32imc-unknown-nuttx-elf that has no atomic CAS instructions)

Thanks for point that, after verification, there is indeed an issue with compiling the standard library on this platform.

Following your suggestion, adopting a method similar to that used on the riscv32imc platform has not been able to pass the compilation:

error[E0599]: no method named `compare_exchange` found for struct `AtomicUsize` in the current scope
  --> /home/huang/Work/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/src/rust/library/std/src/sys/sync/thread_parking/pthread.rs:97:23
   |
97 |         if self.state.compare_exchange(NOTIFIED, EMPTY, Acquire, Relaxed).is_ok() {
   |                       ^^^^^^^^^^^^^^^^ method not found in `AtomicUsize`

error[E0599]: no method named `compare_exchange` found for struct `AtomicUsize` in the current scope
   --> /home/huang/Work/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/src/rust/library/std/src/sys/sync/thread_parking/pthread.rs:102:26
    |
102 |         match self.state.compare_exchange(EMPTY, PARKED, Relaxed, Relaxed) {
    |                          ^^^^^^^^^^^^^^^^ method not found in `AtomicUsize`

error[E0599]: no method named `swap` found for struct `AtomicUsize` in the current scope
   --> /home/huang/Work/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/src/rust/library/std/src/sys/sync/thread_parking/pthread.rs:106:38
    |
106 |                 let old = self.state.swap(EMPTY, Acquire);
    |                                      ^^^^ method not found in `AtomicUsize`

error[E0599]: no method named `swap` found for struct `AtomicUsize` in the current scope
   --> /home/huang/Work/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/src/rust/library/std/src/sys/sync/thread_parking/pthread.rs:124:26

At present, I am planning to keep the current status of the thumbv6m platform until it is able to function properly.

@rustbot review

[taiki-e]

Therefore, std should not actually be supported at thumbv6m-nuttx-eabi at this time.
However, IIUC this platform provide atomic builtins, so this problem should be fixed by just removing +atomics-32 and atomic_cas: false. (as already done in riscv32imc-unknown-nuttx-elf that has no atomic CAS instructions)

Thanks for point that, after verification, there is indeed an issue with compiling the standard library on this platform.

Following your suggestion, adopting a method similar to that used on the riscv32imc platform has not been able to pass the compilation:

Oh, perhaps max_atomic_width: Some(32) needs to be added. (I remember that the behavior was something odd when max_atomic_width was None.)

[no1wudi]

Oh, perhaps max_atomic_width: Some(32) needs to be added. (I remember that the behavior was something odd when max_atomic_width was None.)

Thank you!!! It works with:

        options: TargetOptions {
            families: cvs!["unix"],
            os: "nuttx".into(),
            abi: "eabi".into(),
            llvm_floatabi: Some(FloatAbi::Soft),
            // The ARMv6-M architecture doesn't support unaligned loads/stores so we disable them
            // with +strict-align.
            // The ARMv6-M doesn't support hardware atomic operations, use atomic builtins instead.
            features: "+strict-align".into(),
            max_atomic_width: Some(32),
            ..base::thumb::opts()
        },

[taiki-e]

LGTM

[jieyouxu]

Thanks for the PR! And thanks @taiki-e for the review

[jieyouxu]

@bors r+ rollup

[bors]

📌 Commit e44e345 has been approved by jieyouxu

It is now in the queue for this repository.

[bors]

☔ The latest upstream changes (presumably #136087) made this pull request unmergeable. Please resolve the merge conflicts.