Rollup merge of rust-lang#147302 - esp-rs:xtensa-asm, r=Amanieu

asm! support for the Xtensa architecture

This implements the asm! support for Xtensa. We've been using this code for a few years in [our fork](https://github.com/esp-rs/rust) and it's been working well. I finally found some time to clean it up a bit and start the upstreaming process. This should be one of the final PRs for Xtensa support on the Rust side (minus bug fixes of course). After this, we're mostly just waiting on the LLVM upstreaming which is going well. This PR doesn't cover all possible asm options for Xtensa, but the base ISA plus a few extras that are used in Espressif chips.

r? Amanieu

Author: JonathanBrouwer

compiler/rustc_codegen_gcc/src/asm.rs

@@ -751,6 +751,11 @@ fn reg_class_to_gcc(reg_class: InlineAsmRegClass) -> &'static str {
             | X86InlineAsmRegClass::mmx_reg
             | X86InlineAsmRegClass::tmm_reg,
         ) => unreachable!("clobber-only"),
+        InlineAsmRegClass::Xtensa(XtensaInlineAsmRegClass::reg) => "r",
+        InlineAsmRegClass::Xtensa(XtensaInlineAsmRegClass::freg) => "f",
+        InlineAsmRegClass::Xtensa(
+            XtensaInlineAsmRegClass::sreg | XtensaInlineAsmRegClass::breg,
+        ) => unreachable!("clobber-only"),
         InlineAsmRegClass::SpirV(SpirVInlineAsmRegClass::reg) => {
             bug!("GCC backend does not support SPIR-V")
         }
@@ -872,6 +877,11 @@ fn dummy_output_type<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, reg: InlineAsmRegCl
         InlineAsmRegClass::SpirV(SpirVInlineAsmRegClass::reg) => {
             bug!("GCC backend does not support SPIR-V")
         }
+        InlineAsmRegClass::Xtensa(XtensaInlineAsmRegClass::reg) => cx.type_i32(),
+        InlineAsmRegClass::Xtensa(XtensaInlineAsmRegClass::freg) => cx.type_f32(),
+        InlineAsmRegClass::Xtensa(
+            XtensaInlineAsmRegClass::sreg | XtensaInlineAsmRegClass::breg,
+        ) => unreachable!("clobber-only"),
         InlineAsmRegClass::Err => unreachable!(),
     }
 }
@@ -1070,6 +1080,7 @@ fn modifier_to_gcc(
         InlineAsmRegClass::SpirV(SpirVInlineAsmRegClass::reg) => {
             bug!("LLVM backend does not support SPIR-V")
         }
+        InlineAsmRegClass::Xtensa(_) => None,
         InlineAsmRegClass::Err => unreachable!(),
     }
 }

compiler/rustc_codegen_llvm/src/asm.rs

@@ -278,6 +278,7 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                 }
                 InlineAsmArch::SpirV => {}
                 InlineAsmArch::Wasm32 | InlineAsmArch::Wasm64 => {}
+                InlineAsmArch::Xtensa => {}
                 InlineAsmArch::Bpf => {}
                 InlineAsmArch::Msp430 => {
                     constraints.push("~{sr}".to_string());
@@ -740,6 +741,11 @@ fn reg_to_llvm(reg: InlineAsmRegOrRegClass, layout: Option<&TyAndLayout<'_>>) ->
                 | X86InlineAsmRegClass::kreg0
                 | X86InlineAsmRegClass::tmm_reg,
             ) => unreachable!("clobber-only"),
+            Xtensa(XtensaInlineAsmRegClass::freg) => "f",
+            Xtensa(XtensaInlineAsmRegClass::reg) => "r",
+            Xtensa(XtensaInlineAsmRegClass::sreg | XtensaInlineAsmRegClass::breg) => {
+                unreachable!("clobber-only")
+            }
             Wasm(WasmInlineAsmRegClass::local) => "r",
             Bpf(BpfInlineAsmRegClass::reg) => "r",
             Bpf(BpfInlineAsmRegClass::wreg) => "w",
@@ -845,6 +851,7 @@ fn modifier_to_llvm(
             | X86InlineAsmRegClass::kreg0
             | X86InlineAsmRegClass::tmm_reg,
         ) => unreachable!("clobber-only"),
+        Xtensa(_) => None,
         Wasm(WasmInlineAsmRegClass::local) => None,
         Bpf(_) => None,
         Avr(AvrInlineAsmRegClass::reg_pair)
@@ -939,6 +946,11 @@ fn dummy_output_type<'ll>(cx: &CodegenCx<'ll, '_>, reg: InlineAsmRegClass) -> &'
             | X86InlineAsmRegClass::kreg0
             | X86InlineAsmRegClass::tmm_reg,
         ) => unreachable!("clobber-only"),
+        Xtensa(XtensaInlineAsmRegClass::reg) => cx.type_i32(),
+        Xtensa(XtensaInlineAsmRegClass::freg) => cx.type_f32(),
+        Xtensa(XtensaInlineAsmRegClass::sreg | XtensaInlineAsmRegClass::breg) => {
+            unreachable!("clobber-only")
+        }
         Wasm(WasmInlineAsmRegClass::local) => cx.type_i32(),
         Bpf(BpfInlineAsmRegClass::reg) => cx.type_i64(),
         Bpf(BpfInlineAsmRegClass::wreg) => cx.type_i32(),

compiler/rustc_feature/src/unstable.rs

@@ -775,6 +775,8 @@ declare_features! (
     (unstable, x87_target_feature, "1.85.0", Some(150261)),
     /// Allows use of the `xop` target-feature
     (unstable, xop_target_feature, "1.81.0", Some(127208)),
+    /// Allows use of the Xtensa target-features
+    (unstable, xtensa_target_feature, "CURRENT_RUSTC_VERSION", Some(157063)),
     /// Allows `do yeet` expressions
     (unstable, yeet_expr, "1.62.0", Some(96373)),
     (unstable, yield_expr, "1.87.0", Some(43122)),

compiler/rustc_span/src/symbol.rs

@@ -468,6 +468,7 @@ symbols! {
         async_iterator,
         async_iterator_poll_next,
         async_trait_bounds,
+        atomic,
         atomic_and,
         atomic_cxchg,
         atomic_cxchgweak,
@@ -542,6 +543,7 @@ symbols! {
         braced_empty_structs,
         branch,
         breakpoint,
+        breg,
         bridge,
         bswap,
         built,
@@ -706,6 +708,7 @@ symbols! {
         contracts_internals,
         contracts_requires,
         convert,
+        coprocessor,
         copy,
         copy_closures,
         copy_nonoverlapping,
@@ -881,6 +884,7 @@ symbols! {
         ermsb_target_feature,
         exact_div,
         except,
+        exception,
         exception_handling: "exception-handling",
         exclusive_range_pattern,
         exhaustive_integer_patterns,
@@ -907,6 +911,7 @@ symbols! {
         expr_fragment_specifier_2024,
         extended_key_value_attributes,
         extended_varargs_abi_support,
+        extendedl32r,
         extern_absolute_paths,
         extern_crate_item_prelude,
         extern_crate_self,
@@ -990,6 +995,9 @@ symbols! {
         format_argument,
         format_arguments,
         format_macro,
+        format_placeholder,
+        format_unsafe_arg,
+        fp,
         framework,
         freeze,
         freeze_impls,
@@ -1051,6 +1059,8 @@ symbols! {
         hexagon_target_feature,
         hidden,
         hide,
+        highpriinterrupts,
+        hint,
         homogeneous_aggregate,
         html_favicon_url,
         html_logo_url,
@@ -1111,6 +1121,7 @@ symbols! {
         internal,
         internal_eq_trait_method_impls,
         internal_features,
+        interrupt,
         into_async_iter_into_iter,
         into_future,
         into_iter,
@@ -1206,6 +1217,7 @@ symbols! {
         lt,
         m68k,
         m68k_target_feature,
+        mac16,
         macho: "mach-o",
         macro_at_most_once_rep,
         macro_attr,
@@ -1318,6 +1330,8 @@ symbols! {
         mir_unwind_unreachable,
         mir_variant,
         miri,
+        misc,
+        miscsr,
         mmx_reg,
         modifiers,
         module,
@@ -1566,6 +1580,8 @@ symbols! {
         prelude_import,
         preserves_flags,
         prfchw_target_feature,
+        prid,
+        primitive,
         proc_dash_macro: "proc-macro",
         proc_macro,
         proc_macro_attribute,
@@ -1822,7 +1838,9 @@ symbols! {
         rustdoc_missing_doc_code_examples,
         rustfmt,
         rvalue_static_promotion,
+        rvector,
         rwpi,
+        s32c1i,
         s390x,
         s390x_target_feature,
         s390x_target_feature_vector,
@@ -2052,9 +2070,11 @@ symbols! {
         test_unstable_lint,
         thread,
         thread_local,
+        threadptr,
         three_way_compare,
         thumb2,
         thumb_mode: "thumb-mode",
+        time,
         tmm_reg,
         to_owned_method,
         to_string,
@@ -2278,6 +2298,7 @@ symbols! {
         while_let,
         whole_dash_archive: "whole-archive",
         width,
+        windowed,
         windows,
         windows_subsystem,
         with_negative_coherence,
@@ -2303,9 +2324,11 @@ symbols! {
         x87_target_feature,
         xcoff,
         xer,
+        xloop,
         xmm_reg,
         xop_target_feature,
         xtensa,
+        xtensa_target_feature,
         yeet_desugar_details,
         yeet_expr,
         yes,