Add target to use LLVM wasm backend

The new target is wasm32-experimental-emscripten. Adds a new
configuration option to opt in to building experimental LLVM backends
such as the WebAssembly backend. The target name was chosen to be
similar to the existing wasm32-unknown-emscripten target so that the
build and tests would work with minimal other code changes. When/if the
new target replaces the old target, simply renaming it should just work.

src/bootstrap/config.rs

@@ -60,6 +60,7 @@ 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_link_jobs: Option<u32>,
  pub llvm_clean_rebuild: bool,
 
@@ -189,6 +190,7 @@ struct Llvm {
  version_check: Option<bool>,
  static_libstdcpp: Option<bool>,
  targets: Option<String>,
+ experimental_targets: Option<String>,
  link_jobs: Option<u32>,
  clean_rebuild: Option<bool>,
 }
@@ -350,6 +352,7 @@ impl Config {
  set(&mut config.llvm_static_stdcpp, llvm.static_libstdcpp);
  set(&mut config.llvm_clean_rebuild, llvm.clean_rebuild);
  config.llvm_targets = llvm.targets.clone();
+ config.llvm_experimental_targets = llvm.experimental_targets.clone();
  config.llvm_link_jobs = llvm.link_jobs;
  }
 

src/bootstrap/config.toml.example

@@ -53,6 +53,14 @@
 # Rust team and file an issue if you need assistance in porting!
 #targets = "X86;ARM;AArch64;Mips;PowerPC;SystemZ;JSBackend;MSP430;Sparc;NVPTX;Hexagon"
 
+# 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 = ""
+
 # Cap the number of parallel linker invocations when compiling LLVM.
 # This can be useful when building LLVM with debug info, which significantly
 # increases the size of binaries and consequently the memory required by

src/bootstrap/native.rs

@@ -86,6 +86,11 @@ pub fn llvm(build: &Build, target: &str) {
  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 assertions = if build.config.llvm_assertions {"ON"} else {"OFF"};
 
  cfg.target(target)
@@ -94,6 +99,7 @@ pub fn llvm(build: &Build, target: &str) {
  .profile(profile)
  .define("LLVM_ENABLE_ASSERTIONS", assertions)
  .define("LLVM_TARGETS_TO_BUILD", llvm_targets)
+ .define("LLVM_EXPERIMENTAL_TARGETS_TO_BUILD", llvm_exp_targets)
  .define("LLVM_INCLUDE_EXAMPLES", "OFF")
  .define("LLVM_INCLUDE_TESTS", "OFF")
  .define("LLVM_INCLUDE_DOCS", "OFF")

src/librustc_back/target/mod.rs

@@ -214,6 +214,7 @@ supported_targets! {
  ("le32-unknown-nacl", le32_unknown_nacl),
  ("asmjs-unknown-emscripten", asmjs_unknown_emscripten),
  ("wasm32-unknown-emscripten", wasm32_unknown_emscripten),
+ ("wasm32-experimental-emscripten", wasm32_experimental_emscripten),
 
  ("thumbv6m-none-eabi", thumbv6m_none_eabi),
  ("thumbv7m-none-eabi", thumbv7m_none_eabi),

src/librustc_back/target/wasm32_experimental_emscripten.rs

@@ -0,0 +1,53 @@
+// Copyright 2015 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.
+
+use LinkerFlavor;
+use super::{LinkArgs, Target, TargetOptions};
+use super::emscripten_base::{cmd};
+
+pub fn target() -> Result<Target, String> {
+ let mut post_link_args = LinkArgs::new();
+ post_link_args.insert(LinkerFlavor::Em,
+ vec!["-s".to_string(),
+ "WASM=1".to_string(),
+ "-s".to_string(),
+ "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string()]);
+
+ let opts = TargetOptions {
+ linker: cmd("emcc"),
+ ar: cmd("emar"),
+
+ dynamic_linking: false,
+ executables: true,
+ // Today emcc emits two files - a .js file to bootstrap and
+ // possibly interpret the wasm, and a .wasm file
+ exe_suffix: ".js".to_string(),
+ linker_is_gnu: true,
+ allow_asm: false,
+ obj_is_bitcode: true,
+ is_like_emscripten: true,
+ max_atomic_width: Some(32),
+ post_link_args: post_link_args,
+ target_family: Some("unix".to_string()),
+ .. Default::default()
+ };
+ Ok(Target {
+ llvm_target: "wasm32-unknown-unknown".to_string(),
+ target_endian: "little".to_string(),
+ target_pointer_width: "32".to_string(),
+ target_os: "emscripten".to_string(),
+ target_env: "".to_string(),
+ target_vendor: "unknown".to_string(),
+ data_layout: "e-m:e-p:32:32-i64:64-n32:64-S128".to_string(),
+ arch: "wasm32".to_string(),
+ linker_flavor: LinkerFlavor::Em,
+ options: opts,
+ })
+}

src/librustc_llvm/build.rs

@@ -93,7 +93,7 @@ fn main() {
 
  let mut optional_components =
  vec!["x86", "arm", "aarch64", "mips", "powerpc", "pnacl",
- "systemz", "jsbackend", "msp430", "sparc", "nvptx"];
+ "systemz", "jsbackend", "webassembly", "msp430", "sparc", "nvptx"];
 
  let mut version_cmd = Command::new(&llvm_config);
  version_cmd.arg("--version");

src/librustc_llvm/lib.rs

@@ -389,6 +389,11 @@ pub fn initialize_available_targets() {
  LLVMInitializeHexagonTargetMC,
  LLVMInitializeHexagonAsmPrinter,
  LLVMInitializeHexagonAsmParser);
+ init_target!(llvm_component = "webassembly",
+ LLVMInitializeWebAssemblyTargetInfo,
+ LLVMInitializeWebAssemblyTarget,
+ LLVMInitializeWebAssemblyTargetMC,
+ LLVMInitializeWebAssemblyAsmPrinter);
 }
 
 pub fn last_error() -> Option<String> {