rustc_target: RISC-V: Add atomics/memory-related extensions

This commit adds a part of RISC-V extensions that are mandatory part of
the RVA23U64 profile (application-class processor profile) and related to
memory/atomic constraints.

The Zic64b extension constrains the cache line to naturally-aligned 64 bytes
that would make certain memory operations (like zeroing the memory using
the Zicboz extension) easier.

The Zicbom and Zicbop extensions enable managing cache block-based
operations (the Zicbop contains hints that will work as a NOP when this
extension is absent and the Zicbom contains control instructions).

Of which, the Zicbom extension is going to be discoverable from the Linux
kernel (as of the version 6.15-rc4) and this commit prepares for
corresponding stdarch changes.

The Zicc* extensions add certain constraints to "the main memory" (usually
true on the user mode application on the application-class processor but
those extensions make sure such constraints exist).

Author: a4lg

compiler/rustc_target/src/target_features.rs

@@ -531,7 +531,14 @@ static RISCV_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     ("zfinx", Unstable(sym::riscv_target_feature), &["zicsr"]),
     ("zhinx", Unstable(sym::riscv_target_feature), &["zhinxmin"]),
     ("zhinxmin", Unstable(sym::riscv_target_feature), &["zfinx"]),
+    ("zic64b", Unstable(sym::riscv_target_feature), &[]),
+    ("zicbom", Unstable(sym::riscv_target_feature), &[]),
+    ("zicbop", Unstable(sym::riscv_target_feature), &[]),
     ("zicboz", Unstable(sym::riscv_target_feature), &[]),
+    ("ziccamoa", Unstable(sym::riscv_target_feature), &[]),
+    ("ziccif", Unstable(sym::riscv_target_feature), &[]),
+    ("zicclsm", Unstable(sym::riscv_target_feature), &[]),
+    ("ziccrse", Unstable(sym::riscv_target_feature), &[]),
     ("zicntr", Unstable(sym::riscv_target_feature), &["zicsr"]),
     ("zicond", Unstable(sym::riscv_target_feature), &[]),
     ("zicsr", Unstable(sym::riscv_target_feature), &[]),

tests/ui/check-cfg/target_feature.stderr

@@ -329,7 +329,14 @@ LL |     cfg!(target_feature = "_UNEXPECTED_VALUE");
 `zfinx`
 `zhinx`
 `zhinxmin`
+`zic64b`
+`zicbom`
+`zicbop`
 `zicboz`
+`ziccamoa`
+`ziccif`
+`zicclsm`
+`ziccrse`
 `zicntr`
 `zicond`
 `zicsr`