1 files changed, 64 insertions, 0 deletions
diff --git a/compiler/rustc_target/src/spec/wasm32_unknown_unknown.rs b/compiler/rustc_target/src/spec/wasm32_unknown_unknown.rs
new file mode 100644
index 000000000..4e2927dd9
--- /dev/null
+++ b/compiler/rustc_target/src/spec/wasm32_unknown_unknown.rs
@@ -0,0 +1,64 @@
+//! A "bare wasm" target representing a WebAssembly output that makes zero
+//! assumptions about its environment.
+//!
+//! The `wasm32-unknown-unknown` target is intended to encapsulate use cases
+//! that do not rely on any imported functionality. The binaries generated are
+//! entirely self-contained by default when using the standard library. Although
+//! the standard library is available, most of it returns an error immediately
+//! (e.g. trying to create a TCP stream or something like that).
+//!
+//! This target is more or less managed by the Rust and WebAssembly Working
+//! Group nowadays at <https://github.com/rustwasm>.
+
+use super::wasm_base;
+use super::{LinkerFlavor, LldFlavor, Target};
+use crate::spec::abi::Abi;
+
+pub fn target() -> Target {
+    let mut options = wasm_base::options();
+    options.os = "unknown".into();
+    options.linker_flavor = LinkerFlavor::Lld(LldFlavor::Wasm);
+
+    // This is a default for backwards-compatibility with the original
+    // definition of this target oh-so-long-ago. Once the "wasm" ABI is
+    // stable and the wasm-bindgen project has switched to using it then there's
+    // no need for this and it can be removed.
+    //
+    // Currently this is the reason that this target's ABI is mismatched with
+    // clang's ABI. This means that, in the limit, you can't merge C and Rust
+    // code on this target due to this ABI mismatch.
+    options.default_adjusted_cabi = Some(Abi::Wasm);
+
+    options.add_pre_link_args(
+        LinkerFlavor::Lld(LldFlavor::Wasm),
+        &[
+            // For now this target just never has an entry symbol no matter the output
+            // type, so unconditionally pass this.
+            "--no-entry",
+            // Rust really needs a way for users to specify exports and imports in
+            // the source code. --export-dynamic isn't the right tool for this job,
+            // however it does have the side effect of automatically exporting a lot
+            // of symbols, which approximates what people want when compiling for
+            // wasm32-unknown-unknown expect, so use it for now.
+            "--export-dynamic",
+        ],
+    );
+    options.add_pre_link_args(
+        LinkerFlavor::Gcc,
+        &[
+            // Make sure clang uses LLD as its linker and is configured appropriately
+            // otherwise
+            "--target=wasm32-unknown-unknown",
+            "-Wl,--no-entry",
+            "-Wl,--export-dynamic",
+        ],
+    );
+
+    Target {
+        llvm_target: "wasm32-unknown-unknown".into(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20".into(),
+        arch: "wasm32".into(),
+        options,
+    }
+}