Auto merge of #50200 - alexcrichton:compile-with-clang, r=kennytm

Compile LLVM with Clang on release builders

Attempting to cache in on some rustc compile time wins mentioned in #49879 (comment)

.travis.yml

@@ -230,7 +230,11 @@ install:
           travis_retry curl -fo /usr/local/bin/sccache https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror/2018-04-02-sccache-x86_64-apple-darwin &&
             chmod +x /usr/local/bin/sccache &&
           travis_retry curl -fo /usr/local/bin/stamp https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror/2017-03-17-stamp-x86_64-apple-darwin &&
-            chmod +x /usr/local/bin/stamp
+            chmod +x /usr/local/bin/stamp &&
+          travis_retry curl -f http://releases.llvm.org/6.0.0/clang+llvm-6.0.0-x86_64-apple-darwin.tar.xz | tar xJf - &&
+            export CC=`pwd`/clang+llvm-6.0.0-x86_64-apple-darwin/bin/clang &&
+            export CXX=`pwd`/clang+llvm-6.0.0-x86_64-apple-darwin/bin/clang++ &&
+            export AR=ar
           ;;
     esac
 

appveyor.yml

@@ -138,6 +138,20 @@ install:
   - if defined MINGW_URL 7z x -y %MINGW_ARCHIVE% > nul
   - if defined MINGW_URL set PATH=%CD%\%MINGW_DIR%\bin;C:\msys64\usr\bin;%PATH%
 
+  # If we're compiling for MSVC then we, like most other distribution builders,
+  # switch to clang as the compiler. This'll allow us eventually to enable LTO
+  # amongst LLVM and rustc. Note that we only do this on MSVC as I don't think
+  # clang has an output mode compatible with MinGW that we need. If it does we
+  # should switch to clang for MinGW as well!
+  #
+  # Note that the LLVM installer is an NSIS installer
+  #
+  # Original downloaded here came from
+  # http://releases.llvm.org/6.0.0/LLVM-6.0.0-win64.exe
+  - if NOT defined MINGW_URL appveyor-retry appveyor DownloadFile https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror/LLVM-6.0.0-win64.exe
+  - if NOT defined MINGW_URL .\LLVM-6.0.0-win64.exe /S /NCRC /D=C:\clang-rust
+  - if NOT defined MINGW_URL set RUST_CONFIGURE_ARGS=%RUST_CONFIGURE_ARGS% --set llvm.clang-cl=C:\clang-rust\bin\clang-cl.exe
+
   # Here we do a pretty heinous thing which is to mangle the MinGW installation
   # we just had above. Currently, as of this writing, we're using MinGW-w64
   # builds of gcc, and that's currently at 6.3.0. We use 6.3.0 as it appears to
@@ -166,8 +180,8 @@ install:
   - set PATH=C:\Python27;%PATH%
 
   # Download and install sccache
-  - appveyor-retry appveyor DownloadFile https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror/2018-04-02-sccache-x86_64-pc-windows-msvc
-  - mv 2018-04-02-sccache-x86_64-pc-windows-msvc sccache.exe
+  - appveyor-retry appveyor DownloadFile https://s3-us-west-1.amazonaws.com/rust-lang-ci2/rust-ci-mirror/2018-04-26-sccache-x86_64-pc-windows-msvc
+  - mv 2018-04-26-sccache-x86_64-pc-windows-msvc sccache.exe
   - set PATH=%PATH%;%CD%
 
   # Download and install ninja

config.toml.example

@@ -76,6 +76,10 @@
 # passed to prefer linking to shared libraries.
 #link-shared = false
 
+# On MSVC you can compile LLVM with clang-cl, but the test suite doesn't pass
+# with clang-cl, so this is special in that it only compiles LLVM with clang-cl
+#clang-cl = '/path/to/clang-cl.exe'
+
 # =============================================================================
 # General build configuration options
 # =============================================================================

src/bootstrap/Cargo.toml

@@ -28,6 +28,11 @@ name = "sccache-plus-cl"
 path = "bin/sccache-plus-cl.rs"
 test = false
 
+[[bin]]
+name = "llvm-config-wrapper"
+path = "bin/llvm-config-wrapper.rs"
+test = false
+
 [dependencies]
 build_helper = { path = "../build_helper" }
 cmake = "0.1.23"

src/bootstrap/bin/llvm-config-wrapper.rs

@@ -0,0 +1,27 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// The sheer existence of this file is an awful hack. See the comments in
+// `src/bootstrap/native.rs` for why this is needed when compiling LLD.
+
+use std::env;
+use std::process::{self, Stdio, Command};
+use std::io::{self, Write};
+
+fn main() {
+    let real_llvm_config = env::var_os("LLVM_CONFIG_REAL").unwrap();
+    let mut cmd = Command::new(real_llvm_config);
+    cmd.args(env::args().skip(1)).stderr(Stdio::piped());
+    let output = cmd.output().expect("failed to spawn llvm-config");
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    print!("{}", stdout.replace("\\", "/"));
+    io::stdout().flush().unwrap();
+    process::exit(output.status.code().unwrap_or(1));
+}

src/bootstrap/bin/sccache-plus-cl.rs

@@ -16,8 +16,8 @@ use std::process::{self, Command};
 fn main() {
     let target = env::var("SCCACHE_TARGET").unwrap();
     // Locate the actual compiler that we're invoking
-    env::remove_var("CC");
-    env::remove_var("CXX");
+    env::set_var("CC", env::var_os("SCCACHE_CC").unwrap());
+    env::set_var("CXX", env::var_os("SCCACHE_CXX").unwrap());
     let mut cfg = cc::Build::new();
     cfg.cargo_metadata(false)
        .out_dir("/")
@@ -39,6 +39,12 @@ fn main() {
         cmd.arg(arg);
     }
 
+    if let Ok(s) = env::var("SCCACHE_EXTRA_ARGS") {
+        for s in s.split_whitespace() {
+            cmd.arg(s);
+        }
+    }
+
     let status = cmd.status().expect("failed to spawn");
     process::exit(status.code().unwrap_or(2))
 }

src/bootstrap/builder.rs

@@ -751,7 +751,11 @@ impl<'a> Builder<'a> {
         // the options through environment variables that are fetched and understood by both.
         //
         // FIXME: the guard against msvc shouldn't need to be here
-        if !target.contains("msvc") {
+        if target.contains("msvc") {
+            if let Some(ref cl) = self.config.llvm_clang_cl {
+                cargo.env("CC", cl).env("CXX", cl);
+            }
+        } else {
             let ccache = self.config.ccache.as_ref();
             let ccacheify = |s: &Path| {
                 let ccache = match ccache {

src/bootstrap/config.rs

@@ -82,6 +82,7 @@ pub struct Config {
     pub llvm_version_check: bool,
     pub llvm_static_stdcpp: bool,
     pub llvm_link_shared: bool,
+    pub llvm_clang_cl: Option<String>,
     pub llvm_targets: Option<String>,
     pub llvm_experimental_targets: String,
     pub llvm_link_jobs: Option<u32>,
@@ -250,6 +251,7 @@ struct Llvm {
     experimental_targets: Option<String>,
     link_jobs: Option<u32>,
     link_shared: Option<bool>,
+    clang_cl: Option<String>
 }
 
 #[derive(Deserialize, Default, Clone)]
@@ -504,6 +506,7 @@ impl Config {
             config.llvm_experimental_targets = llvm.experimental_targets.clone()
                 .unwrap_or("WebAssembly".to_string());
             config.llvm_link_jobs = llvm.link_jobs;
+            config.llvm_clang_cl = llvm.clang_cl.clone();
         }
 
         if let Some(ref rust) = toml.rust {