From 1a0a4acd418c6e29fa3f3dce01523ded433d41c0 Mon Sep 17 00:00:00 2001
From: Oliver Scherer <github35764891676564198441@oli-obk.de>
Date: Tue, 11 Aug 2020 11:35:50 +0200
Subject: [PATCH] Add a function to `TyCtxt` for computing an `Allocation` for
 a `static` item's initializer

---
 src/librustc_middle/mir/interpret/queries.rs | 23 ++++++++++++++++++++
 src/librustc_mir/interpret/memory.rs         | 20 ++++-------------
 src/librustc_mir/interpret/mod.rs            |  2 +-
 3 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/src/librustc_middle/mir/interpret/queries.rs b/src/librustc_middle/mir/interpret/queries.rs
index 442e7f6b0f45e..dcc1f8b1a4b3c 100644
--- a/src/librustc_middle/mir/interpret/queries.rs
+++ b/src/librustc_middle/mir/interpret/queries.rs
@@ -74,4 +74,27 @@ impl<'tcx> TyCtxt<'tcx> {
             self.const_eval_validated(inputs)
         }
     }
+
+    /// Evaluate a static's initializer, returning the allocation of the initializer's memory.
+    pub fn eval_static_initializer(
+        self,
+        def_id: DefId,
+    ) -> Result<&'tcx mir::Allocation, ErrorHandled> {
+        trace!("eval_static_initializer: Need to compute {:?}", def_id);
+        assert!(self.is_static(def_id));
+        let instance = ty::Instance::mono(self, def_id);
+        let gid = GlobalId { instance, promoted: None };
+        self.eval_to_allocation(gid, ty::ParamEnv::reveal_all())
+    }
+
+    /// Evaluate anything constant-like, returning the allocation of the final memory.
+    fn eval_to_allocation(
+        self,
+        gid: GlobalId<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+    ) -> Result<&'tcx mir::Allocation, ErrorHandled> {
+        trace!("eval_to_allocation: Need to compute {:?}", gid);
+        let raw_const = self.const_eval_raw(param_env.and(gid))?;
+        Ok(self.global_alloc(raw_const.alloc_id).unwrap_memory())
+    }
 }
diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index 7dfa913fd08bd..6c9e013eb18ba 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -14,13 +14,12 @@ use std::ptr;
 
 use rustc_ast::ast::Mutability;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir::def_id::DefId;
-use rustc_middle::ty::{self, Instance, ParamEnv, TyCtxt};
+use rustc_middle::ty::{Instance, ParamEnv, TyCtxt};
 use rustc_target::abi::{Align, HasDataLayout, Size, TargetDataLayout};
 
 use super::{
-    AllocId, AllocMap, Allocation, AllocationExtra, CheckInAllocMsg, GlobalAlloc, GlobalId,
-    InterpResult, Machine, MayLeak, Pointer, PointerArithmetic, Scalar,
+    AllocId, AllocMap, Allocation, AllocationExtra, CheckInAllocMsg, GlobalAlloc, InterpResult,
+    Machine, MayLeak, Pointer, PointerArithmetic, Scalar,
 };
 use crate::util::pretty;
 
@@ -119,17 +118,6 @@ pub struct Memory<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
     pub tcx: TyCtxt<'tcx>,
 }
 
-/// Return the `tcx` allocation containing the initial value of the given static
-pub fn get_static(tcx: TyCtxt<'tcx>, def_id: DefId) -> InterpResult<'tcx, &'tcx Allocation> {
-    trace!("get_static: Need to compute {:?}", def_id);
-    let instance = Instance::mono(tcx, def_id);
-    let gid = GlobalId { instance, promoted: None };
-    // Use the raw query here to break validation cycles. Later uses of the static
-    // will call the full query anyway.
-    let raw_const = tcx.const_eval_raw(ty::ParamEnv::reveal_all().and(gid))?;
-    Ok(tcx.global_alloc(raw_const.alloc_id).unwrap_memory())
-}
-
 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for Memory<'mir, 'tcx, M> {
     #[inline]
     fn data_layout(&self) -> &TargetDataLayout {
@@ -489,7 +477,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
                     throw_unsup!(ReadExternStatic(def_id));
                 }
 
-                (get_static(tcx, def_id)?, Some(def_id))
+                (tcx.eval_static_initializer(def_id)?, Some(def_id))
             }
         };
         M::before_access_global(memory_extra, id, alloc, def_id, is_write)?;
diff --git a/src/librustc_mir/interpret/mod.rs b/src/librustc_mir/interpret/mod.rs
index 5218b03d65ecc..a931b0bbe9777 100644
--- a/src/librustc_mir/interpret/mod.rs
+++ b/src/librustc_mir/interpret/mod.rs
@@ -21,7 +21,7 @@ pub use rustc_middle::mir::interpret::*; // have all the `interpret` symbols in
 pub use self::eval_context::{Frame, FrameInfo, InterpCx, LocalState, LocalValue, StackPopCleanup};
 pub use self::intern::{intern_const_alloc_recursive, InternKind};
 pub use self::machine::{compile_time_machine, AllocMap, Machine, MayLeak, StackPopJump};
-pub use self::memory::{get_static, AllocCheck, FnVal, Memory, MemoryKind};
+pub use self::memory::{AllocCheck, FnVal, Memory, MemoryKind};
 pub use self::operand::{ImmTy, Immediate, OpTy, Operand};
 pub use self::place::{MPlaceTy, MemPlace, MemPlaceMeta, Place, PlaceTy};
 pub use self::validity::RefTracking;