Support x test --stage 1 ui-fulldeps

Nils had an excellent idea the other day: the same way that rustdoc is
able to load `rustc_driver` from the sysroot, ui-fulldeps tests should
also be able to load it from the sysroot. That allows us to run fulldeps
tests with stage1, without having to fully rebuild the compiler twice.
It does unfortunately have the downside that we're running the tests on
the *bootstrap* compiler, not the in-tree sources, but since most of the
fulldeps tests are for the *API* of the compiler, that seems ok.

I think it's possible to extend this to `run-make-fulldeps`, but I've
run out of energy for tonight.

- Move `plugin` tests into a subdirectory.

  Plugins are loaded at runtime with `dlopen` and so require the ABI of
  the running compile to match the ABI of the compiler linked with
  `rustc_driver`. As a result they can't be supported in stage 1 and have
  to use `// ignore-stage1`.

- Remove `ignore-stage1` from most non-plugin tests

- Ignore diagnostic tests in stage 1. Even though this requires a stage
  2 build to load rustc_driver, it's primarily testing the error message
  that the *running* compiler emits when the diagnostic struct is malformed.

- Pass `-Zforce-unstable-if-unmarked` in stage1, not just stage2. That
  allows running `hash-stable-is-unstable` in stage1, since it now
  suggests adding `rustc_private` to enable loading the crates.

- Add libLLVM.so to the stage0 target sysroot, to allow fulldeps tests
  that act as custom drivers to load it at runtime.

- Pass `--sysroot stage0-sysroot` in compiletest so that we use the
  correct version of std.

Author: jyn514

src/bootstrap/bin/rustc.rs

@@ -150,7 +150,7 @@ fn main() {
     // allow the `rustc_private` feature to link to other unstable crates
     // also in the sysroot. We also do this for host crates, since those
     // may be proc macros, in which case we might ship them.
-    if env::var_os("RUSTC_FORCE_UNSTABLE").is_some() && (stage != "0" || target.is_some()) {
+    if env::var_os("RUSTC_FORCE_UNSTABLE").is_some() {
         cmd.arg("-Z").arg("force-unstable-if-unmarked");
     }
 

src/bootstrap/builder.rs

@@ -1008,9 +1008,24 @@ impl<'a> Builder<'a> {
                 // Avoid deleting the rustlib/ directory we just copied
                 // (in `impl Step for Sysroot`).
                 if !builder.download_rustc() {
+                    builder.verbose(&format!(
+                        "Removing sysroot {} to avoid caching bugs",
+                        sysroot.display()
+                    ));
                     let _ = fs::remove_dir_all(&sysroot);
                     t!(fs::create_dir_all(&sysroot));
                 }
+
+                if self.compiler.stage == 0 {
+                    // The stage 0 compiler for the build triple is always pre-built.
+                    // Ensure that `libLLVM.so` ends up in the target libdir, so that ui-fulldeps tests can use it when run.
+                    dist::maybe_install_llvm_target(
+                        builder,
+                        self.compiler.host,
+                        &builder.sysroot(self.compiler),
+                    );
+                }
+
                 INTERNER.intern_path(sysroot)
             }
         }

src/bootstrap/compile.rs

@@ -1260,6 +1260,7 @@ impl Step for Sysroot {
         };
         let sysroot = sysroot_dir(compiler.stage);
 
+        builder.verbose(&format!("Removing sysroot {} to avoid caching bugs", sysroot.display()));
         let _ = fs::remove_dir_all(&sysroot);
         t!(fs::create_dir_all(&sysroot));
 

src/bootstrap/test.rs

@@ -1448,7 +1448,7 @@ note: if you're sure you want to do this, please open an issue as to why. In the
             crate::detail_exit(1);
         }
 
-        let compiler = self.compiler;
+        let mut compiler = self.compiler;
         let target = self.target;
         let mode = self.mode;
         let suite = self.suite;
@@ -1461,15 +1461,28 @@ note: if you're sure you want to do this, please open an issue as to why. In the
             return;
         }
 
-        if suite == "debuginfo" {
-            builder
-                .ensure(dist::DebuggerScripts { sysroot: builder.sysroot(compiler), host: target });
-        }
+        // Support stage 1 ui-fulldeps. This is somewhat complicated: ui-fulldeps tests for the most
+        // part test the *API* of the compiler, not how it compiles a given file. As a result, we
+        // can run them against the stage 1 sources as long as we build them with the stage 0
+        // bootstrap compiler.
+        // NOTE: Only stage 1 is special cased because we need the rustc_private artifacts to match the
+        // running compiler in stage 2 when plugins run.
+        let stage_id = if suite == "ui-fulldeps" && compiler.stage == 1 {
+            compiler = builder.compiler(compiler.stage - 1, target);
+            format!("stage{}-{}", compiler.stage + 1, target)
+        } else {
+            format!("stage{}-{}", compiler.stage, target)
+        };
 
         if suite.ends_with("fulldeps") {
             builder.ensure(compile::Rustc::new(compiler, target));
         }
 
+        if suite == "debuginfo" {
+            builder
+                .ensure(dist::DebuggerScripts { sysroot: builder.sysroot(compiler), host: target });
+        }
+
         builder.ensure(compile::Std::new(compiler, target));
         // ensure that `libproc_macro` is available on the host.
         builder.ensure(compile::Std::new(compiler, compiler.host));
@@ -1528,7 +1541,7 @@ note: if you're sure you want to do this, please open an issue as to why. In the
         cmd.arg("--src-base").arg(builder.src.join("tests").join(suite));
         cmd.arg("--build-base").arg(testdir(builder, compiler.host).join(suite));
         cmd.arg("--sysroot-base").arg(builder.sysroot(compiler));
-        cmd.arg("--stage-id").arg(format!("stage{}-{}", compiler.stage, target));
+        cmd.arg("--stage-id").arg(stage_id);
         cmd.arg("--suite").arg(suite);
         cmd.arg("--mode").arg(mode);
         cmd.arg("--target").arg(target.rustc_target_arg());

src/tools/compiletest/src/common.rs

@@ -419,7 +419,9 @@ pub struct TargetCfgs {
 
 impl TargetCfgs {
     fn new(config: &Config) -> TargetCfgs {
-        let targets: HashMap<String, TargetCfg> = if config.stage_id.starts_with("stage0-") {
+        let targets: HashMap<String, TargetCfg> = if config.stage_id.starts_with("stage0-")
+            || (config.suite == "ui-fulldeps" && config.stage_id.starts_with("stage1-"))
+        {
             // #[cfg(bootstrap)]
             // Needed only for one cycle, remove during the bootstrap bump.
             Self::collect_all_slow(config)

src/tools/compiletest/src/runtest.rs

@@ -1900,6 +1900,9 @@ impl<'test> TestCx<'test> {
         // Use a single thread for efficiency and a deterministic error message order
         rustc.arg("-Zthreads=1");
 
+        // In stage 0, make sure we use `stage0-sysroot` instead of the bootstrap sysroot.
+        rustc.arg("--sysroot").arg(&self.config.sysroot_base);
+
         // Optionally prevent default --target if specified in test compile-flags.
         let custom_target = self.props.compile_flags.iter().any(|x| x.starts_with("--target"));
 

src/tools/tidy/src/ui_tests.rs

@@ -9,7 +9,7 @@ use std::path::{Path, PathBuf};
 
 // FIXME: The following limits should be reduced eventually.
 const ENTRY_LIMIT: usize = 885;
-const ROOT_ENTRY_LIMIT: usize = 891;
+const ROOT_ENTRY_LIMIT: usize = 894;
 const ISSUES_ENTRY_LIMIT: usize = 1977;
 
 fn check_entries(tests_path: &Path, bad: &mut bool) {

tests/ui-fulldeps/compiler-calls.rs

@@ -2,7 +2,6 @@
 // Test that the Callbacks interface to the compiler works.
 
 // ignore-cross-compile
-// ignore-stage1
 // ignore-remote
 
 #![feature(rustc_private)]

tests/ui-fulldeps/hash-stable-is-unstable.rs

@@ -1,4 +1,3 @@
-// ignore-stage1
 // compile-flags: -Zdeduplicate-diagnostics=yes
 extern crate rustc_data_structures;
 //~^ use of unstable library feature 'rustc_private'

tests/ui-fulldeps/hash-stable-is-unstable.stderr

@@ -1,5 +1,5 @@
 error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:3:1
+  --> $DIR/hash-stable-is-unstable.rs:2:1
    |
 LL | extern crate rustc_data_structures;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -8,7 +8,7 @@ LL | extern crate rustc_data_structures;
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
 error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:5:1
+  --> $DIR/hash-stable-is-unstable.rs:4:1
    |
 LL | extern crate rustc_macros;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -17,7 +17,7 @@ LL | extern crate rustc_macros;
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
 error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:7:1
+  --> $DIR/hash-stable-is-unstable.rs:6:1
    |
 LL | extern crate rustc_query_system;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -26,7 +26,7 @@ LL | extern crate rustc_query_system;
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
 error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:10:5
+  --> $DIR/hash-stable-is-unstable.rs:9:5
    |
 LL | use rustc_macros::HashStable;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -35,7 +35,7 @@ LL | use rustc_macros::HashStable;
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
 error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:13:10
+  --> $DIR/hash-stable-is-unstable.rs:12:10
    |
 LL | #[derive(HashStable)]
    |          ^^^^^^^^^^