Unrolled build for rust-lang#126270

Rollup merge of rust-lang#126270 - GuillaumeGomez:migrate-run-make-const_fn_mir, r=jieyouxu

Migrate run make const fn mir

Part of rust-lang#121876.

r? ```@jieyouxu```

Author: rust-timer

src/tools/run-make-support/src/diff/mod.rs

@@ -1,8 +1,9 @@
 use regex::Regex;
 use similar::TextDiff;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 
 use crate::drop_bomb::DropBomb;
+use crate::fs_wrapper;
 
 #[cfg(test)]
 mod tests;
@@ -17,6 +18,7 @@ pub fn diff() -> Diff {
 pub struct Diff {
     expected: Option<String>,
     expected_name: Option<String>,
+    expected_file: Option<PathBuf>,
     actual: Option<String>,
     actual_name: Option<String>,
     normalizers: Vec<(String, String)>,
@@ -30,6 +32,7 @@ impl Diff {
         Self {
             expected: None,
             expected_name: None,
+            expected_file: None,
             actual: None,
             actual_name: None,
             normalizers: Vec::new(),
@@ -40,9 +43,10 @@ impl Diff {
     /// Specify the expected output for the diff from a file.
     pub fn expected_file<P: AsRef<Path>>(&mut self, path: P) -> &mut Self {
         let path = path.as_ref();
-        let content = std::fs::read_to_string(path).expect("failed to read file");
+        let content = fs_wrapper::read_to_string(path);
         let name = path.to_string_lossy().to_string();
 
+        self.expected_file = Some(path.into());
         self.expected = Some(content);
         self.expected_name = Some(name);
         self
@@ -58,10 +62,7 @@ impl Diff {
     /// Specify the actual output for the diff from a file.
     pub fn actual_file<P: AsRef<Path>>(&mut self, path: P) -> &mut Self {
         let path = path.as_ref();
-        let content = match std::fs::read_to_string(path) {
-            Ok(c) => c,
-            Err(e) => panic!("failed to read `{}`: {:?}", path.display(), e),
-        };
+        let content = fs_wrapper::read_to_string(path);
         let name = path.to_string_lossy().to_string();
 
         self.actual = Some(content);
@@ -104,6 +105,15 @@ impl Diff {
             .to_string();
 
         if !output.is_empty() {
+            // If we can bless (meaning we have a file to write into and the `RUSTC_BLESS_TEST`
+            // environment variable set), then we write into the file and return.
+            if let Some(ref expected_file) = self.expected_file {
+                if std::env::var("RUSTC_BLESS_TEST").is_ok() {
+                    println!("Blessing `{}`", expected_file.display());
+                    fs_wrapper::write(expected_file, actual);
+                    return;
+                }
+            }
             panic!(
                 "test failed: `{}` is different from `{}`\n\n{}",
                 expected_name, actual_name, output

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -18,7 +18,6 @@ run-make/compiler-lookup-paths-2/Makefile
 run-make/compiler-lookup-paths/Makefile
 run-make/compiler-rt-works-on-mingw/Makefile
 run-make/compressed-debuginfo/Makefile
-run-make/const_fn_mir/Makefile
 run-make/crate-hash-rustc-version/Makefile
 run-make/crate-name-priority/Makefile
 run-make/cross-lang-lto-clang/Makefile

tests/run-make/const_fn_mir/Makefile

@@ -0,0 +1,8 @@
+// The `needs-unwind -Cpanic=abort` gives a different MIR output.
+
+use run_make_support::{cwd, diff, rustc};
+
+fn main() {
+    rustc().input("main.rs").emit("mir").output("dump-actual.mir").run();
+    diff().expected_file("dump.mir").actual_file("dump-actual.mir").run();
+}