Make wasm32 buildbot test LLVM backend

This adds the experimental targets option to configure so it can be used
by the builders and changes the wasm32 Dockerfile accordingly. Instead
of using LLVM from the emsdk, the builder's emscripten tools now uses
the Rust in-tree LLVM, since this is the one built with wasm support.

configure

@@ -490,6 +490,7 @@ valopt musl-root-armhf "" "arm-unknown-linux-musleabihf install directory"
 valopt musl-root-armv7 "" "armv7-unknown-linux-musleabihf install directory"
 valopt extra-filename "" "Additional data that is hashed and passed to the -C extra-filename flag"
 valopt qemu-armhf-rootfs "" "rootfs in qemu testing, you probably don't want to use this"
+valopt experimental-targets "" "experimental LLVM targets to build"
 
 if [ -e ${CFG_SRC_DIR}.git ]
 then

src/bootstrap/config.rs

@@ -497,6 +497,9 @@ impl Config {
                 "CFG_TARGET" if value.len() > 0 => {
                     self.target.extend(value.split(" ").map(|s| s.to_string()));
                 }
+                "CFG_EXPERIMENTAL_TARGETS" if value.len() > 0 => {
+                    self.llvm_experimental_targets = Some(value.to_string());
+                }
                 "CFG_MUSL_ROOT" if value.len() > 0 => {
                     self.musl_root = Some(parse_configure_path(value));
                 }

src/ci/docker/disabled/wasm32/Dockerfile

@@ -20,7 +20,7 @@ RUN sh /scripts/dumb-init.sh
 # emscripten
 COPY scripts/emscripten.sh /scripts/
 RUN bash /scripts/emscripten.sh
-COPY wasm32/node.sh /usr/local/bin/node
+COPY disabled/wasm32/node.sh /usr/local/bin/node
 
 # env
 ENV PATH=$PATH:/emsdk-portable
@@ -30,9 +30,9 @@ ENV EMSCRIPTEN=/emsdk-portable/emscripten/1.37.13/
 ENV BINARYEN_ROOT=/emsdk-portable/clang/e1.37.13_64bit/binaryen/
 ENV EM_CONFIG=/emsdk-portable/.emscripten
 
-ENV TARGETS=wasm32-unknown-emscripten
+ENV TARGETS=wasm32-unknown-emscripten,wasm32-experimental-emscripten
 
-ENV RUST_CONFIGURE_ARGS --target=$TARGETS
+ENV RUST_CONFIGURE_ARGS --target=$TARGETS --experimental-targets=WebAssembly
 
 ENV SCRIPT python2.7 ../x.py test --target $TARGETS
 

src/ci/docker/scripts/emscripten.sh

@@ -40,9 +40,12 @@ hide_output ./emsdk install sdk-1.37.13-64bit
 source ./emsdk_env.sh
 echo "main(){}" > a.c
 HOME=/emsdk-portable/ emcc a.c
-HOME=/emsdk-portable/ emcc -s BINARYEN=1 a.c
+HOME=/emsdk-portable/ emcc -s WASM=1 a.c
 rm -f a.*
 
+# Make emscripten use Rust's LLVM
+echo "LLVM_ROOT='/checkout/obj/build/x86_64-unknown-linux-gnu/llvm/bin'" >> /root/.emscripten
+
 # Make emsdk usable by any user
 cp /root/.emscripten /emsdk-portable
 chmod a+rxw -R /emsdk-portable

src/tools/compiletest/src/runtest.rs

@@ -1280,6 +1280,12 @@ actual:\n\
         let extra_link_args = vec!["-L".to_owned(),
                                    aux_dir.to_str().unwrap().to_owned()];
 
+        let mut env = self.props.rustc_env.clone();
+        // Tell emscripten to link using libc produced with LLVM backend
+        if self.config.target.contains("wasm32") && self.config.target.contains("experimental") {
+            env.push(("EMCC_WASM_BACKEND".to_string(), "1".to_string()));
+        }
+
         for rel_ab in &self.props.aux_builds {
             let aux_testpaths = self.compute_aux_test_paths(rel_ab);
             let aux_props = self.props.from_aux_file(&aux_testpaths.file,
@@ -1319,7 +1325,7 @@ actual:\n\
             };
             let aux_args = aux_cx.make_compile_args(crate_type, &aux_testpaths.file, aux_output);
             let auxres = aux_cx.compose_and_run(aux_args,
-                                                Vec::new(),
+                                                env.clone(),
                                                 aux_cx.config.compile_lib_path.to_str().unwrap(),
                                                 Some(aux_dir.to_str().unwrap()),
                                                 None);
@@ -1332,13 +1338,12 @@ actual:\n\
         }
 
         self.compose_and_run(args,
-                             self.props.rustc_env.clone(),
+                             env,
                              self.config.compile_lib_path.to_str().unwrap(),
                              Some(aux_dir.to_str().unwrap()),
                              input)
     }
 
-
     fn compose_and_run(&self,
                        ProcArgs{ args, prog }: ProcArgs,
                        procenv: Vec<(String, String)> ,