Auto merge of #94468 - Amanieu:global_asm_sym, r=nagisa

Implement sym operands for global_asm!

Tracking issue: #93333

This PR is pretty much a complete rewrite of `sym` operand support for inline assembly so that the same implementation can be shared by `asm!` and `global_asm!`. The main changes are:
- At the AST level, `sym` is represented as a special `InlineAsmSym` AST node containing a path instead of an `Expr`.
- At the HIR level, `sym` is split into `SymStatic` and `SymFn` depending on whether the path resolves to a static during AST lowering (defaults to `SynFn` if `get_early_res` fails).
  - `SymFn` is just an `AnonConst`. It runs through typeck and we just collect the resulting type at the end. An error is emitted if the type is not a `FnDef`.
  - `SymStatic` directly holds a path and the `DefId` of the `static` that it is pointing to.
- The representation at the MIR level is mostly unchanged. There is a minor change to THIR where `SymFn` is a constant instead of an expression.
- At the codegen level we need to apply the target's symbol mangling to the result of `tcx.symbol_name()` depending on the target. This is done by calling the LLVM name mangler, which handles all of the details.
  - On Mach-O, all symbols have a leading underscore.
  - On x86 Windows, different mangling is used for cdecl, stdcall, fastcall and vectorcall.
  - No mangling is needed on other platforms.

r? `@nagisa`
cc `@eddyb`

1 files changed, 28 insertions, 4 deletions

diff --git a/compiler/rustc_codegen_gcc/src/asm.rs b/compiler/rustc_codegen_gcc/src/asm.rs
index 8a74c4c07e0..2af050f0c75 100644
--- a/compiler/rustc_codegen_gcc/src/asm.rs
+++ b/compiler/rustc_codegen_gcc/src/asm.rs
@@ -258,9 +258,14 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                 }
 
                 InlineAsmOperandRef::SymFn { instance } => {
+                    // TODO(@Amanieu): Additional mangling is needed on
+                    // some targets to add a leading underscore (Mach-O)
+                    // or byte count suffixes (x86 Windows).
                     constants_len += self.tcx.symbol_name(instance).name.len();
                 }
                 InlineAsmOperandRef::SymStatic { def_id } => {
+                    // TODO(@Amanieu): Additional mangling is needed on
+                    // some targets to add a leading underscore (Mach-O).
                     constants_len += self.tcx.symbol_name(Instance::mono(self.tcx, def_id)).name.len();
                 }
             }
@@ -412,13 +417,16 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                         }
 
                         InlineAsmOperandRef::SymFn { instance } => {
+                            // TODO(@Amanieu): Additional mangling is needed on
+                            // some targets to add a leading underscore (Mach-O)
+                            // or byte count suffixes (x86 Windows).
                             let name = self.tcx.symbol_name(instance).name;
                             template_str.push_str(name);
                         }
 
                         InlineAsmOperandRef::SymStatic { def_id } => {
-                            // TODO(@Commeownist): This may not be sufficient for all kinds of statics.
-                            // Some statics may need the `@plt` suffix, like thread-local vars.
+                            // TODO(@Amanieu): Additional mangling is needed on
+                            // some targets to add a leading underscore (Mach-O).
                             let instance = Instance::mono(self.tcx, def_id);
                             let name = self.tcx.symbol_name(instance).name;
                             template_str.push_str(name);
@@ -656,8 +664,8 @@ fn dummy_output_type<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, reg: InlineAsmRegCl
     }
 }
 
-impl<'gcc, 'tcx> AsmMethods for CodegenCx<'gcc, 'tcx> {
-    fn codegen_global_asm(&self, template: &[InlineAsmTemplatePiece], operands: &[GlobalAsmOperandRef], options: InlineAsmOptions, _line_spans: &[Span]) {
+impl<'gcc, 'tcx> AsmMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
+    fn codegen_global_asm(&self, template: &[InlineAsmTemplatePiece], operands: &[GlobalAsmOperandRef<'tcx>], options: InlineAsmOptions, _line_spans: &[Span]) {
         let asm_arch = self.tcx.sess.asm_arch.unwrap();
 
         // Default to Intel syntax on x86
@@ -690,6 +698,22 @@ impl<'gcc, 'tcx> AsmMethods for CodegenCx<'gcc, 'tcx> {
                             // here unlike normal inline assembly.
                             template_str.push_str(string);
                         }
+
+                        GlobalAsmOperandRef::SymFn { instance } => {
+                            // TODO(@Amanieu): Additional mangling is needed on
+                            // some targets to add a leading underscore (Mach-O)
+                            // or byte count suffixes (x86 Windows).
+                            let name = self.tcx.symbol_name(instance).name;
+                            template_str.push_str(name);
+                        }
+
+                        GlobalAsmOperandRef::SymStatic { def_id } => {
+                            // TODO(@Amanieu): Additional mangling is needed on
+                            // some targets to add a leading underscore (Mach-O).
+                            let instance = Instance::mono(self.tcx, def_id);
+                            let name = self.tcx.symbol_name(instance).name;
+                            template_str.push_str(name);
+                        }
                     }
                 }
             }