Auto merge of rust-lang#90348 - Amanieu:asm_feature_gates, r=joshtriplett

Add features gates for experimental asm features

This PR splits off parts of `asm!` into separate features because they are not ready for stabilization.

Specifically this adds:
- `asm_const` for `const` operands.
- `asm_sym` for `sym` operands.
- `asm_experimental_arch` for architectures other than x86, x86_64, arm, aarch64 and riscv.

r? `@nagisa`

Author: bors

compiler/rustc_ast_lowering/src/asm.rs

@@ -4,7 +4,8 @@ use rustc_ast::*;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
-use rustc_span::{Span, Symbol};
+use rustc_session::parse::feature_err;
+use rustc_span::{sym, Span, Symbol};
 use rustc_target::asm;
 use std::collections::hash_map::Entry;
 use std::fmt::Write;
@@ -18,6 +19,27 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             struct_span_err!(self.sess, sp, E0472, "inline assembly is unsupported on this target")
                 .emit();
         }
+        if let Some(asm_arch) = asm_arch {
+            // Inline assembly is currently only stable for these architectures.
+            let is_stable = matches!(
+                asm_arch,
+                asm::InlineAsmArch::X86
+                    | asm::InlineAsmArch::X86_64
+                    | asm::InlineAsmArch::Arm
+                    | asm::InlineAsmArch::AArch64
+                    | asm::InlineAsmArch::RiscV32
+                    | asm::InlineAsmArch::RiscV64
+            );
+            if !is_stable && !self.sess.features_untracked().asm_experimental_arch {
+                feature_err(
+                    &self.sess.parse_sess,
+                    sym::asm_experimental_arch,
+                    sp,
+                    "inline assembly is not stable yet on this architecture",
+                )
+                .emit();
+            }
+        }
         if asm.options.contains(InlineAsmOptions::ATT_SYNTAX)
             && !matches!(asm_arch, Some(asm::InlineAsmArch::X86 | asm::InlineAsmArch::X86_64))
             && !self.sess.opts.actually_rustdoc
@@ -121,10 +143,30 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             out_expr: out_expr.as_ref().map(|expr| self.lower_expr_mut(expr)),
                         }
                     }
-                    InlineAsmOperand::Const { ref anon_const } => hir::InlineAsmOperand::Const {
-                        anon_const: self.lower_anon_const(anon_const),
-                    },
+                    InlineAsmOperand::Const { ref anon_const } => {
+                        if !self.sess.features_untracked().asm_const {
+                            feature_err(
+                                &self.sess.parse_sess,
+                                sym::asm_const,
+                                *op_sp,
+                                "const operands for inline assembly are unstable",
+                            )
+                            .emit();
+                        }
+                        hir::InlineAsmOperand::Const {
+                            anon_const: self.lower_anon_const(anon_const),
+                        }
+                    }
                     InlineAsmOperand::Sym { ref expr } => {
+                        if !self.sess.features_untracked().asm_sym {
+                            feature_err(
+                                &self.sess.parse_sess,
+                                sym::asm_sym,
+                                *op_sp,
+                                "sym operands for inline assembly are unstable",
+                            )
+                            .emit();
+                        }
                         hir::InlineAsmOperand::Sym { expr: self.lower_expr_mut(expr) }
                     }
                 };

compiler/rustc_feature/src/active.rs

@@ -692,6 +692,15 @@ declare_features! (
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
     (active, doc_auto_cfg, "1.58.0", Some(43781), None),
 
+    /// Allows using `const` operands in inline assembly.
+    (active, asm_const, "1.58.0", Some(72016), None),
+
+    /// Allows using `sym` operands in inline assembly.
+    (active, asm_sym, "1.58.0", Some(72016), None),
+
+    /// Enables experimental inline assembly support for additional architectures.
+    (active, asm_experimental_arch, "1.58.0", Some(72016), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------

compiler/rustc_span/src/symbol.rs

@@ -327,6 +327,9 @@ symbols! {
         as_ptr,
         as_str,
         asm,
+        asm_const,
+        asm_experimental_arch,
+        asm_sym,
         assert,
         assert_inhabited,
         assert_macro,

library/core/src/lib.rs

@@ -193,6 +193,7 @@
 #![feature(try_blocks)]
 #![feature(unboxed_closures)]
 #![feature(unsized_fn_params)]
+#![cfg_attr(not(bootstrap), feature(asm_const))]
 //
 // Target features:
 #![feature(aarch64_target_feature)]

src/doc/unstable-book/src/library-features/global-asm.md

@@ -75,7 +75,7 @@ are concatenated into one or assembled separately.
 constants defined in Rust to be used in assembly code:
 
 ```rust,no_run
-#![feature(global_asm)]
+#![feature(global_asm, asm_const)]
 # #[cfg(any(target_arch="x86", target_arch="x86_64"))]
 # mod x86 {
 const C: i32 = 1234;
@@ -96,7 +96,7 @@ override this by adding `options(att_syntax)` at the end of the macro
 arguments list:
 
 ```rust,no_run
-#![feature(global_asm)]
+#![feature(global_asm, asm_const)]
 # #[cfg(any(target_arch="x86", target_arch="x86_64"))]
 # mod x86 {
 global_asm!("movl ${}, %ecx", const 5, options(att_syntax));

src/test/assembly/asm/aarch64-types.rs

@@ -2,7 +2,7 @@
 // compile-flags: --target aarch64-unknown-linux-gnu
 // needs-llvm-components: aarch64
 
-#![feature(no_core, lang_items, rustc_attrs, repr_simd)]
+#![feature(no_core, lang_items, rustc_attrs, repr_simd, asm_sym)]
 #![crate_type = "rlib"]
 #![no_core]
 #![allow(asm_sub_register, non_camel_case_types)]

src/test/assembly/asm/arm-types.rs

@@ -3,7 +3,7 @@
 // compile-flags: -C target-feature=+neon
 // needs-llvm-components: arm
 
-#![feature(no_core, lang_items, rustc_attrs, repr_simd)]
+#![feature(no_core, lang_items, rustc_attrs, repr_simd, asm_sym)]
 #![crate_type = "rlib"]
 #![no_core]
 #![allow(asm_sub_register, non_camel_case_types)]

src/test/assembly/asm/bpf-types.rs

@@ -3,7 +3,7 @@
 // compile-flags: --target bpfel-unknown-none -C target_feature=+alu32
 // needs-llvm-components: bpf
 
-#![feature(no_core, lang_items, rustc_attrs, repr_simd)]
+#![feature(no_core, lang_items, rustc_attrs, repr_simd, asm_sym, asm_experimental_arch)]
 #![crate_type = "rlib"]
 #![no_core]
 #![allow(asm_sub_register, non_camel_case_types)]

src/test/assembly/asm/global_asm.rs

@@ -2,7 +2,7 @@
 // assembly-output: emit-asm
 // compile-flags: -C llvm-args=--x86-asm-syntax=intel
 
-#![feature(asm, global_asm)]
+#![feature(global_asm, asm_const)]
 #![crate_type = "rlib"]
 
 // CHECK: mov eax, eax

src/test/assembly/asm/hexagon-types.rs

@@ -2,7 +2,7 @@
 // compile-flags: --target hexagon-unknown-linux-musl
 // needs-llvm-components: hexagon
 
-#![feature(no_core, lang_items, rustc_attrs, repr_simd)]
+#![feature(no_core, lang_items, rustc_attrs, repr_simd, asm_sym, asm_experimental_arch)]
 #![crate_type = "rlib"]
 #![no_core]
 #![allow(asm_sub_register, non_camel_case_types)]