Auto merge of #38359 - alexcrichton:sccache, r=brson

rustbuild: Add sccache support

This commit adds support for sccache, a ccache-like compiler which works on MSVC
and stores results into an S3 bucket. This also switches over all Travis and
AppVeyor automation to using sccache to ensure a shared and unified cache over
time which can be shared across builders.

The support for sccache manifests as a new `--enable-sccache` option which
instructs us to configure LLVM differently to use a 'sccache' binary instead of
a 'ccache' binary. All docker images for Travis builds are updated to download
Mozilla's tooltool builds of sccache onto various containers and systems.
Additionally a new `rust-lang-ci-sccache` bucket is configured to hold all of
our ccache goodies.

---

Note that this does not currently change Windows [due to previously written up issues](https://github.com/rust-lang/rust/issues/38119#issuecomment-266631585). Despite that, however, I was curious to get timings for the builds on Travis to see what ranges we're working with. As a result, this is a WIP PR I'm using to gauge build times and such.

4 files changed, 38 insertions, 7 deletions

diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 60f65f62300..b8abcb28c4e 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -38,7 +38,7 @@ use util::push_exe_path;
 /// `src/bootstrap/config.toml.example`.
 #[derive(Default)]
 pub struct Config {
-    pub ccache: bool,
+    pub ccache: Option<String>,
     pub ninja: bool,
     pub verbose: bool,
     pub submodules: bool,
@@ -138,7 +138,7 @@ struct Build {
 /// TOML representation of how the LLVM build is configured.
 #[derive(RustcDecodable, Default)]
 struct Llvm {
-    ccache: Option<bool>,
+    ccache: Option<StringOrBool>,
     ninja: Option<bool>,
     assertions: Option<bool>,
     optimize: Option<bool>,
@@ -147,6 +147,18 @@ struct Llvm {
     static_libstdcpp: Option<bool>,
 }
 
+#[derive(RustcDecodable)]
+enum StringOrBool {
+    String(String),
+    Bool(bool),
+}
+
+impl Default for StringOrBool {
+    fn default() -> StringOrBool {
+        StringOrBool::Bool(false)
+    }
+}
+
 /// TOML representation of how the Rust build is configured.
 #[derive(RustcDecodable, Default)]
 struct Rust {
@@ -247,7 +259,15 @@ impl Config {
         set(&mut config.vendor, build.vendor);
 
         if let Some(ref llvm) = toml.llvm {
-            set(&mut config.ccache, llvm.ccache);
+            match llvm.ccache {
+                Some(StringOrBool::String(ref s)) => {
+                    config.ccache = Some(s.to_string())
+                }
+                Some(StringOrBool::Bool(true)) => {
+                    config.ccache = Some("ccache".to_string());
+                }
+                Some(StringOrBool::Bool(false)) | None => {}
+            }
             set(&mut config.ninja, llvm.ninja);
             set(&mut config.llvm_assertions, llvm.assertions);
             set(&mut config.llvm_optimize, llvm.optimize);
@@ -338,7 +358,6 @@ impl Config {
             }
 
             check! {
-                ("CCACHE", self.ccache),
                 ("MANAGE_SUBMODULES", self.submodules),
                 ("COMPILER_DOCS", self.compiler_docs),
                 ("DOCS", self.docs),
@@ -475,6 +494,12 @@ impl Config {
                     let path = parse_configure_path(value);
                     self.python = Some(path);
                 }
+                "CFG_ENABLE_CCACHE" if value == "1" => {
+                    self.ccache = Some("ccache".to_string());
+                }
+                "CFG_ENABLE_SCCACHE" if value == "1" => {
+                    self.ccache = Some("sccache".to_string());
+                }
                 _ => {}
             }
         }
diff --git a/src/bootstrap/config.toml.example b/src/bootstrap/config.toml.example
index b6774b3af20..9e50e71bf7d 100644
--- a/src/bootstrap/config.toml.example
+++ b/src/bootstrap/config.toml.example
@@ -25,6 +25,8 @@
 
 # Indicates whether ccache is used when building LLVM
 #ccache = false
+# or alternatively ...
+#ccache = "/path/to/ccache"
 
 # If an external LLVM root is specified, we automatically check the version by
 # default to make sure it's within the range that we're expecting, but setting
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index ffa3fe1cbf2..6ba6b8e6c86 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -109,10 +109,10 @@ pub fn llvm(build: &Build, target: &str) {
 
     // MSVC handles compiler business itself
     if !target.contains("msvc") {
-        if build.config.ccache {
-           cfg.define("CMAKE_C_COMPILER", "ccache")
+        if let Some(ref ccache) = build.config.ccache {
+           cfg.define("CMAKE_C_COMPILER", ccache)
               .define("CMAKE_C_COMPILER_ARG1", build.cc(target))
-              .define("CMAKE_CXX_COMPILER", "ccache")
+              .define("CMAKE_CXX_COMPILER", ccache)
               .define("CMAKE_CXX_COMPILER_ARG1", build.cxx(target));
         } else {
            cfg.define("CMAKE_C_COMPILER", build.cc(target))
diff --git a/src/bootstrap/sanity.rs b/src/bootstrap/sanity.rs
index f3fe22698bb..2992099687d 100644
--- a/src/bootstrap/sanity.rs
+++ b/src/bootstrap/sanity.rs
@@ -223,4 +223,8 @@ $ pacman -R cmake && pacman -S mingw-w64-x86_64-cmake
     if build.lldb_version.is_some() {
         build.lldb_python_dir = run(Command::new("lldb").arg("-P")).ok();
     }
+
+    if let Some(ref s) = build.config.ccache {
+        need_cmd(s.as_ref());
+    }
 }