vectorcall ABI: error if sse2 is not available

Author: RalfJung

compiler/rustc_monomorphize/messages.ftl

@@ -22,6 +22,20 @@ monomorphize_abi_error_unsupported_vector_type =
     *[false] defined
   } here
 
+monomorphize_abi_required_target_feature =
+  this function {$is_call ->
+    [true] call
+    *[false] definition
+  } uses ABI "{$abi}" which requires the `{$required_feature}` target feature, which is not enabled{$is_call ->
+    [true] {" "}in the caller
+    *[false] {""}
+  }
+  .label = function {$is_call ->
+    [true] called
+    *[false] defined
+  } here
+  .help = consider enabling it globally (`-C target-feature=+{$required_feature}`) or locally (`#[target_feature(enable="{$required_feature}")]`)
+
 monomorphize_couldnt_dump_mono_stats =
     unexpected error occurred while dumping monomorphization stats: {$error}
 

compiler/rustc_monomorphize/src/errors.rs

@@ -90,3 +90,16 @@ pub(crate) struct AbiErrorUnsupportedVectorType<'a> {
     /// Whether this is a problem at a call site or at a declaration.
     pub is_call: bool,
 }
+
+#[derive(Diagnostic)]
+#[diag(monomorphize_abi_required_target_feature)]
+#[help]
+pub(crate) struct AbiRequiredTargetFeature<'a> {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    pub required_feature: &'a str,
+    pub abi: &'a str,
+    /// Whether this is a problem at a call site or at a declaration.
+    pub is_call: bool,
+}

compiler/rustc_monomorphize/src/mono_checks/abi_check.rs

@@ -30,12 +30,12 @@ fn uses_vector_registers(mode: &PassMode, repr: &BackendRepr) -> bool {
 fn do_check_abi<'tcx>(
     tcx: TyCtxt<'tcx>,
     abi: &FnAbi<'tcx, Ty<'tcx>>,
-    target_feature_def: DefId,
+    def_id: DefId,
     is_call: bool,
     span: impl Fn() -> Span,
 ) {
     let feature_def = tcx.sess.target.features_for_correct_vector_abi();
-    let codegen_attrs = tcx.codegen_fn_attrs(target_feature_def);
+    let codegen_attrs = tcx.codegen_fn_attrs(def_id);
     let have_feature = |feat: Symbol| {
         tcx.sess.unstable_target_features.contains(&feat)
             || codegen_attrs.target_features.iter().any(|x| x.name == feat)
@@ -78,6 +78,15 @@ fn do_check_abi<'tcx>(
             }
         }
     }
+    // The `vectorcall` ABI is special in that it requires SSE2 no matter which types are being passed.
+    if abi.conv == Conv::X86VectorCall && !have_feature(sym::sse2) {
+        tcx.dcx().emit_err(errors::AbiRequiredTargetFeature {
+            span: span(),
+            required_feature: "sse2",
+            abi: "vectorcall",
+            is_call,
+        });
+    }
 }
 
 /// Checks that the ABI of a given instance of a function does not contain vector-passed arguments

tests/ui/abi/vectorcall-abi-checks.rs

@@ -0,0 +1,21 @@
+//@ add-core-stubs
+//@ compile-flags: --crate-type=rlib --target=i586-unknown-linux-gnu -C target-feature=-sse,-sse2
+//@ build-fail
+//@ ignore-pass (test emits codegen-time errors)
+//@ needs-llvm-components: x86
+#![feature(no_core, abi_vectorcall)]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
+
+#[no_mangle]
+pub extern "vectorcall" fn f() {
+    //~^ ABI "vectorcall" which requires the `sse2` target feature
+}
+
+#[no_mangle]
+pub fn call_site() {
+    f();
+    //~^ ABI "vectorcall" which requires the `sse2` target feature
+}

tests/ui/abi/vectorcall-abi-checks.stderr

@@ -0,0 +1,18 @@
+error: this function definition uses ABI "vectorcall" which requires the `sse2` target feature, which is not enabled
+  --> $DIR/vectorcall-abi-checks.rs:13:1
+   |
+LL | pub extern "vectorcall" fn f() {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ function defined here
+   |
+   = help: consider enabling it globally (`-C target-feature=+sse2`) or locally (`#[target_feature(enable="sse2")]`)
+
+error: this function call uses ABI "vectorcall" which requires the `sse2` target feature, which is not enabled in the caller
+  --> $DIR/vectorcall-abi-checks.rs:19:5
+   |
+LL |     f();
+   |     ^^^ function called here
+   |
+   = help: consider enabling it globally (`-C target-feature=+sse2`) or locally (`#[target_feature(enable="sse2")]`)
+
+error: aborting due to 2 previous errors
+