From de34a9135069a559e3a2249b481fe551a5c1a8dd Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Thu, 29 Aug 2024 16:53:07 +0200 Subject: [PATCH] interpret/visitor: make memory order iteration slightly more efficient --- .../rustc_const_eval/src/interpret/visitor.rs | 19 ++++++++++--------- src/tools/miri/src/helpers.rs | 13 +++++-------- 2 files changed, 15 insertions(+), 17 deletions(-) diff --git a/compiler/rustc_const_eval/src/interpret/visitor.rs b/compiler/rustc_const_eval/src/interpret/visitor.rs index fd649d608c691..b02f12e3c7f0b 100644 --- a/compiler/rustc_const_eval/src/interpret/visitor.rs +++ b/compiler/rustc_const_eval/src/interpret/visitor.rs @@ -25,14 +25,15 @@ pub trait ValueVisitor<'tcx, M: Machine<'tcx>>: Sized { } /// This function provides the chance to reorder the order in which fields are visited for - /// `FieldsShape::Aggregate`: The order of fields will be - /// `(0..num_fields).map(aggregate_field_order)`. + /// `FieldsShape::Aggregate`. /// - /// The default means we iterate in source declaration order; alternative this can do an inverse - /// lookup in `memory_index` to use memory field order instead. + /// The default means we iterate in source declaration order; alternatively this can do some + /// work with `memory_index` to iterate in memory order. #[inline(always)] - fn aggregate_field_order(_memory_index: &IndexVec, idx: usize) -> usize { - idx + fn aggregate_field_iter( + memory_index: &IndexVec, + ) -> impl Iterator + 'static { + memory_index.indices() } // Recursive actions, ready to be overloaded. @@ -172,9 +173,9 @@ pub trait ValueVisitor<'tcx, M: Machine<'tcx>>: Sized { &FieldsShape::Union(fields) => { self.visit_union(v, fields)?; } - FieldsShape::Arbitrary { offsets, memory_index } => { - for idx in 0..offsets.len() { - let idx = Self::aggregate_field_order(memory_index, idx); + FieldsShape::Arbitrary { memory_index, .. } => { + for idx in Self::aggregate_field_iter(memory_index) { + let idx = idx.as_usize(); let field = self.ecx().project_field(v, idx)?; self.visit_field(v, idx, &field)?; } diff --git a/src/tools/miri/src/helpers.rs b/src/tools/miri/src/helpers.rs index 0483745621252..a546ad20fef98 100644 --- a/src/tools/miri/src/helpers.rs +++ b/src/tools/miri/src/helpers.rs @@ -630,14 +630,11 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> { self.ecx } - fn aggregate_field_order(memory_index: &IndexVec, idx: usize) -> usize { - // We need to do an *inverse* lookup: find the field that has position `idx` in memory order. - for (src_field, &mem_pos) in memory_index.iter_enumerated() { - if mem_pos as usize == idx { - return src_field.as_usize(); - } - } - panic!("invalid `memory_index`, could not find {}-th field in memory order", idx); + fn aggregate_field_iter( + memory_index: &IndexVec, + ) -> impl Iterator + 'static { + let inverse_memory_index = memory_index.invert_bijective_mapping(); + inverse_memory_index.into_iter() } // Hook to detect `UnsafeCell`.