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Handle reading statics.

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This commit is contained in:
Camille GILLOT 2023-05-13 14:19:31 +00:00
parent 6ad6b4381c
commit 82f0468009
5 changed files with 276 additions and 40 deletions
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124
compiler/rustc_mir_transform/src/dataflow_const_prop.rs
View File

@ -6,7 +6,7 @@ use rustc_const_eval::const_eval::CheckAlignment;
use rustc_const_eval::interpret::{ImmTy, Immediate, InterpCx, OpTy, Projectable};
use rustc_data_structures::fx::FxHashMap;
use rustc_hir::def::DefKind;
use rustc_middle::mir::interpret::{ConstValue, Scalar};
use rustc_middle::mir::interpret::{AllocId, ConstAllocation, ConstValue, InterpResult, Scalar};
use rustc_middle::mir::visit::{MutVisitor, NonMutatingUseContext, PlaceContext, Visitor};
use rustc_middle::mir::*;
use rustc_middle::ty::layout::TyAndLayout;
@ -15,6 +15,7 @@ use rustc_mir_dataflow::value_analysis::{
Map, PlaceIndex, State, TrackElem, ValueAnalysis, ValueAnalysisWrapper, ValueOrPlace,
};
use rustc_mir_dataflow::{lattice::FlatSet, Analysis, Results, ResultsVisitor};
use rustc_span::def_id::DefId;
use rustc_span::{Span, DUMMY_SP};
use rustc_target::abi::{Align, FieldIdx, VariantIdx};
@ -78,7 +79,7 @@ struct ConstAnalysis<'a, 'tcx> {
}
impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
type Value = FlatSet<ScalarInt>;
type Value = FlatSet<Scalar>;
const NAME: &'static str = "ConstAnalysis";
@ -182,7 +183,7 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
if let Some(overflow_target) = overflow_target {
let overflow = match overflow {
FlatSet::Top => FlatSet::Top,
FlatSet::Elem(overflow) => FlatSet::Elem(overflow.into()),
FlatSet::Elem(overflow) => FlatSet::Elem(Scalar::from_bool(overflow)),
FlatSet::Bottom => FlatSet::Bottom,
};
// We have flooded `target` earlier.
@ -204,7 +205,7 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
&& let ty::Array(_, len) = operand_ty.ty.kind()
&& let Some(len) = ConstantKind::Ty(*len).eval(self.tcx, self.param_env).try_to_scalar_int()
{
state.insert_value_idx(target_len, FlatSet::Elem(len), self.map());
state.insert_value_idx(target_len, FlatSet::Elem(len.into()), self.map());
}
}
_ => self.super_assign(target, rvalue, state),
@ -222,7 +223,7 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
if let ty::Array(_, len) = place_ty.ty.kind() {
ConstantKind::Ty(*len)
.eval(self.tcx, self.param_env)
.try_to_scalar_int()
.try_to_scalar()
.map_or(FlatSet::Top, FlatSet::Elem)
} else if let [ProjectionElem::Deref] = place.projection[..] {
state.get_len(place.local.into(), self.map())
@ -281,7 +282,7 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
.bytes(),
_ => return ValueOrPlace::Value(FlatSet::Top),
};
ScalarInt::try_from_target_usize(val, self.tcx).map_or(FlatSet::Top, FlatSet::Elem)
FlatSet::Elem(Scalar::from_target_usize(val, &self.tcx))
}
Rvalue::Discriminant(place) => state.get_discr(place.as_ref(), self.map()),
_ => return self.super_rvalue(rvalue, state),
@ -297,7 +298,7 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
constant
.literal
.eval(self.tcx, self.param_env)
.try_to_scalar_int()
.try_to_scalar()
.map_or(FlatSet::Top, FlatSet::Elem)
}
@ -339,14 +340,21 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
/// The caller must have flooded `place`.
fn assign_operand(
&self,
state: &mut State<FlatSet<ScalarInt>>,
state: &mut State<FlatSet<Scalar>>,
place: PlaceIndex,
operand: &Operand<'tcx>,
) {
match operand {
Operand::Copy(rhs) | Operand::Move(rhs) => {
if let Some(rhs) = self.map.find(rhs.as_ref()) {
state.insert_place_idx(place, rhs, &self.map)
state.insert_place_idx(place, rhs, &self.map);
} else if rhs.projection.first() == Some(&PlaceElem::Deref)
&& let FlatSet::Elem(pointer) = state.get(rhs.local.into(), &self.map)
&& let rhs_ty = self.local_decls[rhs.local].ty
&& let Ok(rhs_layout) = self.tcx.layout_of(self.param_env.and(rhs_ty))
{
let op = ImmTy::from_scalar(pointer, rhs_layout).into();
self.assign_constant(state, place, op, &rhs.projection);
}
}
Operand::Constant(box constant) => {
@ -363,7 +371,7 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
#[instrument(level = "trace", skip(self, state))]
fn assign_constant(
&self,
state: &mut State<FlatSet<ScalarInt>>,
state: &mut State<FlatSet<Scalar>>,
place: PlaceIndex,
mut operand: OpTy<'tcx>,
projection: &[PlaceElem<'tcx>],
@ -371,7 +379,7 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
for &(mut proj_elem) in projection {
if let PlaceElem::Index(index) = proj_elem {
if let FlatSet::Elem(index) = state.get(index.into(), &self.map)
&& let Ok(offset) = index.try_to_target_usize(self.tcx)
&& let Ok(offset) = index.to_target_usize(&self.tcx)
&& let Some(min_length) = offset.checked_add(1)
{
proj_elem = PlaceElem::ConstantIndex { offset, min_length, from_end: false };
@ -406,7 +414,7 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
&mut |place, op| {
if let Ok(imm) = self.ecx.read_immediate_raw(op)
&& let Some(imm) = imm.right()
&& let Immediate::Scalar(Scalar::Int(scalar)) = *imm
&& let Immediate::Scalar(scalar) = *imm
{
state.insert_value_idx(place, FlatSet::Elem(scalar), &self.map);
}
@ -418,11 +426,11 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
fn binary_op(
&self,
state: &mut State<FlatSet<ScalarInt>>,
state: &mut State<FlatSet<Scalar>>,
op: BinOp,
left: &Operand<'tcx>,
right: &Operand<'tcx>,
) -> (FlatSet<ScalarInt>, FlatSet<bool>) {
) -> (FlatSet<Scalar>, FlatSet<bool>) {
let left = self.eval_operand(left, state);
let right = self.eval_operand(right, state);
@ -431,9 +439,7 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
// Both sides are known, do the actual computation.
(FlatSet::Elem(left), FlatSet::Elem(right)) => {
match self.ecx.overflowing_binary_op(op, &left, &right) {
Ok((Scalar::Int(val), overflow, _)) => {
(FlatSet::Elem(val), FlatSet::Elem(overflow))
}
Ok((val, overflow, _)) => (FlatSet::Elem(val), FlatSet::Elem(overflow)),
_ => (FlatSet::Top, FlatSet::Top),
}
}
@ -445,9 +451,6 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
}
let arg_scalar = const_arg.to_scalar();
let Ok(arg_scalar) = arg_scalar.try_to_int() else {
return (FlatSet::Top, FlatSet::Top);
};
let Ok(arg_value) = arg_scalar.to_bits(layout.size) else {
return (FlatSet::Top, FlatSet::Top);
};
@ -473,7 +476,7 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
fn eval_operand(
&self,
op: &Operand<'tcx>,
state: &mut State<FlatSet<ScalarInt>>,
state: &mut State<FlatSet<Scalar>>,
) -> FlatSet<ImmTy<'tcx>> {
let value = match self.handle_operand(op, state) {
ValueOrPlace::Value(value) => value,
@ -492,24 +495,24 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
}
}
fn eval_discriminant(&self, enum_ty: Ty<'tcx>, variant_index: VariantIdx) -> Option<ScalarInt> {
fn eval_discriminant(&self, enum_ty: Ty<'tcx>, variant_index: VariantIdx) -> Option<Scalar> {
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 = ScalarInt::try_from_uint(discr.val, discr_layout.size)?;
let discr_value = Scalar::try_from_uint(discr.val, discr_layout.size)?;
Some(discr_value)
}
fn wrap_immediate(&self, imm: Immediate) -> FlatSet<ScalarInt> {
fn wrap_immediate(&self, imm: Immediate) -> FlatSet<Scalar> {
match imm {
Immediate::Scalar(Scalar::Int(scalar)) => FlatSet::Elem(scalar),
Immediate::Scalar(scalar) => FlatSet::Elem(scalar),
_ => FlatSet::Top,
}
}
fn wrap_immty(&self, val: ImmTy<'tcx>) -> FlatSet<ScalarInt> {
fn wrap_immty(&self, val: ImmTy<'tcx>) -> FlatSet<Scalar> {
self.wrap_immediate(*val)
}
}
@ -550,7 +553,7 @@ impl<'mir, 'tcx>
ResultsVisitor<'mir, 'tcx, Results<'tcx, ValueAnalysisWrapper<ConstAnalysis<'_, 'tcx>>>>
for CollectAndPatch<'tcx, '_>
{
type FlowState = State<FlatSet<ScalarInt>>;
type FlowState = State<FlatSet<Scalar>>;
fn visit_statement_before_primary_effect(
&mut self,
@ -580,14 +583,10 @@ impl<'mir, 'tcx>
// Don't overwrite the assignment if it already uses a constant (to keep the span).
}
StatementKind::Assign(box (place, _)) => {
match state.get(place.as_ref(), &results.analysis.0.map) {
FlatSet::Top => (),
FlatSet::Elem(value) => {
self.assignments.insert(location, value);
}
FlatSet::Bottom => {
// This assignment is either unreachable, or an uninitialized value is assigned.
}
if let FlatSet::Elem(Scalar::Int(value)) =
state.get(place.as_ref(), &results.analysis.0.map)
{
self.assignments.insert(location, value);
}
}
_ => (),
@ -657,7 +656,7 @@ impl<'tcx> MutVisitor<'tcx> for CollectAndPatch<'tcx, '_> {
}
struct OperandCollector<'tcx, 'map, 'locals, 'a> {
state: &'a State<FlatSet<ScalarInt>>,
state: &'a State<FlatSet<Scalar>>,
visitor: &'a mut CollectAndPatch<'tcx, 'locals>,
map: &'map Map,
}
@ -665,7 +664,7 @@ struct OperandCollector<'tcx, 'map, 'locals, 'a> {
impl<'tcx> Visitor<'tcx> for OperandCollector<'tcx, '_, '_, '_> {
fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
if let Some(place) = operand.place() {
if let FlatSet::Elem(value) = self.state.get(place.as_ref(), self.map) {
if let FlatSet::Elem(Scalar::Int(value)) = self.state.get(place.as_ref(), self.map) {
self.visitor.before_effect.insert((location, place), value);
} else if !place.projection.is_empty() {
// Try to propagate into `Index` projections.
@ -676,7 +675,7 @@ impl<'tcx> Visitor<'tcx> for OperandCollector<'tcx, '_, '_, '_> {
fn visit_local(&mut self, local: Local, ctxt: PlaceContext, location: Location) {
if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy | NonMutatingUseContext::Move) = ctxt
&& let FlatSet::Elem(value) = self.state.get(local.into(), self.map)
&& let FlatSet::Elem(Scalar::Int(value)) = self.state.get(local.into(), self.map)
{
self.visitor.before_effect.insert((location, local.into()), value);
}
@ -685,6 +684,34 @@ impl<'tcx> Visitor<'tcx> for OperandCollector<'tcx, '_, '_, '_> {
struct DummyMachine;
/// Macro for machine-specific `InterpError` without allocation.
/// (These will never be shown to the user, but they help diagnose ICEs.)
macro_rules! throw_machine_stop_str {
($($tt:tt)*) => {{
// We make a new local type for it. The type itself does not carry any information,
// but its vtable (for the `MachineStopType` trait) does.
#[derive(Debug)]
struct Zst;
// Printing this type shows the desired string.
impl std::fmt::Display for Zst {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, $($tt)*)
}
}
impl rustc_middle::mir::interpret::MachineStopType for Zst {
fn diagnostic_message(&self) -> rustc_errors::DiagnosticMessage {
self.to_string().into()
}
fn add_args(
self: Box<Self>,
_: &mut dyn FnMut(std::borrow::Cow<'static, str>, rustc_errors::DiagnosticArgValue<'static>),
) {}
}
throw_machine_stop!(Zst)
}};
}
impl<'mir, 'tcx: 'mir> rustc_const_eval::interpret::Machine<'mir, 'tcx> for DummyMachine {
rustc_const_eval::interpret::compile_time_machine!(<'mir, 'tcx>);
type MemoryKind = !;
@ -714,6 +741,27 @@ impl<'mir, 'tcx: 'mir> rustc_const_eval::interpret::Machine<'mir, 'tcx> for Dumm
unimplemented!()
}
fn before_access_global(
_tcx: TyCtxt<'tcx>,
_machine: &Self,
_alloc_id: AllocId,
alloc: ConstAllocation<'tcx>,
_static_def_id: Option<DefId>,
is_write: bool,
) -> InterpResult<'tcx> {
if is_write {
throw_machine_stop_str!("can't write to global");
}
// If the static allocation is mutable, then we can't const prop it as its content
// might be different at runtime.
if alloc.inner().mutability.is_mut() {
throw_machine_stop_str!("can't access mutable globals in ConstProp");
}
Ok(())
}
fn find_mir_or_eval_fn(
_ecx: &mut InterpCx<'mir, 'tcx, Self>,
_instance: ty::Instance<'tcx>,

13
tests/mir-opt/dataflow-const-prop/enum.rs
View File

@ -4,6 +4,7 @@
use std::intrinsics::mir::*;
#[derive(Copy, Clone)]
enum E {
V1(i32),
V2(i32)
@ -22,6 +23,17 @@ fn constant() {
let x = match e { E::V1(x) => x, E::V2(x) => x };
}
// EMIT_MIR enum.statics.DataflowConstProp.diff
fn statics() {
static C: E = E::V1(0);
let e = C;
let x = match e { E::V1(x) => x, E::V2(x) => x };
static RC: &E = &E::V2(4);
let e = RC;
let x = match e { E::V1(x) => x, E::V2(x) => x };
}
#[rustc_layout_scalar_valid_range_start(1)]
#[rustc_nonnull_optimization_guaranteed]
struct NonZeroUsize(usize);
@ -71,6 +83,7 @@ fn multiple(x: bool, i: u8) {
fn main() {
simple();
constant();
statics();
mutate_discriminant();
multiple(false, 5);
}

126
tests/mir-opt/dataflow-const-prop/enum.statics.DataflowConstProp.diff Normal file
View File

@ -0,0 +1,126 @@
- // MIR for `statics` before DataflowConstProp
+ // MIR for `statics` after DataflowConstProp
fn statics() -> () {
let mut _0: ();
let _1: E;
let mut _2: &E;
let mut _4: isize;
let mut _8: &&E;
let mut _10: isize;
scope 1 {
debug e => _1;
let _3: i32;
let _5: i32;
let _6: i32;
scope 2 {
debug x => _3;
let _7: &E;
scope 5 {
debug e => _7;
let _9: &i32;
let _11: &i32;
let _12: &i32;
scope 6 {
debug x => _9;
}
scope 7 {
debug x => _11;
}
scope 8 {
debug x => _12;
}
}
}
scope 3 {
debug x => _5;
}
scope 4 {
debug x => _6;
}
}
bb0: {
StorageLive(_1);
StorageLive(_2);
_2 = const {alloc1: &E};
_1 = (*_2);
StorageDead(_2);
StorageLive(_3);
- _4 = discriminant(_1);
- switchInt(move _4) -> [0: bb3, 1: bb1, otherwise: bb2];
+ _4 = const 0_isize;
+ switchInt(const 0_isize) -> [0: bb3, 1: bb1, otherwise: bb2];
}
bb1: {
StorageLive(_6);
_6 = ((_1 as V2).0: i32);
_3 = _6;
StorageDead(_6);
goto -> bb4;
}
bb2: {
unreachable;
}
bb3: {
StorageLive(_5);
- _5 = ((_1 as V1).0: i32);
- _3 = _5;
+ _5 = const 0_i32;
+ _3 = const 0_i32;
StorageDead(_5);
goto -> bb4;
}
bb4: {
StorageLive(_7);
StorageLive(_8);
_8 = const {alloc2: &&E};
_7 = (*_8);
StorageDead(_8);
StorageLive(_9);
_10 = discriminant((*_7));
switchInt(move _10) -> [0: bb6, 1: bb5, otherwise: bb2];
}
bb5: {
StorageLive(_12);
_12 = &(((*_7) as V2).0: i32);
_9 = &(*_12);
StorageDead(_12);
goto -> bb7;
}
bb6: {
StorageLive(_11);
_11 = &(((*_7) as V1).0: i32);
_9 = _11;
StorageDead(_11);
goto -> bb7;
}
bb7: {
_0 = const ();
StorageDead(_9);
StorageDead(_7);
StorageDead(_3);
StorageDead(_1);
return;
}
}
alloc2 (static: RC, size: 8, align: 8) {
╾───────alloc14───────╼ │ ╾──────╼
}
alloc14 (size: 8, align: 4) {
01 00 00 00 04 00 00 00 │ ........
}
alloc1 (static: statics::C, size: 8, align: 4) {
00 00 00 00 00 00 00 00 │ ........
}

48
tests/mir-opt/dataflow-const-prop/struct.main.DataflowConstProp.diff
View File

@ -8,6 +8,12 @@
let mut _5: i32;
let mut _6: i32;
let mut _11: BigStruct;
let mut _16: &&BigStruct;
let mut _17: &BigStruct;
let mut _18: &BigStruct;
let mut _19: &BigStruct;
let mut _20: &BigStruct;
let mut _21: &BigStruct;
scope 1 {
debug s => _1;
let _2: i32;
@ -25,6 +31,16 @@
debug b => _8;
debug c => _9;
debug d => _10;
let _12: S;
let _13: u8;
let _14: f32;
let _15: S;
scope 5 {
debug a => _12;
debug b => _13;
debug c => _14;
debug d => _15;
}
}
}
}
@ -55,7 +71,7 @@
StorageLive(_11);
_11 = const _;
StorageLive(_7);
- _7 = move (_11.0: S);
- _7 = (_11.0: S);
+ _7 = const S(1_i32);
StorageLive(_8);
- _8 = (_11.1: u8);
@ -64,10 +80,30 @@
- _9 = (_11.2: f32);
+ _9 = const 7f32;
StorageLive(_10);
- _10 = move (_11.3: S);
- _10 = (_11.3: S);
+ _10 = const S(13_i32);
StorageDead(_11);
StorageLive(_16);
_16 = const {alloc1: &&BigStruct};
_17 = deref_copy (*_16);
StorageLive(_12);
_18 = deref_copy (*_16);
_12 = ((*_18).0: S);
StorageLive(_13);
_19 = deref_copy (*_16);
_13 = ((*_19).1: u8);
StorageLive(_14);
_20 = deref_copy (*_16);
_14 = ((*_20).2: f32);
StorageLive(_15);
_21 = deref_copy (*_16);
_15 = ((*_21).3: S);
StorageDead(_16);
_0 = const ();
StorageDead(_15);
StorageDead(_14);
StorageDead(_13);
StorageDead(_12);
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
@ -79,3 +115,11 @@
}
}
alloc1 (static: STAT, size: 8, align: 8) {
╾───────alloc15───────╼ │ ╾──────╼
}
alloc15 (size: 16, align: 4) {
01 00 00 00 00 00 e0 40 0d 00 00 00 05 __ __ __ │ .......@.....░░░
}

5
tests/mir-opt/dataflow-const-prop/struct.rs
View File

@ -1,7 +1,9 @@
// unit-test: DataflowConstProp
#[derive(Copy, Clone)]
struct S(i32);
#[derive(Copy, Clone)]
struct BigStruct(S, u8, f32, S);
// EMIT_MIR struct.main.DataflowConstProp.diff
@ -13,4 +15,7 @@ fn main() {
const VAL: BigStruct = BigStruct(S(1), 5, 7., S(13));
let BigStruct(a, b, c, d) = VAL;
static STAT: &BigStruct = &BigStruct(S(1), 5, 7., S(13));
let BigStruct(a, b, c, d) = *STAT;
}