Rollup merge of rust-lang#126704 - sayantn:sha, r=Amanieu

Added SHA512, SM3, SM4 target-features and `sha512_sm_x86` feature gate

This is an effort towards rust-lang#126624. This adds support for these 3 target-features and introduces the feature flag `sha512_sm_x86`, which would gate these target-features and the yet-to-be-implemented detection and intrinsics in stdarch.

core/src/arch.rs

@@ -4,6 +4,15 @@
 #[stable(feature = "simd_arch", since = "1.27.0")]
 pub use crate::core_arch::arch::*;
 
+#[cfg(bootstrap)]
+#[allow(dead_code)]
+#[unstable(feature = "sha512_sm_x86", issue = "126624")]
+fn dummy() {
+    // AArch64 also has a target feature named `sm4`, so we need `#![feature(sha512_sm_x86)]` in lib.rs
+    // But as the bootstrap compiler doesn't know about this feature yet, we need to convert it to a
+    // library feature until bootstrap gets bumped
+}
+
 /// Inline assembly.
 ///
 /// Refer to [Rust By Example] for a usage guide and the [reference] for

core/src/lib.rs

@@ -260,6 +260,7 @@
 #![feature(powerpc_target_feature)]
 #![feature(riscv_target_feature)]
 #![feature(rtm_target_feature)]
+#![feature(sha512_sm_x86)]
 #![feature(sse4a_target_feature)]
 #![feature(tbm_target_feature)]
 #![feature(wasm_target_feature)]