target-spec: generate target specs on the fly in spirv-builder

Author: Firestar99

Cargo.lock

@@ -12,3 +12,4 @@ spirv = { version = "0.3.0", features = ["serialize", "deserialize"] }
 rspirv = "0.12"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+semver = { version = "1.0.24", features = ["serde"] }

crates/rustc_codegen_spirv-types/Cargo.toml

@@ -3,7 +3,9 @@
 pub use rspirv::spirv::Capability;
 
 mod compile_result;
+mod target_spec;
 pub use compile_result::*;
+pub use target_spec::*;
 
 // HACK(eddyb) allows downstream crates to access the correct version directly.
 pub use serde;

crates/rustc_codegen_spirv-types/src/lib.rs

@@ -0,0 +1,78 @@
+use semver::Version;
+use std::borrow::Cow;
+use std::ffi::OsStr;
+use std::path::Path;
+
+/// Enum for different versions of target specs, to allow changing the target spec for different rust versions.
+/// The version listed in the enum is always the minimum version to require said target spec, with the newest version
+/// always at the top.
+#[allow(non_camel_case_types)]
+#[derive(Copy, Clone, Debug)]
+pub enum TargetSpecVersion {
+    /// rustc 1.76 has been tested to correctly parse modern target_spec jsons.
+    /// Some later version requires them.
+    /// Some earlier version fails with them (notably our 0.9.0 release).
+    Rustc_1_76_0,
+}
+
+impl TargetSpecVersion {
+    pub fn target_arg<'a>(
+        rustc_version: Version,
+        target_env: &'a str,
+        target_spec_folder: &Path,
+    ) -> std::io::Result<Cow<'a, OsStr>> {
+        if let Some(target_spec) = Self::from_rustc_version(rustc_version) {
+            std::fs::create_dir_all(&target_spec_folder)?;
+            let spec_file = target_spec_folder.join(format!("spirv-unknown-{target_env}.json"));
+            std::fs::write(&spec_file, target_spec.format_spec(target_env))?;
+            Ok(Cow::Owned(spec_file.into_os_string()))
+        } else {
+            Ok(Cow::Borrowed(OsStr::new(target_env)))
+        }
+    }
+
+    /// Returns the version of the target spec required for a certain rustc version. May return `None` if the version
+    /// is old enough to not need target specs.
+    pub fn from_rustc_version(rustc_version: Version) -> Option<Self> {
+        if rustc_version >= Version::new(1, 76, 0) {
+            Some(Self::Rustc_1_76_0)
+        } else {
+            None
+        }
+    }
+
+    pub fn format_spec(&self, target_env: &str) -> String {
+        match self {
+            TargetSpecVersion::Rustc_1_76_0 => {
+                format!(
+                    r#"{{
+  "allows-weak-linkage": false,
+  "arch": "spirv",
+  "crt-objects-fallback": "false",
+  "crt-static-allows-dylibs": true,
+  "crt-static-respected": true,
+  "data-layout": "e-m:e-p:32:32:32-i64:64-n8:16:32:64",
+  "dll-prefix": "",
+  "dll-suffix": ".spv.json",
+  "dynamic-linking": true,
+  "emit-debug-gdb-scripts": false,
+  "env": "{target_env}",
+  "linker-flavor": "unix",
+  "linker-is-gnu": false,
+  "llvm-target": "spirv-unknown-{target_env}",
+  "main-needs-argc-argv": false,
+  "metadata": {{
+    "description": null,
+    "host_tools": null,
+    "std": null,
+    "tier": null
+  }},
+  "panic-strategy": "abort",
+  "simd-types-indirect": false,
+  "target-pointer-width": "32"
+}}"#
+                )
+            }
+        }
+    }
+}

crates/rustc_codegen_spirv-types/src/target_spec.rs

@@ -88,11 +88,10 @@ use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 use thiserror::Error;
 
-pub use rustc_codegen_spirv_types::Capability;
-pub use rustc_codegen_spirv_types::{CompileResult, ModuleResult};
-
 #[cfg(feature = "watch")]
 pub use self::watch::{SpirvWatcher, SpirvWatcherError};
+pub use rustc_codegen_spirv_types::Capability;
+pub use rustc_codegen_spirv_types::{CompileResult, ModuleResult, TargetSpecVersion};
 
 #[derive(Debug, Error)]
 #[non_exhaustive]
@@ -113,11 +112,6 @@ pub enum SpirvBuilderError {
     MissingRustcCodegenSpirvDylib,
     #[error("`rustc_codegen_spirv_location` path '{0}' is not a file")]
     RustcCodegenSpirvDylibDoesNotExist(PathBuf),
-    #[error(
-        "Without feature `include-target-specs`, instead of setting a `target`, \
-        you need to set the path of the target spec file of your particular target with `path_to_target_spec`"
-    )]
-    MissingTargetSpec,
     #[error("build failed")]
     BuildFailed,
     #[error("multi-module build cannot be used with print_metadata = MetadataPrintout::Full")]
@@ -458,12 +452,6 @@ pub struct SpirvBuilder {
     #[cfg_attr(feature = "clap", clap(skip))]
     pub toolchain_rustc_version: Option<Version>,
 
-    /// The path of the "target specification" file.
-    ///
-    /// For more info on "target specification" see
-    /// [this RFC](https://rust-lang.github.io/rfcs/0131-target-specification.html).
-    #[cfg_attr(feature = "clap", clap(skip))]
-    pub path_to_target_spec: Option<PathBuf>,
     /// Set the target dir path to use for building shaders. Relative paths will be resolved
     /// relative to the `target` dir of the shader crate, absolute paths are used as is.
     /// Defaults to `spirv-builder`, resulting in the path `./target/spirv-builder`.
@@ -514,7 +502,6 @@ impl Default for SpirvBuilder {
             extensions: Vec::new(),
             extra_args: Vec::new(),
             rustc_codegen_spirv_location: None,
-            path_to_target_spec: None,
             target_dir_path: None,
             toolchain_overwrite: None,
             toolchain_rustc_version: None,
@@ -535,16 +522,6 @@ impl SpirvBuilder {
         }
     }
 
-    /// Sets the path of the "target specification" file.
-    ///
-    /// For more info on "target specification" see
-    /// [this RFC](https://rust-lang.github.io/rfcs/0131-target-specification.html).
-    #[must_use]
-    pub fn target_spec(mut self, p: impl AsRef<Path>) -> Self {
-        self.path_to_target_spec = Some(p.as_ref().to_path_buf());
-        self
-    }
-
     /// Whether to print build.rs cargo metadata (e.g. cargo:rustc-env=var=val). Defaults to [`MetadataPrintout::Full`].
     #[must_use]
     pub fn print_metadata(mut self, v: MetadataPrintout) -> Self {
@@ -802,16 +779,17 @@ fn join_checking_for_separators(strings: Vec<impl Borrow<str>>, sep: &str) -> St
 
 // Returns path to the metadata json.
 fn invoke_rustc(builder: &SpirvBuilder) -> Result<PathBuf, SpirvBuilderError> {
-    let target = builder
-        .target
-        .as_ref()
-        .ok_or(SpirvBuilderError::MissingTarget)?;
     let path_to_crate = builder
         .path_to_crate
         .as_ref()
         .ok_or(SpirvBuilderError::MissingCratePath)?;
+    let target_env;
     {
-        let target_env = target.strip_prefix(SPIRV_TARGET_PREFIX).ok_or_else(|| {
+        let target = builder
+            .target
+            .as_ref()
+            .ok_or(SpirvBuilderError::MissingTarget)?;
+        target_env = target.strip_prefix(SPIRV_TARGET_PREFIX).ok_or_else(|| {
             SpirvBuilderError::NonSpirvTarget {
                 target: target.clone(),
             }
@@ -1032,19 +1010,10 @@ fn invoke_rustc(builder: &SpirvBuilder) -> Result<PathBuf, SpirvBuilderError> {
         cargo.args(extra_cargoflags.split_whitespace());
     }
 
-    // FIXME(eddyb) consider moving `target-specs` into `rustc_codegen_spirv_types`.
-    // FIXME(eddyb) consider the `RUST_TARGET_PATH` env var alternative.
-
-    // NOTE(firestar99) rustc 1.76 has been tested to correctly parse modern
-    // target_spec jsons, some later version requires them, some earlier
-    // version fails with them (notably our 0.9.0 release)
-    if toolchain_rustc_version >= Version::new(1, 76, 0) {
-        let path_opt = builder.path_to_target_spec.clone();
-        let path = path_opt.ok_or(SpirvBuilderError::MissingTargetSpec)?;
-        cargo.arg("--target").arg(path);
-    } else {
-        cargo.arg("--target").arg(target);
-    }
+    let target_spec_dir = target_dir.join("target-specs");
+    let target =
+        TargetSpecVersion::target_arg(toolchain_rustc_version, target_env, &target_spec_dir)?;
+    cargo.arg("--target").arg(target);
 
     if !builder.shader_crate_features.default_features {
         cargo.arg("--no-default-features");