Upgrade Emscripten targets to use upstream LLVM backend

 - Refactors the Emscripten target spec to share code with other wasm
   targets.
 - Replaces the incorrect wasm32 C call ABI with the old asmjs
   version, which is correct for both wasm32 and JS.
 - Updates the varargs ABI used by Emscripten and deletes the old one.
 - Removes the obsolete wasm32-experimental-emscripten target.
 - Temporarily makes Emscripten targets use panic=abort by default
   because supporting unwinding will require an LLVM patch.

Author: tlively

config.toml.example

@@ -377,6 +377,7 @@
 # but you can also optionally enable the "emscripten" backend for asm.js or
 # make this an empty array (but that probably won't get too far in the
 # bootstrap)
+# FIXME: remove the obsolete emscripten backend option.
 #codegen-backends = ["llvm"]
 
 # This is the name of the directory in which codegen backends will get installed

src/bootstrap/test.rs

@@ -1046,11 +1046,9 @@ impl Step for Compiletest {
 
         // Also provide `rust_test_helpers` for the host.
         builder.ensure(native::TestHelpers { target: compiler.host });
+        // As well as the target
+        builder.ensure(native::TestHelpers { target });
 
-        // wasm32 can't build the test helpers
-        if !target.contains("wasm32") {
-            builder.ensure(native::TestHelpers { target });
-        }
         builder.ensure(RemoteCopyLibs { compiler, target });
 
         let mut cmd = builder.tool_cmd(Tool::Compiletest);

src/ci/docker/asmjs/Dockerfile

@@ -11,7 +11,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   cmake \
   sudo \
   gdb \
-  xz-utils
+  xz-utils \
+  bzip2
 
 COPY scripts/emscripten.sh /scripts/
 RUN bash /scripts/emscripten.sh
@@ -20,28 +21,17 @@ COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
 ENV PATH=$PATH:/emsdk-portable
-ENV PATH=$PATH:/emsdk-portable/clang/e1.38.15_64bit/
-ENV PATH=$PATH:/emsdk-portable/emscripten/1.38.15/
-ENV PATH=$PATH:/emsdk-portable/node/8.9.1_64bit/bin/
-ENV EMSCRIPTEN=/emsdk-portable/emscripten/1.38.15/
-ENV BINARYEN_ROOT=/emsdk-portable/clang/e1.38.15_64bit/binaryen/
+ENV PATH=$PATH:/emsdk-portable/upstream/emscripten/
+ENV PATH=$PATH:/emsdk-portable/node/12.9.1_64bit/bin/
+ENV BINARYEN_ROOT=/emsdk-portable/upstream/
 ENV EM_CONFIG=/emsdk-portable/.emscripten
 
 ENV TARGETS=asmjs-unknown-emscripten
 
-ENV RUST_CONFIGURE_ARGS --enable-emscripten --disable-optimize-tests
+# TODO: Run run-fail, libcore, libstd, etc. once exceptions are enabled
+ENV SCRIPT python2.7 ../x.py test --target $TARGETS src/test/ui
 
-ENV SCRIPT python2.7 ../x.py test --target $TARGETS \
-  src/test/ui \
-  src/test/run-fail \
-  src/libstd \
-  src/liballoc \
-  src/libcore
-
-# Debug assertions in rustc are largely covered by other builders, and LLVM
-# assertions cause this builder to slow down by quite a large amount and don't
-# buy us a huge amount over other builders (not sure if we've ever seen an
-# asmjs-specific backend assertion trip), so disable assertions for these
-# tests.
-ENV NO_LLVM_ASSERTIONS=1
+# This is almost identical to the wasm32-unknown-emscripten target, so
+# running with assertions again is not useful
 ENV NO_DEBUG_ASSERTIONS=1
+ENV NO_LLVM_ASSERTIONS=1

src/ci/docker/disabled/wasm32-exp/Dockerfile

@@ -11,22 +11,22 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   cmake \
   sudo \
   gdb \
-  xz-utils
+  xz-utils \
+  bzip2
 
-# emscripten
 COPY scripts/emscripten.sh /scripts/
 RUN bash /scripts/emscripten.sh
 
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
 ENV PATH=$PATH:/emsdk-portable
-ENV PATH=$PATH:/emsdk-portable/clang/e1.38.15_64bit/
-ENV PATH=$PATH:/emsdk-portable/emscripten/1.38.15/
-ENV PATH=$PATH:/emsdk-portable/node/8.9.1_64bit/bin/
-ENV EMSCRIPTEN=/emsdk-portable/emscripten/1.38.15/
-ENV BINARYEN_ROOT=/emsdk-portable/clang/e1.38.15_64bit/binaryen/
+ENV PATH=$PATH:/emsdk-portable/upstream/emscripten/
+ENV PATH=$PATH:/emsdk-portable/node/12.9.1_64bit/bin/
+ENV BINARYEN_ROOT=/emsdk-portable/upstream/
 ENV EM_CONFIG=/emsdk-portable/.emscripten
 
 ENV TARGETS=wasm32-unknown-emscripten
-ENV SCRIPT python2.7 ../x.py test --target $TARGETS
+
+# TODO: Run run-fail, libcore, libstd, etc. once exceptions are enabled
+ENV SCRIPT python2.7 ../x.py test --target $TARGETS src/test/ui

src/ci/docker/disabled/wasm32-exp/node.sh

@@ -17,20 +17,15 @@ exit 1
   set -x
 }
 
-cd /
-curl -fL https://mozilla-games.s3.amazonaws.com/emscripten/releases/emsdk-portable.tar.gz | \
-    tar -xz
-
+git clone https://github.com/emscripten-core/emsdk.git /emsdk-portable
 cd /emsdk-portable
-./emsdk update
-hide_output ./emsdk install sdk-1.38.15-64bit
-./emsdk activate sdk-1.38.15-64bit
+hide_output ./emsdk install 1.38.46-upstream
+./emsdk activate 1.38.46-upstream
 
 # Compile and cache libc
 source ./emsdk_env.sh
 echo "main(){}" > a.c
 HOME=/emsdk-portable/ emcc a.c
-HOME=/emsdk-portable/ emcc -s BINARYEN=1 a.c
 rm -f a.*
 
 # Make emsdk usable by any user

src/ci/docker/disabled/wasm32/Dockerfile

@@ -49,8 +49,10 @@ impl fmt::Debug for c_void {
 /// Basic implementation of a `va_list`.
 // The name is WIP, using `VaListImpl` for now.
 #[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
-              not(target_arch = "x86_64"), not(target_arch = "asmjs")),
+              not(target_arch = "x86_64")),
           all(target_arch = "aarch64", target_os = "ios"),
+          target_arch = "wasm32",
+          target_arch = "asmjs",
           windows))]
 #[repr(transparent)]
 #[unstable(feature = "c_variadic",
@@ -67,8 +69,10 @@ pub struct VaListImpl<'f> {
 }
 
 #[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
-              not(target_arch = "x86_64"), not(target_arch = "asmjs")),
+              not(target_arch = "x86_64")),
           all(target_arch = "aarch64", target_os = "ios"),
+          target_arch = "wasm32",
+          target_arch = "asmjs",
           windows))]
 #[unstable(feature = "c_variadic",
            reason = "the `c_variadic` feature has not been properly tested on \
@@ -137,38 +141,6 @@ pub struct VaListImpl<'f> {
     _marker: PhantomData<&'f mut &'f c_void>,
 }
 
-/// asm.js ABI implementation of a `va_list`.
-// asm.js uses the PNaCl ABI, which specifies that a `va_list` is
-// an array of 4 32-bit integers, according to the old PNaCl docs at
-// https://web.archive.org/web/20130518054430/https://www.chromium.org/nativeclient/pnacl/bitcode-abi#TOC-Derived-Types
-// and clang does the same in `CreatePNaClABIBuiltinVaListDecl` from `lib/AST/ASTContext.cpp`
-#[cfg(all(target_arch = "asmjs", not(windows)))]
-#[repr(C)]
-#[unstable(feature = "c_variadic",
-           reason = "the `c_variadic` feature has not been properly tested on \
-                     all supported platforms",
-           issue = "44930")]
-#[lang = "va_list"]
-pub struct VaListImpl<'f> {
-    inner: [crate::mem::MaybeUninit<i32>; 4],
-    _marker: PhantomData<&'f mut &'f c_void>,
-}
-
-#[cfg(all(target_arch = "asmjs", not(windows)))]
-#[unstable(feature = "c_variadic",
-           reason = "the `c_variadic` feature has not been properly tested on \
-                     all supported platforms",
-           issue = "44930")]
-impl<'f> fmt::Debug for VaListImpl<'f> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        unsafe {
-            write!(f, "va_list* [{:#x}, {:#x}, {:#x}, {:#x}]",
-                   self.inner[0].read(), self.inner[1].read(),
-                   self.inner[2].read(), self.inner[3].read())
-        }
-    }
-}
-
 /// A wrapper for a `va_list`
 #[repr(transparent)]
 #[derive(Debug)]
@@ -178,23 +150,29 @@ impl<'f> fmt::Debug for VaListImpl<'f> {
            issue = "44930")]
 pub struct VaList<'a, 'f: 'a> {
     #[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
-                  not(target_arch = "x86_64"), not(target_arch = "asmjs")),
+                  not(target_arch = "x86_64")),
               all(target_arch = "aarch64", target_os = "ios"),
+              target_arch = "wasm32",
+              target_arch = "asmjs",
               windows))]
     inner: VaListImpl<'f>,
 
     #[cfg(all(any(target_arch = "aarch64", target_arch = "powerpc",
-                  target_arch = "x86_64", target_arch = "asmjs"),
+                  target_arch = "x86_64"),
               any(not(target_arch = "aarch64"), not(target_os = "ios")),
+              not(target_arch = "wasm32"),
+              not(target_arch = "asmjs"),
               not(windows)))]
     inner: &'a mut VaListImpl<'f>,
 
     _marker: PhantomData<&'a mut VaListImpl<'f>>,
 }
 
 #[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
-              not(target_arch = "x86_64"), not(target_arch = "asmjs")),
+              not(target_arch = "x86_64")),
           all(target_arch = "aarch64", target_os = "ios"),
+          target_arch = "wasm32",
+          target_arch = "asmjs",
           windows))]
 #[unstable(feature = "c_variadic",
            reason = "the `c_variadic` feature has not been properly tested on \
@@ -212,8 +190,10 @@ impl<'f> VaListImpl<'f> {
 }
 
 #[cfg(all(any(target_arch = "aarch64", target_arch = "powerpc",
-              target_arch = "x86_64", target_arch = "asmjs"),
+              target_arch = "x86_64"),
           any(not(target_arch = "aarch64"), not(target_os = "ios")),
+          not(target_arch = "wasm32"),
+          not(target_arch = "asmjs"),
           not(windows)))]
 #[unstable(feature = "c_variadic",
            reason = "the `c_variadic` feature has not been properly tested on \

src/ci/docker/scripts/emscripten-wasm.sh

@@ -114,24 +114,8 @@ pub fn black_box<T>(dummy: T) -> T {
     // this. LLVM's intepretation of inline assembly is that it's, well, a black
     // box. This isn't the greatest implementation since it probably deoptimizes
     // more than we want, but it's so far good enough.
-    #[cfg(not(any(
-        target_arch = "asmjs",
-        all(
-            target_arch = "wasm32",
-            target_os = "emscripten"
-        )
-    )))]
     unsafe {
         asm!("" : : "r"(&dummy));
         return dummy;
     }
-
-    // Not all platforms support inline assembly so try to do something without
-    // inline assembly which in theory still hinders at least some optimizations
-    // on those targets. This is the "best effort" scenario.
-    unsafe {
-        let ret = crate::ptr::read_volatile(&dummy);
-        crate::mem::forget(dummy);
-        ret
-    }
 }