Merge from rustc

13 files changed, 166 insertions, 32 deletions

diff --git a/src/doc/edition-guide b/src/doc/edition-guide
-Subproject c7ebae25cb4801a31b6f05353f6d85bfa6feedd
+Subproject 1f07c242f8162a711a5ac5a4ea8fa7ec884ee7a
diff --git a/src/doc/embedded-book b/src/doc/embedded-book
-Subproject f40a8b420ec4b4505d9489965e261f1d5c28ba2
+Subproject ddbf1b4e2858fedb71b7c42eb15c4576517dc12
diff --git a/src/doc/reference b/src/doc/reference
-Subproject c64e52a3d306eac0129f3ad6c6d8806ab99ae2e
+Subproject 23ce619966541bf2c80d45fdfeecf3393e360a1
diff --git a/src/doc/rustc-dev-guide b/src/doc/rustc-dev-guide
-Subproject 07bc9ca9eb1cd6d9fbbf758c2753b748804a134
+Subproject 59d94ea75a0b157e148af14c73c2dd60efb7b60
diff --git a/src/doc/rustc/src/SUMMARY.md b/src/doc/rustc/src/SUMMARY.md
index 795908b32c0..18f76ac6fe0 100644
--- a/src/doc/rustc/src/SUMMARY.md
+++ b/src/doc/rustc/src/SUMMARY.md
@@ -66,9 +66,10 @@
     - [powerpc-unknown-openbsd](platform-support/powerpc-unknown-openbsd.md)
     - [powerpc-unknown-linux-muslspe](platform-support/powerpc-unknown-linux-muslspe.md)
     - [powerpc64-ibm-aix](platform-support/aix.md)
+    - [riscv32e*-unknown-none-elf](platform-support/riscv32e-unknown-none-elf.md)
+    - [riscv32i*-unknown-none-elf](platform-support/riscv32-unknown-none-elf.md)
     - [riscv32im-risc0-zkvm-elf](platform-support/riscv32im-risc0-zkvm-elf.md)
     - [riscv32imac-unknown-xous-elf](platform-support/riscv32imac-unknown-xous-elf.md)
-    - [riscv32*-unknown-none-elf](platform-support/riscv32-unknown-none-elf.md)
     - [riscv64gc-unknown-linux-gnu](platform-support/riscv64gc-unknown-linux-gnu.md)
     - [riscv64gc-unknown-linux-musl](platform-support/riscv64gc-unknown-linux-musl.md)
     - [sparc-unknown-none-elf](./platform-support/sparc-unknown-none-elf.md)
@@ -86,6 +87,7 @@
     - [wasm32-wasip2](platform-support/wasm32-wasip2.md)
     - [wasm32-unknown-emscripten](platform-support/wasm32-unknown-emscripten.md)
     - [wasm32-unknown-unknown](platform-support/wasm32-unknown-unknown.md)
+    - [wasm32v1-none](platform-support/wasm32v1-none.md)
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
     - [\*-win7-windows-msvc](platform-support/win7-windows-msvc.md)
     - [x86_64-fortanix-unknown-sgx](platform-support/x86_64-fortanix-unknown-sgx.md)
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index e9c73ef1c2d..04bb40d750c 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -100,7 +100,7 @@ target | notes
 [`riscv64gc-unknown-linux-gnu`](platform-support/riscv64gc-unknown-linux-gnu.md) | RISC-V Linux (kernel 4.20, glibc 2.29)
 [`riscv64gc-unknown-linux-musl`](platform-support/riscv64gc-unknown-linux-musl.md) | RISC-V Linux (kernel 4.20, musl 1.2.3)
 `s390x-unknown-linux-gnu` | S390x Linux (kernel 3.2, glibc 2.17)
-`x86_64-unknown-freebsd` | 64-bit FreeBSD (version 13.2)
+`x86_64-unknown-freebsd` | 64-bit FreeBSD
 `x86_64-unknown-illumos` | illumos
 `x86_64-unknown-linux-musl` | 64-bit Linux with musl 1.2.3
 [`x86_64-unknown-netbsd`](platform-support/netbsd.md) | NetBSD/amd64
@@ -166,7 +166,7 @@ target | std | notes
 `i586-unknown-linux-musl` | ✓ | 32-bit Linux w/o SSE, musl 1.2.3 [^x86_32-floats-x87]
 [`i686-linux-android`](platform-support/android.md) | ✓ | 32-bit x86 Android [^x86_32-floats-return-ABI]
 [`i686-pc-windows-gnullvm`](platform-support/pc-windows-gnullvm.md) | ✓ | 32-bit x86 MinGW (Windows 10+), LLVM ABI [^x86_32-floats-return-ABI]
-`i686-unknown-freebsd` | ✓ | 32-bit FreeBSD (version 13.2) [^x86_32-floats-return-ABI]
+`i686-unknown-freebsd` | ✓ | 32-bit FreeBSD [^x86_32-floats-return-ABI]
 `i686-unknown-linux-musl` | ✓ | 32-bit Linux with musl 1.2.3 [^x86_32-floats-return-ABI]
 [`i686-unknown-uefi`](platform-support/unknown-uefi.md) | ? | 32-bit UEFI
 [`loongarch64-unknown-none`](platform-support/loongarch-none.md) | * | LoongArch64 Bare-metal (LP64D ABI)
@@ -195,6 +195,7 @@ target | std | notes
 `wasm32-wasi` | ✓ | WebAssembly with WASI (undergoing a [rename to `wasm32-wasip1`][wasi-rename])
 [`wasm32-wasip1`](platform-support/wasm32-wasip1.md) | ✓ | WebAssembly with WASI
 [`wasm32-wasip1-threads`](platform-support/wasm32-wasip1-threads.md) | ✓ | WebAssembly with WASI Preview 1 and threads
+[`wasm32v1-none`](platform-support/wasm32v1-none.md) | * | WebAssembly limited to 1.0 features and no imports
 [`x86_64-apple-ios`](platform-support/apple-ios.md) | ✓ | 64-bit x86 iOS
 [`x86_64-apple-ios-macabi`](platform-support/apple-ios-macabi.md) | ✓ | Mac Catalyst on x86_64
 [`x86_64-fortanix-unknown-sgx`](platform-support/x86_64-fortanix-unknown-sgx.md) | ✓ | [Fortanix ABI] for 64-bit Intel SGX
@@ -257,7 +258,7 @@ target | std | host | notes
 [`aarch64-unknown-teeos`](platform-support/aarch64-unknown-teeos.md) | ? |  | ARM64 TEEOS |
 [`aarch64-unknown-nto-qnx700`](platform-support/nto-qnx.md) | ? |  | ARM64 QNX Neutrino 7.0 RTOS |
 [`aarch64-unknown-nto-qnx710`](platform-support/nto-qnx.md) | ✓ |  | ARM64 QNX Neutrino 7.1 RTOS |
-`aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD (version 13.2)
+`aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD
 [`aarch64-unknown-hermit`](platform-support/hermit.md) | ✓ |  | ARM64 Hermit
 `aarch64-unknown-illumos` | ✓ | ✓ | ARM64 illumos
 `aarch64-unknown-linux-gnu_ilp32` | ✓ | ✓ | ARM64 Linux (ILP32 ABI)
@@ -276,14 +277,14 @@ target | std | host | notes
 `armv4t-unknown-linux-gnueabi` | ? |  | Armv4T Linux
 [`armv5te-none-eabi`](platform-support/armv5te-none-eabi.md) | * |  | Bare Armv5TE
 `armv5te-unknown-linux-uclibceabi` | ? |  | Armv5TE Linux with uClibc
-`armv6-unknown-freebsd` | ✓ | ✓ | Armv6 FreeBSD (version 13.2)
+`armv6-unknown-freebsd` | ✓ | ✓ | Armv6 FreeBSD
 [`armv6-unknown-netbsd-eabihf`](platform-support/netbsd.md) | ✓ | ✓ | Armv6 NetBSD w/hard-float
 [`armv6k-nintendo-3ds`](platform-support/armv6k-nintendo-3ds.md) | ? |  | Armv6k Nintendo 3DS, Horizon (Requires devkitARM toolchain)
 [`armv7-rtems-eabihf`](platform-support/armv7-rtems-eabihf.md) | ? |  | RTEMS OS for ARM BSPs
 [`armv7-sony-vita-newlibeabihf`](platform-support/armv7-sony-vita-newlibeabihf.md) | ✓ |  | Armv7-A Cortex-A9 Sony PlayStation Vita (requires VITASDK toolchain)
 [`armv7-unknown-linux-uclibceabi`](platform-support/armv7-unknown-linux-uclibceabi.md) | ✓ | ✓ | Armv7-A Linux with uClibc, softfloat
 [`armv7-unknown-linux-uclibceabihf`](platform-support/armv7-unknown-linux-uclibceabihf.md) | ✓ | ? | Armv7-A Linux with uClibc, hardfloat
-`armv7-unknown-freebsd` | ✓ | ✓ | Armv7-A FreeBSD (version 13.2)
+`armv7-unknown-freebsd` | ✓ | ✓ | Armv7-A FreeBSD
 [`armv7-unknown-netbsd-eabihf`](platform-support/netbsd.md) | ✓ | ✓ | Armv7-A NetBSD w/hard-float
 [`armv7-unknown-trusty`](platform-support/trusty.md) | ? |  |
 [`armv7-wrs-vxworks-eabihf`](platform-support/vxworks.md) | ✓ |  | Armv7-A for VxWorks
@@ -342,9 +343,9 @@ target | std | host | notes
 [`powerpc-unknown-openbsd`](platform-support/powerpc-unknown-openbsd.md) | * |  |
 [`powerpc-wrs-vxworks-spe`](platform-support/vxworks.md) | ✓ |  |
 [`powerpc-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
-`powerpc64-unknown-freebsd` | ✓ | ✓ | PPC64 FreeBSD (ELFv1 and ELFv2, version 13.2)
-`powerpc64le-unknown-freebsd` |   |   | PPC64LE FreeBSD (version 13.2)
-`powerpc-unknown-freebsd` |   |   | PowerPC FreeBSD (version 13.2)
+`powerpc64-unknown-freebsd` | ✓ | ✓ | PPC64 FreeBSD (ELFv1 and ELFv2)
+`powerpc64le-unknown-freebsd` |   |   | PPC64LE FreeBSD
+`powerpc-unknown-freebsd` |   |   | PowerPC FreeBSD
 `powerpc64-unknown-linux-musl` | ? |  | 64-bit PowerPC Linux with musl 1.2.3
 [`powerpc64-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
 `powerpc64le-unknown-linux-musl` | ? |  | 64-bit PowerPC Linux with musl 1.2.3, Little Endian
@@ -360,7 +361,7 @@ target | std | host | notes
 [`riscv32imafc-esp-espidf`](platform-support/esp-idf.md) | ✓ |  | RISC-V ESP-IDF
 [`riscv32-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
 [`riscv64gc-unknown-hermit`](platform-support/hermit.md) | ✓ |   | RISC-V Hermit
-`riscv64gc-unknown-freebsd` |   |   | RISC-V FreeBSD (version 13.2)
+`riscv64gc-unknown-freebsd` |   |   | RISC-V FreeBSD
 `riscv64gc-unknown-fuchsia` |   |   | RISC-V Fuchsia
 [`riscv64gc-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | RISC-V NetBSD
 [`riscv64gc-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | OpenBSD/riscv64
@@ -413,8 +414,8 @@ target | std | host | notes
 [`riscv32imafc-unknown-nuttx-elf`](platform-support/nuttx.md) | * |  | RISC-V 32bit with NuttX
 [`riscv64imac-unknown-nuttx-elf`](platform-support/nuttx.md) | * |  | RISC-V 64bit with NuttX
 [`riscv64gc-unknown-nuttx-elf`](platform-support/nuttx.md) | * |  | RISC-V 64bit with NuttX
-[`riscv32e-unknown-none-elf`](platform-support/riscv32-unknown-none-elf.md) | * |  | Bare RISC-V (RV32E ISA)
-[`riscv32em-unknown-none-elf`](platform-support/riscv32-unknown-none-elf.md) | * |  | Bare RISC-V (RV32EM ISA)
-[`riscv32emc-unknown-none-elf`](platform-support/riscv32-unknown-none-elf.md) | * |  | Bare RISC-V (RV32EMC ISA)
+[`riscv32e-unknown-none-elf`](platform-support/riscv32e-unknown-none-elf.md) | * |  | Bare RISC-V (RV32E ISA)
+[`riscv32em-unknown-none-elf`](platform-support/riscv32e-unknown-none-elf.md) | * |  | Bare RISC-V (RV32EM ISA)
+[`riscv32emc-unknown-none-elf`](platform-support/riscv32e-unknown-none-elf.md) | * |  | Bare RISC-V (RV32EMC ISA)
 
 [runs on NVIDIA GPUs]: https://github.com/japaric-archived/nvptx#targets
diff --git a/src/doc/rustc/src/platform-support/fuchsia.md b/src/doc/rustc/src/platform-support/fuchsia.md
index 5643c6a0188..0622f4dd564 100644
--- a/src/doc/rustc/src/platform-support/fuchsia.md
+++ b/src/doc/rustc/src/platform-support/fuchsia.md
@@ -525,14 +525,6 @@ ${SDK_PATH}/tools/${ARCH}/ffx repository publish \
     pkg/repo
 ```
 
-Then we can add the repository to `ffx`'s package server as `hello-fuchsia` using:
-
-```sh
-${SDK_PATH}/tools/${ARCH}/ffx repository add-from-pm \
-    --repository hello-fuchsia \
-    pkg/repo
-```
-
 ## Running a Fuchsia component on an emulator
 
 At this point, we are ready to run our Fuchsia
@@ -590,7 +582,8 @@ Now, start a package repository server to serve our
 package to the emulator:
 
 ```sh
-${SDK_PATH}/tools/${ARCH}/ffx repository server start
+${SDK_PATH}/tools/${ARCH}/ffx repository server start \
+    --background --repository hello-fuchsia --repo-path pkg-repo
 ```
 
 Once the repository server is up and running, register it with the target Fuchsia system running in the emulator:
diff --git a/src/doc/rustc/src/platform-support/nuttx.md b/src/doc/rustc/src/platform-support/nuttx.md
index cbbede45f52..433a092aab2 100644
--- a/src/doc/rustc/src/platform-support/nuttx.md
+++ b/src/doc/rustc/src/platform-support/nuttx.md
@@ -35,7 +35,7 @@ The following target names are defined:
 
 ## Building the target
 
-The target can be built by enabled in the `rustc` build:
+The target can be built by enabling it in the `rustc` build:
 
 ```toml
 [build]
diff --git a/src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md b/src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md
index 48a8df0c4a8..73264aba858 100644
--- a/src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md
+++ b/src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md
@@ -132,10 +132,20 @@ As of the time of this writing the proposals that are enabled by default (the
 
 If you're compiling WebAssembly code for an engine that does not support a
 feature in LLVM's default feature set then the feature must be disabled at
-compile time. Note, though, that enabled features may be used in the standard
-library or precompiled libraries shipped via rustup. This means that not only
-does your own code need to be compiled with the correct set of flags but the
-Rust standard library additionally must be recompiled.
+compile time. There are two approaches to choose from:
+
+  - If you are targeting a feature set no smaller than the W3C WebAssembly Core
+    1.0 recommendation -- which is equivalent to the WebAssembly MVP plus the
+    `mutable-globals` feature -- and you are building `no_std`, then you can
+    simply use the [`wasm32v1-none` target](./wasm32v1-none.md) instead of
+    `wasm32-unknown-unknown`, which uses only those minimal features and
+    includes a core and alloc library built with only those minimal features.
+
+  - Otherwise -- if you need std, or if you need to target the ultra-minimal
+    "MVP" feature set, excluding `mutable-globals` -- you will need to manually
+    specify `-Ctarget-cpu=mvp` and also rebuild the stdlib using that target to
+    ensure no features are used in the stdlib. This in turn requires use of a
+    nightly compiler.
 
 Compiling all code for the initial release of WebAssembly looks like:
 
@@ -150,9 +160,9 @@ then used to recompile the standard library in addition to your own code. This
 will produce a binary that uses only the original WebAssembly features by
 default and no proposals since its inception.
 
-To enable individual features it can be done with `-Ctarget-feature=+foo`.
-Available features for Rust code itself are documented in the [reference] and
-can also be found through:
+To enable individual features on either this target or `wasm32v1-none`, pass
+arguments of the form `-Ctarget-feature=+foo`.  Available features for Rust code
+itself are documented in the [reference] and can also be found through:
 
 ```sh
 $ rustc -Ctarget-feature=help --target wasm32-unknown-unknown
diff --git a/src/doc/rustc/src/platform-support/wasm32v1-none.md b/src/doc/rustc/src/platform-support/wasm32v1-none.md
new file mode 100644
index 00000000000..46f89c20113
--- /dev/null
+++ b/src/doc/rustc/src/platform-support/wasm32v1-none.md
@@ -0,0 +1,109 @@
+# `wasm32v1-none`
+
+**Tier: 2**
+
+The `wasm32v1-none` target is a WebAssembly compilation target that:
+
+- Imports nothing from its host environment
+- Enables no proposals / features past the [W3C WebAssembly Core 1.0 spec]
+
+[W3C WebAssembly Core 1.0 spec]: https://www.w3.org/TR/wasm-core-1/
+
+The target is very similar to [`wasm32-unknown-unknown`](./wasm32-unknown-unknown.md) and similarly uses LLVM's `wasm32-unknown-unknown` backend target. It contains only three minor differences:
+
+* Setting the `target-cpu` to `mvp` rather than the default `generic`. Requesting `mvp` disables _all_ WebAssembly proposals / LLVM target feature flags.
+* Enabling the [Import/Export of Mutable Globals] proposal (i.e. the `+mutable-globals` LLVM target feature flag)
+* Not compiling the `std` library at all, rather than compiling it with stubs.
+
+[Import/Export of Mutable Globals]: https://github.com/WebAssembly/mutable-global
+
+## Target maintainers
+
+- Alex Crichton, https://github.com/alexcrichton
+- Graydon Hoare, https://github.com/graydon
+
+## Requirements
+
+This target is cross-compiled. It does not support `std`, only `core` and `alloc`. Since it imports nothing from its environment, any `std` parts that use OS facilities would be stubbed out with functions-that-fail anyways, and the experience of working with the stub `std` in the `wasm32-unknown-unknown` target was deemed not something worth repeating here.
+
+Everything else about this target's requirements, building, usage and testing is the same as what's described in the [`wasm32-unknown-unknown` document](./wasm32-unknown-unknown.md), just using the target string `wasm32v1-none` in place of `wasm32-unknown-unknown`.
+
+## Conditionally compiling code
+
+It's recommended to conditionally compile code for this target with:
+
+```text
+#[cfg(all(target_family = "wasm", target_os = "none"))]
+```
+
+Note that there is no way to tell via `#[cfg]` whether code will be running on
+the web or not.
+
+## Enabled WebAssembly features
+
+As noted above, _no WebAssembly proposals past 1.0_ are enabled on this target by default. Indeed, the entire point of this target is to have a way to compile for a stable "no post-1.0 proposals" subset of WebAssembly _on stable Rust_.
+
+The [W3C WebAssembly Core 1.0 spec] was adopted as a W3C recommendation in December 2019, and includes exactly one "post-MVP" proposal: the [Import/Export of Mutable Globals] proposal.
+
+All subsequent proposals are _disabled_ on this target by default, though they can be individually enabled by passing LLVM target-feature flags.
+
+For reference sake, the set of proposals that LLVM supports at the time of writing, that this target _does not enable by default_, are listed here along with their LLVM target-feature flags:
+
+* Post-1.0 proposals (integrated into the WebAssembly core 2.0 spec):
+    * [Bulk memory] - `+bulk-memory`
+    * [Sign-extending operations] - `+sign-ext`
+    * [Non-trapping fp-to-int operations] - `+nontrapping-fptoint`
+    * [Multi-value] - `+multivalue`
+    * [Reference Types] - `+reference-types`
+    * [Fixed-width SIMD] - `+simd128`
+* Post-2.0 proposals:
+    * [Threads] (supported by atomics) - `+atomics`
+    * [Exception handling]  - `+exception-handling`
+    * [Extended Constant Expressions]  - `+extended-const`
+    * [Half Precision]  - `+half-precision`
+    * [Multiple memories]- `+multimemory`
+    * [Relaxed SIMD] - `+relaxed-simd`
+    * [Tail call] - `+tail-call`
+
+[Bulk memory]: https://github.com/WebAssembly/spec/blob/main/proposals/bulk-memory-operations/Overview.md
+[Sign-extending operations]: https://github.com/WebAssembly/spec/blob/main/proposals/sign-extension-ops/Overview.md
+[Non-trapping fp-to-int operations]: https://github.com/WebAssembly/spec/blob/main/proposals/nontrapping-float-to-int-conversion/Overview.md
+[Multi-value]: https://github.com/WebAssembly/spec/blob/main/proposals/multi-value/Overview.md
+[Reference Types]: https://github.com/WebAssembly/spec/blob/main/proposals/reference-types/Overview.md
+[Fixed-width SIMD]: https://github.com/WebAssembly/spec/blob/main/proposals/simd/SIMD.md
+[Threads]: https://github.com/webassembly/threads
+[Exception handling]: https://github.com/WebAssembly/exception-handling
+[Extended Constant Expressions]: https://github.com/WebAssembly/extended-const
+[Half Precision]: https://github.com/WebAssembly/half-precision
+[Multiple memories]: https://github.com/WebAssembly/multi-memory
+[Relaxed SIMD]: https://github.com/WebAssembly/relaxed-simd
+[Tail call]: https://github.com/WebAssembly/tail-call
+
+Additional proposals in the future are, of course, also not enabled by default.
+
+## Rationale relative to wasm32-unknown-unknown
+
+As noted in the [`wasm32-unknown-unknown` document](./wasm32-unknown-unknown.md), it is possible to compile with `--target wasm32-unknown-unknown` and disable all WebAssembly proposals "by hand", by passing `-Ctarget-cpu=mvp`. Furthermore one can enable proposals one by one by passing LLVM target feature flags, such as `-Ctarget-feature=+mutable-globals`.
+
+Is it therefore reasonable to wonder what the difference is between building with this:
+
+```sh
+$ rustc --target wasm32-unknown-unknown -Ctarget-cpu=mvp -Ctarget-feature=+mutable-globals
+```
+
+and building with this:
+
+```sh
+$ rustc --target wasm32v1-none
+```
+
+The difference is in how the `core` and `alloc` crates are compiled for distribution with the toolchain, and whether it works on _stable_ Rust toolchains or requires _nightly_ ones. Again referring back to the [`wasm32-unknown-unknown` document](./wasm32-unknown-unknown.md), note that to disable all post-MVP proposals on that target one _actually_ has to compile with this:
+
+```sh
+$ export RUSTFLAGS="-Ctarget-cpu=mvp -Ctarget-feature=+mutable-globals"
+$ cargo +nightly build -Zbuild-std=panic_abort,std --target wasm32-unknown-unknown
+```
+
+Which not only rebuilds `std`, `core` and `alloc` (which is somewhat costly and annoying) but more importantly requires the use of nightly Rust toolchains (for the `-Zbuild-std` flag). This is very undesirable for the target audience, which consists of people targeting WebAssembly implementations that prioritize stability, simplicity and/or security over feature support.
+
+This `wasm32v1-none` target exists as an alternative option that works on stable Rust toolchains, without rebuilding the stdlib.
diff --git a/src/doc/rustc/src/symbol-mangling/v0.md b/src/doc/rustc/src/symbol-mangling/v0.md
index 6329e878c5c..109942518fc 100644
--- a/src/doc/rustc/src/symbol-mangling/v0.md
+++ b/src/doc/rustc/src/symbol-mangling/v0.md
@@ -1208,7 +1208,7 @@ The compiler has some latitude in how an entity is encoded as long as the symbol
 
 * Named functions, methods, and statics shall be represented by a *[path]* production.
 
-* Paths should be rooted at the inner-most entity that can act as a path root.
+* Paths should be rooted at the innermost entity that can act as a path root.
   Roots can be crate-ids, inherent impls, trait impls, and (for items within default methods) trait definitions.
 
 * The compiler is free to choose disambiguation indices and namespace tags from
diff --git a/src/doc/unstable-book/src/compiler-flags/regparm.md b/src/doc/unstable-book/src/compiler-flags/regparm.md
new file mode 100644
index 00000000000..8f311f091c0
--- /dev/null
+++ b/src/doc/unstable-book/src/compiler-flags/regparm.md
@@ -0,0 +1,20 @@
+# `regparm`
+
+The tracking issue for this feature is: https://github.com/rust-lang/rust/issues/131749.
+
+------------------------
+
+Option -Zregparm=N causes the compiler to pass N arguments
+in registers EAX, EDX, and ECX instead of on the stack for "C", "cdecl", and "stdcall" fn.
+It is UNSOUND to link together crates that use different values for this flag.
+It is only supported on `x86`.
+
+It is equivalent to [Clang]'s and [GCC]'s `-mregparm`.
+
+Supported values for this option are 0-3.
+
+[Clang]: https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mregparm
+[GCC]: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-regparm-function-attribute_002c-x86
+
+Implementation details:
+For eligible arguments, llvm `inreg` attribute is set.
diff --git a/src/doc/unstable-book/src/compiler-flags/sanitizer.md b/src/doc/unstable-book/src/compiler-flags/sanitizer.md
index 24940f0d6fb..4679acf0a6a 100644
--- a/src/doc/unstable-book/src/compiler-flags/sanitizer.md
+++ b/src/doc/unstable-book/src/compiler-flags/sanitizer.md
@@ -690,7 +690,6 @@ LeakSanitizer is run-time memory leak detector.
 
 LeakSanitizer is supported on the following targets:
 
-* `aarch64-apple-darwin`
 * `aarch64-unknown-linux-gnu`
 * `x86_64-apple-darwin`
 * `x86_64-unknown-linux-gnu`