3 files changed, 33 insertions, 7 deletions
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 74dd4a6fa01..b65c20e398e 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -119,7 +119,28 @@ impl StepDescription {
         }
     }
 
-    fn maybe_run(&self, builder: &Builder, path: Option<&Path>) {
+    fn maybe_run(&self, builder: &Builder, should_run: &ShouldRun, path: Option<&Path>) {
+        if let Some(path) = path {
+            if builder.config.exclude.iter().any(|e| e == path) {
+                eprintln!("Skipping {:?} because this path is excluded", path);
+                return;
+            } else if !builder.config.exclude.is_empty() {
+                eprintln!("{:?} not skipped -- not in {:?}", path, builder.config.exclude);
+            }
+        } else {
+            if !should_run.paths.is_empty() {
+                if should_run.paths.iter().all(|p| builder.config.exclude.contains(&p)) {
+                    eprintln!("Skipping because all of its paths ({:?}) are excluded",
+                        should_run.paths);
+                    return;
+                } else if should_run.paths.len() > 1 {
+                    for path in &should_run.paths {
+                        self.maybe_run(builder, should_run, Some(path));
+                    }
+                    return;
+                }
+            }
+        }
         let build = builder.build;
         let hosts = if self.only_build_targets || self.only_build {
             build.build_triple()
@@ -160,7 +181,7 @@ impl StepDescription {
         if paths.is_empty() {
             for (desc, should_run) in v.iter().zip(should_runs) {
                 if desc.default && should_run.is_really_default {
-                    desc.maybe_run(builder, None);
+                    desc.maybe_run(builder, &should_run, None);
                 }
             }
         } else {
@@ -169,7 +190,7 @@ impl StepDescription {
                 for (desc, should_run) in v.iter().zip(&should_runs) {
                     if should_run.run(path) {
                         attempted_run = true;
-                        desc.maybe_run(builder, Some(path));
+                        desc.maybe_run(builder, &should_run, Some(path));
                     }
                 }
 
@@ -208,13 +229,13 @@ impl<'a> ShouldRun<'a> {
 
     pub fn krate(mut self, name: &str) -> Self {
         for (_, krate_path) in self.builder.crates(name) {
-            self.paths.insert(PathBuf::from(krate_path));
+            self.paths.insert(t!(env::current_dir()).join(krate_path));
         }
         self
     }
 
     pub fn path(mut self, path: &str) -> Self {
-        self.paths.insert(PathBuf::from(path));
+        self.paths.insert(t!(env::current_dir()).join(path));
         self
     }
 
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 4f4fd14ae8c..812ca6d64fb 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -56,6 +56,7 @@ pub struct Config {
     pub sanitizers: bool,
     pub profiler: bool,
     pub ignore_git: bool,
+    pub exclude: Vec<PathBuf>,
 
     pub run_host_only: bool,
 
@@ -311,6 +312,7 @@ impl Config {
         let flags = Flags::parse(&args);
         let file = flags.config.clone();
         let mut config = Config::default();
+        config.exclude = flags.exclude;
         config.llvm_enabled = true;
         config.llvm_optimize = true;
         config.llvm_version_check = true;
diff --git a/src/bootstrap/flags.rs b/src/bootstrap/flags.rs
index 478e496078a..465ebf846d3 100644
--- a/src/bootstrap/flags.rs
+++ b/src/bootstrap/flags.rs
@@ -42,6 +42,7 @@ pub struct Flags {
     pub jobs: Option<u32>,
     pub cmd: Subcommand,
     pub incremental: bool,
+    pub exclude: Vec<PathBuf>,
 }
 
 pub enum Subcommand {
@@ -109,6 +110,7 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`");
         opts.optopt("", "build", "build target of the stage0 compiler", "BUILD");
         opts.optmulti("", "host", "host targets to build", "HOST");
         opts.optmulti("", "target", "target targets to build", "TARGET");
+        opts.optmulti("", "exclude", "build paths to exclude", "PATH");
         opts.optopt("", "on-fail", "command to run on failure", "CMD");
         opts.optopt("", "stage", "stage to build", "N");
         opts.optopt("", "keep-stage", "stage to keep without recompiling", "N");
@@ -358,10 +360,9 @@ Arguments:
             stage = Some(1);
         }
 
-        let cwd = t!(env::current_dir());
         let src = matches.opt_str("src").map(PathBuf::from)
             .or_else(|| env::var_os("SRC").map(PathBuf::from))
-            .unwrap_or(cwd);
+            .unwrap_or(cwd.clone());
 
         Flags {
             verbose: matches.opt_count("verbose"),
@@ -378,6 +379,8 @@ Arguments:
             jobs: matches.opt_str("jobs").map(|j| j.parse().unwrap()),
             cmd,
             incremental: matches.opt_present("incremental"),
+            exclude: split(matches.opt_strs("exclude"))
+                .into_iter().map(|p| cwd.join(p)).collect::<Vec<_>>(),
         }
     }
 }