diff --git a/library/stdarch/crates/core_arch/src/mod.rs b/library/stdarch/crates/core_arch/src/mod.rs
index 12a5b086c695..f2cf11e479ce 100644
--- a/library/stdarch/crates/core_arch/src/mod.rs
+++ b/library/stdarch/crates/core_arch/src/mod.rs
@@ -64,7 +64,7 @@ pub mod arch {
     /// See the [module documentation](../index.html) for more details.
     #[cfg(any(target_arch = "riscv32", doc))]
     #[doc(cfg(any(target_arch = "riscv32")))]
-    #[unstable(feature = "stdsimd", issue = "27731")]
+    #[unstable(feature = "riscv_ext_intrinsics", issue = "114544")]
     pub mod riscv32 {
         pub use crate::core_arch::riscv_shared::*;
     }
@@ -74,7 +74,7 @@ pub mod arch {
     /// See the [module documentation](../index.html) for more details.
     #[cfg(any(target_arch = "riscv64", doc))]
     #[doc(cfg(any(target_arch = "riscv64")))]
-    #[unstable(feature = "stdsimd", issue = "27731")]
+    #[unstable(feature = "riscv_ext_intrinsics", issue = "114544")]
     pub mod riscv64 {
         pub use crate::core_arch::riscv64::*;
         // RISC-V RV64 supports all RV32 instructions as well in current specifications (2022-01-05).
diff --git a/library/stdarch/crates/core_arch/src/riscv_shared/mod.rs b/library/stdarch/crates/core_arch/src/riscv_shared/mod.rs
index ed021df5a91b..b796ee0e77e6 100644
--- a/library/stdarch/crates/core_arch/src/riscv_shared/mod.rs
+++ b/library/stdarch/crates/core_arch/src/riscv_shared/mod.rs
@@ -1,6 +1,7 @@
 //! Shared RISC-V intrinsics
 mod p;
 
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub use p::*;
 
 use crate::arch::asm;
@@ -10,6 +11,7 @@ use crate::arch::asm;
 /// The PAUSE instruction is a HINT that indicates the current hart's rate of instruction retirement
 /// should be temporarily reduced or paused. The duration of its effect must be bounded and may be zero.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub fn pause() {
     unsafe { asm!(".insn i 0x0F, 0, x0, x0, 0x010", options(nomem, nostack)) }
 }
@@ -19,6 +21,7 @@ pub fn pause() {
 /// The NOP instruction does not change any architecturally visible state, except for
 /// advancing the `pc` and incrementing any applicable performance counters.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub fn nop() {
     unsafe { asm!("nop", options(nomem, nostack)) }
 }
@@ -29,6 +32,7 @@ pub fn nop() {
 /// until an interrupt might need servicing. This instruction is a hint,
 /// and a legal implementation is to simply implement WFI as a NOP.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn wfi() {
     asm!("wfi", options(nomem, nostack))
 }
@@ -41,6 +45,7 @@ pub unsafe fn wfi() {
 /// FENCE.I does not ensure that other RISC-V harts' instruction fetches will observe the
 /// local hart's stores in a multiprocessor system.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn fence_i() {
     asm!("fence.i", options(nostack))
 }
@@ -54,6 +59,7 @@ pub unsafe fn fence_i() {
 /// virtual address in parameter `vaddr` and that match the address space identified by integer
 /// parameter `asid`, except for entries containing global mappings.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sfence_vma(vaddr: usize, asid: usize) {
     asm!("sfence.vma {}, {}", in(reg) vaddr, in(reg) asid, options(nostack))
 }
@@ -65,6 +71,7 @@ pub unsafe fn sfence_vma(vaddr: usize, asid: usize) {
 /// The fence also invalidates all address-translation cache entries that contain leaf page
 /// table entries corresponding to the virtual address in parameter `vaddr`, for all address spaces.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sfence_vma_vaddr(vaddr: usize) {
     asm!("sfence.vma {}, x0", in(reg) vaddr, options(nostack))
 }
@@ -78,6 +85,7 @@ pub unsafe fn sfence_vma_vaddr(vaddr: usize) {
 /// address-translation cache entries matching the address space identified by integer
 /// parameter `asid`, except for entries containing global mappings.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sfence_vma_asid(asid: usize) {
     asm!("sfence.vma x0, {}", in(reg) asid, options(nostack))
 }
@@ -88,6 +96,7 @@ pub unsafe fn sfence_vma_asid(asid: usize) {
 /// tables, for all address spaces. The fence also invalidates all address-translation cache entries,
 /// for all address spaces.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sfence_vma_all() {
     asm!("sfence.vma", options(nostack))
 }
@@ -97,6 +106,7 @@ pub unsafe fn sfence_vma_all() {
 /// This instruction invalidates any address-translation cache entries that an
 /// `SFENCE.VMA` instruction with the same values of `vaddr` and `asid` would invalidate.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sinval_vma(vaddr: usize, asid: usize) {
     // asm!("sinval.vma {}, {}", in(reg) vaddr, in(reg) asid, options(nostack))
     asm!(".insn r 0x73, 0, 0x0B, x0, {}, {}", in(reg) vaddr, in(reg) asid, options(nostack))
@@ -107,6 +117,7 @@ pub unsafe fn sinval_vma(vaddr: usize, asid: usize) {
 /// This instruction invalidates any address-translation cache entries that an
 /// `SFENCE.VMA` instruction with the same values of `vaddr` and `asid` would invalidate.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sinval_vma_vaddr(vaddr: usize) {
     asm!(".insn r 0x73, 0, 0x0B, x0, {}, x0", in(reg) vaddr, options(nostack))
 }
@@ -116,6 +127,7 @@ pub unsafe fn sinval_vma_vaddr(vaddr: usize) {
 /// This instruction invalidates any address-translation cache entries that an
 /// `SFENCE.VMA` instruction with the same values of `vaddr` and `asid` would invalidate.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sinval_vma_asid(asid: usize) {
     asm!(".insn r 0x73, 0, 0x0B, x0, x0, {}", in(reg) asid, options(nostack))
 }
@@ -125,6 +137,7 @@ pub unsafe fn sinval_vma_asid(asid: usize) {
 /// This instruction invalidates any address-translation cache entries that an
 /// `SFENCE.VMA` instruction with the same values of `vaddr` and `asid` would invalidate.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sinval_vma_all() {
     asm!(".insn r 0x73, 0, 0x0B, x0, x0, x0", options(nostack))
 }
@@ -134,6 +147,7 @@ pub unsafe fn sinval_vma_all() {
 /// This instruction guarantees that any previous stores already visible to the current RISC-V hart
 /// are ordered before subsequent `SINVAL.VMA` instructions executed by the same hart.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sfence_w_inval() {
     // asm!("sfence.w.inval", options(nostack))
     asm!(".insn i 0x73, 0, x0, x0, 0x180", options(nostack))
@@ -144,6 +158,7 @@ pub unsafe fn sfence_w_inval() {
 /// This instruction guarantees that any previous SINVAL.VMA instructions executed by the current hart
 /// are ordered before subsequent implicit references by that hart to the memory-management data structures.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn sfence_inval_ir() {
     // asm!("sfence.inval.ir", options(nostack))
     asm!(".insn i 0x73, 0, x0, x0, 0x181", options(nostack))
@@ -158,6 +173,7 @@ pub unsafe fn sfence_inval_ir() {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HLV.B`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hlv_b(src: *const i8) -> i8 {
     let value: i8;
     asm!(".insn i 0x73, 0x4, {}, {}, 0x600", out(reg) value, in(reg) src, options(readonly, nostack));
@@ -173,6 +189,7 @@ pub unsafe fn hlv_b(src: *const i8) -> i8 {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HLV.BU`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hlv_bu(src: *const u8) -> u8 {
     let value: u8;
     asm!(".insn i 0x73, 0x4, {}, {}, 0x601", out(reg) value, in(reg) src, options(readonly, nostack));
@@ -188,6 +205,7 @@ pub unsafe fn hlv_bu(src: *const u8) -> u8 {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HLV.H`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hlv_h(src: *const i16) -> i16 {
     let value: i16;
     asm!(".insn i 0x73, 0x4, {}, {}, 0x640", out(reg) value, in(reg) src, options(readonly, nostack));
@@ -203,6 +221,7 @@ pub unsafe fn hlv_h(src: *const i16) -> i16 {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HLV.HU`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hlv_hu(src: *const u16) -> u16 {
     let value: u16;
     asm!(".insn i 0x73, 0x4, {}, {}, 0x641", out(reg) value, in(reg) src, options(readonly, nostack));
@@ -218,6 +237,7 @@ pub unsafe fn hlv_hu(src: *const u16) -> u16 {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HLVX.HU`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hlvx_hu(src: *const u16) -> u16 {
     let insn: u16;
     asm!(".insn i 0x73, 0x4, {}, {}, 0x643", out(reg) insn, in(reg) src, options(readonly, nostack));
@@ -233,6 +253,7 @@ pub unsafe fn hlvx_hu(src: *const u16) -> u16 {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HLV.W`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hlv_w(src: *const i32) -> i32 {
     let value: i32;
     asm!(".insn i 0x73, 0x4, {}, {}, 0x680", out(reg) value, in(reg) src, options(readonly, nostack));
@@ -248,6 +269,7 @@ pub unsafe fn hlv_w(src: *const i32) -> i32 {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HLVX.WU`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hlvx_wu(src: *const u32) -> u32 {
     let insn: u32;
     asm!(".insn i 0x73, 0x4, {}, {}, 0x683", out(reg) insn, in(reg) src, options(readonly, nostack));
@@ -263,6 +285,7 @@ pub unsafe fn hlvx_wu(src: *const u32) -> u32 {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HSV.B`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hsv_b(dst: *mut i8, src: i8) {
     asm!(".insn r 0x73, 0x4, 0x31, x0, {}, {}", in(reg) dst, in(reg) src, options(nostack));
 }
@@ -276,6 +299,7 @@ pub unsafe fn hsv_b(dst: *mut i8, src: i8) {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HSV.H`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hsv_h(dst: *mut i16, src: i16) {
     asm!(".insn r 0x73, 0x4, 0x33, x0, {}, {}", in(reg) dst, in(reg) src, options(nostack));
 }
@@ -289,6 +313,7 @@ pub unsafe fn hsv_h(dst: *mut i16, src: i16) {
 /// This function is unsafe for it accesses the virtual supervisor or user via a `HSV.W`
 /// instruction which is effectively a dereference to any memory address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hsv_w(dst: *mut i32, src: i32) {
     asm!(".insn r 0x73, 0x4, 0x35, x0, {}, {}", in(reg) dst, in(reg) src, options(nostack));
 }
@@ -302,6 +327,7 @@ pub unsafe fn hsv_w(dst: *mut i32, src: i32) {
 ///
 /// This fence specifies a single guest virtual address, and a single guest address-space identifier.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_vvma(vaddr: usize, asid: usize) {
     // asm!("hfence.vvma {}, {}", in(reg) vaddr, in(reg) asid)
     asm!(".insn r 0x73, 0, 0x11, x0, {}, {}", in(reg) vaddr, in(reg) asid, options(nostack))
@@ -316,6 +342,7 @@ pub unsafe fn hfence_vvma(vaddr: usize, asid: usize) {
 ///
 /// This fence specifies a single guest virtual address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_vvma_vaddr(vaddr: usize) {
     asm!(".insn r 0x73, 0, 0x11, x0, {}, x0", in(reg) vaddr, options(nostack))
 }
@@ -329,6 +356,7 @@ pub unsafe fn hfence_vvma_vaddr(vaddr: usize) {
 ///
 /// This fence specifies a single guest address-space identifier.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_vvma_asid(asid: usize) {
     asm!(".insn r 0x73, 0, 0x11, x0, x0, {}", in(reg) asid, options(nostack))
 }
@@ -342,6 +370,7 @@ pub unsafe fn hfence_vvma_asid(asid: usize) {
 ///
 /// This fence applies to any guest address spaces and guest virtual addresses.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_vvma_all() {
     asm!(".insn r 0x73, 0, 0x11, x0, x0, x0", options(nostack))
 }
@@ -354,6 +383,7 @@ pub unsafe fn hfence_vvma_all() {
 /// This fence specifies a single guest physical address, **shifted right by 2 bits**, and a single virtual machine
 /// by virtual machine identifier (VMID).
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_gvma(gaddr: usize, vmid: usize) {
     // asm!("hfence.gvma {}, {}", in(reg) gaddr, in(reg) vmid, options(nostack))
     asm!(".insn r 0x73, 0, 0x31, x0, {}, {}", in(reg) gaddr, in(reg) vmid, options(nostack))
@@ -366,6 +396,7 @@ pub unsafe fn hfence_gvma(gaddr: usize, vmid: usize) {
 ///
 /// This fence specifies a single guest physical address; **the physical address should be shifted right by 2 bits**.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_gvma_gaddr(gaddr: usize) {
     asm!(".insn r 0x73, 0, 0x31, x0, {}, x0", in(reg) gaddr, options(nostack))
 }
@@ -377,6 +408,7 @@ pub unsafe fn hfence_gvma_gaddr(gaddr: usize) {
 ///
 /// This fence specifies a single virtual machine by virtual machine identifier (VMID).
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_gvma_vmid(vmid: usize) {
     asm!(".insn r 0x73, 0, 0x31, x0, x0, {}", in(reg) vmid, options(nostack))
 }
@@ -388,6 +420,7 @@ pub unsafe fn hfence_gvma_vmid(vmid: usize) {
 ///
 /// This fence specifies all guest physical addresses and all virtual machines.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hfence_gvma_all() {
     asm!(".insn r 0x73, 0, 0x31, x0, x0, x0", options(nostack))
 }
@@ -399,6 +432,7 @@ pub unsafe fn hfence_gvma_all() {
 ///
 /// This fence specifies a single guest virtual address, and a single guest address-space identifier.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_vvma(vaddr: usize, asid: usize) {
     // asm!("hinval.vvma {}, {}", in(reg) vaddr, in(reg) asid, options(nostack))
     asm!(".insn r 0x73, 0, 0x13, x0, {}, {}", in(reg) vaddr, in(reg) asid, options(nostack))
@@ -411,6 +445,7 @@ pub unsafe fn hinval_vvma(vaddr: usize, asid: usize) {
 ///
 /// This fence specifies a single guest virtual address.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_vvma_vaddr(vaddr: usize) {
     asm!(".insn r 0x73, 0, 0x13, x0, {}, x0", in(reg) vaddr, options(nostack))
 }
@@ -422,6 +457,7 @@ pub unsafe fn hinval_vvma_vaddr(vaddr: usize) {
 ///
 /// This fence specifies a single guest address-space identifier.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_vvma_asid(asid: usize) {
     asm!(".insn r 0x73, 0, 0x13, x0, x0, {}", in(reg) asid, options(nostack))
 }
@@ -433,6 +469,7 @@ pub unsafe fn hinval_vvma_asid(asid: usize) {
 ///
 /// This fence applies to any guest address spaces and guest virtual addresses.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_vvma_all() {
     asm!(".insn r 0x73, 0, 0x13, x0, x0, x0", options(nostack))
 }
@@ -445,6 +482,7 @@ pub unsafe fn hinval_vvma_all() {
 /// This fence specifies a single guest physical address, **shifted right by 2 bits**, and a single virtual machine
 /// by virtual machine identifier (VMID).
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_gvma(gaddr: usize, vmid: usize) {
     // asm!("hinval.gvma {}, {}", in(reg) gaddr, in(reg) vmid, options(nostack))
     asm!(".insn r 0x73, 0, 0x33, x0, {}, {}", in(reg) gaddr, in(reg) vmid, options(nostack))
@@ -457,6 +495,7 @@ pub unsafe fn hinval_gvma(gaddr: usize, vmid: usize) {
 ///
 /// This fence specifies a single guest physical address; **the physical address should be shifted right by 2 bits**.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_gvma_gaddr(gaddr: usize) {
     asm!(".insn r 0x73, 0, 0x33, x0, {}, x0", in(reg) gaddr, options(nostack))
 }
@@ -468,6 +507,7 @@ pub unsafe fn hinval_gvma_gaddr(gaddr: usize) {
 ///
 /// This fence specifies a single virtual machine by virtual machine identifier (VMID).
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_gvma_vmid(vmid: usize) {
     asm!(".insn r 0x73, 0, 0x33, x0, x0, {}", in(reg) vmid, options(nostack))
 }
@@ -479,6 +519,7 @@ pub unsafe fn hinval_gvma_vmid(vmid: usize) {
 ///
 /// This fence specifies all guest physical addresses and all virtual machines.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub unsafe fn hinval_gvma_all() {
     asm!(".insn r 0x73, 0, 0x33, x0, x0, x0", options(nostack))
 }
@@ -502,6 +543,7 @@ pub unsafe fn hinval_gvma_all() {
 /// [`frrm`]: fn.frrm.html
 /// [`frflags`]: fn.frflags.html
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub fn frcsr() -> u32 {
     let value: u32;
     unsafe { asm!("frcsr {}", out(reg) value, options(nomem, nostack)) };
@@ -513,6 +555,7 @@ pub fn frcsr() -> u32 {
 /// This function swaps the value in `fcsr` by copying the original value to be returned,
 /// and then writing a new value obtained from input variable `value` into `fcsr`.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub fn fscsr(value: u32) -> u32 {
     let original: u32;
     unsafe { asm!("fscsr {}, {}", out(reg) original, in(reg) value, options(nomem, nostack)) }
@@ -535,6 +578,7 @@ pub fn fscsr(value: u32) -> u32 {
 /// | 110 |     | _Reserved for future use._ |
 /// | 111 | DYN | In Rounding Mode register, _reserved_. |
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub fn frrm() -> u32 {
     let value: u32;
     unsafe { asm!("frrm {}", out(reg) value, options(nomem, nostack)) };
@@ -547,6 +591,7 @@ pub fn frrm() -> u32 {
 /// and then writing a new value obtained from the three least-significant bits of
 /// input variable `value` into `frm`.
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub fn fsrm(value: u32) -> u32 {
     let original: u32;
     unsafe { asm!("fsrm {}, {}", out(reg) original, in(reg) value, options(nomem, nostack)) }
@@ -570,6 +615,7 @@ pub fn fsrm(value: u32) -> u32 {
 /// | 1 | UF | Underflow |
 /// | 0 | NX | Inexact |
 #[inline]
+#[unstable(feature = "stdsimd", issue = "27731")]
 pub fn frflags() -> u32 {
     let value: u32;
     unsafe { asm!("frflags {}", out(reg) value, options(nomem, nostack)) };