Add new test directive needs-atomic to support #87377

Author: kei519

Diff for: src/tools/compiletest/src/common.rs

@@ -477,6 +477,16 @@ impl Config {
         ASM_SUPPORTED_ARCHS.contains(&self.target_cfg().arch.as_str())
     }
 
+    pub fn has_atomic(&self, size: Option<u64>) -> bool {
+        if let Some(size) = size {
+            (self.target_cfg().min_atomic_width()..=self.target_cfg().max_atomic_width())
+                .contains(&size)
+                && self.target_cfg().atomic_cas
+        } else {
+            self.target_cfg().atomic_cas
+        }
+    }
+
     pub fn git_config(&self) -> GitConfig<'_> {
         GitConfig {
             git_repository: &self.git_repository,
@@ -645,12 +655,26 @@ pub struct TargetCfg {
     pub(crate) xray: bool,
     #[serde(default = "default_reloc_model")]
     pub(crate) relocation_model: String,
+    #[serde(default)]
+    max_atomic_width: Option<u64>,
+    #[serde(default)]
+    min_atomic_width: Option<u64>,
+    #[serde(default = "default_atomic_cas")]
+    atomic_cas: bool,
 }
 
 impl TargetCfg {
     pub(crate) fn os_and_env(&self) -> String {
         format!("{}-{}", self.os, self.env)
     }
+
+    fn max_atomic_width(&self) -> u64 {
+        self.max_atomic_width.unwrap_or(self.pointer_width as _)
+    }
+
+    fn min_atomic_width(&self) -> u64 {
+        self.min_atomic_width.unwrap_or(8)
+    }
 }
 
 fn default_os() -> String {
@@ -661,6 +685,10 @@ fn default_reloc_model() -> String {
     "pic".into()
 }
 
+fn default_atomic_cas() -> bool {
+    true
+}
+
 #[derive(Eq, PartialEq, Clone, Debug, Default, serde::Deserialize)]
 #[serde(rename_all = "kebab-case")]
 pub enum Endian {

Diff for: src/tools/compiletest/src/directive-list.rs

@@ -127,6 +127,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "min-llvm-version",
     "min-system-llvm-version",
     "needs-asm-support",
+    "needs-atomic",
     "needs-deterministic-layouts",
     "needs-dlltool",
     "needs-dynamic-linking",

Diff for: src/tools/compiletest/src/header/needs.rs

@@ -14,6 +14,43 @@ pub(super) fn handle_needs(
             condition: &mut |_| config.has_asm_support().then_some(IgnoreDecision::Continue),
             ignore_reason: "ignored on targets without inline assembly support",
         },
+        Need {
+            name: "needs-atomic",
+            condition: &mut |comment| {
+                let Some(comment_content) = comment else {
+                    return Some(IgnoreDecision::Continue);
+                };
+                if comment_content.trim().is_empty() {
+                    return Some(IgnoreDecision::Continue);
+                }
+
+                let (size, rest) = match comment_content.trim_start().split_once([':', ' ']) {
+                    Some((size, rest)) => (size, Some(rest)),
+                    None => (comment_content.trim(), None),
+                };
+                eprintln!("size={size}, rest={rest:?}");
+
+                let size = if size == "ptr" {
+                    *comment = rest;
+                    Some(config.target_cfg().pointer_width as _)
+                } else if let Ok(size) = size.parse() {
+                    if ![128, 64, 32, 16, 8].contains(&size) {
+                        return Some(IgnoreDecision::Error {
+                            message: "expected values for `needs-atomic` are: (none), `128`,\
+                                `16`, `32`, `64`, `8`, and `ptr"
+                                .into(),
+                        });
+                    } else {
+                        *comment = rest;
+                        Some(size)
+                    }
+                } else {
+                    None
+                };
+                config.has_atomic(size).then_some(IgnoreDecision::Continue)
+            },
+            ignore_reason: "ignored on targets without atomic operations",
+        },
         Need {
             name: "needs-sanitizer-support",
             condition: &mut |_| cache.sanitizer_support.then_some(IgnoreDecision::Continue),