[clang] [compiler-rt] [llvm] [SystemZ] Add support for half (fp16) (PR #109164)

[Trevor Gross via llvm-commits]

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@@ -126,3 +138,23 @@ define void @f9(ptr %cptr, ptr %aptr, ptr %bptr) {
   store fp128 %c, ptr %cptr
   ret void
 }
+
+; Test f16 copies in which the sign comes from an f16.
+define half @f10(half %a, half %b) {
+; CHECK-LABEL: f10:
+; CHECK: brasl %r14, copysignh at PLT
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tgross35 wrote:

I think `abs` and `copysign` are generally libcall-free, so that would be preferable here if possible.

Not related with that change but as a note, I don't think the `h` suffix exists for `math.h` routines. C23 does specify sized suffixes however, so e.g. `copysignf16` is valid and is provided by both [LLVM's `libc`](https://github.com/llvm/llvm-project/blob/749535ba2808e133682074f712ac6829335f8875/libc/src/math/generic/copysignf16.cpp#L16) and [Rust's builtins](https://docs.rs/compiler_builtins/latest/compiler_builtins/math/full_availability/fn.copysignf16.html).

https://github.com/llvm/llvm-project/pull/109164