Auto merge of #98817 - the8472:dont-optimize-ui-tests, r=Mark-Simulacrum

Only obey optimize-tests flag on UI tests that are run-pass

stage1 UI tests walltime on my machine:

```
optimize-tests = false, master
25.98s

optimize-tests = true, master
34.69s

optimize-tests = true, patched
28.79s
```

Effects:

- faster UI tests
- llvm asserts get exercised less on build-pass tests
- the difference between opt and nopt builds shrinks a bit
- aux libs don't get optimized since they don't have a pass mode and almost never have explicit compile flags

src/bootstrap/test.rs

@@ -1363,13 +1363,10 @@ note: if you're sure you want to do this, please open an issue as to why. In the
         if let Some(ref npm) = builder.config.npm {
             cmd.arg("--npm").arg(npm);
         }
-
-        let mut flags = if is_rustdoc { Vec::new() } else { vec!["-Crpath".to_string()] };
-        if !is_rustdoc {
-            if builder.config.rust_optimize_tests {
-                flags.push("-O".to_string());
-            }
+        if builder.config.rust_optimize_tests {
+            cmd.arg("--optimize-tests");
         }
+        let mut flags = if is_rustdoc { Vec::new() } else { vec!["-Crpath".to_string()] };
         flags.push(format!("-Cdebuginfo={}", builder.config.rust_debuginfo_level_tests));
         flags.push(builder.config.cmd.rustc_args().join(" "));
 

src/tools/compiletest/src/common.rs

@@ -269,6 +269,10 @@ pub struct Config {
     /// Flags to pass to the compiler when building for the target
     pub target_rustcflags: Option<String>,
 
+    /// Whether tests should be optimized by default. Individual test-suites and test files may
+    /// override this setting.
+    pub optimize_tests: bool,
+
     /// What panic strategy the target is built with.  Unwind supports Abort, but
     /// not vice versa.
     pub target_panic: PanicStrategy,

src/tools/compiletest/src/header.rs

@@ -244,6 +244,7 @@ impl TestProps {
 
         // copy over select properties to the aux build:
         props.incremental_dir = self.incremental_dir.clone();
+        props.ignore_pass = true;
         props.load_from(testfile, cfg, config);
 
         props

src/tools/compiletest/src/main.rs

@@ -102,6 +102,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         )
         .optmulti("", "host-rustcflags", "flags to pass to rustc for host", "FLAGS")
         .optmulti("", "target-rustcflags", "flags to pass to rustc for target", "FLAGS")
+        .optflag("", "optimize-tests", "run tests with optimizations enabled")
         .optopt("", "target-panic", "what panic strategy the target supports", "unwind | abort")
         .optflag("", "verbose", "run tests verbosely, showing all output")
         .optflag(
@@ -253,6 +254,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         runtool: matches.opt_str("runtool"),
         host_rustcflags: Some(matches.opt_strs("host-rustcflags").join(" ")),
         target_rustcflags: Some(matches.opt_strs("target-rustcflags").join(" ")),
+        optimize_tests: matches.opt_present("optimize-tests"),
         target_panic: match matches.opt_str("target-panic").as_deref() {
             Some("unwind") | None => PanicStrategy::Unwind,
             Some("abort") => PanicStrategy::Abort,

src/tools/compiletest/src/runtest.rs

@@ -1862,6 +1862,31 @@ impl<'test> TestCx<'test> {
             }
         }
 
+        if self.config.optimize_tests && !is_rustdoc {
+            match self.config.mode {
+                Ui => {
+                    // If optimize-tests is true we still only want to optimize tests that actually get
+                    // executed and that don't specify their own optimization levels.
+                    // Note: aux libs don't have a pass-mode, so they won't get optimized
+                    // unless compile-flags are set in the aux file.
+                    if self.config.optimize_tests
+                        && self.props.pass_mode(&self.config) == Some(PassMode::Run)
+                        && !self
+                            .props
+                            .compile_flags
+                            .iter()
+                            .any(|arg| arg == "-O" || arg.contains("opt-level"))
+                    {
+                        rustc.arg("-O");
+                    }
+                }
+                DebugInfo => { /* debuginfo tests must be unoptimized */ }
+                _ => {
+                    rustc.arg("-O");
+                }
+            }
+        }
+
         match self.config.mode {
             Incremental => {
                 // If we are extracting and matching errors in the new