Run Miri and mir-opt tests without a target linker

Author: saethlin

src/bootstrap/src/core/build_steps/compile.rs

@@ -69,6 +69,16 @@ impl Std {
         }
     }
 
+    pub fn new_for_mir_opt_tests(compiler: Compiler, target: TargetSelection) -> Self {
+        Self {
+            target,
+            compiler,
+            crates: INTERNER.intern_list(vec!["core".to_string(), "alloc".to_string(), "std".to_string()]),
+            force_recompile: false,
+            extra_rust_args: &["-Clinker=definitelyalinker"],
+        }
+    }
+
     pub fn new_with_extra_rust_args(
         compiler: Compiler,
         target: TargetSelection,

src/bootstrap/src/core/build_steps/test.rs

@@ -1612,16 +1612,23 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
                 .ensure(dist::DebuggerScripts { sysroot: builder.sysroot(compiler), host: target });
         }
 
-        builder.ensure(compile::Std::new(compiler, target));
+        if suite == "mir-opt" {
+            builder.ensure(compile::Std::new_for_mir_opt_tests(compiler, target));
+       } else {
+            builder.ensure(compile::Std::new(compiler, target));
+        }
+
         // ensure that `libproc_macro` is available on the host.
         builder.ensure(compile::Std::new(compiler, compiler.host));
 
         // Also provide `rust_test_helpers` for the host.
         builder.ensure(TestHelpers { target: compiler.host });
 
-        // As well as the target, except for plain wasm32, which can't build it
-        if !target.contains("wasm") || target.contains("emscripten") {
-            builder.ensure(TestHelpers { target });
+        if suite != "mir-opt" {
+            // As well as the target, except for plain wasm32, which can't build it
+            if !target.contains("wasm") || target.contains("emscripten") {
+                builder.ensure(TestHelpers { target });
+            }
         }
 
         builder.ensure(RemoteCopyLibs { compiler, target });
@@ -1752,11 +1759,13 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
             cmd.arg("--host-rustcflags").arg(flag);
         }
 
-        let mut targetflags = flags;
-        targetflags.push(format!("-Lnative={}", builder.test_helpers_out(target).display()));
-        targetflags.extend(linker_flags(builder, compiler.host, LldThreads::No));
-        for flag in targetflags {
-            cmd.arg("--target-rustcflags").arg(flag);
+        if mode != "mir-opt" {
+            let mut targetflags = flags;
+            targetflags.push(format!("-Lnative={}", builder.test_helpers_out(target).display()));
+            targetflags.extend(linker_flags(builder, compiler.host, LldThreads::No));
+            for flag in targetflags {
+                cmd.arg("--target-rustcflags").arg(flag);
+            }
         }
 
         cmd.arg("--python").arg(builder.python());

src/bootstrap/src/core/sanity.rs

@@ -62,9 +62,13 @@ impl Finder {
 }
 
 pub fn check(build: &mut Build) {
-    let skip_target_sanity =
+    let mut skip_target_sanity =
         env::var_os("BOOTSTRAP_SKIP_TARGET_SANITY").is_some_and(|s| s == "1" || s == "true");
 
+    if [std::path::PathBuf::from("mir-opt")].as_slice() == build.config.paths {
+        skip_target_sanity = true;
+    }
+
     let path = env::var_os("PATH").unwrap_or_default();
     // On Windows, quotes are invalid characters for filename paths, and if
     // one is present as part of the PATH then that can lead to the system

tests/mir-opt/remove_never_const.rs

@@ -3,9 +3,6 @@
 // consts in codegen. We also have tests for this that catches the error, see
 // tests/ui/consts/const-eval/index-out-of-bounds-never-type.rs.
 
-// Force generation of optimized mir for functions that do not reach codegen.
-// compile-flags: --emit mir,link
-
 #![feature(never_type)]
 
 struct PrintName<T>(T);