From 55769a5ca98452967deb66dc1043a45fe0b2ddba Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Thu, 3 Jun 2021 08:58:12 -0700
Subject: [PATCH] wasm: Make simd types passed via indirection again

This commit updates wasm target specs to use `simd_types_indirect: true`
again. Long ago this was added since wasm simd types were always
translated to `v128` under-the-hood in LLVM, meaning that it didn't
matter whether that target feature was enabled or not. Now, however,
`v128` is conditionally used in codegen depending on target features
enabled, meaning that it's possible to get linker errors about different
signatures in code that correctly uses simd types. The fix is the same
as for all other platforms, which is to pass the type indirectly.
---
 compiler/rustc_target/src/spec/wasm_base.rs |  6 ----
 src/test/ui/simd/wasm-simd-indirect.rs      | 33 +++++++++++++++++++++
 2 files changed, 33 insertions(+), 6 deletions(-)
 create mode 100644 src/test/ui/simd/wasm-simd-indirect.rs

diff --git a/compiler/rustc_target/src/spec/wasm_base.rs b/compiler/rustc_target/src/spec/wasm_base.rs
index 87e740de08e..6c897735194 100644
--- a/compiler/rustc_target/src/spec/wasm_base.rs
+++ b/compiler/rustc_target/src/spec/wasm_base.rs
@@ -103,12 +103,6 @@ pub fn options() -> TargetOptions {
         linker: Some("rust-lld".to_owned()),
         lld_flavor: LldFlavor::Wasm,
 
-        // No need for indirection here, simd types can always be passed by
-        // value as the whole module either has simd or not, which is different
-        // from x86 (for example) where programs can have functions that don't
-        // enable simd features.
-        simd_types_indirect: false,
-
         pre_link_args,
 
         crt_objects_fallback: Some(CrtObjectsFallback::Wasm),
diff --git a/src/test/ui/simd/wasm-simd-indirect.rs b/src/test/ui/simd/wasm-simd-indirect.rs
new file mode 100644
index 00000000000..deac593df43
--- /dev/null
+++ b/src/test/ui/simd/wasm-simd-indirect.rs
@@ -0,0 +1,33 @@
+// build-pass
+
+#![cfg_attr(target_arch = "wasm32", feature(wasm_simd, wasm_target_feature))]
+
+#[cfg(target_arch = "wasm32")]
+fn main() {
+    unsafe {
+        a::api_with_simd_feature();
+    }
+}
+
+#[cfg(target_arch = "wasm32")]
+mod a {
+    use std::arch::wasm32::*;
+
+    #[target_feature(enable = "simd128")]
+    pub unsafe fn api_with_simd_feature() {
+        crate::b::api_takes_v128(u64x2(0, 1));
+    }
+}
+
+#[cfg(target_arch = "wasm32")]
+mod b {
+    use std::arch::wasm32::*;
+
+    #[inline(never)]
+    pub fn api_takes_v128(a: v128) -> v128 {
+        a
+    }
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+fn main() {}