Only run asm tests if they match the current codegen backend

Author: GuillaumeGomez

src/tools/compiletest/src/lib.rs

@@ -31,7 +31,7 @@ use std::time::SystemTime;
 use std::{env, fs, vec};
 
 use build_helper::git::{get_git_modified_files, get_git_untracked_files};
-use camino::{Utf8Path, Utf8PathBuf};
+use camino::{Utf8Component, Utf8Path, Utf8PathBuf};
 use getopts::Options;
 use rayon::iter::{ParallelBridge, ParallelIterator};
 use tracing::debug;
@@ -799,6 +799,25 @@ fn collect_tests_from_dir(
         return Ok(TestCollector::new());
     }
 
+    let mut components = dir.components().rev();
+    if let Some(Utf8Component::Normal(last)) = components.next()
+        && let Some(("asm", backend)) = last.split_once('-')
+        && let Some(Utf8Component::Normal(parent)) = components.next()
+        && parent == "ui"
+        && let Some(Utf8Component::Normal(grand_parent)) = components.next()
+        && grand_parent == "tests"
+        && let Ok(backend) = CodegenBackend::try_from(backend)
+        && backend != cx.config.codegen_backend
+    {
+        // We ignore asm tests which don't match the current codegen backend.
+        println!(
+            "Ignoring tests in `{dir}` because they don't match the configured codegen \
+             backend (`{}`)",
+            cx.config.codegen_backend.as_str(),
+        );
+        return Ok(TestCollector::new());
+    }
+
     // For run-make tests, a "test file" is actually a directory that contains an `rmake.rs`.
     if cx.config.mode == TestMode::RunMake {
         let mut collector = TestCollector::new();