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

Introduce a temporary for discriminant value in MatchBranchSimplification #78191

Merged
merged 1 commit into from
Oct 25, 2020
Merged

Introduce a temporary for discriminant value in MatchBranchSimplification #78191

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
30 changes: 22 additions & 8 deletions compiler/rustc_mir/src/transform/match_branches.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -38,19 +38,16 @@ pub struct MatchBranchSimplification;

impl<'tcx> MirPass<'tcx> for MatchBranchSimplification {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
// FIXME: This optimization can result in unsoundness, because it introduces
// additional uses of a place holding the discriminant value without ensuring that
// it is valid to do so.
if !tcx.sess.opts.debugging_opts.unsound_mir_opts {
if tcx.sess.opts.debugging_opts.mir_opt_level <= 1 {
return;
}

let param_env = tcx.param_env(body.source.def_id());
let bbs = body.basic_blocks_mut();
let (bbs, local_decls) = body.basic_blocks_and_local_decls_mut();
'outer: for bb_idx in bbs.indices() {
let (discr, val, switch_ty, first, second) = match bbs[bb_idx].terminator().kind {
TerminatorKind::SwitchInt {
discr: Operand::Copy(ref place) | Operand::Move(ref place),
discr: ref discr @ (Operand::Copy(_) | Operand::Move(_)),
switch_ty,
ref targets,
..
Expand All @@ -59,7 +56,7 @@ impl<'tcx> MirPass<'tcx> for MatchBranchSimplification {
if target == targets.otherwise() {
continue;
}
(place, value, switch_ty, target, targets.otherwise())
(discr, value, switch_ty, target, targets.otherwise())
}
// Only optimize switch int statements
_ => continue,
Expand Down Expand Up @@ -99,6 +96,10 @@ impl<'tcx> MirPass<'tcx> for MatchBranchSimplification {
// Take ownership of items now that we know we can optimize.
let discr = discr.clone();

// Introduce a temporary for the discriminant value.
let source_info = bbs[bb_idx].terminator().source_info;
let discr_local = local_decls.push(LocalDecl::new(switch_ty, source_info.span));

// We already checked that first and second are different blocks,
// and bb_idx has a different terminator from both of them.
let (from, first, second) = bbs.pick3_mut(bb_idx, first, second);
Expand Down Expand Up @@ -127,7 +128,11 @@ impl<'tcx> MirPass<'tcx> for MatchBranchSimplification {
rustc_span::DUMMY_SP,
);
let op = if f_b { BinOp::Eq } else { BinOp::Ne };
let rhs = Rvalue::BinaryOp(op, Operand::Copy(discr.clone()), const_cmp);
let rhs = Rvalue::BinaryOp(
op,
Operand::Copy(Place::from(discr_local)),
const_cmp,
);
Statement {
source_info: f.source_info,
kind: StatementKind::Assign(box (*lhs, rhs)),
Expand All @@ -138,7 +143,16 @@ impl<'tcx> MirPass<'tcx> for MatchBranchSimplification {
_ => unreachable!(),
}
});

from.statements
.push(Statement { source_info, kind: StatementKind::StorageLive(discr_local) });
from.statements.push(Statement {
source_info,
kind: StatementKind::Assign(box (Place::from(discr_local), Rvalue::Use(discr))),
});
from.statements.extend(new_stmts);
from.statements
.push(Statement { source_info, kind: StatementKind::StorageDead(discr_local) });
from.terminator_mut().kind = first.terminator().kind.clone();
}
}
Expand Down
8 changes: 6 additions & 2 deletions src/test/mir-opt/matches_reduce_branches.bar.MatchBranchSimplification.32bit.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
let mut _8: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:35:9: 35:10
let mut _9: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:35:12: 35:13
let mut _10: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:35:15: 35:16
+ let mut _11: i32; // in scope 0 at $DIR/matches_reduce_branches.rs:19:9: 19:10
scope 1 {
debug a => _2; // in scope 1 at $DIR/matches_reduce_branches.rs:13:9: 13:10
let _3: bool; // in scope 1 at $DIR/matches_reduce_branches.rs:14:9: 14:10
Expand All @@ -33,10 +34,13 @@
StorageLive(_5); // scope 3 at $DIR/matches_reduce_branches.rs:16:9: 16:10
StorageLive(_6); // scope 4 at $DIR/matches_reduce_branches.rs:18:5: 33:6
- switchInt(_1) -> [7_i32: bb2, otherwise: bb1]; // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ _2 = Ne(_1, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:20:13: 20:22
+ _3 = Eq(_1, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:21:13: 21:21
+ StorageLive(_11); // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ _11 = _1; // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ _2 = Ne(_11, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:20:13: 20:22
+ _3 = Eq(_11, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:21:13: 21:21
+ _4 = const false; // scope 4 at $DIR/matches_reduce_branches.rs:22:13: 22:22
+ _5 = const true; // scope 4 at $DIR/matches_reduce_branches.rs:23:13: 23:21
+ StorageDead(_11); // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ goto -> bb3; // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
}

Expand Down
8 changes: 6 additions & 2 deletions src/test/mir-opt/matches_reduce_branches.bar.MatchBranchSimplification.64bit.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
let mut _8: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:35:9: 35:10
let mut _9: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:35:12: 35:13
let mut _10: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:35:15: 35:16
+ let mut _11: i32; // in scope 0 at $DIR/matches_reduce_branches.rs:19:9: 19:10
scope 1 {
debug a => _2; // in scope 1 at $DIR/matches_reduce_branches.rs:13:9: 13:10
let _3: bool; // in scope 1 at $DIR/matches_reduce_branches.rs:14:9: 14:10
Expand All @@ -33,10 +34,13 @@
StorageLive(_5); // scope 3 at $DIR/matches_reduce_branches.rs:16:9: 16:10
StorageLive(_6); // scope 4 at $DIR/matches_reduce_branches.rs:18:5: 33:6
- switchInt(_1) -> [7_i32: bb2, otherwise: bb1]; // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ _2 = Ne(_1, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:20:13: 20:22
+ _3 = Eq(_1, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:21:13: 21:21
+ StorageLive(_11); // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ _11 = _1; // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ _2 = Ne(_11, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:20:13: 20:22
+ _3 = Eq(_11, const 7_i32); // scope 4 at $DIR/matches_reduce_branches.rs:21:13: 21:21
+ _4 = const false; // scope 4 at $DIR/matches_reduce_branches.rs:22:13: 22:22
+ _5 = const true; // scope 4 at $DIR/matches_reduce_branches.rs:23:13: 23:21
+ StorageDead(_11); // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
+ goto -> bb3; // scope 4 at $DIR/matches_reduce_branches.rs:19:9: 19:10
}

Expand Down
6 changes: 5 additions & 1 deletion src/test/mir-opt/matches_reduce_branches.foo.MatchBranchSimplification.32bit.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,12 +6,16 @@
let mut _0: (); // return place in scope 0 at $DIR/matches_reduce_branches.rs:6:25: 6:25
let mut _2: bool; // in scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
let mut _3: isize; // in scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ let mut _4: isize; // in scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26

bb0: {
StorageLive(_2); // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
_3 = discriminant(_1); // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
- switchInt(move _3) -> [0_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ _2 = Eq(_3, const 0_isize); // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
+ StorageLive(_4); // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ _4 = move _3; // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ _2 = Eq(_4, const 0_isize); // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
+ StorageDead(_4); // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
}

Expand Down
6 changes: 5 additions & 1 deletion src/test/mir-opt/matches_reduce_branches.foo.MatchBranchSimplification.64bit.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,12 +6,16 @@
let mut _0: (); // return place in scope 0 at $DIR/matches_reduce_branches.rs:6:25: 6:25
let mut _2: bool; // in scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
let mut _3: isize; // in scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ let mut _4: isize; // in scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26

bb0: {
StorageLive(_2); // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
_3 = discriminant(_1); // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
- switchInt(move _3) -> [0_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ _2 = Eq(_3, const 0_isize); // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
+ StorageLive(_4); // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ _4 = move _3; // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ _2 = Eq(_4, const 0_isize); // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
+ StorageDead(_4); // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
+ goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:7:22: 7:26
}

Expand Down
116 changes: 116 additions & 0 deletions ...test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.32bit.diff
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,116 @@
- // MIR for `match_nested_if` before MatchBranchSimplification
+ // MIR for `match_nested_if` after MatchBranchSimplification

fn match_nested_if() -> bool {
let mut _0: bool; // return place in scope 0 at $DIR/matches_reduce_branches.rs:38:25: 38:29
let _1: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:39:9: 39:12
let mut _2: (); // in scope 0 at $DIR/matches_reduce_branches.rs:39:21: 39:23
let mut _3: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
let mut _4: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
let mut _5: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
let mut _6: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:24: 40:28
+ let mut _7: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
+ let mut _8: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
+ let mut _9: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ let mut _10: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
scope 1 {
debug val => _1; // in scope 1 at $DIR/matches_reduce_branches.rs:39:9: 39:12
}

bb0: {
StorageLive(_1); // scope 0 at $DIR/matches_reduce_branches.rs:39:9: 39:12
StorageLive(_2); // scope 0 at $DIR/matches_reduce_branches.rs:39:21: 39:23
StorageLive(_3); // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
StorageLive(_4); // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
StorageLive(_5); // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
StorageLive(_6); // scope 0 at $DIR/matches_reduce_branches.rs:40:24: 40:28
_6 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:40:24: 40:28
- switchInt(_6) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
+ StorageLive(_7); // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
+ _7 = _6; // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
+ _5 = Ne(_7, const false); // scope 0 at $DIR/matches_reduce_branches.rs:40:42: 40:47
+ StorageDead(_7); // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
+ goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
}

bb1: {
_5 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:40:30: 40:34
goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
}

bb2: {
_5 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:40:42: 40:47
goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:48
}

bb3: {
StorageDead(_6); // scope 0 at $DIR/matches_reduce_branches.rs:40:47: 40:48
- switchInt(_5) -> [false: bb4, otherwise: bb5]; // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
+ StorageLive(_8); // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
+ _8 = _5; // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
+ _4 = Ne(_8, const false); // scope 0 at $DIR/matches_reduce_branches.rs:40:62: 40:67
+ StorageDead(_8); // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
+ goto -> bb6; // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
}

bb4: {
_4 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:40:62: 40:67
goto -> bb6; // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
}

bb5: {
_4 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:40:50: 40:54
goto -> bb6; // scope 0 at $DIR/matches_reduce_branches.rs:40:18: 40:68
}

bb6: {
StorageDead(_5); // scope 0 at $DIR/matches_reduce_branches.rs:40:67: 40:68
- switchInt(_4) -> [false: bb7, otherwise: bb8]; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ StorageLive(_9); // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ _9 = _4; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ _3 = Ne(_9, const false); // scope 0 at $DIR/matches_reduce_branches.rs:40:82: 40:87
+ StorageDead(_9); // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ goto -> bb9; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
}

bb7: {
_3 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:40:82: 40:87
goto -> bb9; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
}

bb8: {
_3 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:40:70: 40:74
goto -> bb9; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
}

bb9: {
StorageDead(_4); // scope 0 at $DIR/matches_reduce_branches.rs:40:87: 40:88
- switchInt(move _3) -> [false: bb11, otherwise: bb10]; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ StorageLive(_10); // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ _10 = move _3; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ StorageDead(_3); // scope 0 at $DIR/matches_reduce_branches.rs:40:95: 40:96
+ _1 = Ne(_10, const false); // scope 0 at $DIR/matches_reduce_branches.rs:41:14: 41:19
+ StorageDead(_10); // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
+ goto -> bb12; // scope 0 at $DIR/matches_reduce_branches.rs:40:15: 40:88
}

bb10: {
StorageDead(_3); // scope 0 at $DIR/matches_reduce_branches.rs:40:95: 40:96
_1 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:40:92: 40:96
goto -> bb12; // scope 0 at $DIR/matches_reduce_branches.rs:39:15: 42:6
}

bb11: {
StorageDead(_3); // scope 0 at $DIR/matches_reduce_branches.rs:40:95: 40:96
_1 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:41:14: 41:19
goto -> bb12; // scope 0 at $DIR/matches_reduce_branches.rs:39:15: 42:6
}

bb12: {
StorageDead(_2); // scope 0 at $DIR/matches_reduce_branches.rs:42:6: 42:7
_0 = _1; // scope 1 at $DIR/matches_reduce_branches.rs:43:5: 43:8
StorageDead(_1); // scope 0 at $DIR/matches_reduce_branches.rs:44:1: 44:2
return; // scope 0 at $DIR/matches_reduce_branches.rs:44:2: 44:2
}
}

Loading