Auto merge of #115764 - RalfJung:const-by-ref-alloc-id, r=oli-obk

some ConstValue refactoring

In particular, use AllocId instead of Allocation in ConstValue::ByRef. This helps avoid redundant AllocIds when a  `ByRef` constant gets put back into the interpreter.

r? `@oli-obk`

Fixes rust-lang/rust#105536

src/eval.rs

@@ -382,7 +382,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
             .unwrap()
             .unwrap();
 
-            let main_ptr = ecx.create_fn_alloc_ptr(FnVal::Instance(entry_instance));
+            let main_ptr = ecx.fn_ptr(FnVal::Instance(entry_instance));
 
             // Inlining of `DEFAULT` from
             // https://github.com/rust-lang/rust/blob/master/compiler/rustc_session/src/config/sigpipe.rs.

src/machine.rs

@@ -711,7 +711,7 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
                 let layout = this.machine.layouts.const_raw_ptr;
                 let dlsym = Dlsym::from_str("signal".as_bytes(), &this.tcx.sess.target.os)?
                     .expect("`signal` must be an actual dlsym on android");
-                let ptr = this.create_fn_alloc_ptr(FnVal::Other(dlsym));
+                let ptr = this.fn_ptr(FnVal::Other(dlsym));
                 let val = ImmTy::from_scalar(Scalar::from_pointer(ptr, this), layout);
                 Self::alloc_extern_static(this, "signal", val)?;
                 // A couple zero-initialized pointer-sized extern statics.

src/shims/backtrace.rs

@@ -63,7 +63,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 // to reconstruct the needed frame information in `handle_miri_resolve_frame`.
                 // Note that we never actually read or write anything from/to this pointer -
                 // all of the data is represented by the pointer value itself.
-                let fn_ptr = this.create_fn_alloc_ptr(FnVal::Instance(instance));
+                let fn_ptr = this.fn_ptr(FnVal::Instance(instance));
                 fn_ptr.wrapping_offset(Size::from_bytes(pos.0), this)
             })
             .collect();
@@ -159,7 +159,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
         // Reconstruct the original function pointer,
         // which we pass to user code.
-        let fn_ptr = this.create_fn_alloc_ptr(FnVal::Instance(fn_instance));
+        let fn_ptr = this.fn_ptr(FnVal::Instance(fn_instance));
 
         let num_fields = dest.layout.fields.count();
 

src/shims/unix/foreign_items.rs

@@ -232,7 +232,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 let symbol = this.read_pointer(symbol)?;
                 let symbol_name = this.read_c_str(symbol)?;
                 if let Some(dlsym) = Dlsym::from_str(symbol_name, &this.tcx.sess.target.os)? {
-                    let ptr = this.create_fn_alloc_ptr(FnVal::Other(dlsym));
+                    let ptr = this.fn_ptr(FnVal::Other(dlsym));
                     this.write_pointer(ptr, dest)?;
                 } else {
                     this.write_null(dest)?;

src/shims/windows/foreign_items.rs

@@ -335,7 +335,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 this.read_target_isize(hModule)?;
                 let name = this.read_c_str(this.read_pointer(lpProcName)?)?;
                 if let Some(dlsym) = Dlsym::from_str(name, &this.tcx.sess.target.os)? {
-                    let ptr = this.create_fn_alloc_ptr(FnVal::Other(dlsym));
+                    let ptr = this.fn_ptr(FnVal::Other(dlsym));
                     this.write_pointer(ptr, dest)?;
                 } else {
                     this.write_null(dest)?;