From 85c102757a744956989e5217484a6f650eed3146 Mon Sep 17 00:00:00 2001 From: Ariel Ben-Yehuda Date: Mon, 31 Jul 2017 23:25:27 +0300 Subject: [PATCH] rustc_mir: don't build unused unwind cleanup blocks The unused blocks are removed by SimplifyCfg, but they can cause a significant performance slowdown before they are removed. --- src/librustc_mir/build/scope.rs | 89 ++++++++++++++++++---------- src/test/mir-opt/basic_assignment.rs | 26 ++++---- src/test/mir-opt/end_region_4.rs | 38 ++++++------ src/test/mir-opt/end_region_5.rs | 27 ++++----- src/test/mir-opt/end_region_6.rs | 28 ++++----- src/test/mir-opt/end_region_7.rs | 36 +++++------ src/test/mir-opt/end_region_8.rs | 75 ++++++++++++----------- src/test/mir-opt/issue-41110.rs | 15 +++-- 8 files changed, 181 insertions(+), 153 deletions(-) diff --git a/src/librustc_mir/build/scope.rs b/src/librustc_mir/build/scope.rs index 2b52198c25065..bf39e52bd1b28 100644 --- a/src/librustc_mir/build/scope.rs +++ b/src/librustc_mir/build/scope.rs @@ -200,6 +200,15 @@ pub struct BreakableScope<'tcx> { pub break_destination: Lvalue<'tcx>, } +impl DropKind { + fn may_panic(&self) -> bool { + match *self { + DropKind::Value { .. } => true, + DropKind::Storage => false + } + } +} + impl<'tcx> Scope<'tcx> { /// Invalidate all the cached blocks in the scope. /// @@ -337,9 +346,13 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> { mut block: BasicBlock) -> BlockAnd<()> { debug!("pop_scope({:?}, {:?})", extent, block); - // We need to have `cached_block`s available for all the drops, so we call diverge_cleanup - // to make sure all the `cached_block`s are filled in. - self.diverge_cleanup(); + // If we are emitting a `drop` statement, we need to have the cached + // diverge cleanup pads ready in case that drop panics. + let may_panic = + self.scopes.last().unwrap().drops.iter().any(|s| s.kind.may_panic()); + if may_panic { + self.diverge_cleanup(); + } let scope = self.scopes.pop().unwrap(); assert_eq!(scope.extent, extent.0); unpack!(block = build_scope_drops(&mut self.cfg, @@ -370,6 +383,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> { let len = self.scopes.len(); assert!(scope_count < len, "should not use `exit_scope` to pop ALL scopes"); let tmp = self.get_unit_temp(); + + // If we are emitting a `drop` statement, we need to have the cached + // diverge cleanup pads ready in case that drop panics. + let may_panic = + self.scopes[(len - scope_count)..].iter().any(|s| s.drops.iter().any(|s| s.kind.may_panic())); + if may_panic { + self.diverge_cleanup(); + } + { let mut rest = &mut self.scopes[(len - scope_count)..]; while let Some((scope, rest_)) = {rest}.split_last_mut() { @@ -736,45 +758,48 @@ fn build_scope_drops<'tcx>(cfg: &mut CFG<'tcx>, mut block: BasicBlock, arg_count: usize) -> BlockAnd<()> { + debug!("build_scope_drops({:?} -> {:?})", block, scope); let mut iter = scope.drops.iter().rev().peekable(); while let Some(drop_data) = iter.next() { let source_info = scope.source_info(drop_data.span); - if let DropKind::Value { .. } = drop_data.kind { - // Try to find the next block with its cached block - // for us to diverge into in case the drop panics. - let on_diverge = iter.peek().iter().filter_map(|dd| { - match dd.kind { - DropKind::Value { cached_block } => cached_block, - DropKind::Storage => None - } - }).next(); - // If there’s no `cached_block`s within current scope, - // we must look for one in the enclosing scope. - let on_diverge = on_diverge.or_else(||{ - earlier_scopes.iter().rev().flat_map(|s| s.cached_block()).next() - }); - let next = cfg.start_new_block(); - cfg.terminate(block, source_info, TerminatorKind::Drop { - location: drop_data.location.clone(), - target: next, - unwind: on_diverge - }); - block = next; - } match drop_data.kind { - DropKind::Value { .. } | - DropKind::Storage => { - // Only temps and vars need their storage dead. - match drop_data.location { - Lvalue::Local(index) if index.index() > arg_count => {} - _ => continue - } + DropKind::Value { .. } => { + // Try to find the next block with its cached block + // for us to diverge into in case the drop panics. + let on_diverge = iter.peek().iter().filter_map(|dd| { + match dd.kind { + DropKind::Value { cached_block: None } => + span_bug!(drop_data.span, "cached block not present?"), + DropKind::Value { cached_block } => cached_block, + DropKind::Storage => None + } + }).next(); + // If there’s no `cached_block`s within current scope, + // we must look for one in the enclosing scope. + let on_diverge = on_diverge.or_else(|| { + earlier_scopes.iter().rev().flat_map(|s| s.cached_block()).next() + }); + let next = cfg.start_new_block(); + cfg.terminate(block, source_info, TerminatorKind::Drop { + location: drop_data.location.clone(), + target: next, + unwind: on_diverge + }); + block = next; + } + DropKind::Storage => {} + } + // Drop the storage for both value and storage drops. + // Only temps and vars need their storage dead. + match drop_data.location { + Lvalue::Local(index) if index.index() > arg_count => { cfg.push(block, Statement { source_info: source_info, kind: StatementKind::StorageDead(drop_data.location.clone()) }); } + _ => continue } } block.unit() diff --git a/src/test/mir-opt/basic_assignment.rs b/src/test/mir-opt/basic_assignment.rs index ef5158a403a93..6afc344ced847 100644 --- a/src/test/mir-opt/basic_assignment.rs +++ b/src/test/mir-opt/basic_assignment.rs @@ -47,39 +47,39 @@ fn main() { // StorageDead(_3); // StorageLive(_4); // _4 = std::option::Option>::None; +// StorageLive(_5); // StorageLive(_6); -// StorageLive(_7); -// _7 = _4; -// replace(_6 <- _7) -> [return: bb6, unwind: bb7]; +// _6 = _4; +// replace(_5 <- _6) -> [return: bb1, unwind: bb7]; // } // bb1: { -// resume; +// drop(_6) -> [return: bb8, unwind: bb5]; // } // bb2: { -// drop(_4) -> bb1; +// resume; // } // bb3: { -// goto -> bb2; +// drop(_4) -> bb2; // } // bb4: { -// drop(_6) -> bb3; +// goto -> bb3; // } // bb5: { -// goto -> bb4; +// drop(_5) -> bb4; // } // bb6: { -// drop(_7) -> [return: bb8, unwind: bb4]; +// goto -> bb5; // } // bb7: { -// drop(_7) -> bb5; +// drop(_6) -> bb6; // } // bb8: { -// StorageDead(_7); +// StorageDead(_6); // _0 = (); -// drop(_6) -> [return: bb9, unwind: bb2]; +// drop(_5) -> [return: bb9, unwind: bb3]; // } // bb9: { -// StorageDead(_6); +// StorageDead(_5); // drop(_4) -> bb10; // } // bb10: { diff --git a/src/test/mir-opt/end_region_4.rs b/src/test/mir-opt/end_region_4.rs index 16ade9f96fd1e..bfb1b3b652890 100644 --- a/src/test/mir-opt/end_region_4.rs +++ b/src/test/mir-opt/end_region_4.rs @@ -32,41 +32,41 @@ fn foo(i: i32) { // START rustc.node4.SimplifyCfg-qualify-consts.after.mir // let mut _0: (); // let _1: D; -// let _3: i32; -// let _4: &'6_2rce i32; +// let _2: i32; +// let _3: &'6_2rce i32; // let _7: &'6_4rce i32; -// let mut _5: (); -// let mut _6: i32; -// +// let mut _4: (); +// let mut _5: i32; +// let mut _6: (); // bb0: { // StorageLive(_1); // _1 = D::{{constructor}}(const 0i32,); +// StorageLive(_2); +// _2 = const 0i32; // StorageLive(_3); -// _3 = const 0i32; -// StorageLive(_4); -// _4 = &'6_2rce _3; -// StorageLive(_6); -// _6 = (*_4); -// _5 = const foo(_6) -> [return: bb2, unwind: bb3]; +// _3 = &'6_2rce _2; +// StorageLive(_5); +// _5 = (*_3); +// _4 = const foo(_5) -> [return: bb1, unwind: bb3]; // } // bb1: { -// resume; -// } -// bb2: { -// StorageDead(_6); +// StorageDead(_5); // StorageLive(_7); -// _7 = &'6_4rce _3; +// _7 = &'6_4rce _2; // _0 = (); // StorageDead(_7); // EndRegion('6_4rce); -// StorageDead(_4); -// EndRegion('6_2rce); // StorageDead(_3); +// EndRegion('6_2rce); +// StorageDead(_2); // drop(_1) -> bb4; // } +// bb2: { +// resume; +// } // bb3: { // EndRegion('6_2rce); -// drop(_1) -> bb1; +// drop(_1) -> bb2; // } // bb4: { // StorageDead(_1); diff --git a/src/test/mir-opt/end_region_5.rs b/src/test/mir-opt/end_region_5.rs index 513632a4cdf38..773a348a93977 100644 --- a/src/test/mir-opt/end_region_5.rs +++ b/src/test/mir-opt/end_region_5.rs @@ -31,32 +31,31 @@ fn foo(f: F) where F: FnOnce() -> i32 { // let mut _0: (); // let _1: D; // let mut _2: (); -// let mut _3: (); -// let mut _4: [closure@NodeId(18) d: &'19mce D]; -// let mut _5: &'19mce D; -// +// let mut _3: [closure@NodeId(18) d:&'19mce D]; +// let mut _4: &'19mce D; +// let mut _5: (); // bb0: { // StorageLive(_1); // _1 = D::{{constructor}}(const 0i32,); +// StorageLive(_3); // StorageLive(_4); -// StorageLive(_5); -// _5 = &'19mce _1; -// _4 = [closure@NodeId(18)] { d: _5 }; -// StorageDead(_5); -// _3 = const foo(_4) -> [return: bb2, unwind: bb3]; +// _4 = &'19mce _1; +// _3 = [closure@NodeId(18)] { d: _4 }; +// StorageDead(_4); +// _2 = const foo(_3) -> [return: bb1, unwind: bb3]; // } // bb1: { -// resume; -// } -// bb2: { -// StorageDead(_4); +// StorageDead(_3); // EndRegion('19mce); // _0 = (); // drop(_1) -> bb4; // } +// bb2: { +// resume; +// } // bb3: { // EndRegion('19mce); -// drop(_1) -> bb1; +// drop(_1) -> bb2; // } // bb4: { // StorageDead(_1); diff --git a/src/test/mir-opt/end_region_6.rs b/src/test/mir-opt/end_region_6.rs index e82556f3ce4bb..112c93843e042 100644 --- a/src/test/mir-opt/end_region_6.rs +++ b/src/test/mir-opt/end_region_6.rs @@ -27,35 +27,35 @@ fn foo(f: F) where F: FnOnce() -> i32 { // END RUST SOURCE // START rustc.node4.SimplifyCfg-qualify-consts.after.mir +// fn main() -> () { // let mut _0: (); // let _1: D; // let mut _2: (); -// let mut _3: (); -// let mut _4: [closure@NodeId(22) d:&'23mce D]; -// let mut _5: &'23mce D; -// +// let mut _3: [closure@NodeId(22) d:&'23mce D]; +// let mut _4: &'23mce D; +// let mut _5: (); // bb0: { // StorageLive(_1); // _1 = D::{{constructor}}(const 0i32,); +// StorageLive(_3); // StorageLive(_4); -// StorageLive(_5); -// _5 = &'23mce _1; -// _4 = [closure@NodeId(22)] { d: _5 }; -// StorageDead(_5); -// _3 = const foo(_4) -> [return: bb2, unwind: bb3]; +// _4 = &'23mce _1; +// _3 = [closure@NodeId(22)] { d: _4 }; +// StorageDead(_4); +// _2 = const foo(_3) -> [return: bb1, unwind: bb3]; // } // bb1: { -// resume; -// } -// bb2: { -// StorageDead(_4); +// StorageDead(_3); // EndRegion('23mce); // _0 = (); // drop(_1) -> bb4; // } +// bb2: { +// resume; +// } // bb3: { // EndRegion('23mce); -// drop(_1) -> bb1; +// drop(_1) -> bb2; // } // bb4: { // StorageDead(_1); diff --git a/src/test/mir-opt/end_region_7.rs b/src/test/mir-opt/end_region_7.rs index 3fbd3f368659d..913986ae816a6 100644 --- a/src/test/mir-opt/end_region_7.rs +++ b/src/test/mir-opt/end_region_7.rs @@ -31,18 +31,18 @@ fn foo(f: F) where F: FnOnce() -> i32 { // let mut _0: (); // let _1: D; // let mut _2: (); -// let mut _3: (); -// let mut _4: [closure@NodeId(22) d:D]; -// let mut _5: D; +// let mut _3: [closure@NodeId(22) d:D]; +// let mut _4: D; +// let mut _5: (); // // bb0: { // StorageLive(_1); // _1 = D::{{constructor}}(const 0i32,); +// StorageLive(_3); // StorageLive(_4); -// StorageLive(_5); -// _5 = _1; -// _4 = [closure@NodeId(22)] { d: _5 }; -// drop(_5) -> [return: bb4, unwind: bb3]; +// _4 = _1; +// _3 = [closure@NodeId(22)] { d: _4 }; +// drop(_4) -> [return: bb4, unwind: bb3]; // } // bb1: { // resume; @@ -51,17 +51,17 @@ fn foo(f: F) where F: FnOnce() -> i32 { // drop(_1) -> bb1; // } // bb3: { -// drop(_4) -> bb2; +// drop(_3) -> bb2; // } // bb4: { -// StorageDead(_5); -// _3 = const foo(_4) -> [return: bb5, unwind: bb3]; +// StorageDead(_4); +// _2 = const foo(_3) -> [return: bb5, unwind: bb3]; // } // bb5: { -// drop(_4) -> [return: bb6, unwind: bb2]; +// drop(_3) -> [return: bb6, unwind: bb2]; // } // bb6: { -// StorageDead(_4); +// StorageDead(_3); // _0 = (); // drop(_1) -> bb7; // } @@ -76,16 +76,16 @@ fn foo(f: F) where F: FnOnce() -> i32 { // fn main::{{closure}}(_1: [closure@NodeId(22) d:D]) -> i32 { // let mut _0: i32; // let _2: &'14_0rce D; -// let mut _3: (); -// let mut _4: i32; +// let mut _3: i32; +// let mut _4: (); // // bb0: { // StorageLive(_2); // _2 = &'14_0rce (_1.0: D); -// StorageLive(_4); -// _4 = ((*_2).0: i32); -// _0 = _4; -// StorageDead(_4); +// StorageLive(_3); +// _3 = ((*_2).0: i32); +// _0 = _3; +// StorageDead(_3); // StorageDead(_2); // EndRegion('14_0rce); // drop(_1) -> bb1; diff --git a/src/test/mir-opt/end_region_8.rs b/src/test/mir-opt/end_region_8.rs index 7fb3f0b91181a..dc8f8ea11f51c 100644 --- a/src/test/mir-opt/end_region_8.rs +++ b/src/test/mir-opt/end_region_8.rs @@ -29,44 +29,43 @@ fn foo(f: F) where F: FnOnce() -> i32 { // END RUST SOURCE // START rustc.node4.SimplifyCfg-qualify-consts.after.mir // fn main() -> () { -// let mut _0: (); -// let _1: D; -// let _3: &'6_1rce D; -// let mut _2: (); -// let mut _4: (); -// let mut _5: [closure@NodeId(22) r:&'6_1rce D]; -// let mut _6: &'6_1rce D; -// -// bb0: { -// StorageLive(_1); -// _1 = D::{{constructor}}(const 0i32,); -// StorageLive(_3); -// _3 = &'6_1rce _1; -// StorageLive(_5); -// StorageLive(_6); -// _6 = _3; -// _5 = [closure@NodeId(22)] { r: _6 }; -// StorageDead(_6); -// _4 = const foo(_5) -> [return: bb2, unwind: bb3]; -// } -// bb1: { -// resume; -// } -// bb2: { -// StorageDead(_5); -// _0 = (); -// StorageDead(_3); -// EndRegion('6_1rce); -// drop(_1) -> bb4; -// } -// bb3: { -// EndRegion('6_1rce); -// drop(_1) -> bb1; -// } -// bb4: { -// StorageDead(_1); -// return; -// } +// let mut _0: (); +// let _1: D; +// let _2: &'6_1rce D; +// let mut _3: (); +// let mut _4: [closure@NodeId(22) r:&'6_1rce D]; +// let mut _5: &'6_1rce D; +// let mut _6: (); +// bb0: { +// StorageLive(_1); +// _1 = D::{{constructor}}(const 0i32,); +// StorageLive(_2); +// _2 = &'6_1rce _1; +// StorageLive(_4); +// StorageLive(_5); +// _5 = _2; +// _4 = [closure@NodeId(22)] { r: _5 }; +// StorageDead(_5); +// _3 = const foo(_4) -> [return: bb1, unwind: bb3]; +// } +// bb1: { +// StorageDead(_4); +// _0 = (); +// StorageDead(_2); +// EndRegion('6_1rce); +// drop(_1) -> bb4; +// } +// bb2: { +// resume; +// } +// bb3: { +// EndRegion('6_1rce); +// drop(_1) -> bb2; +// } +// bb4: { +// StorageDead(_1); +// return; +// } // } // END rustc.node4.SimplifyCfg-qualify-consts.after.mir diff --git a/src/test/mir-opt/issue-41110.rs b/src/test/mir-opt/issue-41110.rs index fec635b3abf60..1daa18256dcee 100644 --- a/src/test/mir-opt/issue-41110.rs +++ b/src/test/mir-opt/issue-41110.rs @@ -34,18 +34,23 @@ impl S { // END RUST SOURCE // START rustc.node4.ElaborateDrops.after.mir +// let mut _0: (); +// let _1: (); // let mut _2: S; -// let mut _3: (); +// let mut _3: S; // let mut _4: S; -// let mut _5: S; +// let mut _5: (); // let mut _6: bool; // // bb0: { // END rustc.node4.ElaborateDrops.after.mir // START rustc.node13.ElaborateDrops.after.mir -// let mut _2: (); -// let mut _4: (); -// let mut _5: S; +// let mut _0: (); +// let _1: S; +// let mut _2: S; +// let mut _3: (); +// let mut _4: S; +// let mut _5: (); // let mut _6: S; // let mut _7: bool; //