Rollup merge of rust-lang#107711 - calebzulawski:movbe, r=pnkfelix

Stabilize movbe target feature

Almost all "old" x86 target features are stable.  As far as I can tell, these are the last two unstable features in the `x86-64-v2` or `x86-64-v3` microarchitecture levels, so I'm not sure if it was an oversight or if they're still unstable for a reason (see rust-lang#106323 for `f16c`).

Note that this only stabilizes the target features, and not the intrinsics.

cc ```@Amanieu```

r? ```@rust-lang/lang```

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -192,7 +192,7 @@ const X86_ALLOWED_FEATURES: &[(&str, Option<Symbol>)] = &[
     ("fxsr", None),
     ("gfni", Some(sym::avx512_target_feature)),
     ("lzcnt", None),
-    ("movbe", Some(sym::movbe_target_feature)),
+    ("movbe", None),
     ("pclmulqdq", None),
     ("popcnt", None),
     ("rdrand", None),
@@ -394,7 +394,6 @@ pub fn from_target_feature(
                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
-                Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,

compiler/rustc_feature/src/accepted.rs

@@ -90,7 +90,7 @@ declare_features! (
     (accepted, clone_closures, "1.26.0", Some(44490), None),
     /// Allows coercing non capturing closures to function pointers.
     (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
-    /// Allows using `cmpxchg16b` from `core::arch::x86_64`.
+    /// Allows using the CMPXCHG16B target feature.
     (accepted, cmpxchg16b_target_feature, "CURRENT_RUSTC_VERSION", Some(44839), None),
     /// Allows usage of the `compile_error!` macro.
     (accepted, compile_error, "1.20.0", Some(40872), None),
@@ -238,6 +238,8 @@ declare_features! (
     (accepted, min_const_unsafe_fn, "1.33.0", Some(55607), None),
     /// Allows using `Self` and associated types in struct expressions and patterns.
     (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
+    /// Allows using the MOVBE target feature.
+    (accepted, movbe_target_feature, "CURRENT_RUSTC_VERSION", Some(44839), None),
     /// Allows patterns with concurrent by-move and by-ref bindings.
     /// For example, you can write `Foo(a, ref b)` where `a` is by-move and `b` is by-ref.
     (accepted, move_ref_pattern, "1.49.0", Some(68354), None),

compiler/rustc_feature/src/active.rs

@@ -259,7 +259,6 @@ declare_features! (
     (active, ermsb_target_feature, "1.49.0", Some(44839), None),
     (active, hexagon_target_feature, "1.27.0", Some(44839), None),
     (active, mips_target_feature, "1.27.0", Some(44839), None),
-    (active, movbe_target_feature, "1.34.0", Some(44839), None),
     (active, powerpc_target_feature, "1.27.0", Some(44839), None),
     (active, riscv_target_feature, "1.45.0", Some(44839), None),
     (active, rtm_target_feature, "1.35.0", Some(44839), None),