tests: add sanity-check assembly test for every target

Adds a basic assembly test checking that each target can produce assembly
and update the target tier policy to require this.

Signed-off-by: David Wood <david@davidtw.co>

Author: davidtwco

compiler/rustc_target/src/spec/targets/asmjs_unknown_emscripten.rs

@@ -246,6 +246,8 @@ approved by the appropriate team for that shared code before acceptance.
     introducing unconditional uses of features that another variation of the
     target may not have; use conditional compilation or runtime detection, as
     appropriate, to let each target run code supported by that target.
+- Tier 3 targets must be able to produce assembly using at least one of
+  rustc's supported backends from any host target.
 
 If a tier 3 target stops meeting these requirements, or the target maintainers
 no longer have interest or time, or the target shows no signs of activity and

src/doc/rustc/src/target-tier-policy.md

@@ -70,6 +70,7 @@ pub mod pal;
 pub mod rustdoc_css_themes;
 pub mod rustdoc_gui_tests;
 pub mod style;
+pub mod target_policy;
 pub mod target_specific_tests;
 pub mod tests_placement;
 pub mod ui_tests;

src/tools/tidy/src/lib.rs

@@ -109,6 +109,7 @@ fn main() {
         // Checks that only make sense for the compiler.
         check!(error_codes, &root_path, &[&compiler_path, &librustdoc_path], verbose);
         check!(fluent_alphabetical, &compiler_path, bless);
+        check!(target_policy, &root_path);
 
         // Checks that only make sense for the std libs.
         check!(pal, &library_path);

src/tools/tidy/src/main.rs

@@ -0,0 +1,52 @@
+//! Tests for target tier policy compliance.
+//!
+//! As of writing, only checks that sanity-check assembly test for targets doesn't miss any targets.
+
+use crate::walk::{filter_not_rust, walk};
+use std::{collections::HashSet, path::Path};
+
+const TARGET_DEFINITIONS_PATH: &str = "compiler/rustc_target/src/spec/targets/";
+const ASSEMBLY_TEST_PATH: &str = "tests/assembly/targets/";
+const REVISION_LINE_START: &str = "// revisions: ";
+const EXCEPTIONS: &[&str] = &[
+    // FIXME: disabled since it fails on CI saying the csky component is missing
+    "csky_unknown_linux_gnuabiv2",
+    "csky_unknown_linux_gnuabiv2hf",
+];
+
+pub fn check(root_path: &Path, bad: &mut bool) {
+    let mut targets_to_find = HashSet::new();
+
+    let definitions_path = root_path.join(TARGET_DEFINITIONS_PATH);
+    for defn in ignore::WalkBuilder::new(&definitions_path)
+        .max_depth(Some(1))
+        .filter_entry(|e| !filter_not_rust(e.path()))
+        .build()
+    {
+        let defn = defn.unwrap();
+        // Skip directory itself.
+        if defn.path() == definitions_path {
+            continue;
+        }
+
+        let path = defn.path();
+        let target_name = path.file_stem().unwrap().to_string_lossy().into_owned();
+        let _ = targets_to_find.insert(target_name);
+    }
+
+    walk(&root_path.join(ASSEMBLY_TEST_PATH), |_, _| false, &mut |_, contents| {
+        for line in contents.lines() {
+            let Some(_) = line.find(REVISION_LINE_START) else {
+                continue;
+            };
+            let (_, target_name) = line.split_at(REVISION_LINE_START.len());
+            targets_to_find.remove(target_name);
+        }
+    });
+
+    for target in targets_to_find {
+        if !EXCEPTIONS.contains(&target.as_str()) {
+            tidy_error!(bad, "{ASSEMBLY_TEST_PATH}: missing assembly test for {target}")
+        }
+    }
+}

src/tools/tidy/src/target_policy.rs

@@ -0,0 +1,21 @@
+// assembly-output: emit-asm
+// ignore-tidy-linelength
+// revisions: nvptx64_nvidia_cuda
+// [nvptx64_nvidia_cuda] compile-flags: --target nvptx64-nvidia-cuda
+// [nvptx64_nvidia_cuda] needs-llvm-components: nvptx
+
+// Sanity-check that each target can produce assembly code.
+
+#![feature(no_core, lang_items)]
+#![no_std]
+#![no_core]
+#![crate_type = "lib"]
+
+#[lang = "sized"]
+trait Sized {}
+
+pub fn test() -> u8 {
+    42
+}
+
+// CHECK: .version

tests/assembly/targets/targets-elf.rs

@@ -0,0 +1,93 @@
+// assembly-output: emit-asm
+// ignore-tidy-linelength
+// revisions: aarch64_pc_windows_msvc
+// [aarch64_pc_windows_msvc] compile-flags: --target aarch64-pc-windows-msvc
+// [aarch64_pc_windows_msvc] needs-llvm-components: aarch64
+// revisions: aarch64_pc_windows_gnullvm
+// [aarch64_pc_windows_gnullvm] compile-flags: --target aarch64-pc-windows-gnullvm
+// [aarch64_pc_windows_gnullvm] needs-llvm-components: aarch64
+// revisions: aarch64_unknown_uefi
+// [aarch64_unknown_uefi] compile-flags: --target aarch64-unknown-uefi
+// [aarch64_unknown_uefi] needs-llvm-components: aarch64
+// revisions: aarch64_uwp_windows_msvc
+// [aarch64_uwp_windows_msvc] compile-flags: --target aarch64-uwp-windows-msvc
+// [aarch64_uwp_windows_msvc] needs-llvm-components: aarch64
+// revisions: avr_unknown_gnu_atmega328
+// [avr_unknown_gnu_atmega328] compile-flags: --target avr-unknown-gnu-atmega328
+// [avr_unknown_gnu_atmega328] needs-llvm-components: avr
+// revisions: bpfeb_unknown_none
+// [bpfeb_unknown_none] compile-flags: --target bpfeb-unknown-none
+// [bpfeb_unknown_none] needs-llvm-components: bpf
+// revisions: bpfel_unknown_none
+// [bpfel_unknown_none] compile-flags: --target bpfel-unknown-none
+// [bpfel_unknown_none] needs-llvm-components: bpf
+// revisions: i586_pc_windows_msvc
+// [i586_pc_windows_msvc] compile-flags: --target i586-pc-windows-msvc
+// [i586_pc_windows_msvc] needs-llvm-components: x86
+// revisions: i686_pc_windows_gnu
+// [i686_pc_windows_gnu] compile-flags: --target i686-pc-windows-gnu
+// [i686_pc_windows_gnu] needs-llvm-components: x86
+// revisions: i686_pc_windows_msvc
+// [i686_pc_windows_msvc] compile-flags: --target i686-pc-windows-msvc
+// [i686_pc_windows_msvc] needs-llvm-components: x86
+// revisions: i686_pc_windows_gnullvm
+// [i686_pc_windows_gnullvm] compile-flags: --target i686-pc-windows-gnullvm
+// [i686_pc_windows_gnullvm] needs-llvm-components: x86
+// revisions: i686_uwp_windows_gnu
+// [i686_uwp_windows_gnu] compile-flags: --target i686-uwp-windows-gnu
+// [i686_uwp_windows_gnu] needs-llvm-components: x86
+// revisions: i686_unknown_uefi
+// [i686_unknown_uefi] compile-flags: --target i686-unknown-uefi
+// [i686_unknown_uefi] needs-llvm-components: x86
+// revisions: i686_uwp_windows_msvc
+// [i686_uwp_windows_msvc] compile-flags: --target i686-uwp-windows-msvc
+// [i686_uwp_windows_msvc] needs-llvm-components: x86
+// revisions: i686_win7_windows_msvc
+// [i686_win7_windows_msvc] compile-flags: --target i686-win7-windows-msvc
+// [i686_win7_windows_msvc] needs-llvm-components: x86
+// revisions: powerpc64_ibm_aix
+// [powerpc64_ibm_aix] compile-flags: --target powerpc64-ibm-aix
+// [powerpc64_ibm_aix] needs-llvm-components: powerpc
+// revisions: thumbv7a_uwp_windows_msvc
+// [thumbv7a_uwp_windows_msvc] compile-flags: --target thumbv7a-uwp-windows-msvc
+// [thumbv7a_uwp_windows_msvc] needs-llvm-components: arm
+// revisions: thumbv7a_pc_windows_msvc
+// [thumbv7a_pc_windows_msvc] compile-flags: --target thumbv7a-pc-windows-msvc
+// [thumbv7a_pc_windows_msvc] needs-llvm-components: arm
+// revisions: x86_64_pc_windows_gnu
+// [x86_64_pc_windows_gnu] compile-flags: --target x86_64-pc-windows-gnu
+// [x86_64_pc_windows_gnu] needs-llvm-components: x86
+// revisions: x86_64_pc_windows_gnullvm
+// [x86_64_pc_windows_gnullvm] compile-flags: --target x86_64-pc-windows-gnullvm
+// [x86_64_pc_windows_gnullvm] needs-llvm-components: x86
+// revisions: x86_64_pc_windows_msvc
+// [x86_64_pc_windows_msvc] compile-flags: --target x86_64-pc-windows-msvc
+// [x86_64_pc_windows_msvc] needs-llvm-components: x86
+// revisions: x86_64_unknown_uefi
+// [x86_64_unknown_uefi] compile-flags: --target x86_64-unknown-uefi
+// [x86_64_unknown_uefi] needs-llvm-components: x86
+// revisions: x86_64_uwp_windows_gnu
+// [x86_64_uwp_windows_gnu] compile-flags: --target x86_64-uwp-windows-gnu
+// [x86_64_uwp_windows_gnu] needs-llvm-components: x86
+// revisions: x86_64_uwp_windows_msvc
+// [x86_64_uwp_windows_msvc] compile-flags: --target x86_64-uwp-windows-msvc
+// [x86_64_uwp_windows_msvc] needs-llvm-components: x86
+// revisions: x86_64_win7_windows_msvc
+// [x86_64_win7_windows_msvc] compile-flags: --target x86_64-win7-windows-msvc
+// [x86_64_win7_windows_msvc] needs-llvm-components: x86
+
+// Sanity-check that each target can produce assembly code.
+
+#![feature(no_core, lang_items)]
+#![no_std]
+#![no_core]
+#![crate_type = "lib"]
+
+#[lang = "sized"]
+trait Sized {}
+
+pub fn test() -> u8 {
+    42
+}
+
+// CHECK: .file