arm: only f32 and f64 are valid HFA bases

compiler/rustc_target/src/callconv/arm.rs

@@ -25,9 +25,9 @@ where
 
         let valid_unit = match unit.kind {
             RegKind::Integer => false,
-            RegKind::Float => true,
-            RegKind::PpcF128 => unreachable!(),
+            RegKind::Float => unit.size.bits() == 32 || unit.size.bits() == 64,
             RegKind::Vector { .. } => unit.size.bits() == 64 || unit.size.bits() == 128,
+            RegKind::PpcF128 => unreachable!(),
         };
 
         valid_unit.then_some(Uniform::consecutive(unit, size))

tests/codegen-llvm/arm-abi/homogeneous-aggregate.rs

@@ -11,7 +11,7 @@
 // Test that homogeneous aggregates are passed and returned with the correct ABI on 32-bit arm.
 
 #![feature(no_core, lang_items)]
-#![feature(arm_target_feature)]
+#![feature(arm_target_feature, f16, f128)]
 #![crate_type = "lib"]
 #![no_core]
 
@@ -151,6 +151,20 @@ pub extern "C" fn test_floats_5(a: Floats5) {
     hint::black_box(a);
 }
 
+// Only f32 and f64 qualify as an HFA base.
+
+// linux:   define void @test_f16([2 x i32] %0)
+#[unsafe(no_mangle)]
+pub extern "C" fn test_f16(a: [f16; 3]) {
+    hint::black_box(a);
+}
+
+// linux:   define void @test_f128([2 x i64] %0)
+#[unsafe(no_mangle)]
+pub extern "C" fn test_f128(a: [f128; 1]) {
+    hint::black_box(a);
+}
+
 // Just a big struct, note how watchOS passes it indirectly.
 #[repr(C)]
 pub struct Ints6 {