Always inline f16 and f128

Author: tgross35

compiler/rustc_mir_transform/src/cross_crate_inline.rs

@@ -50,6 +50,16 @@ fn cross_crate_inlinable(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
         _ => {}
     }
 
+    let sig = tcx.fn_sig(def_id).instantiate_identity();
+    for ty in sig.inputs().skip_binder().iter().chain(std::iter::once(&sig.output().skip_binder()))
+    {
+        // FIXME(f16_f128): in order to avoid crashes building `core`, always inline to skip
+        // codegen if the function is not used.
+        if ty == &tcx.types.f16 || ty == &tcx.types.f128 {
+            return true;
+        }
+    }
+
     // Don't do any inference when incremental compilation is enabled; the additional inlining that
     // inference permits also creates more work for small edits.
     if tcx.sess.opts.incremental.is_some() {

tests/codegen/float/f16-f128-inline.rs

@@ -0,0 +1,29 @@
+//! Ensure that functions using `f16` and `f128` are always inlined
+
+#![crate_type = "lib"]
+#![feature(f128)]
+#![feature(f16)]
+
+#[no_mangle]
+pub fn f16_arg(a: f16) {
+    // CHECK-NOT: f16_arg
+    todo!()
+}
+
+#[no_mangle]
+pub fn f16_ret() -> f16 {
+    // CHECK-NOT: f16_ret
+    todo!()
+}
+
+#[no_mangle]
+pub fn f128_arg(a: f128) {
+    // CHECK-NOT: f128_arg
+    todo!()
+}
+
+#[no_mangle]
+pub fn f128_ret() -> f128 {
+    // CHECK-NOT: f128_ret
+    todo!()
+}