macros: Always emit f16_enabled and f128_enabled attributes

Once we start addinf `f16` and `f128` routines, we will need to have
this cfg for almost all uses of `for_each_function`. Rather than needing
to specify this each time, always emit `#[cfg(f16_enabled)]` or
`#[cfg(f128_enabled)]` for each function that uses `f16` or `f128`,
respectively.

library/compiler-builtins/libm/crates/libm-test/src/lib.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(f16_enabled, feature(f16))]
+#![cfg_attr(f128_enabled, feature(f128))]
 #![allow(clippy::unusual_byte_groupings)] // sometimes we group by sign_exp_sig
 
 pub mod domain;

library/compiler-builtins/libm/crates/libm-test/src/mpfloat.rs

@@ -50,9 +50,11 @@ macro_rules! impl_mp_op {
     (
         fn_name: $fn_name:ident,
         RustFn: fn($_fty:ty,) -> $_ret:ty,
+        attrs: [$($attr:meta),*],
         fn_extra: $fn_name_normalized:expr,
     ) => {
         paste::paste! {
+            $(#[$attr])*
             impl MpOp for crate::op::$fn_name::Routine {
                 type MpTy = MpFloat;
 
@@ -72,9 +74,11 @@ macro_rules! impl_mp_op {
     (
         fn_name: $fn_name:ident,
         RustFn: fn($_fty:ty, $_fty2:ty,) -> $_ret:ty,
+        attrs: [$($attr:meta),*],
         fn_extra: $fn_name_normalized:expr,
     ) => {
         paste::paste! {
+            $(#[$attr])*
             impl MpOp for crate::op::$fn_name::Routine {
                 type MpTy = (MpFloat, MpFloat);
 
@@ -95,9 +99,11 @@ macro_rules! impl_mp_op {
     (
         fn_name: $fn_name:ident,
         RustFn: fn($_fty:ty, $_fty2:ty, $_fty3:ty,) -> $_ret:ty,
+        attrs: [$($attr:meta),*],
         fn_extra: $fn_name_normalized:expr,
     ) => {
         paste::paste! {
+            $(#[$attr])*
             impl MpOp for crate::op::$fn_name::Routine {
                 type MpTy = (MpFloat, MpFloat, MpFloat);
 

library/compiler-builtins/libm/crates/libm-test/src/op.rs

@@ -112,8 +112,11 @@ macro_rules! do_thing {
         RustFn: $RustFn:ty,
         RustArgs: $RustArgs:ty,
         RustRet: $RustRet:ty,
+        attrs: [$($attr:meta),*],
+
     ) => {
         paste::paste! {
+            $(#[$attr])*
             pub mod $fn_name {
                 use super::*;
                 pub struct Routine;