Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Check projection types before inlining MIR #100571

Merged
merged 3 commits into from
Aug 25, 2022
Merged

Check projection types before inlining MIR #100571

Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
e4fd2bd
Refactor cost computation as a visitor.
cjgillot Aug 15, 2022
10e71df
Also validate types before inlining.
cjgillot Aug 15, 2022
911cbae
Add test.
cjgillot Aug 21, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
214 changes: 122 additions & 92 deletions compiler/rustc_mir_transform/src/inline.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -409,118 +409,56 @@ impl<'tcx> Inliner<'tcx> {
debug!(" final inline threshold = {}", threshold);

// FIXME: Give a bonus to functions with only a single caller
let mut first_block = true;
let mut cost = 0;
let diverges = matches!(
callee_body.basic_blocks()[START_BLOCK].terminator().kind,
TerminatorKind::Unreachable | TerminatorKind::Call { target: None, .. }
);
if diverges && !matches!(callee_attrs.inline, InlineAttr::Always) {
return Err("callee diverges unconditionally");
}

let mut checker = CostChecker {
tcx: self.tcx,
param_env: self.param_env,
instance: callsite.callee,
callee_body,
cost: 0,
};

// Traverse the MIR manually so we can account for the effects of
// inlining on the CFG.
// Traverse the MIR manually so we can account for the effects of inlining on the CFG.
let mut work_list = vec![START_BLOCK];
let mut visited = BitSet::new_empty(callee_body.basic_blocks().len());
while let Some(bb) = work_list.pop() {
if !visited.insert(bb.index()) {
continue;
}

let blk = &callee_body.basic_blocks()[bb];
checker.visit_basic_block_data(bb, blk);

for stmt in &blk.statements {
// Don't count StorageLive/StorageDead in the inlining cost.
match stmt.kind {
StatementKind::StorageLive(_)
| StatementKind::StorageDead(_)
| StatementKind::Deinit(_)
| StatementKind::Nop => {}
_ => cost += INSTR_COST,
}
}
let term = blk.terminator();
let mut is_drop = false;
match term.kind {
TerminatorKind::Drop { ref place, target, unwind }
| TerminatorKind::DropAndReplace { ref place, target, unwind, .. } => {
is_drop = true;
work_list.push(target);
// If the place doesn't actually need dropping, treat it like
// a regular goto.
let ty = callsite.callee.subst_mir(self.tcx, &place.ty(callee_body, tcx).ty);
if ty.needs_drop(tcx, self.param_env) {
cost += CALL_PENALTY;
if let Some(unwind) = unwind {
cost += LANDINGPAD_PENALTY;
work_list.push(unwind);
}
} else {
cost += INSTR_COST;
}
}

TerminatorKind::Unreachable | TerminatorKind::Call { target: None, .. }
if first_block =>
{
// If the function always diverges, don't inline
// unless the cost is zero
threshold = 0;
}
wesleywiser marked this conversation as resolved.
Show resolved Hide resolved

TerminatorKind::Call { func: Operand::Constant(ref f), cleanup, .. } => {
if let ty::FnDef(def_id, _) =
*callsite.callee.subst_mir(self.tcx, &f.literal.ty()).kind()
{
// Don't give intrinsics the extra penalty for calls
if tcx.is_intrinsic(def_id) {
cost += INSTR_COST;
} else {
cost += CALL_PENALTY;
}
} else {
cost += CALL_PENALTY;
}
if cleanup.is_some() {
cost += LANDINGPAD_PENALTY;
}
}
TerminatorKind::Assert { cleanup, .. } => {
cost += CALL_PENALTY;

if cleanup.is_some() {
cost += LANDINGPAD_PENALTY;
}
}
TerminatorKind::Resume => cost += RESUME_PENALTY,
TerminatorKind::InlineAsm { cleanup, .. } => {
cost += INSTR_COST;
if let TerminatorKind::Drop { ref place, target, unwind }
| TerminatorKind::DropAndReplace { ref place, target, unwind, .. } = term.kind
{
work_list.push(target);

if cleanup.is_some() {
cost += LANDINGPAD_PENALTY;
// If the place doesn't actually need dropping, treat it like a regular goto.
let ty = callsite.callee.subst_mir(self.tcx, &place.ty(callee_body, tcx).ty);
if ty.needs_drop(tcx, self.param_env) && let Some(unwind) = unwind {
work_list.push(unwind);
}
}
_ => cost += INSTR_COST,
}

if !is_drop {
for succ in term.successors() {
work_list.push(succ);
}
} else {
work_list.extend(term.successors())
}

first_block = false;
}

// Count up the cost of local variables and temps, if we know the size
// use that, otherwise we use a moderately-large dummy cost.

let ptr_size = tcx.data_layout.pointer_size.bytes();

for v in callee_body.vars_and_temps_iter() {
let ty = callsite.callee.subst_mir(self.tcx, &callee_body.local_decls[v].ty);
// Cost of the var is the size in machine-words, if we know
// it.
if let Some(size) = type_size_of(tcx, self.param_env, ty) {
cost += ((size + ptr_size - 1) / ptr_size) as usize;
} else {
cost += UNKNOWN_SIZE_COST;
}
checker.visit_local_decl(v, &callee_body.local_decls[v]);
}

let cost = checker.cost;
if let InlineAttr::Always = callee_attrs.inline {
debug!("INLINING {:?} because inline(always) [cost={}]", callsite, cost);
Ok(())
Expand Down Expand Up @@ -790,6 +728,98 @@ fn type_size_of<'tcx>(
tcx.layout_of(param_env.and(ty)).ok().map(|layout| layout.size.bytes())
}

/// Verify that the callee body is compatible with the caller.
///
/// This visitor mostly computes the inlining cost,
/// but also needs to verify that types match because of normalization failure.
struct CostChecker<'b, 'tcx> {
tcx: TyCtxt<'tcx>,
param_env: ParamEnv<'tcx>,
cost: usize,
callee_body: &'b Body<'tcx>,
instance: ty::Instance<'tcx>,
}

impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
// Don't count StorageLive/StorageDead in the inlining cost.
match statement.kind {
StatementKind::StorageLive(_)
| StatementKind::StorageDead(_)
| StatementKind::Deinit(_)
| StatementKind::Nop => {}
_ => self.cost += INSTR_COST,
}

self.super_statement(statement, location);
}

fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
let tcx = self.tcx;
match terminator.kind {
TerminatorKind::Drop { ref place, unwind, .. }
| TerminatorKind::DropAndReplace { ref place, unwind, .. } => {
// If the place doesn't actually need dropping, treat it like a regular goto.
let ty = self.instance.subst_mir(tcx, &place.ty(self.callee_body, tcx).ty);
if ty.needs_drop(tcx, self.param_env) {
self.cost += CALL_PENALTY;
if unwind.is_some() {
self.cost += LANDINGPAD_PENALTY;
}
} else {
self.cost += INSTR_COST;
}
}
TerminatorKind::Call { func: Operand::Constant(ref f), cleanup, .. } => {
let fn_ty = self.instance.subst_mir(tcx, &f.literal.ty());
self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind() && tcx.is_intrinsic(def_id) {
// Don't give intrinsics the extra penalty for calls
INSTR_COST
} else {
CALL_PENALTY
};
if cleanup.is_some() {
self.cost += LANDINGPAD_PENALTY;
}
}
TerminatorKind::Assert { cleanup, .. } => {
self.cost += CALL_PENALTY;
if cleanup.is_some() {
self.cost += LANDINGPAD_PENALTY;
}
}
TerminatorKind::Resume => self.cost += RESUME_PENALTY,
TerminatorKind::InlineAsm { cleanup, .. } => {
self.cost += INSTR_COST;
if cleanup.is_some() {
self.cost += LANDINGPAD_PENALTY;
}
}
_ => self.cost += INSTR_COST,
}

self.super_terminator(terminator, location);
}

/// Count up the cost of local variables and temps, if we know the size
/// use that, otherwise we use a moderately-large dummy cost.
fn visit_local_decl(&mut self, local: Local, local_decl: &LocalDecl<'tcx>) {
let tcx = self.tcx;
let ptr_size = tcx.data_layout.pointer_size.bytes();

let ty = self.instance.subst_mir(tcx, &local_decl.ty);
// Cost of the var is the size in machine-words, if we know
// it.
if let Some(size) = type_size_of(tcx, self.param_env, ty) {
self.cost += ((size + ptr_size - 1) / ptr_size) as usize;
} else {
self.cost += UNKNOWN_SIZE_COST;
}

self.super_local_decl(local, local_decl)
}
}

/**
* Integrator.
*
Expand Down