Auto merge of #46115 - alexcrichton:add-wasm-target, r=kennytm

rustbuild: Enable WebAssembly backend by default

This commit alters how we compile LLVM by default enabling the WebAssembly
backend. This then also adds the wasm32-unknown-unknown target to get compiled
on the `cross` builder and distributed through rustup. Tests are not yet enabled
for this target but that should hopefully be coming soon!

12 files changed, 148 insertions, 107 deletions

diff --git a/config.toml.example b/config.toml.example
index df0142b8d46..a9281a31b13 100644
--- a/config.toml.example
+++ b/config.toml.example
@@ -60,10 +60,9 @@
 # LLVM experimental targets to build support for. These targets are specified in
 # the same format as above, but since these targets are experimental, they are
 # not built by default and the experimental Rust compilation targets that depend
-# on them will not work unless the user opts in to building them. Possible
-# experimental LLVM targets include WebAssembly for the
-# wasm32-experimental-emscripten Rust target.
-#experimental-targets = ""
+# on them will not work unless the user opts in to building them. By default the
+# `WebAssembly` target is enabled when compiling LLVM from scratch.
+#experimental-targets = "WebAssembly"
 
 # Cap the number of parallel linker invocations when compiling LLVM.
 # This can be useful when building LLVM with debug info, which significantly
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 35e62f17f2e..d43cd54ddce 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -76,7 +76,7 @@ pub struct Config {
     pub llvm_static_stdcpp: bool,
     pub llvm_link_shared: bool,
     pub llvm_targets: Option<String>,
-    pub llvm_experimental_targets: Option<String>,
+    pub llvm_experimental_targets: String,
     pub llvm_link_jobs: Option<u32>,
 
     // rust codegen options
@@ -447,7 +447,8 @@ impl Config {
             set(&mut config.llvm_static_stdcpp, llvm.static_libstdcpp);
             set(&mut config.llvm_link_shared, llvm.link_shared);
             config.llvm_targets = llvm.targets.clone();
-            config.llvm_experimental_targets = llvm.experimental_targets.clone();
+            config.llvm_experimental_targets = llvm.experimental_targets.clone()
+                .unwrap_or("WebAssembly".to_string());
             config.llvm_link_jobs = llvm.link_jobs;
         }
 
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index fce6755aea9..ac068ebe651 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -110,10 +110,7 @@ impl Step for Llvm {
             None => "X86;ARM;AArch64;Mips;PowerPC;SystemZ;JSBackend;MSP430;Sparc;NVPTX;Hexagon",
         };
 
-        let llvm_exp_targets = match build.config.llvm_experimental_targets {
-            Some(ref s) => s,
-            None => "",
-        };
+        let llvm_exp_targets = &build.config.llvm_experimental_targets;
 
         let assertions = if build.config.llvm_assertions {"ON"} else {"OFF"};
 
diff --git a/src/ci/docker/cross2/Dockerfile b/src/ci/docker/cross2/Dockerfile
index cc260382f49..f16d97d39ef 100644
--- a/src/ci/docker/cross2/Dockerfile
+++ b/src/ci/docker/cross2/Dockerfile
@@ -47,6 +47,7 @@ ENV \
 ENV TARGETS=x86_64-unknown-fuchsia
 ENV TARGETS=$TARGETS,aarch64-unknown-fuchsia
 ENV TARGETS=$TARGETS,sparcv9-sun-solaris
+ENV TARGETS=$TARGETS,wasm32-unknown-unknown
 ENV TARGETS=$TARGETS,x86_64-sun-solaris
 ENV TARGETS=$TARGETS,x86_64-unknown-linux-gnux32
 
diff --git a/src/librustc_driver/driver.rs b/src/librustc_driver/driver.rs
index 8f2917fed7a..b1e9bc7e47c 100644
--- a/src/librustc_driver/driver.rs
+++ b/src/librustc_driver/driver.rs
@@ -56,6 +56,7 @@ use std::sync::mpsc;
 use syntax::{ast, diagnostics, visit};
 use syntax::attr;
 use syntax::ext::base::ExtCtxt;
+use syntax::fold::Folder;
 use syntax::parse::{self, PResult};
 use syntax::util::node_count::NodeCounter;
 use syntax;
@@ -63,6 +64,7 @@ use syntax_ext;
 use arena::DroplessArena;
 
 use derive_registrar;
+use pretty::ReplaceBodyWithLoop;
 
 use profile;
 
@@ -809,6 +811,12 @@ pub fn phase_2_configure_and_expand<F>(sess: &Session,
                                          sess.diagnostic())
     });
 
+    // If we're actually rustdoc then there's no need to actually compile
+    // anything, so switch everything to just looping
+    if sess.opts.actually_rustdoc {
+        krate = ReplaceBodyWithLoop::new(sess).fold_crate(krate);
+    }
+
     // If we're in rustdoc we're always compiling as an rlib, but that'll trip a
     // bunch of checks in the `modify` function below. For now just skip this
     // step entirely if we're rustdoc as it's not too useful anyway.
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index c5cce70c945..bda721d0783 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -565,7 +565,9 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
                 control.after_hir_lowering.stop = Compilation::Stop;
 
                 control.after_parse.callback = box move |state| {
-                    state.krate = Some(pretty::fold_crate(state.krate.take().unwrap(), ppm));
+                    state.krate = Some(pretty::fold_crate(state.session,
+                                                          state.krate.take().unwrap(),
+                                                          ppm));
                 };
                 control.after_hir_lowering.callback = box move |state| {
                     pretty::print_after_hir_lowering(state.session,
@@ -587,7 +589,7 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
                 control.after_parse.stop = Compilation::Stop;
 
                 control.after_parse.callback = box move |state| {
-                    let krate = pretty::fold_crate(state.krate.take().unwrap(), ppm);
+                    let krate = pretty::fold_crate(state.session, state.krate.take().unwrap(), ppm);
                     pretty::print_after_parsing(state.session,
                                                 state.input,
                                                 &krate,
diff --git a/src/librustc_driver/pretty.rs b/src/librustc_driver/pretty.rs
index bf1579acf53..d930739c9f0 100644
--- a/src/librustc_driver/pretty.rs
+++ b/src/librustc_driver/pretty.rs
@@ -638,13 +638,14 @@ impl UserIdentifiedItem {
 //    ambitious form of the closed RFC #1637. See also [#34511].
 //
 // [#34511]: https://github.com/rust-lang/rust/issues/34511#issuecomment-322340401
-pub struct ReplaceBodyWithLoop {
+pub struct ReplaceBodyWithLoop<'a> {
     within_static_or_const: bool,
+    sess: &'a Session,
 }
 
-impl ReplaceBodyWithLoop {
-    pub fn new() -> ReplaceBodyWithLoop {
-        ReplaceBodyWithLoop { within_static_or_const: false }
+impl<'a> ReplaceBodyWithLoop<'a> {
+    pub fn new(sess: &'a Session) -> ReplaceBodyWithLoop<'a> {
+        ReplaceBodyWithLoop { within_static_or_const: false, sess }
     }
 
     fn run<R, F: FnOnce(&mut Self) -> R>(&mut self, is_const: bool, action: F) -> R {
@@ -691,7 +692,7 @@ impl ReplaceBodyWithLoop {
     }
 }
 
-impl fold::Folder for ReplaceBodyWithLoop {
+impl<'a> fold::Folder for ReplaceBodyWithLoop<'a> {
     fn fold_item_kind(&mut self, i: ast::ItemKind) -> ast::ItemKind {
         let is_const = match i {
             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => true,
@@ -723,11 +724,13 @@ impl fold::Folder for ReplaceBodyWithLoop {
     }
 
     fn fold_block(&mut self, b: P<ast::Block>) -> P<ast::Block> {
-        fn expr_to_block(rules: ast::BlockCheckMode, e: Option<P<ast::Expr>>) -> P<ast::Block> {
+        fn expr_to_block(rules: ast::BlockCheckMode,
+                         e: Option<P<ast::Expr>>,
+                         sess: &Session) -> P<ast::Block> {
             P(ast::Block {
                 stmts: e.map(|e| {
                         ast::Stmt {
-                            id: ast::DUMMY_NODE_ID,
+                            id: sess.next_node_id(),
                             span: e.span,
                             node: ast::StmtKind::Expr(e),
                         }
@@ -735,22 +738,22 @@ impl fold::Folder for ReplaceBodyWithLoop {
                     .into_iter()
                     .collect(),
                 rules,
-                id: ast::DUMMY_NODE_ID,
+                id: sess.next_node_id(),
                 span: syntax_pos::DUMMY_SP,
             })
         }
 
         if !self.within_static_or_const {
 
-            let empty_block = expr_to_block(BlockCheckMode::Default, None);
+            let empty_block = expr_to_block(BlockCheckMode::Default, None, self.sess);
             let loop_expr = P(ast::Expr {
                 node: ast::ExprKind::Loop(empty_block, None),
-                id: ast::DUMMY_NODE_ID,
+                id: self.sess.next_node_id(),
                 span: syntax_pos::DUMMY_SP,
                 attrs: ast::ThinVec::new(),
             });
 
-            expr_to_block(b.rules, Some(loop_expr))
+            expr_to_block(b.rules, Some(loop_expr), self.sess)
 
         } else {
             fold::noop_fold_block(b, self)
@@ -829,9 +832,9 @@ fn print_flowgraph<'a, 'tcx, W: Write>(variants: Vec<borrowck_dot::Variant>,
     }
 }
 
-pub fn fold_crate(krate: ast::Crate, ppm: PpMode) -> ast::Crate {
+pub fn fold_crate(sess: &Session, krate: ast::Crate, ppm: PpMode) -> ast::Crate {
     if let PpmSource(PpmEveryBodyLoops) = ppm {
-        let mut fold = ReplaceBodyWithLoop::new();
+        let mut fold = ReplaceBodyWithLoop::new(sess);
         fold.fold_crate(krate)
     } else {
         krate
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 9172bfcde3f..456a00947ae 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -10,7 +10,6 @@
 
 use rustc_lint;
 use rustc_driver::{driver, target_features, abort_on_err};
-use rustc_driver::pretty::ReplaceBodyWithLoop;
 use rustc::session::{self, config};
 use rustc::hir::def_id::DefId;
 use rustc::hir::def::Def;
@@ -26,7 +25,6 @@ use rustc_metadata::cstore::CStore;
 
 use syntax::codemap;
 use syntax::feature_gate::UnstableFeatures;
-use syntax::fold::Folder;
 use errors;
 use errors::emitter::ColorConfig;
 
@@ -157,7 +155,6 @@ pub fn run_core(search_paths: SearchPaths,
     let control = &driver::CompileController::basic();
 
     let krate = panictry!(driver::phase_1_parse_input(control, &sess, &input));
-    let krate = ReplaceBodyWithLoop::new().fold_crate(krate);
 
     let name = link::find_crate_name(Some(&sess), &krate.attrs, &input);
 
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 3aa674415f0..ee0d9a7f3e2 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -31,7 +31,6 @@ use rustc_back::dynamic_lib::DynamicLibrary;
 use rustc_back::tempdir::TempDir;
 use rustc_driver::{self, driver, Compilation};
 use rustc_driver::driver::phase_2_configure_and_expand;
-use rustc_driver::pretty::ReplaceBodyWithLoop;
 use rustc_metadata::cstore::CStore;
 use rustc_resolve::MakeGlobMap;
 use rustc_trans;
@@ -39,7 +38,6 @@ use rustc_trans::back::link;
 use syntax::ast;
 use syntax::codemap::CodeMap;
 use syntax::feature_gate::UnstableFeatures;
-use syntax::fold::Folder;
 use syntax_pos::{BytePos, DUMMY_SP, Pos, Span};
 use errors;
 use errors::emitter::ColorConfig;
@@ -97,7 +95,6 @@ pub fn run(input: &str,
     let krate = panictry!(driver::phase_1_parse_input(&driver::CompileController::basic(),
                                                       &sess,
                                                       &input));
-    let krate = ReplaceBodyWithLoop::new().fold_crate(krate);
     let driver::ExpansionResult { defs, mut hir_forest, .. } = {
         phase_2_configure_and_expand(
             &sess,
diff --git a/src/libstd/os/mod.rs b/src/libstd/os/mod.rs
index 122f15d1d4c..ac7809451d1 100644
--- a/src/libstd/os/mod.rs
+++ b/src/libstd/os/mod.rs
@@ -13,35 +13,53 @@
 #![stable(feature = "os", since = "1.0.0")]
 #![allow(missing_docs, bad_style, missing_debug_implementations)]
 
-#[cfg(all(not(dox), any(target_os = "redox", unix)))]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use sys::ext as unix;
-#[cfg(all(not(dox), windows))]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use sys::ext as windows;
-
-#[cfg(dox)]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use sys::unix_ext as unix;
-#[cfg(dox)]
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use sys::windows_ext as windows;
-
-#[cfg(any(dox, target_os = "linux", target_os = "l4re"))]
-#[doc(cfg(target_os = "linux"))]
-pub mod linux;
-
-#[cfg(all(not(dox), target_os = "android"))]    pub mod android;
-#[cfg(all(not(dox), target_os = "bitrig"))]     pub mod bitrig;
-#[cfg(all(not(dox), target_os = "dragonfly"))]  pub mod dragonfly;
-#[cfg(all(not(dox), target_os = "freebsd"))]    pub mod freebsd;
-#[cfg(all(not(dox), target_os = "haiku"))]      pub mod haiku;
-#[cfg(all(not(dox), target_os = "ios"))]        pub mod ios;
-#[cfg(all(not(dox), target_os = "macos"))]      pub mod macos;
-#[cfg(all(not(dox), target_os = "netbsd"))]     pub mod netbsd;
-#[cfg(all(not(dox), target_os = "openbsd"))]    pub mod openbsd;
-#[cfg(all(not(dox), target_os = "solaris"))]    pub mod solaris;
-#[cfg(all(not(dox), target_os = "emscripten"))] pub mod emscripten;
-#[cfg(all(not(dox), target_os = "fuchsia"))]    pub mod fuchsia;
+cfg_if! {
+    if #[cfg(dox)] {
+
+        // When documenting libstd we want to show unix/windows/linux modules as
+        // these are the "main modules" that are used across platforms. This
+        // should help show platform-specific functionality in a hopefully
+        // cross-platform way in the documentation
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        pub use sys::unix_ext as unix;
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        pub use sys::windows_ext as windows;
+
+        #[doc(cfg(target_os = "linux"))]
+        pub mod linux;
+
+    } else {
+
+        // If we're not documenting libstd then we just expose everything as we
+        // otherwise would.
+
+        #[cfg(target_os = "android")]    pub mod android;
+        #[cfg(target_os = "bitrig")]     pub mod bitrig;
+        #[cfg(target_os = "dragonfly")]  pub mod dragonfly;
+        #[cfg(target_os = "freebsd")]    pub mod freebsd;
+        #[cfg(target_os = "haiku")]      pub mod haiku;
+        #[cfg(target_os = "ios")]        pub mod ios;
+        #[cfg(target_os = "macos")]      pub mod macos;
+        #[cfg(target_os = "netbsd")]     pub mod netbsd;
+        #[cfg(target_os = "openbsd")]    pub mod openbsd;
+        #[cfg(target_os = "solaris")]    pub mod solaris;
+        #[cfg(target_os = "emscripten")] pub mod emscripten;
+        #[cfg(target_os = "fuchsia")]    pub mod fuchsia;
+
+        #[cfg(any(target_os = "redox", unix))]
+        #[stable(feature = "rust1", since = "1.0.0")]
+        pub use sys::ext as unix;
+
+        #[cfg(windows)]
+        #[stable(feature = "rust1", since = "1.0.0")]
+        pub use sys::ext as windows;
+
+        #[cfg(any(target_os = "linux", target_os = "l4re"))]
+        pub mod linux;
+
+    }
+}
 
 pub mod raw;
diff --git a/src/libstd/sys/mod.rs b/src/libstd/sys/mod.rs
index 27d6433b329..be8cb88416b 100644
--- a/src/libstd/sys/mod.rs
+++ b/src/libstd/sys/mod.rs
@@ -32,49 +32,66 @@
 
 #![allow(missing_debug_implementations)]
 
-pub use self::imp::*;
-
-#[cfg(unix)]
-#[path = "unix/mod.rs"]
-mod imp;
-
-#[cfg(windows)]
-#[path = "windows/mod.rs"]
-mod imp;
-
-#[cfg(target_os = "redox")]
-#[path = "redox/mod.rs"]
-mod imp;
-
-#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
-#[path = "wasm/mod.rs"]
-mod imp;
-
-// Import essential modules from both platforms when documenting.
-
-#[cfg(all(dox, not(unix)))]
-use os::linux as platform;
-
-#[cfg(all(dox, not(any(unix, target_os = "redox"))))]
-#[path = "unix/ext/mod.rs"]
-pub mod unix_ext;
-
-#[cfg(all(dox, any(unix, target_os = "redox")))]
-pub use self::ext as unix_ext;
-
-
-#[cfg(all(dox, not(windows)))]
-#[macro_use]
-#[path = "windows/compat.rs"]
-mod compat;
-
-#[cfg(all(dox, not(windows)))]
-#[path = "windows/c.rs"]
-mod c;
-
-#[cfg(all(dox, not(windows)))]
-#[path = "windows/ext/mod.rs"]
-pub mod windows_ext;
-
-#[cfg(all(dox, windows))]
-pub use self::ext as windows_ext;
+cfg_if! {
+    if #[cfg(unix)] {
+        mod unix;
+        pub use self::unix::*;
+    } else if #[cfg(windows)] {
+        mod windows;
+        pub use self::windows::*;
+    } else if #[cfg(target_os = "redox")] {
+        mod redox;
+        pub use self::redox::*;
+    } else if #[cfg(target_arch = "wasm32")] {
+        mod wasm;
+        pub use self::wasm::*;
+    } else {
+        compile_error!("libstd doesn't compile for this platform yet");
+    }
+}
+
+// Import essential modules from both platforms when documenting. These are
+// then later used in the `std::os` module when documenting, for example,
+// Windows when we're compiling for Linux.
+
+#[cfg(dox)]
+cfg_if! {
+    if #[cfg(any(unix, target_os = "redox"))] {
+        // On unix we'll document what's already available
+        pub use self::ext as unix_ext;
+    } else if #[cfg(target_arch = "wasm32")] {
+        // On wasm right now the module below doesn't compile (missing things
+        // in `libc` which is empty) so just omit everything with an empty module
+        #[unstable(issue = "0", feature = "std_internals")]
+        pub mod unix_ext {}
+    } else {
+        // On other platforms like Windows document the bare bones of unix
+        use os::linux as platform;
+        #[path = "unix/ext/mod.rs"]
+        pub mod unix_ext;
+    }
+}
+
+#[cfg(dox)]
+cfg_if! {
+    if #[cfg(windows)] {
+        // On windows we'll just be documenting what's already available
+        pub use self::ext as windows_ext;
+    } else if #[cfg(target_arch = "wasm32")] {
+        // On wasm right now the shim below doesn't compile, so just omit it
+        #[unstable(issue = "0", feature = "std_internals")]
+        pub mod windows_ext {}
+    } else {
+        // On all other platforms (aka linux/osx/etc) then pull in a "minimal"
+        // amount of windows goop which ends up compiling
+        #[macro_use]
+        #[path = "windows/compat.rs"]
+        mod compat;
+
+        #[path = "windows/c.rs"]
+        mod c;
+
+        #[path = "windows/ext/mod.rs"]
+        pub mod windows_ext;
+    }
+}
diff --git a/src/tools/build-manifest/src/main.rs b/src/tools/build-manifest/src/main.rs
index 524ba7908bd..c4e696e1760 100644
--- a/src/tools/build-manifest/src/main.rs
+++ b/src/tools/build-manifest/src/main.rs
@@ -84,6 +84,7 @@ static TARGETS: &'static [&'static str] = &[
     "sparc64-unknown-linux-gnu",
     "sparcv9-sun-solaris",
     "wasm32-unknown-emscripten",
+    "wasm32-unknown-unknown",
     "x86_64-linux-android",
     "x86_64-apple-darwin",
     "x86_64-apple-ios",