Skip to content

Improve liveness analysis for generators #84333

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

Merged
merged 1 commit into from
Aug 25, 2021
+107 −23
Merged

Improve liveness analysis for generators #84333

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
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
14 changes: 11 additions & 3 deletions compiler/rustc_passes/src/liveness.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -435,7 +435,10 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
}

// live nodes required for interesting control flow:
hir::ExprKind::If(..) | hir::ExprKind::Match(..) | hir::ExprKind::Loop(..) => {
hir::ExprKind::If(..)
| hir::ExprKind::Match(..)
| hir::ExprKind::Loop(..)
| hir::ExprKind::Yield(..) => {
self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span, expr.hir_id));
intravisit::walk_expr(self, expr);
}
Expand Down Expand Up @@ -469,7 +472,6 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
| hir::ExprKind::InlineAsm(..)
| hir::ExprKind::LlvmInlineAsm(..)
| hir::ExprKind::Box(..)
| hir::ExprKind::Yield(..)
| hir::ExprKind::Type(..)
| hir::ExprKind::Err
| hir::ExprKind::Path(hir::QPath::TypeRelative(..))
Expand Down Expand Up @@ -866,6 +868,13 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
// at the label ident
hir::ExprKind::Loop(ref blk, ..) => self.propagate_through_loop(expr, &blk, succ),

hir::ExprKind::Yield(ref e, ..) => {
let yield_ln = self.live_node(expr.hir_id, expr.span);
self.init_from_succ(yield_ln, succ);
self.merge_from_succ(yield_ln, self.exit_ln);
self.propagate_through_expr(e, yield_ln)
}

hir::ExprKind::If(ref cond, ref then, ref else_opt) => {
//
// (cond)
Expand Down Expand Up @@ -1025,7 +1034,6 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
| hir::ExprKind::Type(ref e, _)
| hir::ExprKind::DropTemps(ref e)
| hir::ExprKind::Unary(_, ref e)
| hir::ExprKind::Yield(ref e, _)
| hir::ExprKind::Repeat(ref e, _) => self.propagate_through_expr(&e, succ),

hir::ExprKind::InlineAsm(ref asm) => {
Expand Down
36 changes: 36 additions & 0 deletions src/test/ui/liveness/liveness-upvars.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
// edition:2018
// check-pass
#![feature(generators)]
#![warn(unused)]
#![allow(unreachable_code)]

Expand Down Expand Up @@ -105,4 +106,39 @@ pub fn h<T: Copy + Default + std::fmt::Debug>() {
};
}

async fn yield_now() {
todo!();
}

pub fn async_generator() {
let mut state: u32 = 0;

let _ = async {
state = 1;
yield_now().await;
state = 2;
yield_now().await;
state = 3;
};

let _ = async move {
state = 4; //~ WARN value assigned to `state` is never read
//~| WARN unused variable: `state`
yield_now().await;
state = 5; //~ WARN value assigned to `state` is never read
};
}

pub fn generator() {
let mut s: u32 = 0;
let _ = |_| {
s = 0;
yield ();
s = 1; //~ WARN value assigned to `s` is never read
yield (s = 2);
s = yield (); //~ WARN value assigned to `s` is never read
s = 3;
};
}

fn main() {}
80 changes: 60 additions & 20 deletions src/test/ui/liveness/liveness-upvars.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,150 +1,190 @@
warning: value assigned to `last` is never read
--> $DIR/liveness-upvars.rs:9:9
--> $DIR/liveness-upvars.rs:10:9
|
LL | last = Some(s);
| ^^^^
|
note: the lint level is defined here
--> $DIR/liveness-upvars.rs:3:9
--> $DIR/liveness-upvars.rs:4:9
|
LL | #![warn(unused)]
| ^^^^^^
= note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`
= help: maybe it is overwritten before being read?

warning: unused variable: `last`
--> $DIR/liveness-upvars.rs:9:9
--> $DIR/liveness-upvars.rs:10:9
|
LL | last = Some(s);
| ^^^^
|
note: the lint level is defined here
--> $DIR/liveness-upvars.rs:3:9
--> $DIR/liveness-upvars.rs:4:9
|
LL | #![warn(unused)]
| ^^^^^^
= note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`
= help: did you mean to capture by reference instead?

warning: unused variable: `sum`
--> $DIR/liveness-upvars.rs:21:9
--> $DIR/liveness-upvars.rs:22:9
|
LL | sum += x;
| ^^^
|
= help: did you mean to capture by reference instead?

warning: value captured by `c` is never read
--> $DIR/liveness-upvars.rs:31:9
--> $DIR/liveness-upvars.rs:32:9
|
LL | c = 1;
| ^
|
= help: did you mean to capture by reference instead?

warning: value captured by `c` is never read
--> $DIR/liveness-upvars.rs:35:9
--> $DIR/liveness-upvars.rs:36:9
|
LL | c = 1;
| ^
|
= help: did you mean to capture by reference instead?

warning: unused variable: `c`
--> $DIR/liveness-upvars.rs:41:9
--> $DIR/liveness-upvars.rs:42:9
|
LL | c += 1;
| ^
|
= help: did you mean to capture by reference instead?

warning: value assigned to `c` is never read
--> $DIR/liveness-upvars.rs:44:9
--> $DIR/liveness-upvars.rs:45:9
|
LL | c += 1;
| ^
|
= help: maybe it is overwritten before being read?

warning: unused variable: `c`
--> $DIR/liveness-upvars.rs:44:9
--> $DIR/liveness-upvars.rs:45:9
|
LL | c += 1;
| ^
|
= help: did you mean to capture by reference instead?

warning: value assigned to `c` is never read
--> $DIR/liveness-upvars.rs:57:9
--> $DIR/liveness-upvars.rs:58:9
|
LL | c += 1;
| ^
|
= help: maybe it is overwritten before being read?

warning: value assigned to `c` is never read
--> $DIR/liveness-upvars.rs:63:9
--> $DIR/liveness-upvars.rs:64:9
|
LL | c += 1;
| ^
|
= help: maybe it is overwritten before being read?

warning: value assigned to `d` is never read
--> $DIR/liveness-upvars.rs:72:13
--> $DIR/liveness-upvars.rs:73:13
|
LL | d = Some("d1");
| ^
|
= help: maybe it is overwritten before being read?

warning: value assigned to `e` is never read
--> $DIR/liveness-upvars.rs:76:13
--> $DIR/liveness-upvars.rs:77:13
|
LL | e = Some("e1");
| ^
|
= help: maybe it is overwritten before being read?

warning: value assigned to `e` is never read
--> $DIR/liveness-upvars.rs:78:13
--> $DIR/liveness-upvars.rs:79:13
|
LL | e = Some("e2");
| ^
|
= help: maybe it is overwritten before being read?

warning: unused variable: `e`
--> $DIR/liveness-upvars.rs:76:13
--> $DIR/liveness-upvars.rs:77:13
|
LL | e = Some("e1");
| ^
|
= help: did you mean to capture by reference instead?

warning: value assigned to `v` is never read
--> $DIR/liveness-upvars.rs:86:13
--> $DIR/liveness-upvars.rs:87:13
|
LL | v = T::default();
| ^
|
= help: maybe it is overwritten before being read?

warning: value assigned to `z` is never read
--> $DIR/liveness-upvars.rs:98:17
--> $DIR/liveness-upvars.rs:99:17
|
LL | z = T::default();
| ^
|
= help: maybe it is overwritten before being read?

warning: unused variable: `z`
--> $DIR/liveness-upvars.rs:98:17
--> $DIR/liveness-upvars.rs:99:17
|
LL | z = T::default();
| ^
|
= help: did you mean to capture by reference instead?

warning: 17 warnings emitted
warning: value assigned to `state` is never read
--> $DIR/liveness-upvars.rs:125:9
|
LL | state = 4;
| ^^^^^
|
= help: maybe it is overwritten before being read?

warning: value assigned to `state` is never read
--> $DIR/liveness-upvars.rs:128:9
|
LL | state = 5;
| ^^^^^
|
= help: maybe it is overwritten before being read?

warning: unused variable: `state`
--> $DIR/liveness-upvars.rs:125:9
|
LL | state = 4;
| ^^^^^
|
= help: did you mean to capture by reference instead?

warning: value assigned to `s` is never read
--> $DIR/liveness-upvars.rs:137:9
|
LL | s = 1;
| ^
|
= help: maybe it is overwritten before being read?

warning: value assigned to `s` is never read
--> $DIR/liveness-upvars.rs:139:9
|
LL | s = yield ();
| ^
|
= help: maybe it is overwritten before being read?

warning: 22 warnings emitted