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Fix async return handling #92

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Fix async return handling #92

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791ed01
Fix async return handling
JustusAdam Feb 8, 2024
8ce816d
Use Language items
JustusAdam Feb 8, 2024
5bc82f6
Cleaning changes
JustusAdam Feb 8, 2024
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134 changes: 93 additions & 41 deletions crates/flowistry/src/pdg/construct.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,17 +6,17 @@ use flowistry_pdg::{CallString, GlobalLocation, RichLocation};
use itertools::Itertools;
use log::{debug, trace};
use petgraph::graph::DiGraph;
use rustc_abi::FieldIdx;
use rustc_abi::{FieldIdx, VariantIdx};
use rustc_borrowck::consumers::{
places_conflict, BodyWithBorrowckFacts, PlaceConflictBias,
};
use rustc_hash::{FxHashMap, FxHashSet};
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_middle::{
mir::{
visit::Visitor, AggregateKind, BasicBlock, Body, Location, Operand, Place, PlaceElem,
Rvalue, Statement, StatementKind, Terminator, TerminatorEdges, TerminatorKind,
RETURN_PLACE,
visit::Visitor, AggregateKind, BasicBlock, Body, HasLocalDecls, Location, Operand,
Place, PlaceElem, Rvalue, Statement, StatementKind, Terminator, TerminatorEdges,
TerminatorKind, RETURN_PLACE,
},
ty::{GenericArg, GenericArgsRef, List, ParamEnv, TyCtxt, TyKind},
};
Expand Down Expand Up @@ -201,6 +201,25 @@ struct CallingContext<'tcx> {
call_stack: Vec<DefId>,
}

/// Stores ids that are needed to construct projections around async functions.
struct AsyncInfo {
poll_ready_variant_idx: VariantIdx,
poll_ready_field_idx: FieldIdx,
}

impl AsyncInfo {
fn make(tcx: TyCtxt) -> Option<Rc<Self>> {
let lang_items = tcx.lang_items();
let poll_def = tcx.adt_def(lang_items.poll()?);
let ready_vid = lang_items.poll_ready_variant()?;
assert_eq!(poll_def.variant_with_id(ready_vid).fields.len(), 1);
Some(Rc::new(Self {
poll_ready_variant_idx: poll_def.variant_index_with_id(ready_vid),
poll_ready_field_idx: 0_u32.into(),
}))
}
}

pub struct GraphConstructor<'tcx> {
tcx: TyCtxt<'tcx>,
params: PdgParams<'tcx>,
Expand All @@ -212,6 +231,7 @@ pub struct GraphConstructor<'tcx> {
body_assignments: utils::BodyAssignments,
calling_context: Option<CallingContext<'tcx>>,
start_loc: FxHashSet<RichLocation>,
async_info: Rc<AsyncInfo>,
}

macro_rules! trylet {
Expand All @@ -226,11 +246,20 @@ macro_rules! trylet {
impl<'tcx> GraphConstructor<'tcx> {
/// Creates a [`GraphConstructor`] at the root of the PDG.
pub fn root(params: PdgParams<'tcx>) -> Self {
GraphConstructor::new(params, None)
let tcx = params.tcx;
GraphConstructor::new(
params,
None,
AsyncInfo::make(tcx).expect("async functions are not defined"),
)
}

/// Creates [`GraphConstructor`] for a function resolved as `fn_resolution` in a given `calling_context`.
fn new(params: PdgParams<'tcx>, calling_context: Option<CallingContext<'tcx>>) -> Self {
fn new(
params: PdgParams<'tcx>,
calling_context: Option<CallingContext<'tcx>>,
async_info: Rc<AsyncInfo>,
) -> Self {
let tcx = params.tcx;
let def_id = params.root.def_id().expect_local();
let body_with_facts = borrowck_facts::get_body_with_borrowck_facts(tcx, def_id);
Expand Down Expand Up @@ -261,6 +290,7 @@ impl<'tcx> GraphConstructor<'tcx> {
def_id,
calling_context,
body_assignments,
async_info,
}
}

Expand Down Expand Up @@ -662,41 +692,57 @@ impl<'tcx> GraphConstructor<'tcx> {
let parent_body = &self.body;
let translate_to_parent = |child: Place<'tcx>| -> Option<Place<'tcx>> {
trace!(" Translating child place: {child:?}");
let (parent_place, child_projection) = if child.local == RETURN_PLACE {
(destination, &child.projection[..])
} else {
match call_kind {
// Map arguments to the argument array
CallKind::Direct => (
args[child.local.as_usize() - 1].place()?,
let (parent_place, child_projection) = match call_kind {
// Async return must be handled special, because it gets wrapped in `Poll::Ready`
CallKind::AsyncPoll if child.local == RETURN_PLACE => {
let async_info = self.async_info.as_ref();
let in_poll = destination.project_deeper(
&[PlaceElem::Downcast(None, async_info.poll_ready_variant_idx)],
tcx,
);
let field_idx = async_info.poll_ready_field_idx;
let child_inner_return_type = in_poll
.ty(parent_body.local_decls(), tcx)
.field_ty(tcx, field_idx);
(
in_poll.project_deeper(
&[PlaceElem::Field(field_idx, child_inner_return_type)],
tcx,
),
&child.projection[..],
),
// Map arguments to projections of the future, the poll's first argument
CallKind::AsyncPoll => {
if child.local.as_usize() == 1 {
let PlaceElem::Field(idx, _) = child.projection[0] else {
panic!("Unexpected non-projection of async context")
};
(args[idx.as_usize()].place()?, &child.projection[1 ..])
} else {
return None;
}
)
}
_ if child.local == RETURN_PLACE => (destination, &child.projection[..]),
// Map arguments to the argument array
CallKind::Direct => (
args[child.local.as_usize() - 1].place()?,
&child.projection[..],
),
// Map arguments to projections of the future, the poll's first argument
CallKind::AsyncPoll => {
if child.local.as_usize() == 1 {
let PlaceElem::Field(idx, _) = child.projection[0] else {
panic!("Unexpected non-projection of async context")
};
(args[idx.as_usize()].place()?, &child.projection[1 ..])
} else {
return None;
}
// Map closure captures to the first argument.
// Map formal parameters to the second argument.
CallKind::Indirect => {
if child.local.as_usize() == 1 {
(args[0].place()?, &child.projection[..])
} else {
let tuple_arg = args[1].place()?;
let _projection = child.projection.to_vec();
let field = FieldIdx::from_usize(child.local.as_usize() - 2);
let field_ty = tuple_arg.ty(parent_body.as_ref(), tcx).field_ty(tcx, field);
(
tuple_arg.project_deeper(&[PlaceElem::Field(field, field_ty)], tcx),
&child.projection[..],
)
}
}
// Map closure captures to the first argument.
// Map formal parameters to the second argument.
CallKind::Indirect => {
if child.local.as_usize() == 1 {
(args[0].place()?, &child.projection[..])
} else {
let tuple_arg = args[1].place()?;
let _projection = child.projection.to_vec();
let field = FieldIdx::from_usize(child.local.as_usize() - 2);
let field_ty = tuple_arg.ty(parent_body.as_ref(), tcx).field_ty(tcx, field);
(
tuple_arg.project_deeper(&[PlaceElem::Field(field, field_ty)], tcx),
&child.projection[..],
)
}
}
};
Expand Down Expand Up @@ -730,7 +776,8 @@ impl<'tcx> GraphConstructor<'tcx> {
param_env,
call_stack,
};
let child_constructor = GraphConstructor::new(params, Some(calling_context));
let child_constructor =
GraphConstructor::new(params, Some(calling_context), self.async_info.clone());

if let Some(callback) = &self.params.call_change_callback {
let info = CallInfo {
Expand Down Expand Up @@ -941,7 +988,12 @@ impl<'tcx> GraphConstructor<'tcx> {
call_string,
call_stack,
};
return GraphConstructor::new(params, Some(calling_context)).construct_partial();
return GraphConstructor::new(
params,
Some(calling_context),
self.async_info.clone(),
)
.construct_partial();
}

let mut analysis = DfAnalysis(self)
Expand Down
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