From 0e68cbd45dc169e807b470687f4e8f270ac97039 Mon Sep 17 00:00:00 2001 From: Camille GILLOT <gillot.camille@gmail.com> Date: Sat, 15 Apr 2023 16:03:36 +0000 Subject: [PATCH 1/4] Remove useless special case. --- .../src/dataflow_const_prop.rs | 15 --------------- 1 file changed, 15 deletions(-) diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs index a56c5cc5c12f9..809a0a386e339 100644 --- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs +++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs @@ -520,21 +520,6 @@ impl<'tcx, 'map, 'a> Visitor<'tcx> for OperandCollector<'tcx, 'map, 'a> { _ => (), } } - - fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { - match rvalue { - Rvalue::Discriminant(place) => { - match self.state.get_discr(place.as_ref(), self.visitor.map) { - FlatSet::Top => (), - FlatSet::Elem(value) => { - self.visitor.before_effect.insert((location, *place), value); - } - FlatSet::Bottom => (), - } - } - _ => self.super_rvalue(rvalue, location), - } - } } struct DummyMachine; From 629cdb42d364a7de2845d24204c7018e1f9cd406 Mon Sep 17 00:00:00 2001 From: Camille GILLOT <gillot.camille@gmail.com> Date: Sat, 15 Apr 2023 16:04:20 +0000 Subject: [PATCH 2/4] Move eval_discriminant. --- .../src/dataflow_const_prop.rs | 30 +++++++++---------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs index 809a0a386e339..2f1e93664522e 100644 --- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs +++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs @@ -70,22 +70,6 @@ struct ConstAnalysis<'a, 'tcx> { param_env: ty::ParamEnv<'tcx>, } -impl<'tcx> ConstAnalysis<'_, 'tcx> { - fn eval_discriminant( - &self, - enum_ty: Ty<'tcx>, - variant_index: VariantIdx, - ) -> Option<ScalarTy<'tcx>> { - if !enum_ty.is_enum() { - return None; - } - let discr = enum_ty.discriminant_for_variant(self.tcx, variant_index)?; - let discr_layout = self.tcx.layout_of(self.param_env.and(discr.ty)).ok()?; - let discr_value = Scalar::try_from_uint(discr.val, discr_layout.size)?; - Some(ScalarTy(discr_value, discr.ty)) - } -} - impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> { type Value = FlatSet<ScalarTy<'tcx>>; @@ -377,6 +361,20 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> { } } + fn eval_discriminant( + &self, + enum_ty: Ty<'tcx>, + variant_index: VariantIdx, + ) -> Option<ScalarTy<'tcx>> { + if !enum_ty.is_enum() { + return None; + } + let discr = enum_ty.discriminant_for_variant(self.tcx, variant_index)?; + let discr_layout = self.tcx.layout_of(self.param_env.and(discr.ty)).ok()?; + let discr_value = Scalar::try_from_uint(discr.val, discr_layout.size)?; + Some(ScalarTy(discr_value, discr.ty)) + } + fn wrap_scalar(&self, scalar: Scalar, ty: Ty<'tcx>) -> FlatSet<ScalarTy<'tcx>> { FlatSet::Elem(ScalarTy(scalar, ty)) } From dd452ae70ecee1d3e07ca9fc10ce8220b2821578 Mon Sep 17 00:00:00 2001 From: Camille GILLOT <gillot.camille@gmail.com> Date: Sat, 15 Apr 2023 16:05:19 +0000 Subject: [PATCH 3/4] Simplify logic. --- compiler/rustc_mir_transform/src/dataflow_const_prop.rs | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs index 2f1e93664522e..3fdf556e15ea2 100644 --- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs +++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs @@ -157,12 +157,10 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> { // Flood everything now, so we can use `insert_value_idx` directly later. state.flood(target.as_ref(), self.map()); - let target = self.map().find(target.as_ref()); + let Some(target) = self.map().find(target.as_ref()) else { return }; - let value_target = target - .and_then(|target| self.map().apply(target, TrackElem::Field(0_u32.into()))); - let overflow_target = target - .and_then(|target| self.map().apply(target, TrackElem::Field(1_u32.into()))); + let value_target = self.map().apply(target, TrackElem::Field(0_u32.into())); + let overflow_target = self.map().apply(target, TrackElem::Field(1_u32.into())); if value_target.is_some() || overflow_target.is_some() { let (val, overflow) = self.binary_op(state, *op, left, right); From dd78b997b59b298a8e869db0def714c0630dcf94 Mon Sep 17 00:00:00 2001 From: Camille GILLOT <gillot.camille@gmail.com> Date: Sat, 15 Apr 2023 16:27:55 +0000 Subject: [PATCH 4/4] Reduce rightward drift. --- .../src/dataflow_const_prop.rs | 72 +++++++++---------- 1 file changed, 35 insertions(+), 37 deletions(-) diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs index 3fdf556e15ea2..d0823a8597da9 100644 --- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs +++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs @@ -110,48 +110,46 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> { // we must make sure that all `target as Variant#i` are `Top`. state.flood(target.as_ref(), self.map()); - if let Some(target_idx) = self.map().find(target.as_ref()) { - let (variant_target, variant_index) = match **kind { - AggregateKind::Tuple | AggregateKind::Closure(..) => { - (Some(target_idx), None) - } - AggregateKind::Adt(def_id, variant_index, ..) => { - match self.tcx.def_kind(def_id) { - DefKind::Struct => (Some(target_idx), None), - DefKind::Enum => ( - self.map.apply(target_idx, TrackElem::Variant(variant_index)), - Some(variant_index), - ), - _ => (None, None), - } - } - _ => (None, None), - }; - if let Some(variant_target_idx) = variant_target { - for (field_index, operand) in operands.iter().enumerate() { - if let Some(field) = self.map().apply( - variant_target_idx, - TrackElem::Field(FieldIdx::from_usize(field_index)), - ) { - let result = self.handle_operand(operand, state); - state.insert_idx(field, result, self.map()); - } + let Some(target_idx) = self.map().find(target.as_ref()) else { return }; + + let (variant_target, variant_index) = match **kind { + AggregateKind::Tuple | AggregateKind::Closure(..) => (Some(target_idx), None), + AggregateKind::Adt(def_id, variant_index, ..) => { + match self.tcx.def_kind(def_id) { + DefKind::Struct => (Some(target_idx), None), + DefKind::Enum => ( + self.map.apply(target_idx, TrackElem::Variant(variant_index)), + Some(variant_index), + ), + _ => return, } } - if let Some(variant_index) = variant_index - && let Some(discr_idx) = self.map().apply(target_idx, TrackElem::Discriminant) - { - // We are assigning the discriminant as part of an aggregate. - // This discriminant can only alias a variant field's value if the operand - // had an invalid value for that type. - // Using invalid values is UB, so we are allowed to perform the assignment - // without extra flooding. - let enum_ty = target.ty(self.local_decls, self.tcx).ty; - if let Some(discr_val) = self.eval_discriminant(enum_ty, variant_index) { - state.insert_value_idx(discr_idx, FlatSet::Elem(discr_val), &self.map); + _ => return, + }; + if let Some(variant_target_idx) = variant_target { + for (field_index, operand) in operands.iter().enumerate() { + if let Some(field) = self.map().apply( + variant_target_idx, + TrackElem::Field(FieldIdx::from_usize(field_index)), + ) { + let result = self.handle_operand(operand, state); + state.insert_idx(field, result, self.map()); } } } + if let Some(variant_index) = variant_index + && let Some(discr_idx) = self.map().apply(target_idx, TrackElem::Discriminant) + { + // We are assigning the discriminant as part of an aggregate. + // This discriminant can only alias a variant field's value if the operand + // had an invalid value for that type. + // Using invalid values is UB, so we are allowed to perform the assignment + // without extra flooding. + let enum_ty = target.ty(self.local_decls, self.tcx).ty; + if let Some(discr_val) = self.eval_discriminant(enum_ty, variant_index) { + state.insert_value_idx(discr_idx, FlatSet::Elem(discr_val), &self.map); + } + } } Rvalue::CheckedBinaryOp(op, box (left, right)) => { // Flood everything now, so we can use `insert_value_idx` directly later.