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Support inlining diverging function calls
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Additionally introduce storage markers for all temporaries created by
the inliner. The temporary introduced for destination rebrorrow, didn't
use them previously.
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tmiasko committed Nov 9, 2020
1 parent dc4d74d commit ffa70d7
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Showing 7 changed files with 256 additions and 76 deletions.
152 changes: 76 additions & 76 deletions compiler/rustc_mir/src/transform/inline.rs
Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,8 @@ pub struct Inline;
#[derive(Copy, Clone, Debug)]
struct CallSite<'tcx> {
callee: Instance<'tcx>,
bb: BasicBlock,
block: BasicBlock,
target: Option<BasicBlock>,
source_info: SourceInfo,
}

Expand Down Expand Up @@ -175,8 +176,7 @@ impl Inliner<'tcx> {

// Only consider direct calls to functions
let terminator = bb_data.terminator();
// FIXME: Handle inlining of diverging calls
if let TerminatorKind::Call { func: ref op, destination: Some(_), .. } = terminator.kind {
if let TerminatorKind::Call { func: ref op, ref destination, .. } = terminator.kind {
if let ty::FnDef(callee_def_id, substs) = *op.ty(caller_body, self.tcx).kind() {
// To resolve an instance its substs have to be fully normalized, so
// we do this here.
Expand All @@ -190,7 +190,12 @@ impl Inliner<'tcx> {
return None;
}

return Some(CallSite { callee, bb, source_info: terminator.source_info });
return Some(CallSite {
callee,
block: bb,
target: destination.map(|(_, target)| target),
source_info: terminator.source_info,
});
}
}

Expand Down Expand Up @@ -398,9 +403,9 @@ impl Inliner<'tcx> {
caller_body: &mut Body<'tcx>,
mut callee_body: Body<'tcx>,
) {
let terminator = caller_body[callsite.bb].terminator.take().unwrap();
let terminator = caller_body[callsite.block].terminator.take().unwrap();
match terminator.kind {
TerminatorKind::Call { args, destination: Some(destination), cleanup, .. } => {
TerminatorKind::Call { args, destination, cleanup, .. } => {
// If the call is something like `a[*i] = f(i)`, where
// `i : &mut usize`, then just duplicating the `a[*i]`
// Place could result in two different locations if `f`
Expand All @@ -417,43 +422,39 @@ impl Inliner<'tcx> {
false
}

let dest = if dest_needs_borrow(destination.0) {
trace!("creating temp for return destination");
let dest = Rvalue::Ref(
self.tcx.lifetimes.re_erased,
BorrowKind::Mut { allow_two_phase_borrow: false },
destination.0,
);

let ty = dest.ty(caller_body, self.tcx);

let temp = LocalDecl::new(ty, callsite.source_info.span);

let tmp = caller_body.local_decls.push(temp);
let tmp = Place::from(tmp);

let stmt = Statement {
source_info: callsite.source_info,
kind: StatementKind::Assign(box (tmp, dest)),
};
caller_body[callsite.bb].statements.push(stmt);
self.tcx.mk_place_deref(tmp)
let dest = if let Some((destination_place, _)) = destination {
if dest_needs_borrow(destination_place) {
trace!("creating temp for return destination");
let dest = Rvalue::Ref(
self.tcx.lifetimes.re_erased,
BorrowKind::Mut { allow_two_phase_borrow: false },
destination_place,
);
let dest_ty = dest.ty(caller_body, self.tcx);
let temp = Place::from(self.new_call_temp(caller_body, &callsite, dest_ty));
caller_body[callsite.block].statements.push(Statement {
source_info: callsite.source_info,
kind: StatementKind::Assign(box (temp, dest)),
});
self.tcx.mk_place_deref(temp)
} else {
destination_place
}
} else {
destination.0
trace!("creating temp for return place");
Place::from(self.new_call_temp(caller_body, &callsite, callee_body.return_ty()))
};

let return_block = destination.1;

// Copy the arguments if needed.
let args: Vec<_> = self.make_call_args(args, &callsite, caller_body, return_block);
let args: Vec<_> = self.make_call_args(args, &callsite, caller_body);

let mut integrator = Integrator {
args: &args,
new_locals: Local::new(caller_body.local_decls.len())..,
new_scopes: SourceScope::new(caller_body.source_scopes.len())..,
new_blocks: BasicBlock::new(caller_body.basic_blocks().len())..,
destination: dest,
return_block,
return_block: callsite.target,
cleanup_block: cleanup,
in_cleanup_block: false,
tcx: self.tcx,
Expand Down Expand Up @@ -502,7 +503,7 @@ impl Inliner<'tcx> {
caller_body.var_debug_info.extend(callee_body.var_debug_info.drain(..));
caller_body.basic_blocks_mut().extend(callee_body.basic_blocks_mut().drain(..));

caller_body[callsite.bb].terminator = Some(Terminator {
caller_body[callsite.block].terminator = Some(Terminator {
source_info: callsite.source_info,
kind: TerminatorKind::Goto { target: integrator.map_block(START_BLOCK) },
});
Expand All @@ -526,7 +527,6 @@ impl Inliner<'tcx> {
args: Vec<Operand<'tcx>>,
callsite: &CallSite<'tcx>,
caller_body: &mut Body<'tcx>,
return_block: BasicBlock,
) -> Vec<Local> {
let tcx = self.tcx;

Expand Down Expand Up @@ -557,18 +557,8 @@ impl Inliner<'tcx> {
// `callee_body.spread_arg == None`, instead of special-casing closures.
if tcx.is_closure(callsite.callee.def_id()) {
let mut args = args.into_iter();
let self_ = self.create_temp_if_necessary(
args.next().unwrap(),
callsite,
caller_body,
return_block,
);
let tuple = self.create_temp_if_necessary(
args.next().unwrap(),
callsite,
caller_body,
return_block,
);
let self_ = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
let tuple = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
assert!(args.next().is_none());

let tuple = Place::from(tuple);
Expand All @@ -588,13 +578,13 @@ impl Inliner<'tcx> {
Operand::Move(tcx.mk_place_field(tuple, Field::new(i), ty.expect_ty()));

// Spill to a local to make e.g., `tmp0`.
self.create_temp_if_necessary(tuple_field, callsite, caller_body, return_block)
self.create_temp_if_necessary(tuple_field, callsite, caller_body)
});

closure_ref_arg.chain(tuple_tmp_args).collect()
} else {
args.into_iter()
.map(|a| self.create_temp_if_necessary(a, callsite, caller_body, return_block))
.map(|a| self.create_temp_if_necessary(a, callsite, caller_body))
.collect()
}
}
Expand All @@ -606,46 +596,52 @@ impl Inliner<'tcx> {
arg: Operand<'tcx>,
callsite: &CallSite<'tcx>,
caller_body: &mut Body<'tcx>,
return_block: BasicBlock,
) -> Local {
// FIXME: Analysis of the usage of the arguments to avoid
// unnecessary temporaries.

// Reuse the operand if it is a moved temporary.
if let Operand::Move(place) = &arg {
if let Some(local) = place.as_local() {
if caller_body.local_kind(local) == LocalKind::Temp {
// Reuse the operand if it's a temporary already
return local;
}
}
}

// Otherwise, create a temporary for the argument.
trace!("creating temp for argument {:?}", arg);
// Otherwise, create a temporary for the arg
let arg = Rvalue::Use(arg);

let ty = arg.ty(caller_body, self.tcx);

let arg_tmp = LocalDecl::new(ty, callsite.source_info.span);
let arg_tmp = caller_body.local_decls.push(arg_tmp);

caller_body[callsite.bb].statements.push(Statement {
let arg_ty = arg.ty(caller_body, self.tcx);
let local = self.new_call_temp(caller_body, callsite, arg_ty);
caller_body[callsite.block].statements.push(Statement {
source_info: callsite.source_info,
kind: StatementKind::StorageLive(arg_tmp),
kind: StatementKind::Assign(box (Place::from(local), Rvalue::Use(arg))),
});
caller_body[callsite.bb].statements.push(Statement {
local
}

/// Introduces a new temporary into the caller body that is live for the duration of the call.
fn new_call_temp(
&self,
caller_body: &mut Body<'tcx>,
callsite: &CallSite<'tcx>,
ty: Ty<'tcx>,
) -> Local {
let local = caller_body.local_decls.push(LocalDecl::new(ty, callsite.source_info.span));

caller_body[callsite.block].statements.push(Statement {
source_info: callsite.source_info,
kind: StatementKind::Assign(box (Place::from(arg_tmp), arg)),
kind: StatementKind::StorageLive(local),
});
caller_body[return_block].statements.insert(
0,
Statement {
source_info: callsite.source_info,
kind: StatementKind::StorageDead(arg_tmp),
},
);

arg_tmp

if let Some(block) = callsite.target {
caller_body[block].statements.insert(
0,
Statement {
source_info: callsite.source_info,
kind: StatementKind::StorageDead(local),
},
);
}

local
}
}

Expand All @@ -670,7 +666,7 @@ struct Integrator<'a, 'tcx> {
new_scopes: RangeFrom<SourceScope>,
new_blocks: RangeFrom<BasicBlock>,
destination: Place<'tcx>,
return_block: BasicBlock,
return_block: Option<BasicBlock>,
cleanup_block: Option<BasicBlock>,
in_cleanup_block: bool,
tcx: TyCtxt<'tcx>,
Expand Down Expand Up @@ -810,7 +806,11 @@ impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
}
}
TerminatorKind::Return => {
terminator.kind = TerminatorKind::Goto { target: self.return_block };
terminator.kind = if let Some(tgt) = self.return_block {
TerminatorKind::Goto { target: tgt }
} else {
TerminatorKind::Unreachable
}
}
TerminatorKind::Resume => {
if let Some(tgt) = self.cleanup_block {
Expand Down
40 changes: 40 additions & 0 deletions src/test/mir-opt/inline/inline-diverging.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
// Tests inlining of diverging calls.
//
// ignore-wasm32-bare compiled with panic=abort by default
#![crate_type = "lib"]

// EMIT_MIR inline_diverging.f.Inline.diff
pub fn f() {
sleep();
}

// EMIT_MIR inline_diverging.g.Inline.diff
pub fn g(i: i32) -> u32 {
if i > 0 {
i as u32
} else {
panic();
}
}

// EMIT_MIR inline_diverging.h.Inline.diff
pub fn h() {
call_twice(sleep);
}

#[inline(always)]
pub fn call_twice<R, F: Fn() -> R>(f: F) -> (R, R) {
let a = f();
let b = f();
(a, b)
}

#[inline(always)]
fn panic() -> ! {
panic!();
}

#[inline(always)]
fn sleep() -> ! {
loop {}
}
26 changes: 26 additions & 0 deletions src/test/mir-opt/inline/inline_diverging.f.Inline.diff
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
- // MIR for `f` before Inline
+ // MIR for `f` after Inline

fn f() -> () {
let mut _0: (); // return place in scope 0 at $DIR/inline-diverging.rs:7:12: 7:12
let mut _1: !; // in scope 0 at $DIR/inline-diverging.rs:7:12: 9:2
let _2: !; // in scope 0 at $DIR/inline-diverging.rs:8:5: 8:12
+ let mut _3: !; // in scope 0 at $DIR/inline-diverging.rs:8:5: 8:12
+ scope 1 (inlined sleep) { // at $DIR/inline-diverging.rs:8:5: 8:12
+ }

bb0: {
StorageLive(_2); // scope 0 at $DIR/inline-diverging.rs:8:5: 8:12
- sleep(); // scope 0 at $DIR/inline-diverging.rs:8:5: 8:12
- // mir::Constant
- // + span: $DIR/inline-diverging.rs:8:5: 8:10
- // + literal: Const { ty: fn() -> ! {sleep}, val: Value(Scalar(<ZST>)) }
+ StorageLive(_3); // scope 0 at $DIR/inline-diverging.rs:8:5: 8:12
+ goto -> bb1; // scope 0 at $DIR/inline-diverging.rs:8:5: 8:12
+ }
+
+ bb1: {
+ goto -> bb1; // scope 1 at $DIR/inline-diverging.rs:8:5: 8:12
}
}

52 changes: 52 additions & 0 deletions src/test/mir-opt/inline/inline_diverging.g.Inline.diff
Original file line number Diff line number Diff line change
@@ -0,0 +1,52 @@
- // MIR for `g` before Inline
+ // MIR for `g` after Inline

fn g(_1: i32) -> u32 {
debug i => _1; // in scope 0 at $DIR/inline-diverging.rs:12:10: 12:11
let mut _0: u32; // return place in scope 0 at $DIR/inline-diverging.rs:12:21: 12:24
let mut _2: bool; // in scope 0 at $DIR/inline-diverging.rs:13:8: 13:13
let mut _3: i32; // in scope 0 at $DIR/inline-diverging.rs:13:8: 13:9
let mut _4: i32; // in scope 0 at $DIR/inline-diverging.rs:14:9: 14:10
let mut _5: !; // in scope 0 at $DIR/inline-diverging.rs:15:12: 17:6
let _6: !; // in scope 0 at $DIR/inline-diverging.rs:16:9: 16:16
+ let mut _7: !; // in scope 0 at $DIR/inline-diverging.rs:16:9: 16:16
+ scope 1 (inlined panic) { // at $DIR/inline-diverging.rs:16:9: 16:16
+ }

bb0: {
StorageLive(_2); // scope 0 at $DIR/inline-diverging.rs:13:8: 13:13
StorageLive(_3); // scope 0 at $DIR/inline-diverging.rs:13:8: 13:9
_3 = _1; // scope 0 at $DIR/inline-diverging.rs:13:8: 13:9
_2 = Gt(move _3, const 0_i32); // scope 0 at $DIR/inline-diverging.rs:13:8: 13:13
StorageDead(_3); // scope 0 at $DIR/inline-diverging.rs:13:12: 13:13
switchInt(_2) -> [false: bb1, otherwise: bb2]; // scope 0 at $DIR/inline-diverging.rs:13:5: 17:6
}

bb1: {
StorageLive(_6); // scope 0 at $DIR/inline-diverging.rs:16:9: 16:16
- panic(); // scope 0 at $DIR/inline-diverging.rs:16:9: 16:16
+ StorageLive(_7); // scope 0 at $DIR/inline-diverging.rs:16:9: 16:16
+ begin_panic::<&str>(const "explicit panic"); // scope 1 at $DIR/inline-diverging.rs:16:9: 16:16
// mir::Constant
- // + span: $DIR/inline-diverging.rs:16:9: 16:14
- // + literal: Const { ty: fn() -> ! {panic}, val: Value(Scalar(<ZST>)) }
+ // + span: $DIR/inline-diverging.rs:16:9: 16:16
+ // + literal: Const { ty: fn(&str) -> ! {std::rt::begin_panic::<&str>}, val: Value(Scalar(<ZST>)) }
+ // ty::Const
+ // + ty: &str
+ // + val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 })
+ // mir::Constant
+ // + span: $DIR/inline-diverging.rs:16:9: 16:16
+ // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 }) }
}

bb2: {
StorageLive(_4); // scope 0 at $DIR/inline-diverging.rs:14:9: 14:10
_4 = _1; // scope 0 at $DIR/inline-diverging.rs:14:9: 14:10
_0 = move _4 as u32 (Misc); // scope 0 at $DIR/inline-diverging.rs:14:9: 14:17
StorageDead(_4); // scope 0 at $DIR/inline-diverging.rs:14:16: 14:17
StorageDead(_2); // scope 0 at $DIR/inline-diverging.rs:18:1: 18:2
return; // scope 0 at $DIR/inline-diverging.rs:18:2: 18:2
}
}

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