diff options
18 files changed, 197 insertions, 51 deletions
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs index d405d044cae..5c8c51c8bbc 100644 --- a/compiler/rustc_interface/src/tests.rs +++ b/compiler/rustc_interface/src/tests.rs @@ -818,8 +818,8 @@ fn test_unstable_options_tracking_hash() { tracked!(min_function_alignment, Some(Align::EIGHT)); tracked!(mir_emit_retag, true); tracked!(mir_enable_passes, vec![("DestProp".to_string(), false)]); - tracked!(mir_keep_place_mention, true); tracked!(mir_opt_level, Some(4)); + tracked!(mir_preserve_ub, true); tracked!(move_size_limit, Some(4096)); tracked!(mutable_noalias, false); tracked!(next_solver, NextSolverConfig { coherence: true, globally: true }); diff --git a/compiler/rustc_mir_transform/src/early_otherwise_branch.rs b/compiler/rustc_mir_transform/src/early_otherwise_branch.rs index d49f5d9f9c3..c7feb9e949b 100644 --- a/compiler/rustc_mir_transform/src/early_otherwise_branch.rs +++ b/compiler/rustc_mir_transform/src/early_otherwise_branch.rs @@ -223,7 +223,7 @@ impl<'tcx> crate::MirPass<'tcx> for EarlyOtherwiseBranch { // Since this optimization adds new basic blocks and invalidates others, // clean up the cfg to make it nicer for other passes if should_cleanup { - simplify_cfg(body); + simplify_cfg(tcx, body); } } diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs index 69e80ed54ea..c5732194424 100644 --- a/compiler/rustc_mir_transform/src/inline.rs +++ b/compiler/rustc_mir_transform/src/inline.rs @@ -63,7 +63,7 @@ impl<'tcx> crate::MirPass<'tcx> for Inline { let _guard = span.enter(); if inline::<NormalInliner<'tcx>>(tcx, body) { debug!("running simplify cfg on {:?}", body.source); - simplify_cfg(body); + simplify_cfg(tcx, body); deref_finder(tcx, body); } } @@ -99,7 +99,7 @@ impl<'tcx> crate::MirPass<'tcx> for ForceInline { let _guard = span.enter(); if inline::<ForceInliner<'tcx>>(tcx, body) { debug!("running simplify cfg on {:?}", body.source); - simplify_cfg(body); + simplify_cfg(tcx, body); deref_finder(tcx, body); } } diff --git a/compiler/rustc_mir_transform/src/match_branches.rs b/compiler/rustc_mir_transform/src/match_branches.rs index 5059837328e..b37241185c9 100644 --- a/compiler/rustc_mir_transform/src/match_branches.rs +++ b/compiler/rustc_mir_transform/src/match_branches.rs @@ -43,7 +43,7 @@ impl<'tcx> crate::MirPass<'tcx> for MatchBranchSimplification { } if should_cleanup { - simplify_cfg(body); + simplify_cfg(tcx, body); } } diff --git a/compiler/rustc_mir_transform/src/remove_place_mention.rs b/compiler/rustc_mir_transform/src/remove_place_mention.rs index 15fe77d5319..cb598ceb4df 100644 --- a/compiler/rustc_mir_transform/src/remove_place_mention.rs +++ b/compiler/rustc_mir_transform/src/remove_place_mention.rs @@ -8,7 +8,7 @@ pub(super) struct RemovePlaceMention; impl<'tcx> crate::MirPass<'tcx> for RemovePlaceMention { fn is_enabled(&self, sess: &rustc_session::Session) -> bool { - !sess.opts.unstable_opts.mir_keep_place_mention + !sess.opts.unstable_opts.mir_preserve_ub } fn run_pass(&self, _: TyCtxt<'tcx>, body: &mut Body<'tcx>) { diff --git a/compiler/rustc_mir_transform/src/remove_unneeded_drops.rs b/compiler/rustc_mir_transform/src/remove_unneeded_drops.rs index 8a8cdafc690..43f80508e4a 100644 --- a/compiler/rustc_mir_transform/src/remove_unneeded_drops.rs +++ b/compiler/rustc_mir_transform/src/remove_unneeded_drops.rs @@ -35,7 +35,7 @@ impl<'tcx> crate::MirPass<'tcx> for RemoveUnneededDrops { // if we applied optimizations, we potentially have some cfg to cleanup to // make it easier for further passes if should_simplify { - simplify_cfg(body); + simplify_cfg(tcx, body); } } diff --git a/compiler/rustc_mir_transform/src/simplify.rs b/compiler/rustc_mir_transform/src/simplify.rs index 5947637cded..4f2cce8ac10 100644 --- a/compiler/rustc_mir_transform/src/simplify.rs +++ b/compiler/rustc_mir_transform/src/simplify.rs @@ -26,6 +26,13 @@ //! Here the block (`{ return; }`) has the return type `char`, rather than `()`, but the MIR we //! naively generate still contains the `_a = ()` write in the unreachable block "after" the //! return. +//! +//! **WARNING**: This is one of the few optimizations that runs on built and analysis MIR, and +//! so its effects may affect the type-checking, borrow-checking, and other analysis of MIR. +//! We must be extremely careful to only apply optimizations that preserve UB and all +//! non-determinism, since changes here can affect which programs compile in an insta-stable way. +//! The normal logic that a program with UB can be changed to do anything does not apply to +//! pre-"runtime" MIR! use rustc_index::{Idx, IndexSlice, IndexVec}; use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor}; @@ -66,8 +73,8 @@ impl SimplifyCfg { } } -pub(super) fn simplify_cfg(body: &mut Body<'_>) { - CfgSimplifier::new(body).simplify(); +pub(super) fn simplify_cfg<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + CfgSimplifier::new(tcx, body).simplify(); remove_dead_blocks(body); // FIXME: Should probably be moved into some kind of pass manager @@ -79,9 +86,9 @@ impl<'tcx> crate::MirPass<'tcx> for SimplifyCfg { self.name() } - fn run_pass(&self, _: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { debug!("SimplifyCfg({:?}) - simplifying {:?}", self.name(), body.source); - simplify_cfg(body); + simplify_cfg(tcx, body); } fn is_required(&self) -> bool { @@ -90,12 +97,13 @@ impl<'tcx> crate::MirPass<'tcx> for SimplifyCfg { } struct CfgSimplifier<'a, 'tcx> { + preserve_switch_reads: bool, basic_blocks: &'a mut IndexSlice<BasicBlock, BasicBlockData<'tcx>>, pred_count: IndexVec<BasicBlock, u32>, } impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> { - fn new(body: &'a mut Body<'tcx>) -> Self { + fn new(tcx: TyCtxt<'tcx>, body: &'a mut Body<'tcx>) -> Self { let mut pred_count = IndexVec::from_elem(0u32, &body.basic_blocks); // we can't use mir.predecessors() here because that counts @@ -110,9 +118,12 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> { } } + // Preserve `SwitchInt` reads on built and analysis MIR, or if `-Zmir-preserve-ub`. + let preserve_switch_reads = matches!(body.phase, MirPhase::Built | MirPhase::Analysis(_)) + || tcx.sess.opts.unstable_opts.mir_preserve_ub; let basic_blocks = body.basic_blocks_mut(); - CfgSimplifier { basic_blocks, pred_count } + CfgSimplifier { preserve_switch_reads, basic_blocks, pred_count } } fn simplify(mut self) { @@ -253,9 +264,15 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> { // turn a branch with all successors identical to a goto fn simplify_branch(&mut self, terminator: &mut Terminator<'tcx>) -> bool { - match terminator.kind { - TerminatorKind::SwitchInt { .. } => {} - _ => return false, + // Removing a `SwitchInt` terminator may remove reads that result in UB, + // so we must not apply this optimization before borrowck or when + // `-Zmir-preserve-ub` is set. + if self.preserve_switch_reads { + return false; + } + + let TerminatorKind::SwitchInt { .. } = terminator.kind else { + return false; }; let first_succ = { diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs index 1b0794f79d3..36eee5f3086 100644 --- a/compiler/rustc_session/src/options.rs +++ b/compiler/rustc_session/src/options.rs @@ -2322,12 +2322,12 @@ options! { mir_include_spans: MirIncludeSpans = (MirIncludeSpans::default(), parse_mir_include_spans, [UNTRACKED], "include extra comments in mir pretty printing, like line numbers and statement indices, \ details about types, etc. (boolean for all passes, 'nll' to enable in NLL MIR only, default: 'nll')"), - mir_keep_place_mention: bool = (false, parse_bool, [TRACKED], - "keep place mention MIR statements, interpreted e.g., by miri; implies -Zmir-opt-level=0 \ - (default: no)"), #[rustc_lint_opt_deny_field_access("use `Session::mir_opt_level` instead of this field")] mir_opt_level: Option<usize> = (None, parse_opt_number, [TRACKED], "MIR optimization level (0-4; default: 1 in non optimized builds and 2 in optimized builds)"), + mir_preserve_ub: bool = (false, parse_bool, [TRACKED], + "keep place mention statements and reads in trivial SwitchInt terminators, which are interpreted \ + e.g., by miri; implies -Zmir-opt-level=0 (default: no)"), mir_strip_debuginfo: MirStripDebugInfo = (MirStripDebugInfo::None, parse_mir_strip_debuginfo, [TRACKED], "Whether to remove some of the MIR debug info from methods. Default: None"), move_size_limit: Option<usize> = (None, parse_opt_number, [TRACKED], diff --git a/src/tools/miri/src/lib.rs b/src/tools/miri/src/lib.rs index 5921ba86639..b6b2684dc6d 100644 --- a/src/tools/miri/src/lib.rs +++ b/src/tools/miri/src/lib.rs @@ -169,7 +169,7 @@ pub const MIRI_DEFAULT_ARGS: &[&str] = &[ "-Zalways-encode-mir", "-Zextra-const-ub-checks", "-Zmir-emit-retag", - "-Zmir-keep-place-mention", + "-Zmir-preserve-ub", "-Zmir-opt-level=0", "-Zmir-enable-passes=-CheckAlignment,-CheckNull", // Deduplicating diagnostics means we miss events when tracking what happens during an diff --git a/src/tools/miri/tests/fail/read_from_trivial_switch.rs b/src/tools/miri/tests/fail/read_from_trivial_switch.rs new file mode 100644 index 00000000000..d34b1cd5820 --- /dev/null +++ b/src/tools/miri/tests/fail/read_from_trivial_switch.rs @@ -0,0 +1,14 @@ +// Ensure that we don't optimize out `SwitchInt` reads even if that terminator +// branches to the same basic block on every target, since the operand may have +// side-effects that affect analysis of the MIR. +// +// See <https://github.com/rust-lang/miri/issues/4237>. + +use std::mem::MaybeUninit; + +fn main() { + let uninit: MaybeUninit<i32> = MaybeUninit::uninit(); + let bad_ref: &i32 = unsafe { uninit.assume_init_ref() }; + let &(0 | _) = bad_ref; + //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory +} diff --git a/src/tools/miri/tests/fail/read_from_trivial_switch.stderr b/src/tools/miri/tests/fail/read_from_trivial_switch.stderr new file mode 100644 index 00000000000..6b3d4539b96 --- /dev/null +++ b/src/tools/miri/tests/fail/read_from_trivial_switch.stderr @@ -0,0 +1,15 @@ +error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory + --> tests/fail/read_from_trivial_switch.rs:LL:CC + | +LL | let &(0 | _) = bad_ref; + | ^^^^^^^^ using uninitialized data, but this operation requires initialized memory + | + = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior + = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information + = note: BACKTRACE: + = note: inside `main` at tests/fail/read_from_trivial_switch.rs:LL:CC + +note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace + +error: aborting due to 1 previous error + diff --git a/tests/mir-opt/building/match/exponential_or.match_tuple.SimplifyCfg-initial.after.mir b/tests/mir-opt/building/match/exponential_or.match_tuple.SimplifyCfg-initial.after.mir index d52241b459e..2a965fe67b9 100644 --- a/tests/mir-opt/building/match/exponential_or.match_tuple.SimplifyCfg-initial.after.mir +++ b/tests/mir-opt/building/match/exponential_or.match_tuple.SimplifyCfg-initial.after.mir @@ -24,43 +24,47 @@ fn match_tuple(_1: (u32, bool, Option<i32>, u32)) -> u32 { bb1: { _0 = const 0_u32; - goto -> bb10; + goto -> bb11; } bb2: { - _2 = discriminant((_1.2: std::option::Option<i32>)); - switchInt(move _2) -> [0: bb4, 1: bb3, otherwise: bb1]; + switchInt(copy (_1.1: bool)) -> [0: bb3, otherwise: bb3]; } bb3: { - switchInt(copy (((_1.2: std::option::Option<i32>) as Some).0: i32)) -> [1: bb4, 8: bb4, otherwise: bb1]; + _2 = discriminant((_1.2: std::option::Option<i32>)); + switchInt(move _2) -> [0: bb5, 1: bb4, otherwise: bb1]; } bb4: { - _5 = Le(const 6_u32, copy (_1.3: u32)); - switchInt(move _5) -> [0: bb5, otherwise: bb7]; + switchInt(copy (((_1.2: std::option::Option<i32>) as Some).0: i32)) -> [1: bb5, 8: bb5, otherwise: bb1]; } bb5: { - _3 = Le(const 13_u32, copy (_1.3: u32)); - switchInt(move _3) -> [0: bb1, otherwise: bb6]; + _5 = Le(const 6_u32, copy (_1.3: u32)); + switchInt(move _5) -> [0: bb6, otherwise: bb8]; } bb6: { - _4 = Le(copy (_1.3: u32), const 16_u32); - switchInt(move _4) -> [0: bb1, otherwise: bb8]; + _3 = Le(const 13_u32, copy (_1.3: u32)); + switchInt(move _3) -> [0: bb1, otherwise: bb7]; } bb7: { - _6 = Le(copy (_1.3: u32), const 9_u32); - switchInt(move _6) -> [0: bb5, otherwise: bb8]; + _4 = Le(copy (_1.3: u32), const 16_u32); + switchInt(move _4) -> [0: bb1, otherwise: bb9]; } bb8: { - falseEdge -> [real: bb9, imaginary: bb1]; + _6 = Le(copy (_1.3: u32), const 9_u32); + switchInt(move _6) -> [0: bb6, otherwise: bb9]; } bb9: { + falseEdge -> [real: bb10, imaginary: bb1]; + } + + bb10: { StorageLive(_7); _7 = copy (_1.0: u32); StorageLive(_8); @@ -74,10 +78,10 @@ fn match_tuple(_1: (u32, bool, Option<i32>, u32)) -> u32 { StorageDead(_9); StorageDead(_8); StorageDead(_7); - goto -> bb10; + goto -> bb11; } - bb10: { + bb11: { return; } } diff --git a/tests/mir-opt/dead-store-elimination/place_mention.rs b/tests/mir-opt/dead-store-elimination/place_mention.rs index 5e4a286a208..1848a028297 100644 --- a/tests/mir-opt/dead-store-elimination/place_mention.rs +++ b/tests/mir-opt/dead-store-elimination/place_mention.rs @@ -2,7 +2,7 @@ // and don't remove it as a dead store. // //@ test-mir-pass: DeadStoreElimination-initial -//@ compile-flags: -Zmir-keep-place-mention +//@ compile-flags: -Zmir-preserve-ub // EMIT_MIR place_mention.main.DeadStoreElimination-initial.diff fn main() { diff --git a/tests/mir-opt/or_pattern.single_switchint.SimplifyCfg-initial.after.mir b/tests/mir-opt/or_pattern.single_switchint.SimplifyCfg-initial.after.mir index 889ff6f9f5e..be0931eaa61 100644 --- a/tests/mir-opt/or_pattern.single_switchint.SimplifyCfg-initial.after.mir +++ b/tests/mir-opt/or_pattern.single_switchint.SimplifyCfg-initial.after.mir @@ -14,7 +14,7 @@ fn single_switchint() -> () { } bb1: { - switchInt(copy (_2.0: i32)) -> [3: bb8, 4: bb8, otherwise: bb7]; + switchInt(copy (_2.0: i32)) -> [3: bb9, 4: bb9, otherwise: bb8]; } bb2: { @@ -22,7 +22,7 @@ fn single_switchint() -> () { } bb3: { - falseEdge -> [real: bb12, imaginary: bb4]; + falseEdge -> [real: bb14, imaginary: bb4]; } bb4: { @@ -30,43 +30,51 @@ fn single_switchint() -> () { } bb5: { - falseEdge -> [real: bb11, imaginary: bb6]; + falseEdge -> [real: bb13, imaginary: bb6]; } bb6: { - falseEdge -> [real: bb10, imaginary: bb1]; + switchInt(copy (_2.1: bool)) -> [0: bb7, otherwise: bb7]; } bb7: { - _1 = const 5_i32; - goto -> bb13; + falseEdge -> [real: bb12, imaginary: bb1]; } bb8: { - falseEdge -> [real: bb9, imaginary: bb7]; + _1 = const 5_i32; + goto -> bb15; } bb9: { - _1 = const 4_i32; - goto -> bb13; + switchInt(copy (_2.1: bool)) -> [0: bb10, otherwise: bb10]; } bb10: { - _1 = const 3_i32; - goto -> bb13; + falseEdge -> [real: bb11, imaginary: bb8]; } bb11: { - _1 = const 2_i32; - goto -> bb13; + _1 = const 4_i32; + goto -> bb15; } bb12: { - _1 = const 1_i32; - goto -> bb13; + _1 = const 3_i32; + goto -> bb15; } bb13: { + _1 = const 2_i32; + goto -> bb15; + } + + bb14: { + _1 = const 1_i32; + goto -> bb15; + } + + bb15: { StorageDead(_2); StorageDead(_1); _0 = const (); diff --git a/tests/mir-opt/read_from_trivial_switch.main.SimplifyCfg-initial.diff b/tests/mir-opt/read_from_trivial_switch.main.SimplifyCfg-initial.diff new file mode 100644 index 00000000000..87758408a1c --- /dev/null +++ b/tests/mir-opt/read_from_trivial_switch.main.SimplifyCfg-initial.diff @@ -0,0 +1,49 @@ +- // MIR for `main` before SimplifyCfg-initial ++ // MIR for `main` after SimplifyCfg-initial + + fn main() -> () { + let mut _0: (); + let _1: &i32; + let _2: i32; + scope 1 { + debug ref_ => _1; + scope 2 { + } + } + + bb0: { + StorageLive(_1); + StorageLive(_2); + _2 = const 1_i32; + _1 = &_2; + FakeRead(ForLet(None), _1); + PlaceMention(_1); +- switchInt(copy (*_1)) -> [0: bb2, otherwise: bb1]; ++ switchInt(copy (*_1)) -> [0: bb1, otherwise: bb1]; + } + + bb1: { +- goto -> bb5; +- } +- +- bb2: { +- goto -> bb5; +- } +- +- bb3: { +- goto -> bb1; +- } +- +- bb4: { +- FakeRead(ForMatchedPlace(None), _1); +- unreachable; +- } +- +- bb5: { + _0 = const (); + StorageDead(_2); + StorageDead(_1); + return; + } + } + diff --git a/tests/mir-opt/read_from_trivial_switch.rs b/tests/mir-opt/read_from_trivial_switch.rs new file mode 100644 index 00000000000..1c64c1d45e8 --- /dev/null +++ b/tests/mir-opt/read_from_trivial_switch.rs @@ -0,0 +1,15 @@ +// Ensure that we don't optimize out `SwitchInt` reads even if that terminator +// branches to the same basic block on every target, since the operand may have +// side-effects that affect analysis of the MIR. +// +// See <https://github.com/rust-lang/miri/issues/4237>. + +//@ test-mir-pass: SimplifyCfg-initial +//@ compile-flags: -Zmir-preserve-ub + +// EMIT_MIR read_from_trivial_switch.main.SimplifyCfg-initial.diff +fn main() { + let ref_ = &1i32; + // CHECK: switchInt + let &(0 | _) = ref_; +} diff --git a/tests/ui/pattern/uninit-trivial.rs b/tests/ui/pattern/uninit-trivial.rs new file mode 100644 index 00000000000..6ea6796c1c1 --- /dev/null +++ b/tests/ui/pattern/uninit-trivial.rs @@ -0,0 +1,8 @@ +// Regression test for the semantic changes in +// <https://github.com/rust-lang/rust/pull/139042>. + +fn main() { + let x; + let (0 | _) = x; + //~^ ERROR used binding `x` isn't initialized +} diff --git a/tests/ui/pattern/uninit-trivial.stderr b/tests/ui/pattern/uninit-trivial.stderr new file mode 100644 index 00000000000..2ff8557c945 --- /dev/null +++ b/tests/ui/pattern/uninit-trivial.stderr @@ -0,0 +1,16 @@ +error[E0381]: used binding `x` isn't initialized + --> $DIR/uninit-trivial.rs:6:10 + | +LL | let x; + | - binding declared here but left uninitialized +LL | let (0 | _) = x; + | ^^^^^ `x` used here but it isn't initialized + | +help: consider assigning a value + | +LL | let x = 42; + | ++++ + +error: aborting due to 1 previous error + +For more information about this error, try `rustc --explain E0381`. |