interpret: clean up deduplicating allocation functions

Author: RalfJung

Diff for: compiler/rustc_const_eval/src/interpret/place.rs

@@ -5,8 +5,7 @@
 use std::assert_matches::assert_matches;
 
 use either::{Either, Left, Right};
-use rustc_abi::{Align, BackendRepr, HasDataLayout, Size};
-use rustc_ast::Mutability;
+use rustc_abi::{BackendRepr, HasDataLayout, Size};
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::{bug, mir, span_bug};
@@ -1018,40 +1017,31 @@ where
         self.allocate_dyn(layout, kind, MemPlaceMeta::None)
     }
 
-    /// Allocates a sequence of bytes in the interpreter's memory.
-    /// For immutable allocations, uses deduplication to reuse existing memory.
-    /// For mutable allocations, creates a new unique allocation.
-    pub fn allocate_bytes(
+    /// Allocates a sequence of bytes in the interpreter's memory with alignment 1.
+    /// This is allocated in immutable global memory and deduplicated.
+    pub fn allocate_bytes_dedup(
         &mut self,
         bytes: &[u8],
-        align: Align,
-        kind: MemoryKind<M::MemoryKind>,
-        mutbl: Mutability,
     ) -> InterpResult<'tcx, Pointer<M::Provenance>> {
-        // Use cache for immutable strings.
-        if mutbl.is_not() {
-            // Use dedup'd allocation function.
-            let salt = M::get_global_alloc_salt(self, None);
-            let id = self.tcx.allocate_bytes_dedup(bytes, salt);
-
-            // Turn untagged "global" pointers (obtained via `tcx`) into the machine pointer to the allocation.
-            M::adjust_alloc_root_pointer(&self, Pointer::from(id), Some(kind))
-        } else {
-            // Allocate new memory for mutable data.
-            self.allocate_bytes_ptr(bytes, align, kind, mutbl)
-        }
+        let salt = M::get_global_alloc_salt(self, None);
+        let id = self.tcx.allocate_bytes_dedup(bytes, salt);
+
+        // Turn untagged "global" pointers (obtained via `tcx`) into the machine pointer to the allocation.
+        M::adjust_alloc_root_pointer(
+            &self,
+            Pointer::from(id),
+            M::GLOBAL_KIND.map(MemoryKind::Machine),
+        )
     }
 
-    /// Allocates a string in the interpreter's memory with metadata for length.
-    /// Uses `allocate_bytes` internally but adds string-specific metadata handling.
-    pub fn allocate_str(
+    /// Allocates a string in the interpreter's memory, returning it as a (wide) place.
+    /// This is allocated in immutable global memory and deduplicated.
+    pub fn allocate_str_dedup(
         &mut self,
         str: &str,
-        kind: MemoryKind<M::MemoryKind>,
-        mutbl: Mutability,
     ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {
         let bytes = str.as_bytes();
-        let ptr = self.allocate_bytes(bytes, Align::ONE, kind, mutbl)?;
+        let ptr = self.allocate_bytes_dedup(bytes)?;
 
         // Create length metadata for the string.
         let meta = Scalar::from_target_usize(u64::try_from(bytes.len()).unwrap(), self);

Diff for: compiler/rustc_const_eval/src/util/caller_location.rs

@@ -1,7 +1,7 @@
 use rustc_hir::LangItem;
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::LayoutOf;
-use rustc_middle::ty::{self, Mutability};
+use rustc_middle::ty::{self};
 use rustc_middle::{bug, mir};
 use rustc_span::symbol::Symbol;
 use tracing::trace;
@@ -20,12 +20,9 @@ fn alloc_caller_location<'tcx>(
     // This can fail if rustc runs out of memory right here. Trying to emit an error would be
     // pointless, since that would require allocating more memory than these short strings.
     let file = if loc_details.file {
-        ecx.allocate_str(filename.as_str(), MemoryKind::CallerLocation, Mutability::Not).unwrap()
+        ecx.allocate_str_dedup(filename.as_str()).unwrap()
     } else {
-        // FIXME: This creates a new allocation each time. It might be preferable to
-        // perform this allocation only once, and re-use the `MPlaceTy`.
-        // See https://github.com/rust-lang/rust/pull/89920#discussion_r730012398
-        ecx.allocate_str("<redacted>", MemoryKind::CallerLocation, Mutability::Not).unwrap()
+        ecx.allocate_str_dedup("<redacted>").unwrap()
     };
     let file = file.map_provenance(CtfeProvenance::as_immutable);
     let line = if loc_details.line { Scalar::from_u32(line) } else { Scalar::from_u32(0) };

Diff for: compiler/rustc_middle/src/ty/context.rs

@@ -1479,7 +1479,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self.mk_adt_def_from_data(ty::AdtDefData::new(self, did, kind, variants, repr))
     }
 
-    /// Allocates a read-only byte or string literal for `mir::interpret`.
+    /// Allocates a read-only byte or string literal for `mir::interpret` with alignment 1.
     /// Returns the same `AllocId` if called again with the same bytes.
     pub fn allocate_bytes_dedup(self, bytes: &[u8], salt: usize) -> interpret::AllocId {
         // Create an allocation that just contains these bytes.

Diff for: src/tools/miri/src/shims/backtrace.rs

@@ -1,5 +1,4 @@
 use rustc_abi::{ExternAbi, Size};
-use rustc_ast::ast::Mutability;
 use rustc_middle::ty::layout::LayoutOf as _;
 use rustc_middle::ty::{self, Instance, Ty};
 use rustc_span::{BytePos, Loc, Symbol, hygiene};
@@ -179,14 +178,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         match flags {
             0 => {
-                // These are "mutable" allocations as we consider them to be owned by the callee.
-                let name_alloc =
-                    this.allocate_str(&name, MiriMemoryKind::Rust.into(), Mutability::Mut)?;
-                let filename_alloc =
-                    this.allocate_str(&filename, MiriMemoryKind::Rust.into(), Mutability::Mut)?;
-
-                this.write_immediate(name_alloc.to_ref(this), &this.project_field(dest, 0)?)?;
-                this.write_immediate(filename_alloc.to_ref(this), &this.project_field(dest, 1)?)?;
+                throw_unsup_format!("miri_resolve_frame: v0 is not supported any more");
             }
             1 => {
                 this.write_scalar(

Diff for: src/tools/miri/src/shims/panic.rs

@@ -12,7 +12,6 @@
 //!   metadata we remembered when pushing said frame.
 
 use rustc_abi::ExternAbi;
-use rustc_ast::Mutability;
 use rustc_middle::{mir, ty};
 use rustc_target::spec::PanicStrategy;
 
@@ -161,7 +160,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let this = self.eval_context_mut();
 
         // First arg: message.
-        let msg = this.allocate_str(msg, MiriMemoryKind::Machine.into(), Mutability::Not)?;
+        let msg = this.allocate_str_dedup(msg)?;
 
         // Call the lang item.
         let panic = this.tcx.lang_items().panic_fn().unwrap();
@@ -180,7 +179,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let this = self.eval_context_mut();
 
         // First arg: message.
-        let msg = this.allocate_str(msg, MiriMemoryKind::Machine.into(), Mutability::Not)?;
+        let msg = this.allocate_str_dedup(msg)?;
 
         // Call the lang item.
         let panic = this.tcx.lang_items().panic_nounwind().unwrap();