[llvm] [AArch64] fix copy from GPR32 to FPR16 (PR #176594)

[David Green via llvm-commits]

================
@@ -8,3 +9,28 @@ define void @test_asm() {
   call void asm sideeffect "mov x0, $0", "r"(i64 42)
   ret void
 }
+
+; regression test for https://github.com/llvm/llvm-project/issues/79822
+define i16 @test_16bit_reg(i16 %x) {
+; CHECK-LABEL: test_16bit_reg
+; CHECK: fmov s0, w0 
+; CHECK: fmov w0, s0 
+  %ret = call i16 asm "", "=&{h0},0"(i16 %x)
----------------
davemgreen wrote:

```suggestion
  %ret = call i16 asm "nop", "=&{h0},0"(i16 %x)
```
Will help make the test clearer

https://github.com/llvm/llvm-project/pull/176594