Rollup merge of rust-lang#136356 - pthariensflame:patch-1, r=tgross35

Docs for f16 and f128: correct a typo and add details

CC: rust-lang#116909; corrects and expands rust-lang#124750.

Author: jieyouxu

library/core/src/primitive_docs.rs

@@ -1160,9 +1160,9 @@ impl<T> (T,) {}
 ///
 /// Note that most common platforms will not support `f16` in hardware without enabling extra target
 /// features, with the notable exception of Apple Silicon (also known as M1, M2, etc.) processors.
-/// Hardware support on x86-64 requires the avx512fp16 feature, while RISC-V requires Zhf.
-/// Usually the fallback implementation will be to use `f32` hardware if it exists, and convert
-/// between `f16` and `f32` when performing math.
+/// Hardware support on x86/x86-64 requires the avx512fp16 or avx10.1 features, while RISC-V requires
+/// Zfh, and Arm/AArch64 requires FEAT_FP16.  Usually the fallback implementation will be to use `f32`
+/// hardware if it exists, and convert between `f16` and `f32` when performing math.
 ///
 /// *[See also the `std::f16::consts` module](crate::f16::consts).*
 ///
@@ -1344,10 +1344,10 @@ mod prim_f64 {}
 /// quad-precision values][wikipedia] for more information.
 ///
 /// Note that no platforms have hardware support for `f128` without enabling target specific features,
-/// as for all instruction set architectures `f128` is considered an optional feature.
-/// Only Power ISA ("PowerPC") and RISC-V specify it, and only certain microarchitectures
-/// actually implement it. For x86-64 and AArch64, ISA support is not even specified,
-/// so it will always be a software implementation significantly slower than `f64`.
+/// as for all instruction set architectures `f128` is considered an optional feature.  Only Power ISA
+/// ("PowerPC") and RISC-V (via the Q extension) specify it, and only certain microarchitectures
+/// actually implement it. For x86-64 and AArch64, ISA support is not even specified, so it will always
+/// be a software implementation significantly slower than `f64`.
 ///
 /// _Note: `f128` support is incomplete. Many platforms will not be able to link math functions. On
 /// x86 in particular, these functions do link but their results are always incorrect._