From ddb16e2884cdfe3c1c7eff8a431d1165213f7842 Mon Sep 17 00:00:00 2001
From: Caleb Zulawski <caleb.zulawski@gmail.com>
Date: Sun, 21 May 2023 21:51:57 -0400
Subject: [PATCH 1/2] Fix #[inline(always)] on closures with target feature 1.1

---
 .../rustc_codegen_ssa/src/codegen_attrs.rs     | 17 ++++++++++++++++-
 .../issue-108655-inline-always-closure.rs      | 18 ++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/rfcs/rfc-2396-target_feature-11/issue-108655-inline-always-closure.rs

diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index d6c2301276262..1fa4b8783f6ff 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -493,7 +493,22 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     });
 
     // #73631: closures inherit `#[target_feature]` annotations
-    if tcx.features().target_feature_11 && tcx.is_closure(did.to_def_id()) {
+    //
+    // If this closure is marked `#[inline(always)]`, simply skip adding `#[target_feature]`.
+    //
+    // At this point, `unsafe` has already been checked and `#[target_feature]` only affects codegen.
+    // Emitting both `#[inline(always)]` and `#[target_feature]` can potentially result in an
+    // ICE, because LLVM errors when the function fails to be inlined due to a target feature
+    // mismatch.
+    //
+    // Using `#[inline(always)]` implies that this closure will most likely be inlined into
+    // its parent function, which effectively inherits the features anyway. Boxing this closure
+    // would result in this closure being compiled without the inherited target features, but this
+    // is probably a poor usage of `#[inline(always)]` and easily avoided by not using the attribute.
+    if tcx.features().target_feature_11
+        && tcx.is_closure(did.to_def_id())
+        && codegen_fn_attrs.inline != InlineAttr::Always
+    {
         let owner_id = tcx.parent(did.to_def_id());
         if tcx.def_kind(owner_id).has_codegen_attrs() {
             codegen_fn_attrs
diff --git a/tests/ui/rfcs/rfc-2396-target_feature-11/issue-108655-inline-always-closure.rs b/tests/ui/rfcs/rfc-2396-target_feature-11/issue-108655-inline-always-closure.rs
new file mode 100644
index 0000000000000..bc886400099a5
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2396-target_feature-11/issue-108655-inline-always-closure.rs
@@ -0,0 +1,18 @@
+// Tests #108655: closures in `#[target_feature]` functions can still be marked #[inline(always)]
+
+// check-pass
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+// only-x86_64
+
+#![feature(target_feature_11)]
+
+#[target_feature(enable = "avx")]
+pub unsafe fn test() {
+    ({
+        #[inline(always)]
+        move || {}
+    })();
+}
+
+fn main() {}

From cdb9de7e8bd70c7e3580ec28b37af879e555f45d Mon Sep 17 00:00:00 2001
From: Caleb Zulawski <caleb.zulawski@gmail.com>
Date: Sun, 16 Jul 2023 21:25:46 -0400
Subject: [PATCH 2/2] Add codegen test ensuring always-inline closures don't
 bypass target features

---
 .../codegen/target-feature-inline-closure.rs  | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 tests/codegen/target-feature-inline-closure.rs

diff --git a/tests/codegen/target-feature-inline-closure.rs b/tests/codegen/target-feature-inline-closure.rs
new file mode 100644
index 0000000000000..d075706173fd1
--- /dev/null
+++ b/tests/codegen/target-feature-inline-closure.rs
@@ -0,0 +1,33 @@
+// only-x86_64
+// compile-flags: -Copt-level=3
+
+#![crate_type = "lib"]
+#![feature(target_feature_11)]
+
+#[cfg(target_arch = "x86_64")]
+use std::arch::x86_64::*;
+
+// CHECK-LABEL: @with_avx
+#[no_mangle]
+#[cfg(target_arch = "x86_64")]
+#[target_feature(enable = "avx")]
+fn with_avx(x: __m256) -> __m256 {
+    // CHECK: fadd
+    let add = {
+        #[inline(always)]
+        |x, y| unsafe { _mm256_add_ps(x, y) }
+    };
+    add(x, x)
+}
+
+// CHECK-LABEL: @without_avx
+#[no_mangle]
+#[cfg(target_arch = "x86_64")]
+unsafe fn without_avx(x: __m256) -> __m256 {
+    // CHECK-NOT: fadd
+    let add = {
+        #[inline(always)]
+        |x, y| unsafe { _mm256_add_ps(x, y) }
+    };
+    add(x, x)
+}