multivers: add the --cpus option similar to the one in Cargo.toml

Author: ronnychevalier

src/cli.rs

@@ -7,8 +7,10 @@ pub enum Cargo {
     Multivers(Args),
 }
 
+/// Type of information to print on stdout
 #[derive(clap::ValueEnum, Clone, Copy)]
 pub enum Print {
+    /// Prints the list of CPU features supported by the target
     CpuFeatures,
 }
 
@@ -22,6 +24,15 @@ pub struct Args {
     #[clap(long, value_name = "INFORMATION")]
     pub print: Option<Print>,
 
+    /// Comma-separated list of CPUs to use as a target
+    #[clap(
+        long,
+        use_value_delimiter = true,
+        value_delimiter = ',',
+        value_name = "CPUs"
+    )]
+    pub cpus: Option<Vec<String>>,
+
     /// Comma-separated list of CPU features to exclude from the builds
     #[clap(
         long,
@@ -46,6 +57,7 @@ pub struct Args {
 }
 
 impl Args {
+    /// Returns the target given on the command line or the default target that rustc uses to build if none is provided
     pub fn target(&self) -> anyhow::Result<String> {
         self.target
             .as_ref()

src/features.rs

@@ -40,8 +40,11 @@ pub struct Cpus {
 }
 
 impl Cpus {
-    pub fn builder<'a>(target: impl Into<String>) -> anyhow::Result<CpusBuilder<'a>> {
-        CpusBuilder::new(target)
+    pub fn builder<'a>(
+        target: impl Into<String>,
+        cpus: Option<Vec<String>>,
+    ) -> anyhow::Result<CpusBuilder<'a>> {
+        CpusBuilder::new(target, cpus)
     }
 
     /// Returns a sorted and deduplicated iterator of CPU features set for each CPU
@@ -72,12 +75,16 @@ pub struct CpusBuilder<'a> {
 }
 
 impl<'a> CpusBuilder<'a> {
-    pub fn new(target: impl Into<String>) -> anyhow::Result<Self> {
+    pub fn new(target: impl Into<String>, cpus: Option<Vec<String>>) -> anyhow::Result<Self> {
         let target = target.into();
         let triple = Triple::from_str(&target).context("Failed to parse the target")?;
-        let iter = Rustc::cpus_from_target(&target)
-            .context("Failed to get the set of CPUs for the target")?
-            .into_par_iter();
+        let iter = if let Some(cpus) = cpus {
+            cpus
+        } else {
+            Rustc::cpus_from_target(&target)
+                .context("Failed to get the set of CPUs for the target")?
+        }
+        .into_par_iter();
 
         Ok(Self {
             iter,

src/main.rs

@@ -22,7 +22,7 @@ fn main() -> anyhow::Result<()> {
     if matches!(args.print, Some(Print::CpuFeatures)) {
         let target = args.target()?;
 
-        let cpus = Cpus::builder(&target)
+        let cpus = Cpus::builder(&target, args.cpus)
             .context("Failed to get the set of CPU features for the target")?
             .build();
         let mut stdout = std::io::stdout().lock();
@@ -38,8 +38,5 @@ fn main() -> anyhow::Result<()> {
         "You must run cargo multivers with Rust nightly channel. For example, you can run: `cargo +nightly multivers`"
     );
 
-    let multivers = Multivers::from_args(args)?;
-    multivers.build()?;
-
-    Ok(())
+    Multivers::from_args(args)?.build()
 }

src/metadata.rs

@@ -30,15 +30,15 @@ impl<'de> Deserialize<'de> for ArchitectureWrapper {
 
 #[derive(PartialEq, Eq, Hash, Debug)]
 pub struct TargetMetadata {
-    pub cpus: Vec<String>,
+    pub cpus: Option<Vec<String>>,
 }
 
 impl<'de> Deserialize<'de> for TargetMetadata {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
         D: Deserializer<'de>,
     {
-        let mut metadata = HashMap::<String, Vec<String>>::deserialize(deserializer)?;
+        let mut metadata = HashMap::<String, Option<Vec<String>>>::deserialize(deserializer)?;
         let cpus = metadata.remove("cpus").unwrap_or_default();
 
         Ok(Self { cpus })
@@ -55,7 +55,7 @@ impl<'de> Deserialize<'de> for TargetMetadata {
 /// ```
 #[derive(Debug)]
 pub struct MultiversMetadata {
-    pub targets: HashMap<Architecture, TargetMetadata>,
+    targets: HashMap<Architecture, TargetMetadata>,
 }
 
 impl MultiversMetadata {
@@ -67,12 +67,14 @@ impl MultiversMetadata {
 
         let mut metadata: HashMap<String, serde_json::Value> =
             serde_json::from_value(package.metadata.clone())?;
-        let metadata = match metadata.remove("multivers") {
-            Some(metadata) => metadata,
-            None => return Ok(None),
+        let Some(metadata) = metadata.remove("multivers") else {
+            return Ok(None);
         };
 
         let targets: HashMap<ArchitectureWrapper, _> = serde_json::from_value(metadata)?;
+        if targets.is_empty() {
+            return Ok(None);
+        }
 
         Ok(Some(Self {
             targets: targets
@@ -81,4 +83,8 @@ impl MultiversMetadata {
                 .collect(),
         }))
     }
+
+    pub fn get(&self, k: &Architecture) -> Option<&TargetMetadata> {
+        self.targets.get(k)
+    }
 }

src/multivers.rs

@@ -43,6 +43,7 @@ struct BuildsDescription {
     builds: Vec<BuildDescription>,
 }
 
+/// Build multiple versions of the same binary, each with a different CPU features set, merged into a single portable optimized binary
 pub struct Multivers {
     metadata: Metadata,
     target: String,
@@ -68,7 +69,7 @@ impl Multivers {
         // See https://github.com/rust-lang/cargo/issues/4423
         let target = args.target()?;
 
-        let cpus = Cpus::builder(&target)
+        let cpus = Cpus::builder(&target, args.cpus)
             .context("Failed to get the set of CPU features for the target")?
             .exclude_features(args.exclude_cpu_features.as_deref())
             .build();
@@ -101,19 +102,17 @@ impl Multivers {
         })
     }
 
-    fn build_package(&self, package: &Package) -> anyhow::Result<BuildsDescription> {
-        let triple = Triple::from_str(&self.target).context("Failed to parse the target")?;
-        let manifest_path = package.manifest_path.as_std_path().to_path_buf();
-        let features_list = self.features.features.join(" ");
-        let mut rust_flags = std::env::var("RUST_FLAGS").unwrap_or_default();
-
-        let metadata = MultiversMetadata::from_package(package)
-            .context("Failed to parse package's metadata")?;
-        let cpu_features: Vec<CpuFeatures> = if let Some(metadata) = metadata {
-            if let Some(target_metadata) = metadata.targets.get(&triple.architecture) {
-                target_metadata
-                    .cpus
-                    .iter()
+    fn cpu_features(
+        &self,
+        triple: &Triple,
+        metadata: Option<&MultiversMetadata>,
+    ) -> Vec<CpuFeatures> {
+        if let Some(metadata) = metadata {
+            if let Some(cpus) = metadata
+                .get(&triple.architecture)
+                .and_then(|t| t.cpus.as_ref())
+            {
+                cpus.iter()
                     .filter_map(|cpu| self.cpus.get(cpu))
                     .unique()
                     .cloned()
@@ -123,7 +122,19 @@ impl Multivers {
             }
         } else {
             self.cpus.features_sets().cloned().collect()
-        };
+        }
+    }
+
+    fn build_package(&self, package: &Package) -> anyhow::Result<BuildsDescription> {
+        let triple: Triple =
+            Triple::from_str(&self.target).context("Failed to parse the target")?;
+        let manifest_path = package.manifest_path.as_std_path().to_path_buf();
+        let features_list = self.features.features.join(" ");
+        let mut rust_flags = std::env::var("RUST_FLAGS").unwrap_or_default();
+
+        let metadata = MultiversMetadata::from_package(package)
+            .context("Failed to parse package's metadata")?;
+        let cpu_features = self.cpu_features(&triple, metadata.as_ref());
 
         self.progress.set_length(cpu_features.len() as u64);
         self.progress.set_prefix("Building");