rustc: Tweak default linker selection

This commit refactors how the path to the linker that we're going to invoke is
selected. Previously all targets listed *both* a `LinkerFlavor` and a `linker`
(path) option, but this meant that whenever you changed one you had to change
the other. The purpose of this commit is to avoid coupling these where possible.

Target specifications now only unconditionally define the *flavor* of the linker
that they're using by default. If not otherwise specified each flavor now
implies a particular default linker to run. As a result, this means that if
you'd like to test out `ld` for example you should be able to do:

    rustc -Z linker-flavor=ld foo.rs

whereas previously you had to do

    rustc -Z linker-flavor=ld -C linker=ld foo.rs

This will hopefully make it a bit easier to tinker around with variants that
should otherwise be well known to work, for example with LLD, `ld` on OSX, etc.

26 files changed, 83 insertions, 118 deletions

diff --git a/src/bootstrap/dist.rs b/src/bootstrap/dist.rs
index 02ef7c0e1ff..576e5078247 100644
--- a/src/bootstrap/dist.rs
+++ b/src/bootstrap/dist.rs
@@ -606,8 +606,10 @@ impl Step for Std {
         let mut src = builder.sysroot_libdir(compiler, target).to_path_buf();
         src.pop(); // Remove the trailing /lib folder from the sysroot_libdir
         cp_filtered(&src, &dst, &|path| {
-            path.file_name().and_then(|s| s.to_str()) !=
-                Some(build.config.rust_codegen_backends_dir.as_str())
+            let name = path.file_name().and_then(|s| s.to_str());
+            name != Some(build.config.rust_codegen_backends_dir.as_str()) &&
+                name != Some("bin")
+
         });
 
         let mut cmd = rust_installer(builder);
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index 987d70fd047..7888f0b938d 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -208,7 +208,7 @@ impl Step for Llvm {
             cfg.define("LLVM_NATIVE_BUILD", build.llvm_out(build.build).join("build"));
         }
 
-        configure_cmake(build, target, &mut cfg);
+        configure_cmake(build, target, &mut cfg, false);
 
         // FIXME: we don't actually need to build all LLVM tools and all LLVM
         //        libraries here, e.g. we just want a few components and a few
@@ -241,7 +241,8 @@ fn check_llvm_version(build: &Build, llvm_config: &Path) {
 
 fn configure_cmake(build: &Build,
                    target: Interned<String>,
-                   cfg: &mut cmake::Config) {
+                   cfg: &mut cmake::Config,
+                   building_dist_binaries: bool) {
     if build.config.ninja {
         cfg.generator("Ninja");
     }
@@ -294,8 +295,10 @@ fn configure_cmake(build: &Build,
     cfg.build_arg("-j").build_arg(build.jobs().to_string());
     cfg.define("CMAKE_C_FLAGS", build.cflags(target).join(" "));
     let mut cxxflags = build.cflags(target).join(" ");
-    if build.config.llvm_static_stdcpp && !target.contains("windows") {
-        cxxflags.push_str(" -static-libstdc++");
+    if building_dist_binaries {
+        if build.config.llvm_static_stdcpp && !target.contains("windows") {
+            cxxflags.push_str(" -static-libstdc++");
+        }
     }
     cfg.define("CMAKE_CXX_FLAGS", cxxflags);
     if let Some(ar) = build.ar(target) {
@@ -350,7 +353,7 @@ impl Step for Lld {
         t!(fs::create_dir_all(&out_dir));
 
         let mut cfg = cmake::Config::new(build.src.join("src/tools/lld"));
-        configure_cmake(build, target, &mut cfg);
+        configure_cmake(build, target, &mut cfg, true);
 
         cfg.out_dir(&out_dir)
            .profile("Release")
diff --git a/src/librustc_back/lib.rs b/src/librustc_back/lib.rs
index 141c8954a33..9de56cca339 100644
--- a/src/librustc_back/lib.rs
+++ b/src/librustc_back/lib.rs
@@ -57,6 +57,9 @@ pub enum LinkerFlavor {
          RustcEncodable, RustcDecodable)]
 pub enum LldFlavor {
     Wasm,
+    Ld64,
+    Ld,
+    Link,
 }
 
 impl ToJson for LinkerFlavor {
@@ -94,6 +97,9 @@ flavor_mappings! {
     ((LinkerFlavor::Ld), "ld"),
     ((LinkerFlavor::Msvc), "msvc"),
     ((LinkerFlavor::Lld(LldFlavor::Wasm)), "wasm-ld"),
+    ((LinkerFlavor::Lld(LldFlavor::Ld64)), "ld64.lld"),
+    ((LinkerFlavor::Lld(LldFlavor::Ld)), "ld.lld"),
+    ((LinkerFlavor::Lld(LldFlavor::Link)), "lld-link"),
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
diff --git a/src/librustc_back/target/aarch64_unknown_cloudabi.rs b/src/librustc_back/target/aarch64_unknown_cloudabi.rs
index 59c82e06a67..a5d0e5bf166 100644
--- a/src/librustc_back/target/aarch64_unknown_cloudabi.rs
+++ b/src/librustc_back/target/aarch64_unknown_cloudabi.rs
@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
     let mut base = super::cloudabi_base::opts();
     base.max_atomic_width = Some(128);
     base.abi_blacklist = super::arm_base::abi_blacklist();
-    base.linker = "aarch64-unknown-cloudabi-cc".to_string();
+    base.linker = Some("aarch64-unknown-cloudabi-cc".to_string());
 
     Ok(Target {
         llvm_target: "aarch64-unknown-cloudabi".to_string(),
diff --git a/src/librustc_back/target/armv7_unknown_cloudabi_eabihf.rs b/src/librustc_back/target/armv7_unknown_cloudabi_eabihf.rs
index faa2c4fdceb..fa66a35abbf 100644
--- a/src/librustc_back/target/armv7_unknown_cloudabi_eabihf.rs
+++ b/src/librustc_back/target/armv7_unknown_cloudabi_eabihf.rs
@@ -17,7 +17,7 @@ pub fn target() -> TargetResult {
     base.max_atomic_width = Some(64);
     base.features = "+v7,+vfp3,+neon".to_string();
     base.abi_blacklist = super::arm_base::abi_blacklist();
-    base.linker = "armv7-unknown-cloudabi-eabihf-cc".to_string();
+    base.linker = Some("armv7-unknown-cloudabi-eabihf-cc".to_string());
 
     Ok(Target {
         llvm_target: "armv7-unknown-cloudabi-eabihf".to_string(),
diff --git a/src/librustc_back/target/asmjs_unknown_emscripten.rs b/src/librustc_back/target/asmjs_unknown_emscripten.rs
index 5d9f0f6012b..f114926740a 100644
--- a/src/librustc_back/target/asmjs_unknown_emscripten.rs
+++ b/src/librustc_back/target/asmjs_unknown_emscripten.rs
@@ -10,7 +10,6 @@
 
 use LinkerFlavor;
 use super::{LinkArgs, Target, TargetOptions};
-use super::emscripten_base::{cmd};
 
 pub fn target() -> Result<Target, String> {
     let mut args = LinkArgs::new();
@@ -19,8 +18,6 @@ pub fn target() -> Result<Target, String> {
                      "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string()]);
 
     let opts = TargetOptions {
-        linker: cmd("emcc"),
-
         dynamic_linking: false,
         executables: true,
         exe_suffix: ".js".to_string(),
diff --git a/src/librustc_back/target/emscripten_base.rs b/src/librustc_back/target/emscripten_base.rs
deleted file mode 100644
index bacada3f5ab..00000000000
--- a/src/librustc_back/target/emscripten_base.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-// Copyright 2014-2015 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.
-
-pub fn cmd(name: &str) -> String {
-    if cfg!(windows) {
-        format!("{}.bat", name)
-    } else {
-        name.to_string()
-    }
-}
diff --git a/src/librustc_back/target/haiku_base.rs b/src/librustc_back/target/haiku_base.rs
index 112f424f7a8..a1ccb632cab 100644
--- a/src/librustc_back/target/haiku_base.rs
+++ b/src/librustc_back/target/haiku_base.rs
@@ -13,7 +13,6 @@ use std::default::Default;
 
 pub fn opts() -> TargetOptions {
     TargetOptions {
-        linker: "cc".to_string(),
         dynamic_linking: true,
         executables: true,
         has_rpath: false,
diff --git a/src/librustc_back/target/i686_unknown_cloudabi.rs b/src/librustc_back/target/i686_unknown_cloudabi.rs
index e244f443d3e..69c3b298cab 100644
--- a/src/librustc_back/target/i686_unknown_cloudabi.rs
+++ b/src/librustc_back/target/i686_unknown_cloudabi.rs
@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
     let mut base = super::cloudabi_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = Some(64);
-    base.linker = "i686-unknown-cloudabi-cc".to_string();
+    base.linker = Some("i686-unknown-cloudabi-cc".to_string());
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m32".to_string());
     base.stack_probes = true;
 
diff --git a/src/librustc_back/target/l4re_base.rs b/src/librustc_back/target/l4re_base.rs
index 31d428d2668..7cb7f8d613d 100644
--- a/src/librustc_back/target/l4re_base.rs
+++ b/src/librustc_back/target/l4re_base.rs
@@ -73,7 +73,6 @@ pub fn opts() -> Result<TargetOptions, String> {
         has_elf_tls: false,
         exe_allocation_crate: None,
         panic_strategy: PanicStrategy::Abort,
-        linker: "ld".to_string(),
         pre_link_args,
         post_link_args,
         target_family: Some("unix".to_string()),
diff --git a/src/librustc_back/target/mod.rs b/src/librustc_back/target/mod.rs
index be69127d8f2..0a3e1826f3a 100644
--- a/src/librustc_back/target/mod.rs
+++ b/src/librustc_back/target/mod.rs
@@ -58,7 +58,6 @@ mod arm_base;
 mod bitrig_base;
 mod cloudabi_base;
 mod dragonfly_base;
-mod emscripten_base;
 mod freebsd_base;
 mod haiku_base;
 mod linux_base;
@@ -279,8 +278,8 @@ pub struct TargetOptions {
     /// Whether the target is built-in or loaded from a custom target specification.
     pub is_builtin: bool,
 
-    /// Linker to invoke. Defaults to "cc".
-    pub linker: String,
+    /// Linker to invoke
+    pub linker: Option<String>,
 
     /// Linker arguments that are unconditionally passed *before* any
     /// user-defined libraries.
@@ -482,7 +481,7 @@ impl Default for TargetOptions {
     fn default() -> TargetOptions {
         TargetOptions {
             is_builtin: false,
-            linker: option_env!("CFG_DEFAULT_LINKER").unwrap_or("cc").to_string(),
+            linker: option_env!("CFG_DEFAULT_LINKER").map(|s| s.to_string()),
             pre_link_args: LinkArgs::new(),
             post_link_args: LinkArgs::new(),
             asm_args: Vec::new(),
@@ -732,7 +731,7 @@ impl Target {
         }
 
         key!(is_builtin, bool);
-        key!(linker);
+        key!(linker, optional);
         key!(pre_link_args, link_args);
         key!(pre_link_objects_exe, list);
         key!(pre_link_objects_dll, list);
diff --git a/src/librustc_back/target/msp430_none_elf.rs b/src/librustc_back/target/msp430_none_elf.rs
index 966df897f01..d0f512ae47c 100644
--- a/src/librustc_back/target/msp430_none_elf.rs
+++ b/src/librustc_back/target/msp430_none_elf.rs
@@ -32,7 +32,7 @@ pub fn target() -> TargetResult {
             // to gcc to get object files. For this reason we have a hard
             // dependency on this specific gcc.
             asm_args: vec!["-mcpu=msp430".to_string()],
-            linker: "msp430-elf-gcc".to_string(),
+            linker: Some("msp430-elf-gcc".to_string()),
             no_integrated_as: true,
 
             // There are no atomic instructions available in the MSP430
diff --git a/src/librustc_back/target/thumb_base.rs b/src/librustc_back/target/thumb_base.rs
index 6bb496649a8..6a8f52f5093 100644
--- a/src/librustc_back/target/thumb_base.rs
+++ b/src/librustc_back/target/thumb_base.rs
@@ -45,7 +45,7 @@ pub fn opts() -> TargetOptions {
         executables: true,
         // In 99%+ of cases, we want to use the `arm-none-eabi-gcc` compiler (there aren't many
         // options around)
-        linker: "arm-none-eabi-gcc".to_string(),
+        linker: Some("arm-none-eabi-gcc".to_string()),
         // Because these devices have very little resources having an unwinder is too onerous so we
         // default to "abort" because the "unwind" strategy is very rare.
         panic_strategy: PanicStrategy::Abort,
diff --git a/src/librustc_back/target/wasm32_experimental_emscripten.rs b/src/librustc_back/target/wasm32_experimental_emscripten.rs
index a261c982b3f..13dee3a5768 100644
--- a/src/librustc_back/target/wasm32_experimental_emscripten.rs
+++ b/src/librustc_back/target/wasm32_experimental_emscripten.rs
@@ -10,7 +10,6 @@
 
 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();
@@ -24,8 +23,6 @@ pub fn target() -> Result<Target, String> {
                                "-g3".to_string()]);
 
     let opts = TargetOptions {
-        linker: cmd("emcc"),
-
         dynamic_linking: false,
         executables: true,
         // Today emcc emits two files - a .js file to bootstrap and
diff --git a/src/librustc_back/target/wasm32_unknown_emscripten.rs b/src/librustc_back/target/wasm32_unknown_emscripten.rs
index 4823541f226..2770e67e30a 100644
--- a/src/librustc_back/target/wasm32_unknown_emscripten.rs
+++ b/src/librustc_back/target/wasm32_unknown_emscripten.rs
@@ -10,7 +10,6 @@
 
 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();
@@ -21,8 +20,6 @@ pub fn target() -> Result<Target, String> {
                                "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string()]);
 
     let opts = TargetOptions {
-        linker: cmd("emcc"),
-
         dynamic_linking: false,
         executables: true,
         // Today emcc emits two files - a .js file to bootstrap and
diff --git a/src/librustc_back/target/wasm32_unknown_unknown.rs b/src/librustc_back/target/wasm32_unknown_unknown.rs
index c771762cfc8..1d84e137517 100644
--- a/src/librustc_back/target/wasm32_unknown_unknown.rs
+++ b/src/librustc_back/target/wasm32_unknown_unknown.rs
@@ -22,8 +22,6 @@ use super::{Target, TargetOptions, PanicStrategy};
 
 pub fn target() -> Result<Target, String> {
     let opts = TargetOptions {
-        linker: "lld".to_string(),
-
         // we allow dynamic linking, but only cdylibs. Basically we allow a
         // final library artifact that exports some symbols (a wasm module) but
         // we don't allow intermediate `dylib` crate types
diff --git a/src/librustc_back/target/windows_base.rs b/src/librustc_back/target/windows_base.rs
index 30038400f6c..05b6247c951 100644
--- a/src/librustc_back/target/windows_base.rs
+++ b/src/librustc_back/target/windows_base.rs
@@ -75,7 +75,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         // FIXME(#13846) this should be enabled for windows
         function_sections: false,
-        linker: "gcc".to_string(),
+        linker: Some("gcc".to_string()),
         dynamic_linking: true,
         executables: true,
         dll_prefix: "".to_string(),
diff --git a/src/librustc_back/target/windows_msvc_base.rs b/src/librustc_back/target/windows_msvc_base.rs
index e0bf36ee407..34aa17267f8 100644
--- a/src/librustc_back/target/windows_msvc_base.rs
+++ b/src/librustc_back/target/windows_msvc_base.rs
@@ -20,7 +20,6 @@ pub fn opts() -> TargetOptions {
 
     TargetOptions {
         function_sections: true,
-        linker: "link.exe".to_string(),
         dynamic_linking: true,
         executables: true,
         dll_prefix: "".to_string(),
diff --git a/src/librustc_back/target/x86_64_rumprun_netbsd.rs b/src/librustc_back/target/x86_64_rumprun_netbsd.rs
index 18f6380b6ee..3158665a2e2 100644
--- a/src/librustc_back/target/x86_64_rumprun_netbsd.rs
+++ b/src/librustc_back/target/x86_64_rumprun_netbsd.rs
@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
     let mut base = super::netbsd_base::opts();
     base.cpu = "x86-64".to_string();
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m64".to_string());
-    base.linker = "x86_64-rumprun-netbsd-gcc".to_string();
+    base.linker = Some("x86_64-rumprun-netbsd-gcc".to_string());
     base.max_atomic_width = Some(64);
 
     base.dynamic_linking = false;
diff --git a/src/librustc_back/target/x86_64_unknown_cloudabi.rs b/src/librustc_back/target/x86_64_unknown_cloudabi.rs
index 1ce3c6444f1..d1a9cb1cd7e 100644
--- a/src/librustc_back/target/x86_64_unknown_cloudabi.rs
+++ b/src/librustc_back/target/x86_64_unknown_cloudabi.rs
@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
     let mut base = super::cloudabi_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = Some(64);
-    base.linker = "x86_64-unknown-cloudabi-cc".to_string();
+    base.linker = Some("x86_64-unknown-cloudabi-cc".to_string());
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m64".to_string());
     base.stack_probes = true;
 
diff --git a/src/librustc_trans/Cargo.toml b/src/librustc_trans/Cargo.toml
index 4b9c93088a5..805d2086ee4 100644
--- a/src/librustc_trans/Cargo.toml
+++ b/src/librustc_trans/Cargo.toml
@@ -11,6 +11,7 @@ test = false
 
 [dependencies]
 bitflags = "1.0"
+cc = "1.0.1"
 flate2 = "1.0"
 jobserver = "0.1.5"
 libc = "0.2"
@@ -34,9 +35,6 @@ syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 tempdir = "0.3"
 
-[target."cfg(windows)".dependencies]
-cc = "1.0.1"
-
 [features]
 # Used to communicate the feature to `rustc_back` in the same manner that the
 # `rustc` driver script communicate this.
diff --git a/src/librustc_trans/back/command.rs b/src/librustc_trans/back/command.rs
index e5e0a4e3ba0..ecf7bf5036e 100644
--- a/src/librustc_trans/back/command.rs
+++ b/src/librustc_trans/back/command.rs
@@ -81,17 +81,6 @@ impl Command {
         self
     }
 
-    pub fn envs<I, K, V>(&mut self, envs: I) -> &mut Command
-        where I: IntoIterator<Item=(K, V)>,
-              K: AsRef<OsStr>,
-              V: AsRef<OsStr>
-    {
-        for (key, value) in envs {
-            self._env(key.as_ref(), value.as_ref());
-        }
-        self
-    }
-
     fn _env(&mut self, key: &OsStr, value: &OsStr) {
         self.env.push((key.to_owned(), value.to_owned()));
     }
@@ -112,6 +101,9 @@ impl Command {
                 let mut c = process::Command::new(p);
                 c.arg("-flavor").arg(match flavor {
                     LldFlavor::Wasm => "wasm",
+                    LldFlavor::Ld => "gnu",
+                    LldFlavor::Link => "link",
+                    LldFlavor::Ld64 => "darwin",
                 });
                 c
             }
diff --git a/src/librustc_trans/back/link.rs b/src/librustc_trans/back/link.rs
index c134203a773..636b3984117 100644
--- a/src/librustc_trans/back/link.rs
+++ b/src/librustc_trans/back/link.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use cc::windows_registry;
 use super::archive::{ArchiveBuilder, ArchiveConfig};
 use super::bytecode::RLIB_BYTECODE_EXTENSION;
 use super::linker::Linker;
@@ -35,7 +36,6 @@ use llvm;
 use std::ascii;
 use std::char;
 use std::env;
-use std::ffi::OsString;
 use std::fmt;
 use std::fs;
 use std::io;
@@ -58,9 +58,7 @@ pub use rustc_trans_utils::link::{find_crate_name, filename_for_input, default_o
 // The third parameter is for env vars, used on windows to set up the
 // path for MSVC to find its DLLs, and gcc to find its bundled
 // toolchain
-pub fn get_linker(sess: &Session) -> (PathBuf, Command, Vec<(OsString, OsString)>) {
-    let envs = vec![("PATH".into(), command_path(sess))];
-
+pub fn get_linker(sess: &Session) -> (PathBuf, Command) {
     // If our linker looks like a batch script on Windows then to execute this
     // we'll need to spawn `cmd` explicitly. This is primarily done to handle
     // emscripten where the linker is `emcc.bat` and needs to be spawned as
@@ -75,60 +73,57 @@ pub fn get_linker(sess: &Session) -> (PathBuf, Command, Vec<(OsString, OsString)
                 return Command::bat_script(linker)
             }
         }
-        Command::new(linker)
-    };
-
-    if let Some(ref linker) = sess.opts.cg.linker {
-        (linker.clone(), cmd(linker), envs)
-    } else if sess.target.target.options.is_like_msvc {
-        let (cmd, envs) = msvc_link_exe_cmd(sess);
-        (PathBuf::from("link.exe"), cmd, envs)
-    } else if let LinkerFlavor::Lld(f) = sess.linker_flavor() {
-        let linker = PathBuf::from(&sess.target.target.options.linker);
-        let cmd = Command::lld(&linker, f);
-        (linker, cmd, envs)
-    } else {
-        let linker = PathBuf::from(&sess.target.target.options.linker);
-        let cmd = cmd(&linker);
-        (linker, cmd, envs)
-    }
-}
+        match sess.linker_flavor() {
+            LinkerFlavor::Lld(f) => Command::lld(linker, f),
+            _ => Command::new(linker),
 
-#[cfg(windows)]
-pub fn msvc_link_exe_cmd(sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
-    use cc::windows_registry;
+        }
+    };
 
-    let target = &sess.opts.target_triple;
-    let tool = windows_registry::find_tool(target, "link.exe");
+    let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple, "link.exe");
 
-    if let Some(tool) = tool {
-        let mut cmd = Command::new(tool.path());
-        cmd.args(tool.args());
-        for &(ref k, ref v) in tool.env() {
-            cmd.env(k, v);
-        }
-        let envs = tool.env().to_vec();
-        (cmd, envs)
-    } else {
-        debug!("Failed to locate linker.");
-        (Command::new("link.exe"), vec![])
-    }
-}
+    let linker_path = sess.opts.cg.linker.as_ref().map(|s| &**s)
+        .or(sess.target.target.options.linker.as_ref().map(|s| s.as_ref()))
+        .unwrap_or(match sess.linker_flavor() {
+            LinkerFlavor::Msvc => {
+                msvc_tool.as_ref().map(|t| t.path()).unwrap_or("link.exe".as_ref())
+            }
+            LinkerFlavor::Em if cfg!(windows) => "emcc.bat".as_ref(),
+            LinkerFlavor::Em => "emcc".as_ref(),
+            LinkerFlavor::Gcc => "cc".as_ref(),
+            LinkerFlavor::Ld => "ld".as_ref(),
+            LinkerFlavor::Lld(_) => "lld".as_ref(),
+        });
 
-#[cfg(not(windows))]
-pub fn msvc_link_exe_cmd(_sess: &Session) -> (Command, Vec<(OsString, OsString)>) {
-    (Command::new("link.exe"), vec![])
-}
+    let mut cmd = cmd(linker_path);
 
-fn command_path(sess: &Session) -> OsString {
     // The compiler's sysroot often has some bundled tools, so add it to the
     // PATH for the child.
     let mut new_path = sess.host_filesearch(PathKind::All)
                            .get_tools_search_paths();
-    if let Some(path) = env::var_os("PATH") {
-        new_path.extend(env::split_paths(&path));
+    let mut msvc_changed_path = false;
+    if sess.target.target.options.is_like_msvc {
+        if let Some(ref tool) = msvc_tool {
+            cmd.args(tool.args());
+            for &(ref k, ref v) in tool.env() {
+                if k == "PATH" {
+                    new_path.extend(env::split_paths(v));
+                    msvc_changed_path = true;
+                } else {
+                    cmd.env(k, v);
+                }
+            }
+        }
     }
-    env::join_paths(new_path).unwrap()
+
+    if !msvc_changed_path {
+        if let Some(path) = env::var_os("PATH") {
+            new_path.extend(env::split_paths(&path));
+        }
+    }
+    cmd.env("PATH", env::join_paths(new_path).unwrap());
+
+    (linker_path.to_path_buf(), cmd)
 }
 
 pub fn remove(sess: &Session, path: &Path) {
@@ -618,9 +613,7 @@ fn link_natively(sess: &Session,
     let flavor = sess.linker_flavor();
 
     // The invocations of cc share some flags across platforms
-    let (pname, mut cmd, envs) = get_linker(sess);
-    // This will set PATH on windows
-    cmd.envs(envs);
+    let (pname, mut cmd) = get_linker(sess);
 
     let root = sess.target_filesearch(PathKind::Native).get_lib_path();
     if let Some(args) = sess.target.target.options.pre_link_args.get(&flavor) {
diff --git a/src/librustc_trans/back/linker.rs b/src/librustc_trans/back/linker.rs
index a82270c5272..a3ff39a47a2 100644
--- a/src/librustc_trans/back/linker.rs
+++ b/src/librustc_trans/back/linker.rs
@@ -45,6 +45,7 @@ impl LinkerInfo {
                          cmd: Command,
                          sess: &'a Session) -> Box<Linker+'a> {
         match sess.linker_flavor() {
+            LinkerFlavor::Lld(LldFlavor::Link) |
             LinkerFlavor::Msvc => {
                 Box::new(MsvcLinker {
                     cmd,
@@ -68,6 +69,9 @@ impl LinkerInfo {
                     is_ld: false,
                 }) as Box<Linker>
             }
+
+            LinkerFlavor::Lld(LldFlavor::Ld) |
+            LinkerFlavor::Lld(LldFlavor::Ld64) |
             LinkerFlavor::Ld => {
                 Box::new(GccLinker {
                     cmd,
diff --git a/src/librustc_trans/back/write.rs b/src/librustc_trans/back/write.rs
index 1664aa9d0b3..78b26a37485 100644
--- a/src/librustc_trans/back/write.rs
+++ b/src/librustc_trans/back/write.rs
@@ -1369,7 +1369,7 @@ fn start_executing_work(tcx: TyCtxt,
 
     let assembler_cmd = if modules_config.no_integrated_as {
         // HACK: currently we use linker (gcc) as our assembler
-        let (name, mut cmd, _) = get_linker(sess);
+        let (name, mut cmd) = get_linker(sess);
         cmd.args(&sess.target.target.options.asm_args);
         Some(Arc::new(AssemblerCommand {
             name,
diff --git a/src/librustc_trans/lib.rs b/src/librustc_trans/lib.rs
index 51ad17fe205..0b8da10b78e 100644
--- a/src/librustc_trans/lib.rs
+++ b/src/librustc_trans/lib.rs
@@ -62,7 +62,6 @@ extern crate rustc_trans_utils;
 extern crate syntax_pos;
 extern crate rustc_errors as errors;
 extern crate serialize;
-#[cfg(windows)]
 extern crate cc; // Used to locate MSVC
 extern crate tempdir;