Add a cache for const_val_to_op

Author: saethlin

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -4,10 +4,13 @@ use std::{fmt, mem};
 use either::{Either, Left, Right};
 
 use hir::CRATE_HIR_ID;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sync::Lock;
 use rustc_hir::{self as hir, def_id::DefId, definitions::DefPathData};
 use rustc_index::IndexVec;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::{ErrorHandled, InvalidMetaKind, ReportedErrorInfo};
+use rustc_middle::mir::ConstValue;
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::layout::{
     self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers,
@@ -47,6 +50,9 @@ pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
 
     /// The recursion limit (cached from `tcx.recursion_limit(())`)
     pub recursion_limit: Limit,
+
+    pub const_cache:
+        Lock<FxHashMap<(ConstValue<'tcx>, TyAndLayout<'tcx>, Span), OpTy<'tcx, M::Provenance>>>,
 }
 
 // The Phantomdata exists to prevent this type from being `Send`. If it were sent across a thread
@@ -440,6 +446,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             param_env,
             memory: Memory::new(),
             recursion_limit: tcx.recursion_limit(),
+            const_cache: Lock::new(FxHashMap::default()),
         }
     }
 

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -748,6 +748,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             })
         };
         let layout = from_known_layout(self.tcx, self.param_env, layout, || self.layout_of(ty))?;
+        let span = self.cur_span();
+        if let Some(op) = self.const_cache.lock().get(&(val_val, layout, span)).cloned() {
+            return Ok(op);
+        }
         let imm = match val_val {
             mir::ConstValue::Indirect { alloc_id, offset } => {
                 // We rely on mutability being set correctly in that allocation to prevent writes
@@ -764,7 +768,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 Immediate::new_slice(self.global_base_pointer(ptr)?.into(), meta, self)
             }
         };
-        Ok(OpTy { op: Operand::Immediate(imm), layout })
+        let res = OpTy { op: Operand::Immediate(imm), layout };
+        self.const_cache.lock().insert((val_val, layout, span), res.clone());
+        Ok(res)
     }
 }