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.

7 files changed, 55 insertions, 164 deletions

diff --git a/src/librustc_target/abi/call/asmjs.rs b/src/librustc_target/abi/call/asmjs.rs
deleted file mode 100644
index 92c86372a86..00000000000
--- a/src/librustc_target/abi/call/asmjs.rs
+++ /dev/null
@@ -1,47 +0,0 @@
-use crate::abi::call::{FnType, ArgType, Uniform};
-use crate::abi::{HasDataLayout, LayoutOf, TyLayout, TyLayoutMethods};
-
-// Data layout: e-p:32:32-i64:64-v128:32:128-n32-S128
-
-// See the https://github.com/kripken/emscripten-fastcomp-clang repository.
-// The class `EmscriptenABIInfo` in `/lib/CodeGen/TargetInfo.cpp` contains the ABI definitions.
-
-fn classify_ret_ty<'a, Ty, C>(cx: &C, ret: &mut ArgType<'a, Ty>)
-    where Ty: TyLayoutMethods<'a, C> + Copy,
-          C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout
-{
-    if ret.layout.is_aggregate() {
-        if let Some(unit) = ret.layout.homogeneous_aggregate(cx).unit() {
-            let size = ret.layout.size;
-            if unit.size == size {
-                ret.cast_to(Uniform {
-                    unit,
-                    total: size
-                });
-                return;
-            }
-        }
-
-        ret.make_indirect();
-    }
-}
-
-fn classify_arg_ty<Ty>(arg: &mut ArgType<'_, Ty>) {
-    if arg.layout.is_aggregate() {
-        arg.make_indirect_byval();
-    }
-}
-
-pub fn compute_abi_info<'a, Ty, C>(cx: &C, fty: &mut FnType<'a, Ty>)
-    where Ty: TyLayoutMethods<'a, C> + Copy,
-          C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout
-{
-    if !fty.ret.is_ignore() {
-        classify_ret_ty(cx, &mut fty.ret);
-    }
-
-    for arg in &mut fty.args {
-        if arg.is_ignore() { continue; }
-        classify_arg_ty(arg);
-    }
-}
diff --git a/src/librustc_target/abi/call/mod.rs b/src/librustc_target/abi/call/mod.rs
index bc21113527e..c6853ebd019 100644
--- a/src/librustc_target/abi/call/mod.rs
+++ b/src/librustc_target/abi/call/mod.rs
@@ -5,7 +5,6 @@ use crate::spec::{self, HasTargetSpec};
 mod aarch64;
 mod amdgpu;
 mod arm;
-mod asmjs;
 mod hexagon;
 mod mips;
 mod mips64;
@@ -557,14 +556,6 @@ impl<'a, Ty> FnType<'a, Ty> {
             "powerpc" => powerpc::compute_abi_info(cx, self),
             "powerpc64" => powerpc64::compute_abi_info(cx, self),
             "s390x" => s390x::compute_abi_info(cx, self),
-            "asmjs" => asmjs::compute_abi_info(cx, self),
-            "wasm32" => {
-                if cx.target_spec().llvm_target.contains("emscripten") {
-                    asmjs::compute_abi_info(cx, self)
-                } else {
-                    wasm32::compute_abi_info(self)
-                }
-            }
             "msp430" => msp430::compute_abi_info(self),
             "sparc" => sparc::compute_abi_info(cx, self),
             "sparc64" => sparc64::compute_abi_info(cx, self),
@@ -573,6 +564,7 @@ impl<'a, Ty> FnType<'a, Ty> {
             "hexagon" => hexagon::compute_abi_info(self),
             "riscv32" => riscv::compute_abi_info(self, 32),
             "riscv64" => riscv::compute_abi_info(self, 64),
+            "wasm32" | "asmjs" => wasm32::compute_abi_info(cx, self),
             a => return Err(format!("unrecognized arch \"{}\" in target specification", a))
         }
 
diff --git a/src/librustc_target/abi/call/wasm32.rs b/src/librustc_target/abi/call/wasm32.rs
index 1fdcbb8e39b..698da2a3aaa 100644
--- a/src/librustc_target/abi/call/wasm32.rs
+++ b/src/librustc_target/abi/call/wasm32.rs
@@ -1,16 +1,38 @@
-use crate::abi::call::{FnType, ArgType};
+use crate::abi::call::{FnType, ArgType, Uniform};
+use crate::abi::{HasDataLayout, LayoutOf, TyLayout, TyLayoutMethods};
 
-fn classify_ret_ty<Ty>(ret: &mut ArgType<'_, Ty>) {
-    ret.extend_integer_width_to(32);
+fn classify_ret_ty<'a, Ty, C>(cx: &C, ret: &mut ArgType<'a, Ty>)
+    where Ty: TyLayoutMethods<'a, C> + Copy,
+          C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout
+{
+    if ret.layout.is_aggregate() {
+        if let Some(unit) = ret.layout.homogeneous_aggregate(cx).unit() {
+            let size = ret.layout.size;
+            if unit.size == size {
+                ret.cast_to(Uniform {
+                    unit,
+                    total: size
+                });
+                return;
+            }
+        }
+
+        ret.make_indirect();
+    }
 }
 
 fn classify_arg_ty<Ty>(arg: &mut ArgType<'_, Ty>) {
-    arg.extend_integer_width_to(32);
+    if arg.layout.is_aggregate() {
+        arg.make_indirect_byval();
+    }
 }
 
-pub fn compute_abi_info<Ty>(fty: &mut FnType<'_, Ty>) {
+pub fn compute_abi_info<'a, Ty, C>(cx: &C, fty: &mut FnType<'a, Ty>)
+    where Ty: TyLayoutMethods<'a, C> + Copy,
+          C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout
+{
     if !fty.ret.is_ignore() {
-        classify_ret_ty(&mut fty.ret);
+        classify_ret_ty(cx, &mut fty.ret);
     }
 
     for arg in &mut fty.args {
diff --git a/src/librustc_target/spec/asmjs_unknown_emscripten.rs b/src/librustc_target/spec/asmjs_unknown_emscripten.rs
index 6dc140cf160..e8f9c1f3d61 100644
--- a/src/librustc_target/spec/asmjs_unknown_emscripten.rs
+++ b/src/librustc_target/spec/asmjs_unknown_emscripten.rs
@@ -1,40 +1,10 @@
-use super::{LinkArgs, LinkerFlavor, Target, TargetOptions};
+use super::{LinkerFlavor, Target, wasm32_unknown_emscripten};
 
 pub fn target() -> Result<Target, String> {
-    let mut args = LinkArgs::new();
-    args.insert(LinkerFlavor::Em,
-                vec!["-s".to_string(),
-                     "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string(),
-                     "-s".to_string(),
-                     "ABORTING_MALLOC=0".to_string(),
-                     "-s".to_string(),
-                     "WASM=0".to_string()]);
-
-    let opts = TargetOptions {
-        dynamic_linking: false,
-        executables: true,
-        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: args,
-        target_family: Some("unix".to_string()),
-        codegen_backend: "emscripten".to_string(),
-        .. Default::default()
-    };
-    Ok(Target {
-        llvm_target: "asmjs-unknown-emscripten".to_string(),
-        target_endian: "little".to_string(),
-        target_pointer_width: "32".to_string(),
-        target_c_int_width: "32".to_string(),
-        target_os: "emscripten".to_string(),
-        target_env: String::new(),
-        target_vendor: "unknown".to_string(),
-        data_layout: "e-p:32:32-i64:64-v128:32:128-n32-S128".to_string(),
-        arch: "asmjs".to_string(),
-        linker_flavor: LinkerFlavor::Em,
-        options: opts,
-    })
+    let mut target = wasm32_unknown_emscripten::target()?;
+    target.options.post_link_args
+        .entry(LinkerFlavor::Em)
+        .or_default()
+        .extend(vec!["-s".to_string(), "WASM=0".to_string()]);
+    Ok(target)
 }
diff --git a/src/librustc_target/spec/mod.rs b/src/librustc_target/spec/mod.rs
index 25add0cc6a4..cf1a84dec97 100644
--- a/src/librustc_target/spec/mod.rs
+++ b/src/librustc_target/spec/mod.rs
@@ -462,7 +462,6 @@ supported_targets! {
     ("wasm32-unknown-emscripten", wasm32_unknown_emscripten),
     ("wasm32-unknown-unknown", wasm32_unknown_unknown),
     ("wasm32-wasi", wasm32_wasi),
-    ("wasm32-experimental-emscripten", wasm32_experimental_emscripten),
 
     ("thumbv6m-none-eabi", thumbv6m_none_eabi),
     ("thumbv7m-none-eabi", thumbv7m_none_eabi),
diff --git a/src/librustc_target/spec/wasm32_experimental_emscripten.rs b/src/librustc_target/spec/wasm32_experimental_emscripten.rs
deleted file mode 100644
index b802bee25ae..00000000000
--- a/src/librustc_target/spec/wasm32_experimental_emscripten.rs
+++ /dev/null
@@ -1,44 +0,0 @@
-use super::{LinkArgs, LinkerFlavor, Target, TargetOptions};
-
-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(),
-                               "ASSERTIONS=1".to_string(),
-                               "-s".to_string(),
-                               "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string(),
-                               "-g3".to_string()]);
-
-    let opts = TargetOptions {
-        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,
-        link_env: vec![("EMCC_WASM_BACKEND".to_string(), "1".to_string())],
-        allow_asm: false,
-        obj_is_bitcode: true,
-        is_like_emscripten: true,
-        max_atomic_width: Some(32),
-        post_link_args,
-        limit_rdylib_exports: false,
-        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_c_int_width: "32".to_string(),
-        target_os: "emscripten".to_string(),
-        target_env: String::new(),
-        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,
-    })
-}
diff --git a/src/librustc_target/spec/wasm32_unknown_emscripten.rs b/src/librustc_target/spec/wasm32_unknown_emscripten.rs
index e0df36884bf..90f3d2fc52d 100644
--- a/src/librustc_target/spec/wasm32_unknown_emscripten.rs
+++ b/src/librustc_target/spec/wasm32_unknown_emscripten.rs
@@ -1,45 +1,44 @@
-use super::{LinkArgs, LinkerFlavor, Target, TargetOptions};
+use super::wasm32_base;
+use super::{LinkArgs, LinkerFlavor, Target, TargetOptions, PanicStrategy};
 
 pub fn target() -> Result<Target, String> {
-    // FIXME(nikic) BINARYEN_TRAP_MODE=clamp is needed to avoid trapping in our
-    // -Zsaturating-float-casts implementation. This can be dropped if/when
-    // we have native fpto[su]i.sat intrinsics, or the implementation otherwise
-    // stops relying on non-trapping fpto[su]i.
     let mut post_link_args = LinkArgs::new();
     post_link_args.insert(LinkerFlavor::Em,
                           vec!["-s".to_string(),
-                               "BINARYEN=1".to_string(),
-                               "-s".to_string(),
                                "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string(),
                                "-s".to_string(),
-                               "BINARYEN_TRAP_MODE='clamp'".to_string()]);
+                               "ASSERTIONS=1".to_string(),
+                               "-s".to_string(),
+                               "DISABLE_EXCEPTION_CATCHING=1".to_string(),
+                               // FIXME(tlively): Enable this linker option once libc type errors
+                               // are resolved. See https://github.com/rust-lang/libc/pull/1478.
+                               // "-Wl,--fatal-warnings".to_string(),
+                               ]);
 
     let opts = TargetOptions {
-        dynamic_linking: false,
-        executables: true,
-        // Today emcc emits two files - a .js file to bootstrap and
-        // possibly interpret the wasm, and a .wasm file
+        // emcc emits two files - a .js file to instantiate the wasm and supply platform
+        // functionality, and a .wasm file.
         exe_suffix: ".js".to_string(),
+        linker: None,
         linker_is_gnu: true,
-        allow_asm: false,
-        obj_is_bitcode: true,
         is_like_emscripten: true,
-        max_atomic_width: Some(32),
+        // FIXME(tlively): Emscripten supports unwinding, but we would have to pass
+        // -enable-emscripten-cxx-exceptions to LLVM at codegen time and merge
+        // https://reviews.llvm.org/rG5c3cdef84b82464756bb571c13c31cf7773860c3to use it.
+        panic_strategy: PanicStrategy::Abort,
         post_link_args,
-        limit_rdylib_exports: false,
         target_family: Some("unix".to_string()),
-        codegen_backend: "emscripten".to_string(),
-        .. Default::default()
+        .. wasm32_base::options()
     };
     Ok(Target {
-        llvm_target: "asmjs-unknown-emscripten".to_string(),
+        llvm_target: "wasm32-unknown-emscripten".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
         target_os: "emscripten".to_string(),
         target_env: String::new(),
         target_vendor: "unknown".to_string(),
-        data_layout: "e-p:32:32-i64:64-v128:32:128-n32-S128".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,