diff --git a/Cargo.toml b/Cargo.toml
index 54a1c5456e4..86ac2c040fd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -31,4 +31,3 @@ cargo_miri = ["cargo_metadata"]
 
 [dev-dependencies]
 compiletest_rs = { version = "0.3.4", features = ["tmp"] }
-dirs = "1.0.2"
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index a521217fc5c..9a2fd02f88c 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -1,7 +1,6 @@
 #![feature(slice_concat_ext)]
 
 extern crate compiletest_rs as compiletest;
-extern crate dirs;
 
 use std::slice::SliceConcatExt;
 use std::path::{PathBuf, Path};
@@ -31,7 +30,21 @@ fn rustc_lib_path() -> PathBuf {
     option_env!("RUSTC_LIB_PATH").unwrap().into()
 }
 
-fn compile_fail(sysroot: &Path, path: &str, target: &str, host: &str, fullmir: bool) {
+fn have_fullmir() -> bool {
+    // We assume we have full MIR when MIRI_SYSROOT is set or when we are in rustc
+    std::env::var("MIRI_SYSROOT").is_ok() || rustc_test_suite().is_some()
+}
+
+fn compile_fail(sysroot: &Path, path: &str, target: &str, host: &str, need_fullmir: bool) {
+    if need_fullmir && !have_fullmir() {
+        eprintln!(
+            "## Skipping compile-fail tests in {} against miri for target {} due to missing mir",
+            path,
+            target
+        );
+        return;
+    }
+
     eprintln!(
         "## Running compile-fail tests in {} against miri for target {}",
         path,
@@ -45,28 +58,16 @@ fn compile_fail(sysroot: &Path, path: &str, target: &str, host: &str, fullmir: b
         config.run_lib_path = rustc_lib_path();
         config.compile_lib_path = rustc_lib_path();
     }
-    // if we are building as part of the rustc test suite, we already have fullmir for everything
-    if fullmir && rustc_test_suite().is_none() {
-        if host != target {
-            // skip fullmir on nonhost
-            return;
-        }
-        let sysroot = dirs::home_dir().unwrap()
-            .join(".xargo")
-            .join("HOST");
-        flags.push(format!("--sysroot {}", sysroot.to_str().unwrap()));
-        config.src_base = PathBuf::from(path.to_string());
-    } else {
-        flags.push(format!("--sysroot {}", sysroot.to_str().unwrap()));
-        config.src_base = PathBuf::from(path.to_string());
-    }
+    flags.push(format!("--sysroot {}", sysroot.display()));
+    config.src_base = PathBuf::from(path.to_string());
     flags.push("-Zmir-emit-validate=1".to_owned());
     config.target_rustcflags = Some(flags.join(" "));
     config.target = target.to_owned();
+    config.host = host.to_owned();
     compiletest::run_tests(&config);
 }
 
-fn run_pass(path: &str) {
+fn rustc_pass(sysroot: &Path, path: &str) {
     eprintln!("## Running run-pass tests in {} against rustc", path);
     let mut config = compiletest::Config::default().tempdir();
     config.mode = "run-pass".parse().expect("Invalid mode");
@@ -75,7 +76,7 @@ fn run_pass(path: &str) {
         config.rustc_path = rustc_path;
         config.run_lib_path = rustc_lib_path();
         config.compile_lib_path = rustc_lib_path();
-        config.target_rustcflags = Some(format!("-Dwarnings --sysroot {}", get_sysroot().display()));
+        config.target_rustcflags = Some(format!("-Dwarnings --sysroot {}", sysroot.display()));
     } else {
         config.target_rustcflags = Some("-Dwarnings".to_owned());
     }
@@ -83,7 +84,16 @@ fn run_pass(path: &str) {
     compiletest::run_tests(&config);
 }
 
-fn miri_pass(path: &str, target: &str, host: &str, fullmir: bool, opt: bool) {
+fn miri_pass(sysroot: &Path, path: &str, target: &str, host: &str, need_fullmir: bool, opt: bool) {
+    if need_fullmir && !have_fullmir() {
+        eprintln!(
+            "## Skipping run-pass tests in {} against miri for target {} due to missing mir",
+            path,
+            target
+        );
+        return;
+    }
+
     let opt_str = if opt { " with optimizations" } else { "" };
     eprintln!(
         "## Running run-pass tests in {} against miri for target {}{}",
@@ -102,21 +112,9 @@ fn miri_pass(path: &str, target: &str, host: &str, fullmir: bool, opt: bool) {
         config.compile_lib_path = rustc_lib_path();
     }
     let mut flags = Vec::new();
-    // Control miri logging. This is okay despite concurrent test execution as all tests
-    // will set this env var to the same value.
-    env::set_var("MIRI_LOG", "warn");
-    // if we are building as part of the rustc test suite, we already have fullmir for everything
-    if fullmir && rustc_test_suite().is_none() {
-        if host != target {
-            // skip fullmir on nonhost
-            return;
-        }
-        let sysroot = dirs::home_dir().unwrap()
-            .join(".xargo")
-            .join("HOST");
-
+    flags.push(format!("--sysroot {}", sysroot.display()));
+    if have_fullmir() {
         flags.push("-Zmiri-start-fn".to_owned());
-        flags.push(format!("--sysroot {}", sysroot.to_str().unwrap()));
     }
     if opt {
         flags.push("-Zmir-opt-level=3".to_owned());
@@ -125,6 +123,9 @@ fn miri_pass(path: &str, target: &str, host: &str, fullmir: bool, opt: bool) {
         // For now, only validate without optimizations.  Inlining breaks validation.
         flags.push("-Zmir-emit-validate=1".to_owned());
     }
+    // Control miri logging. This is okay despite concurrent test execution as all tests
+    // will set this env var to the same value.
+    env::set_var("MIRI_LOG", "warn");
     config.target_rustcflags = Some(flags.join(" "));
     compiletest::run_tests(&config);
 }
@@ -181,9 +182,9 @@ fn run_pass_miri(opt: bool) {
     let host = get_host();
 
     for_all_targets(&sysroot, |target| {
-        miri_pass("tests/run-pass", &target, &host, false, opt);
+        miri_pass(&sysroot, "tests/run-pass", &target, &host, false, opt);
     });
-    miri_pass("tests/run-pass-fullmir", &host, &host, true, opt);
+    miri_pass(&sysroot, "tests/run-pass-fullmir", &host, &host, true, opt);
 }
 
 #[test]
@@ -201,8 +202,9 @@ fn run_pass_miri_opt() {
 
 #[test]
 fn run_pass_rustc() {
-    run_pass("tests/run-pass");
-    run_pass("tests/run-pass-fullmir");
+    let sysroot = get_sysroot();
+    rustc_pass(&sysroot, "tests/run-pass");
+    rustc_pass(&sysroot, "tests/run-pass-fullmir");
 }
 
 #[test]