Auto merge of #65501 - alexcrichton:remove-emscripten-backend, r=Mark-Simulacrum

Remove `src/llvm-emscripten` submodule

With #65251 landed there's no need to build two LLVM backends and ship
them with rustc, every target we have now uses the same LLVM backend!

This removes the `src/llvm-emscripten` submodule and additionally
removes all support from rustbuild for building the emscripten LLVM
backend. Multiple codegen backend support is left in place for now, and
this is intended to be an easy 10-15 minute win on CI times by avoiding
having to build LLVM twice.

Author: bors

Diff for: .gitmodules

@@ -28,9 +28,6 @@
 [submodule "src/doc/rust-by-example"]
 	path = src/doc/rust-by-example
 	url = https://github.com/rust-lang/rust-by-example.git
-[submodule "src/llvm-emscripten"]
-	path = src/llvm-emscripten
-	url = https://github.com/rust-lang/llvm.git
 [submodule "src/stdarch"]
 	path = src/stdarch
 	url = https://github.com/rust-lang/stdarch.git

Diff for: config.toml.example

@@ -374,10 +374,7 @@
 
 # This is an array of the codegen backends that will be compiled for the rustc
 # that's being compiled. The default is to only build the LLVM codegen backend,
-# 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.
+# and currently the only standard option supported is `"llvm"`
 #codegen-backends = ["llvm"]
 
 # This is the name of the directory in which codegen backends will get installed

Diff for: src/bootstrap/bootstrap.py

@@ -734,10 +734,6 @@ def update_submodules(self):
             if module.endswith("llvm-project"):
                 if self.get_toml('llvm-config') and self.get_toml('lld') != 'true':
                     continue
-            if module.endswith("llvm-emscripten"):
-                backends = self.get_toml('codegen-backends')
-                if backends is None or not 'emscripten' in backends:
-                    continue
             check = self.check_submodule(module, slow_submodules)
             filtered_submodules.append((module, check))
             submodules_names.append(module)

Diff for: src/bootstrap/compile.rs

@@ -210,7 +210,6 @@ pub fn std_cargo(builder: &Builder<'_>,
             // config.toml equivalent) is used
             let llvm_config = builder.ensure(native::Llvm {
                 target: builder.config.build,
-                emscripten: false,
             });
             cargo.env("LLVM_CONFIG", llvm_config);
             cargo.env("RUSTC_BUILD_SANITIZERS", "1");
@@ -615,36 +614,27 @@ pub fn build_codegen_backend(builder: &Builder<'_>,
                              compiler: &Compiler,
                              target: Interned<String>,
                              backend: Interned<String>) -> String {
-    let mut features = String::new();
-
     match &*backend {
-        "llvm" | "emscripten" => {
+        "llvm" => {
             // Build LLVM for our target. This will implicitly build the
             // host LLVM if necessary.
             let llvm_config = builder.ensure(native::Llvm {
                 target,
-                emscripten: backend == "emscripten",
             });
 
-            if backend == "emscripten" {
-                features.push_str(" emscripten");
-            }
-
             builder.info(&format!("Building stage{} codegen artifacts ({} -> {}, {})",
                      compiler.stage, &compiler.host, target, backend));
 
             // Pass down configuration from the LLVM build into the build of
             // librustc_llvm and librustc_codegen_llvm.
-            if builder.is_rust_llvm(target) && backend != "emscripten" {
+            if builder.is_rust_llvm(target) {
                 cargo.env("LLVM_RUSTLLVM", "1");
             }
 
             cargo.env("LLVM_CONFIG", &llvm_config);
-            if backend != "emscripten" {
-                let target_config = builder.config.target_config.get(&target);
-                if let Some(s) = target_config.and_then(|c| c.llvm_config.as_ref()) {
-                    cargo.env("CFG_LLVM_ROOT", s);
-                }
+            let target_config = builder.config.target_config.get(&target);
+            if let Some(s) = target_config.and_then(|c| c.llvm_config.as_ref()) {
+                cargo.env("CFG_LLVM_ROOT", s);
             }
             // Some LLVM linker flags (-L and -l) may be needed to link librustc_llvm.
             if let Some(ref s) = builder.config.llvm_ldflags {
@@ -662,9 +652,7 @@ pub fn build_codegen_backend(builder: &Builder<'_>,
                                          "libstdc++.a");
                 cargo.env("LLVM_STATIC_STDCPP", file);
             }
-            if builder.config.llvm_link_shared ||
-                (builder.config.llvm_thin_lto && backend != "emscripten")
-            {
+            if builder.config.llvm_link_shared || builder.config.llvm_thin_lto {
                 cargo.env("LLVM_LINK_SHARED", "1");
             }
             if builder.config.llvm_use_libcxx {
@@ -676,8 +664,7 @@ pub fn build_codegen_backend(builder: &Builder<'_>,
         }
         _ => panic!("unknown backend: {}", backend),
     }
-
-    features
+    String::new()
 }
 
 /// Creates the `codegen-backends` folder for a compiler that's about to be

Diff for: src/bootstrap/config.rs

@@ -668,7 +668,6 @@ impl Config {
 
     pub fn llvm_enabled(&self) -> bool {
         self.rust_codegen_backends.contains(&INTERNER.intern_str("llvm"))
-        || self.rust_codegen_backends.contains(&INTERNER.intern_str("emscripten"))
     }
 }
 

Diff for: src/bootstrap/configure.py

@@ -55,7 +55,6 @@ def v(*args):
 o("dist-src", "rust.dist-src", "when building tarballs enables building a source tarball")
 o("cargo-native-static", "build.cargo-native-static", "static native libraries in cargo")
 o("profiler", "build.profiler", "build the profiler runtime")
-o("emscripten", None, "compile the emscripten backend as well as LLVM")
 o("full-tools", None, "enable all tools")
 o("lld", "rust.lld", "build lld")
 o("lldb", "rust.lldb", "build lldb")
@@ -335,10 +334,8 @@ def set(key, value):
         set('build.host', value.split(','))
     elif option.name == 'target':
         set('build.target', value.split(','))
-    elif option.name == 'emscripten':
-        set('rust.codegen-backends', ['llvm', 'emscripten'])
     elif option.name == 'full-tools':
-        set('rust.codegen-backends', ['llvm', 'emscripten'])
+        set('rust.codegen-backends', ['llvm'])
         set('rust.lld', True)
         set('rust.llvm-tools', True)
         set('build.extended', True)

Diff for: src/bootstrap/dist.rs

@@ -826,17 +826,13 @@ fn copy_src_dirs(builder: &Builder<'_>, src_dirs: &[&str], exclude_dirs: &[&str]
 
         const LLVM_TEST: &[&str] = &[
             "llvm-project/llvm/test", "llvm-project\\llvm\\test",
-            "llvm-emscripten/test", "llvm-emscripten\\test",
         ];
         if LLVM_TEST.iter().any(|path| spath.contains(path)) &&
             (spath.ends_with(".ll") ||
              spath.ends_with(".td") ||
              spath.ends_with(".s")) {
             return false
         }
-        if spath.contains("test/emscripten") || spath.contains("test\\emscripten") {
-            return false
-        }
 
         let full_path = Path::new(dir).join(path);
         if exclude_dirs.iter().any(|excl| full_path == Path::new(excl)) {

Diff for: src/bootstrap/lib.rs

@@ -232,7 +232,6 @@ pub struct Build {
     miri_info: channel::GitInfo,
     rustfmt_info: channel::GitInfo,
     in_tree_llvm_info: channel::GitInfo,
-    emscripten_llvm_info: channel::GitInfo,
     local_rebuild: bool,
     fail_fast: bool,
     doc_tests: DocTests,
@@ -351,7 +350,6 @@ impl Build {
 
         // we always try to use git for LLVM builds
         let in_tree_llvm_info = channel::GitInfo::new(false, &src.join("src/llvm-project"));
-        let emscripten_llvm_info = channel::GitInfo::new(false, &src.join("src/llvm-emscripten"));
 
         let mut build = Build {
             initial_rustc: config.initial_rustc.clone(),
@@ -376,7 +374,6 @@ impl Build {
             miri_info,
             rustfmt_info,
             in_tree_llvm_info,
-            emscripten_llvm_info,
             cc: HashMap::new(),
             cxx: HashMap::new(),
             ar: HashMap::new(),
@@ -553,10 +550,6 @@ impl Build {
         self.out.join(&*target).join("llvm")
     }
 
-    fn emscripten_llvm_out(&self, target: Interned<String>) -> PathBuf {
-        self.out.join(&*target).join("llvm-emscripten")
-    }
-
     fn lld_out(&self, target: Interned<String>) -> PathBuf {
         self.out.join(&*target).join("lld")
     }

Diff for: src/bootstrap/native.rs

@@ -28,7 +28,6 @@ use crate::GitRepo;
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct Llvm {
     pub target: Interned<String>,
-    pub emscripten: bool,
 }
 
 impl Step for Llvm {
@@ -40,46 +39,35 @@ impl Step for Llvm {
         run.path("src/llvm-project")
             .path("src/llvm-project/llvm")
             .path("src/llvm")
-            .path("src/llvm-emscripten")
     }
 
     fn make_run(run: RunConfig<'_>) {
-        let emscripten = run.path.ends_with("llvm-emscripten");
         run.builder.ensure(Llvm {
             target: run.target,
-            emscripten,
         });
     }
 
     /// Compile LLVM for `target`.
     fn run(self, builder: &Builder<'_>) -> PathBuf {
         let target = self.target;
-        let emscripten = self.emscripten;
 
         // If we're using a custom LLVM bail out here, but we can only use a
         // custom LLVM for the build triple.
-        if !self.emscripten {
-            if let Some(config) = builder.config.target_config.get(&target) {
-                if let Some(ref s) = config.llvm_config {
-                    check_llvm_version(builder, s);
-                    return s.to_path_buf()
-                }
+        if let Some(config) = builder.config.target_config.get(&target) {
+            if let Some(ref s) = config.llvm_config {
+                check_llvm_version(builder, s);
+                return s.to_path_buf()
             }
         }
 
-        let (llvm_info, root, out_dir, llvm_config_ret_dir) = if emscripten {
-            let info = &builder.emscripten_llvm_info;
-            let dir = builder.emscripten_llvm_out(target);
-            let config_dir = dir.join("bin");
-            (info, "src/llvm-emscripten", dir, config_dir)
-        } else {
-            let info = &builder.in_tree_llvm_info;
-            let mut dir = builder.llvm_out(builder.config.build);
-            if !builder.config.build.contains("msvc") || builder.config.ninja {
-                dir.push("build");
-            }
-            (info, "src/llvm-project/llvm", builder.llvm_out(target), dir.join("bin"))
-        };
+        let llvm_info = &builder.in_tree_llvm_info;
+        let root = "src/llvm-project/llvm";
+        let out_dir = builder.llvm_out(target);
+        let mut llvm_config_ret_dir = builder.llvm_out(builder.config.build);
+        if !builder.config.build.contains("msvc") || builder.config.ninja {
+            llvm_config_ret_dir.push("build");
+        }
+        llvm_config_ret_dir.push("bin");
 
         let build_llvm_config = llvm_config_ret_dir
             .join(exe("llvm-config", &*builder.config.build));
@@ -107,8 +95,7 @@ impl Step for Llvm {
             }
         }
 
-        let descriptor = if emscripten { "Emscripten " } else { "" };
-        builder.info(&format!("Building {}LLVM for {}", descriptor, target));
+        builder.info(&format!("Building LLVM for {}", target));
         let _time = util::timeit(&builder);
         t!(fs::create_dir_all(&out_dir));
 
@@ -123,23 +110,15 @@ impl Step for Llvm {
 
         // NOTE: remember to also update `config.toml.example` when changing the
         // defaults!
-        let llvm_targets = if self.emscripten {
-            "JSBackend"
-        } else {
-            match builder.config.llvm_targets {
-                Some(ref s) => s,
-                None => "AArch64;ARM;Hexagon;MSP430;Mips;NVPTX;PowerPC;RISCV;\
-                         Sparc;SystemZ;WebAssembly;X86",
-            }
+        let llvm_targets = match &builder.config.llvm_targets {
+            Some(s) => s,
+            None => "AArch64;ARM;Hexagon;MSP430;Mips;NVPTX;PowerPC;RISCV;\
+                     Sparc;SystemZ;WebAssembly;X86",
         };
 
-        let llvm_exp_targets = if self.emscripten {
-            ""
-        } else {
-            match builder.config.llvm_experimental_targets {
-                Some(ref s) => s,
-                None => "",
-            }
+        let llvm_exp_targets = match builder.config.llvm_experimental_targets {
+            Some(ref s) => s,
+            None => "",
         };
 
         let assertions = if builder.config.llvm_assertions {"ON"} else {"OFF"};
@@ -163,25 +142,23 @@ impl Step for Llvm {
            .define("LLVM_TARGET_ARCH", target.split('-').next().unwrap())
            .define("LLVM_DEFAULT_TARGET_TRIPLE", target);
 
-        if builder.config.llvm_thin_lto && !emscripten {
+        if builder.config.llvm_thin_lto {
             cfg.define("LLVM_ENABLE_LTO", "Thin");
             if !target.contains("apple") {
                cfg.define("LLVM_ENABLE_LLD", "ON");
             }
         }
 
-        let want_lldb = builder.config.lldb_enabled && !self.emscripten;
-
         // This setting makes the LLVM tools link to the dynamic LLVM library,
         // which saves both memory during parallel links and overall disk space
         // for the tools. We don't do this on every platform as it doesn't work
         // equally well everywhere.
-        if builder.llvm_link_tools_dynamically(target) && !emscripten {
+        if builder.llvm_link_tools_dynamically(target) {
             cfg.define("LLVM_LINK_LLVM_DYLIB", "ON");
         }
 
         // For distribution we want the LLVM tools to be *statically* linked to libstdc++
-        if builder.config.llvm_tools_enabled || want_lldb {
+        if builder.config.llvm_tools_enabled || builder.config.lldb_enabled {
             if !target.contains("windows") {
                 if target.contains("apple") {
                     cfg.define("CMAKE_EXE_LINKER_FLAGS", "-static-libstdc++");
@@ -209,7 +186,7 @@ impl Step for Llvm {
             enabled_llvm_projects.push("compiler-rt");
         }
 
-        if want_lldb {
+        if builder.config.lldb_enabled {
             enabled_llvm_projects.push("clang");
             enabled_llvm_projects.push("lldb");
             // For the time being, disable code signing.
@@ -234,10 +211,9 @@ impl Step for Llvm {
         }
 
         // http://llvm.org/docs/HowToCrossCompileLLVM.html
-        if target != builder.config.build && !emscripten {
+        if target != builder.config.build {
             builder.ensure(Llvm {
                 target: builder.config.build,
-                emscripten: false,
             });
             // FIXME: if the llvm root for the build triple is overridden then we
             //        should use llvm-tblgen from there, also should verify that it
@@ -481,7 +457,6 @@ impl Step for Lld {
 
         let llvm_config = builder.ensure(Llvm {
             target: self.target,
-            emscripten: false,
         });
 
         let out_dir = builder.lld_out(target);

Diff for: src/bootstrap/test.rs

@@ -1163,7 +1163,7 @@ impl Step for Compiletest {
                     }).to_string()
             })
         };
-        let lldb_exe = if builder.config.lldb_enabled && !target.contains("emscripten") {
+        let lldb_exe = if builder.config.lldb_enabled {
             // Test against the lldb that was just built.
             builder.llvm_out(target).join("bin").join("lldb")
         } else {
@@ -1232,7 +1232,6 @@ impl Step for Compiletest {
         if builder.config.llvm_enabled() {
             let llvm_config = builder.ensure(native::Llvm {
                 target: builder.config.build,
-                emscripten: false,
             });
             if !builder.config.dry_run {
                 let llvm_version = output(Command::new(&llvm_config).arg("--version"));

Diff for: src/ci/docker/dist-various-1/Dockerfile

@@ -139,7 +139,6 @@ ENV RUST_CONFIGURE_ARGS \
       --musl-root-aarch64=/musl-aarch64 \
       --musl-root-mips=/musl-mips \
       --musl-root-mipsel=/musl-mipsel \
-      --enable-emscripten \
       --disable-docs
 
 ENV SCRIPT \

Diff for: src/ci/init_repo.sh

@@ -47,7 +47,7 @@ function fetch_github_commit_archive {
     rm $cached
 }
 
-included="src/llvm-project src/llvm-emscripten src/doc/book src/doc/rust-by-example"
+included="src/llvm-project src/doc/book src/doc/rust-by-example"
 modules="$(git config --file .gitmodules --get-regexp '\.path$' | cut -d' ' -f2)"
 modules=($modules)
 use_git=""

Diff for: src/librustc_codegen_llvm/Cargo.toml

@@ -12,9 +12,3 @@ test = false
 
 [dependencies]
 rustc_llvm = { path = "../librustc_llvm" }
-
-[features]
-# This is used to convince Cargo to separately cache builds of `rustc_codegen_llvm`
-# when this option is enabled or not. That way we can build two, cache two
-# artifacts, and have nice speedy rebuilds.
-emscripten = ["rustc_llvm/emscripten"]