Support using custom rustflags for targets

This is necessary for AVR and AMDGPU. We currently just hardcode some
flags in the binary, which is good enough. There's a new column which
keeps track of the used flags and shows them for a build.

A migration makes sure that the older results are properly backfilled
with the flags to make them build.

migrations/20250704160556_reset-missing-target-cpu.sql

@@ -0,0 +1,8 @@
+-- Add migration script here
+
+ALTER TABLE build_info
+    ADD COLUMN rustflags VARCHAR;
+
+DELETE FROM build_info WHERE target IN ('avr-none', 'amdgcn-amd-amdhsa') AND mode = 'core';
+
+DELETE FROM finished_nightly WHERE nightly > '2025-02-11';

src/build.rs

@@ -18,6 +18,22 @@ use crate::{
     nightlies::Nightlies,
 };
 
+struct CustomBuildFlags {
+    target: &'static str,
+    flags: &'static [&'static str],
+}
+
+const CUSTOM_CORE_FLAGS: &[CustomBuildFlags] = &[
+    CustomBuildFlags {
+        target: "avr-none",
+        flags: &["-Ctarget-cpu=atmega328p"],
+    },
+    CustomBuildFlags {
+        target: "amdgcn-amd-amdhsa",
+        flags: &["-Ctarget-cpu=gfx1100"],
+    },
+];
+
 pub struct Toolchain(String);
 impl Toolchain {
     pub fn from_nightly(nightly: &str) -> Self {
@@ -44,9 +60,7 @@ pub async fn background_builder(db: Db) -> Result<()> {
 }
 
 async fn background_builder_inner(db: &Db) -> Result<()> {
-    let nightlies = Nightlies::fetch()
+    let nightlies = Nightlies::fetch().await.wrap_err("fetching nightlies")?;
-        .await
-        .wrap_err("fetching nightlies")?;
     let already_finished = db
         .finished_nightlies()
         .await
@@ -243,6 +257,7 @@ async fn build_single_target(db: &Db, nightly: &str, target: &str, mode: BuildMo
         status: result.status,
         stderr: result.stderr,
         mode,
+        rustflags: result.rustflags,
     })
     .await?;
 
@@ -252,6 +267,7 @@ async fn build_single_target(db: &Db, nightly: &str, target: &str, mode: BuildMo
 struct BuildResult {
     status: Status,
     stderr: String,
+    rustflags: Option<String>,
 }
 
 /// Build a target core in a temporary directory and see whether it passes or not.
@@ -261,6 +277,8 @@ async fn build_target(
     target: &str,
     mode: BuildMode,
 ) -> Result<BuildResult> {
+    let mut rustflags = None;
+
     let output = match mode {
         BuildMode::Core => {
             let init = Command::new("cargo")
@@ -277,11 +295,22 @@ async fn build_target(
             std::fs::write(&librs, "#![no_std]\n")
                 .wrap_err_with(|| format!("writing to {}", librs.display()))?;
 
-            Command::new("cargo")
+            let mut cmd = Command::new("cargo");
-                .arg(format!("+{toolchain}"))
+            cmd.arg(format!("+{toolchain}"))
                 .args(["build", "-Zbuild-std=core", "--release"])
-                .args(["--target", target])
+                .args(["--target", target]);
-                .current_dir(tmpdir)
+
+            let extra_flags = CUSTOM_CORE_FLAGS
+                .iter()
+                .find(|flags| flags.target == target);
+
+            if let Some(extra_flags) = extra_flags {
+                let flags = extra_flags.flags.join(" ");
+                cmd.env("RUSTFLAGS", &flags);
+                rustflags = Some(flags);
+            }
+
+            cmd.current_dir(tmpdir)
                 .output()
                 .await
                 .wrap_err("spawning cargo build")?
@@ -307,5 +336,9 @@ async fn build_target(
 
     info!("Finished build");
 
-    Ok(BuildResult { status, stderr })
+    Ok(BuildResult {
+        status,
+        stderr,
+        rustflags,
+    })
 }

src/db.rs

@@ -48,6 +48,7 @@ pub struct FullBuildInfo {
     pub status: Status,
     pub stderr: String,
     pub mode: BuildMode,
+    pub rustflags: Option<String>,
 }
 
 #[derive(Debug, PartialEq, Clone, Copy, sqlx::Type, Serialize, Deserialize)]
@@ -95,13 +96,14 @@ impl Db {
 
     pub async fn insert(&self, info: FullBuildInfo) -> Result<()> {
         sqlx::query(
-            "INSERT INTO build_info (nightly, target, status, stderr, mode) VALUES (?, ?, ?, ?, ?);",
+            "INSERT INTO build_info (nightly, target, status, stderr, mode, rustflags) VALUES (?, ?, ?, ?, ?, ?);",
         )
         .bind(info.nightly)
         .bind(info.target)
         .bind(info.status)
         .bind(info.stderr)
         .bind(info.mode)
+        .bind(info.rustflags)
         .execute(&self.conn)
         .await
         .wrap_err("inserting build info into database")?;
@@ -173,7 +175,7 @@ impl Db {
         mode: BuildMode,
     ) -> Result<Option<FullBuildInfo>> {
         let result = sqlx::query_as::<_, FullBuildInfo>(
-            "SELECT nightly, target, status, stderr, mode FROM build_info
+            "SELECT nightly, target, status, stderr, mode, rustflags FROM build_info
             WHERE nightly = ? AND target = ? AND mode = ?",
         )
         .bind(nightly)

src/web.rs

@@ -41,6 +41,19 @@ struct BuildQuery {
 }
 
 async fn web_build(State(state): State<AppState>, Query(query): Query<BuildQuery>) -> Response {
+    use askama::Template;
+    #[derive(askama::Template)]
+    #[template(path = "build.html")]
+    struct BuildPage {
+        nightly: String,
+        target: String,
+        stderr: String,
+        mode: BuildMode,
+        rustflags: Option<String>,
+        version: &'static str,
+        status: Status,
+    }    
+
     match state
         .db
         .build_status_full(
@@ -51,15 +64,16 @@ async fn web_build(State(state): State<AppState>, Query(query): Query<BuildQuery
         .await
     {
         Ok(Some(build)) => {
-            let page = include_str!("../static/build.html")
+            let page = BuildPage {
-                .replace("{{nightly}}", &query.nightly)
+                nightly: query.nightly,
-                .replace("{{target}}", &query.target)
+                target: query.target,
-                .replace("{{stderr}}", &build.stderr)
+                stderr: build.stderr,
-                .replace("{{mode}}", &build.mode.to_string())
+                mode: build.mode,
-                .replace("{{version}}", crate::VERSION)
+                rustflags: build.rustflags,
-                .replace("{{status}}", &build.status.to_string());
+                version: crate::VERSION,
-
+                status: build.status,
-            Html(page).into_response()
+            };
+            Html(page.render().unwrap()).into_response()
         }
         Ok(None) => StatusCode::NOT_FOUND.into_response(),
         Err(err) => {

templates/build.html

@@ -17,6 +17,11 @@
     <div style="margin-top: 20px" class="{{status}} build-indicator-big">
       {{status}}
     </div>
+    {% if let Some(rustflags) = rustflags %}
+    <p>
+      Using rustflags: <b><code>{{rustflags}}</code></b>
+    </p>
+    {% endif %}
     <pre>
 {{stderr}}
     </pre>