Rollup merge of rust-lang#101402 - saethlin:inline-asm-hook, r=oli-obk

Add a Machine hook for inline assembly

I'm sketching out some support in Miri to "execute" inline assembly. I want this because there are codebases which have very simple inline assembly like hand-written syscall wrappers, and it would be nice to test such code without modification.

r? `@oli-obk`

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -6,6 +6,7 @@ use std::borrow::{Borrow, Cow};
 use std::fmt::Debug;
 use std::hash::Hash;
 
+use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
 use rustc_middle::mir;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::def_id::DefId;
@@ -323,6 +324,15 @@ pub trait Machine<'mir, 'tcx>: Sized {
         kind: Option<MemoryKind<Self::MemoryKind>>,
     ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance, Self::AllocExtra>>>;
 
+    fn eval_inline_asm(
+        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        _template: &'tcx [InlineAsmTemplatePiece],
+        _operands: &[mir::InlineAsmOperand<'tcx>],
+        _options: InlineAsmOptions,
+    ) -> InterpResult<'tcx> {
+        throw_unsup_format!("inline assembly is not supported")
+    }
+
     /// Hook for performing extra checks on a memory read access.
     ///
     /// Takes read-only access to the allocation so we can keep all the memory read

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 
+use rustc_ast::ast::InlineAsmOptions;
 use rustc_middle::ty::layout::{FnAbiOf, LayoutOf};
 use rustc_middle::ty::Instance;
 use rustc_middle::{
@@ -166,8 +167,16 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 terminator.kind
             ),
 
-            // Inline assembly can't be interpreted.
-            InlineAsm { .. } => throw_unsup_format!("inline assembly is not supported"),
+            InlineAsm { template, ref operands, options, destination, .. } => {
+                M::eval_inline_asm(self, template, operands, options)?;
+                if options.contains(InlineAsmOptions::NORETURN) {
+                    throw_ub_format!("returned from noreturn inline assembly");
+                }
+                self.go_to_block(
+                    destination
+                        .expect("InlineAsm terminators without noreturn must have a destination"),
+                )
+            }
         }
 
         Ok(())