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Resolve unsound hoisting of discriminant in EarlyOtherwiseBranch

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This commit is contained in:
DianQK 2024-02-21 22:44:48 +08:00
parent fc1a4c5cc9
commit 31e74771f0
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15 changed files with 507 additions and 272 deletions
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164
compiler/rustc_mir_transform/src/early_otherwise_branch.rs
View File

@ -1,6 +1,6 @@
use rustc_middle::mir::patch::MirPatch;
use rustc_middle::mir::*;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::ty::{Ty, TyCtxt};
use std::fmt::Debug;
use super::simplify::simplify_cfg;
@ -11,6 +11,7 @@
/// let y: Option<()>;
/// match (x,y) {
/// (Some(_), Some(_)) => {0},
/// (None, None) => {2},
/// _ => {1}
/// }
/// ```
@ -23,10 +24,10 @@
/// if discriminant_x == discriminant_y {
/// match x {
/// Some(_) => 0,
/// _ => 1, // <----
/// } // | Actually the same bb
/// } else { // |
/// 1 // <--------------
/// None => 2,
/// }
/// } else {
/// 1
/// }
/// ```
///
@ -47,18 +48,18 @@
/// | | |
/// ================= | | |
/// | BBU | <-| | | ============================
/// |---------------| | \-------> | BBD |
/// |---------------| | | |--------------------------|
/// | unreachable | | | | _dl = discriminant(P) |
/// ================= | | |--------------------------|
/// | | | switchInt(_dl) |
/// ================= | | | d | ---> BBD.2
/// |---------------| \-------> | BBD |
/// |---------------| | |--------------------------|
/// | unreachable | | | _dl = discriminant(P) |
/// ================= | |--------------------------|
/// | | switchInt(_dl) |
/// ================= | | d | ---> BBD.2
/// | BB9 | <--------------- | otherwise |
/// |---------------| ============================
/// | ... |
/// =================
/// ```
/// Where the `otherwise` branch on `BB1` is permitted to either go to `BBU` or to `BB9`. In the
/// Where the `otherwise` branch on `BB1` is permitted to either go to `BBU`. In the
/// code:
/// - `BB1` is `parent` and `BBC, BBD` are children
/// - `P` is `child_place`
@ -78,7 +79,7 @@
/// |---------------------| | | switchInt(Q) |
/// | switchInt(_t) | | | c | ---> BBC.2
/// | false | --------/ | d | ---> BBD.2
/// | otherwise | ---------------- | otherwise |
/// | otherwise | /--------- | otherwise |
/// ======================= | ============================
/// |
/// ================= |
@ -87,10 +88,6 @@
/// | ... |
/// =================
/// ```
///
/// This is only correct for some `P`, since `P` is now computed outside the original `switchInt`.
/// The filter on which `P` are allowed (together with discussion of its correctness) is found in
/// `may_hoist`.
pub struct EarlyOtherwiseBranch;
impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
@ -217,85 +214,6 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
}
}
/// Returns true if computing the discriminant of `place` may be hoisted out of the branch
fn may_hoist<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, place: Place<'tcx>) -> bool {
// FIXME(JakobDegen): This is unsound. Someone could write code like this:
// ```rust
// let Q = val;
// if discriminant(P) == otherwise {
// let ptr = &mut Q as *mut _ as *mut u8;
// unsafe { *ptr = 10; } // Any invalid value for the type
// }
//
// match P {
// A => match Q {
// A => {
// // code
// }
// _ => {
// // don't use Q
// }
// }
// _ => {
// // don't use Q
// }
// };
// ```
//
// Hoisting the `discriminant(Q)` out of the `A` arm causes us to compute the discriminant of an
// invalid value, which is UB.
//
// In order to fix this, we would either need to show that the discriminant computation of
// `place` is computed in all branches, including the `otherwise` branch, or we would need
// another analysis pass to determine that the place is fully initialized. It might even be best
// to have the hoisting be performed in a different pass and just do the CFG changing in this
// pass.
for (place, proj) in place.iter_projections() {
match proj {
// Dereferencing in the computation of `place` might cause issues from one of two
// categories. First, the referent might be invalid. We protect against this by
// dereferencing references only (not pointers). Second, the use of a reference may
// invalidate other references that are used later (for aliasing reasons). Consider
// where such an invalidated reference may appear:
// - In `Q`: Not possible since `Q` is used as the operand of a `SwitchInt` and so
// cannot contain referenced data.
// - In `BBU`: Not possible since that block contains only the `unreachable` terminator
// - In `BBC.2, BBD.2`: Not possible, since `discriminant(P)` was computed prior to
// reaching that block in the input to our transformation, and so any data
// invalidated by that computation could not have been used there.
// - In `BB9`: Not possible since control flow might have reached `BB9` via the
// `otherwise` branch in `BBC, BBD` in the input to our transformation, which would
// have invalidated the data when computing `discriminant(P)`
// So dereferencing here is correct.
ProjectionElem::Deref => match place.ty(body.local_decls(), tcx).ty.kind() {
ty::Ref(..) => {}
_ => return false,
},
// Field projections are always valid
ProjectionElem::Field(..) => {}
// We cannot allow
// downcasts either, since the correctness of the downcast may depend on the parent
// branch being taken. An easy example of this is
// ```
// Q = discriminant(_3)
// P = (_3 as Variant)
// ```
// However, checking if the child and parent place are the same and only erroring then
// is not sufficient either, since the `discriminant(_3) == 1` (or whatever) check may
// be replaced by another optimization pass with any other condition that can be proven
// equivalent.
ProjectionElem::Downcast(..) => {
return false;
}
// We cannot allow indexing since the index may be out of bounds.
_ => {
return false;
}
}
}
true
}
#[derive(Debug)]
struct OptimizationData<'tcx> {
destination: BasicBlock,
@ -315,18 +233,40 @@ fn evaluate_candidate<'tcx>(
return None;
};
let parent_ty = parent_discr.ty(body.local_decls(), tcx);
let parent_dest = {
let poss = targets.otherwise();
// If the fallthrough on the parent is trivially unreachable, we can let the
// children choose the destination
if bbs[poss].statements.len() == 0
&& bbs[poss].terminator().kind == TerminatorKind::Unreachable
{
None
} else {
Some(poss)
if !bbs[targets.otherwise()].is_empty_unreachable() {
// Someone could write code like this:
// ```rust
// let Q = val;
// if discriminant(P) == otherwise {
// let ptr = &mut Q as *mut _ as *mut u8;
// // It may be difficult for us to effectively determine whether values are valid.
// // Invalid values can come from all sorts of corners.
// unsafe { *ptr = 10; }
// }
//
// match P {
// A => match Q {
// A => {
// // code
// }
// _ => {
// // don't use Q
// }
// }
// _ => {
// // don't use Q
// }
// };
// ```
//
// Hoisting the `discriminant(Q)` out of the `A` arm causes us to compute the discriminant of an
// invalid value, which is UB.
// In order to fix this, **we would either need to show that the discriminant computation of
// `place` is computed in all branches**.
// FIXME(#95162) For the moment, we adopt a conservative approach and
// consider only the `otherwise` branch has no statements and an unreachable terminator.
return None;
}
};
let (_, child) = targets.iter().next()?;
let child_terminator = &bbs[child].terminator();
let TerminatorKind::SwitchInt { targets: child_targets, discr: child_discr } =
@ -344,13 +284,7 @@ fn evaluate_candidate<'tcx>(
let (_, Rvalue::Discriminant(child_place)) = &**boxed else {
return None;
};
let destination = parent_dest.unwrap_or(child_targets.otherwise());
// Verify that the optimization is legal in general
// We can hoist evaluating the child discriminant out of the branch
if !may_hoist(tcx, body, *child_place) {
return None;
}
let destination = child_targets.otherwise();
// Verify that the optimization is legal for each branch
for (value, child) in targets.iter() {
@ -411,5 +345,5 @@ fn verify_candidate_branch<'tcx>(
if let Some(_) = iter.next() {
return false;
}
return true;
true
}

39
tests/mir-opt/early_otherwise_branch.opt1.EarlyOtherwiseBranch.diff
View File

@ -12,8 +12,6 @@
let mut _7: isize;
let _8: u32;
let _9: u32;
+ let mut _10: isize;
+ let mut _11: bool;
scope 1 {
debug a => _8;
debug b => _9;
@ -29,28 +27,20 @@
StorageDead(_5);
StorageDead(_4);
_7 = discriminant((_3.0: std::option::Option<u32>));
- switchInt(move _7) -> [1: bb2, otherwise: bb1];
+ StorageLive(_10);
+ _10 = discriminant((_3.1: std::option::Option<u32>));
+ StorageLive(_11);
+ _11 = Ne(_7, move _10);
+ StorageDead(_10);
+ switchInt(move _11) -> [0: bb4, otherwise: bb1];
switchInt(move _7) -> [1: bb2, 0: bb1, otherwise: bb5];
}
bb1: {
+ StorageDead(_11);
_0 = const 1_u32;
- goto -> bb4;
+ goto -> bb3;
goto -> bb4;
}
bb2: {
- _6 = discriminant((_3.1: std::option::Option<u32>));
- switchInt(move _6) -> [1: bb3, otherwise: bb1];
- }
-
- bb3: {
_6 = discriminant((_3.1: std::option::Option<u32>));
switchInt(move _6) -> [1: bb3, 0: bb1, otherwise: bb5];
}
bb3: {
StorageLive(_8);
_8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
StorageLive(_9);
@ -58,19 +48,16 @@
_0 = const 0_u32;
StorageDead(_9);
StorageDead(_8);
- goto -> bb4;
+ goto -> bb3;
goto -> bb4;
}
- bb4: {
+ bb3: {
bb4: {
StorageDead(_3);
return;
+ }
+
+ bb4: {
+ StorageDead(_11);
+ switchInt(_7) -> [1: bb2, otherwise: bb1];
}
bb5: {
unreachable;
}
}

57
tests/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff
View File

@ -13,8 +13,6 @@
let mut _8: isize;
let _9: u32;
let _10: u32;
+ let mut _11: isize;
+ let mut _12: bool;
scope 1 {
debug a => _9;
debug b => _10;
@ -30,33 +28,25 @@
StorageDead(_5);
StorageDead(_4);
_8 = discriminant((_3.0: std::option::Option<u32>));
- switchInt(move _8) -> [0: bb3, 1: bb2, otherwise: bb1];
+ StorageLive(_11);
+ _11 = discriminant((_3.1: std::option::Option<u32>));
+ StorageLive(_12);
+ _12 = Ne(_8, move _11);
+ StorageDead(_11);
+ switchInt(move _12) -> [0: bb5, otherwise: bb1];
switchInt(move _8) -> [0: bb3, 1: bb2, otherwise: bb7];
}
bb1: {
+ StorageDead(_12);
_0 = const 1_u32;
- goto -> bb6;
+ goto -> bb4;
goto -> bb6;
}
bb2: {
- _6 = discriminant((_3.1: std::option::Option<u32>));
- switchInt(move _6) -> [1: bb4, otherwise: bb1];
- }
-
- bb3: {
- _7 = discriminant((_3.1: std::option::Option<u32>));
- switchInt(move _7) -> [0: bb5, otherwise: bb1];
- }
-
- bb4: {
_6 = discriminant((_3.1: std::option::Option<u32>));
switchInt(move _6) -> [1: bb4, 0: bb1, otherwise: bb7];
}
bb3: {
_7 = discriminant((_3.1: std::option::Option<u32>));
switchInt(move _7) -> [0: bb5, 1: bb1, otherwise: bb7];
}
bb4: {
StorageLive(_9);
_9 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
StorageLive(_10);
@ -64,26 +54,21 @@
_0 = const 0_u32;
StorageDead(_10);
StorageDead(_9);
- goto -> bb6;
+ goto -> bb4;
goto -> bb6;
}
- bb5: {
+ bb3: {
_0 = const 0_u32;
- goto -> bb6;
+ goto -> bb4;
bb5: {
_0 = const 2_u32;
goto -> bb6;
}
- bb6: {
+ bb4: {
bb6: {
StorageDead(_3);
return;
+ }
+
+ bb5: {
+ StorageDead(_12);
+ switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb1];
}
bb7: {
unreachable;
}
}

106
tests/mir-opt/early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff
View File

@ -1,76 +1,104 @@
- // MIR for `opt3` before EarlyOtherwiseBranch
+ // MIR for `opt3` after EarlyOtherwiseBranch
fn opt3(_1: Option<u32>, _2: Option<bool>) -> u32 {
fn opt3(_1: Option2<u32>, _2: Option2<bool>) -> u32 {
debug x => _1;
debug y => _2;
let mut _0: u32;
let mut _3: (std::option::Option<u32>, std::option::Option<bool>);
let mut _4: std::option::Option<u32>;
let mut _5: std::option::Option<bool>;
let mut _3: (Option2<u32>, Option2<bool>);
let mut _4: Option2<u32>;
let mut _5: Option2<bool>;
let mut _6: isize;
let mut _7: isize;
let _8: u32;
let _9: bool;
+ let mut _10: isize;
+ let mut _11: bool;
let mut _8: isize;
let mut _9: isize;
let _10: u32;
let _11: bool;
+ let mut _12: isize;
+ let mut _13: bool;
scope 1 {
debug a => _8;
debug b => _9;
debug a => _10;
debug b => _11;
}
bb0: {
StorageLive(_3);
StorageLive(_4);
_4 = _1;
_4 = move _1;
StorageLive(_5);
_5 = _2;
_5 = move _2;
_3 = (move _4, move _5);
StorageDead(_5);
StorageDead(_4);
_7 = discriminant((_3.0: std::option::Option<u32>));
- switchInt(move _7) -> [1: bb2, otherwise: bb1];
+ StorageLive(_10);
+ _10 = discriminant((_3.1: std::option::Option<bool>));
+ StorageLive(_11);
+ _11 = Ne(_7, move _10);
+ StorageDead(_10);
+ switchInt(move _11) -> [0: bb4, otherwise: bb1];
_9 = discriminant((_3.0: Option2<u32>));
- switchInt(move _9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb9];
+ StorageLive(_12);
+ _12 = discriminant((_3.1: Option2<bool>));
+ StorageLive(_13);
+ _13 = Ne(_9, move _12);
+ StorageDead(_12);
+ switchInt(move _13) -> [0: bb6, otherwise: bb1];
}
bb1: {
+ StorageDead(_11);
+ StorageDead(_13);
_0 = const 1_u32;
- goto -> bb4;
+ goto -> bb3;
- goto -> bb8;
+ goto -> bb5;
}
bb2: {
- _6 = discriminant((_3.1: std::option::Option<bool>));
- switchInt(move _6) -> [1: bb3, otherwise: bb1];
- _6 = discriminant((_3.1: Option2<bool>));
- switchInt(move _6) -> [0: bb5, otherwise: bb1];
- }
-
- bb3: {
StorageLive(_8);
_8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
StorageLive(_9);
_9 = (((_3.1: std::option::Option<bool>) as Some).0: bool);
- _7 = discriminant((_3.1: Option2<bool>));
- switchInt(move _7) -> [1: bb6, otherwise: bb1];
- }
-
- bb4: {
- _8 = discriminant((_3.1: Option2<bool>));
- switchInt(move _8) -> [2: bb7, otherwise: bb1];
- }
-
- bb5: {
StorageLive(_10);
_10 = (((_3.0: Option2<u32>) as Some).0: u32);
StorageLive(_11);
_11 = (((_3.1: Option2<bool>) as Some).0: bool);
_0 = const 0_u32;
StorageDead(_9);
StorageDead(_8);
- goto -> bb4;
+ goto -> bb3;
StorageDead(_11);
StorageDead(_10);
- goto -> bb8;
+ goto -> bb5;
}
- bb4: {
- bb6: {
+ bb3: {
_0 = const 2_u32;
- goto -> bb8;
+ goto -> bb5;
}
- bb7: {
+ bb4: {
_0 = const 3_u32;
- goto -> bb8;
+ goto -> bb5;
}
- bb8: {
+ bb5: {
StorageDead(_3);
return;
+ }
+
+ bb4: {
+ StorageDead(_11);
+ switchInt(_7) -> [1: bb2, otherwise: bb1];
}
- bb9: {
- unreachable;
+ bb6: {
+ StorageDead(_13);
+ switchInt(_9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb1];
}
}

104
tests/mir-opt/early_otherwise_branch.opt4.EarlyOtherwiseBranch.diff Normal file
View File

@ -0,0 +1,104 @@
- // MIR for `opt4` before EarlyOtherwiseBranch
+ // MIR for `opt4` after EarlyOtherwiseBranch
fn opt4(_1: Option2<u32>, _2: Option2<u32>) -> u32 {
debug x => _1;
debug y => _2;
let mut _0: u32;
let mut _3: (Option2<u32>, Option2<u32>);
let mut _4: Option2<u32>;
let mut _5: Option2<u32>;
let mut _6: isize;
let mut _7: isize;
let mut _8: isize;
let mut _9: isize;
let _10: u32;
let _11: u32;
+ let mut _12: isize;
+ let mut _13: bool;
scope 1 {
debug a => _10;
debug b => _11;
}
bb0: {
StorageLive(_3);
StorageLive(_4);
_4 = move _1;
StorageLive(_5);
_5 = move _2;
_3 = (move _4, move _5);
StorageDead(_5);
StorageDead(_4);
_9 = discriminant((_3.0: Option2<u32>));
- switchInt(move _9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb9];
+ StorageLive(_12);
+ _12 = discriminant((_3.1: Option2<u32>));
+ StorageLive(_13);
+ _13 = Ne(_9, move _12);
+ StorageDead(_12);
+ switchInt(move _13) -> [0: bb6, otherwise: bb1];
}
bb1: {
+ StorageDead(_13);
_0 = const 1_u32;
- goto -> bb8;
+ goto -> bb5;
}
bb2: {
- _6 = discriminant((_3.1: Option2<u32>));
- switchInt(move _6) -> [0: bb5, otherwise: bb1];
- }
-
- bb3: {
- _7 = discriminant((_3.1: Option2<u32>));
- switchInt(move _7) -> [1: bb6, otherwise: bb1];
- }
-
- bb4: {
- _8 = discriminant((_3.1: Option2<u32>));
- switchInt(move _8) -> [2: bb7, otherwise: bb1];
- }
-
- bb5: {
StorageLive(_10);
_10 = (((_3.0: Option2<u32>) as Some).0: u32);
StorageLive(_11);
_11 = (((_3.1: Option2<u32>) as Some).0: u32);
_0 = const 0_u32;
StorageDead(_11);
StorageDead(_10);
- goto -> bb8;
+ goto -> bb5;
}
- bb6: {
+ bb3: {
_0 = const 2_u32;
- goto -> bb8;
+ goto -> bb5;
}
- bb7: {
+ bb4: {
_0 = const 3_u32;
- goto -> bb8;
+ goto -> bb5;
}
- bb8: {
+ bb5: {
StorageDead(_3);
return;
}
- bb9: {
- unreachable;
+ bb6: {
+ StorageDead(_13);
+ switchInt(_9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb1];
}
}

32
tests/mir-opt/early_otherwise_branch.rs
View File

@ -1,5 +1,14 @@
// skip-filecheck
//@ unit-test: EarlyOtherwiseBranch
//@ compile-flags: -Zmir-enable-passes=+UnreachableEnumBranching
enum Option2<T> {
Some(T),
None,
Other,
}
// We can't optimize it because y may be an invalid value.
// EMIT_MIR early_otherwise_branch.opt1.EarlyOtherwiseBranch.diff
fn opt1(x: Option<u32>, y: Option<u32>) -> u32 {
match (x, y) {
@ -8,20 +17,34 @@ fn opt1(x: Option<u32>, y: Option<u32>) -> u32 {
}
}
// FIXME: `switchInt` will have three targets after `UnreachableEnumBranching`,
// otherwise is unreachable. We can consume the UB fact to transform back to if else pattern.
// EMIT_MIR early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff
fn opt2(x: Option<u32>, y: Option<u32>) -> u32 {
match (x, y) {
(Some(a), Some(b)) => 0,
(None, None) => 0,
(None, None) => 2,
_ => 1,
}
}
// optimize despite different types
// EMIT_MIR early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff
fn opt3(x: Option<u32>, y: Option<bool>) -> u32 {
fn opt3(x: Option2<u32>, y: Option2<bool>) -> u32 {
match (x, y) {
(Some(a), Some(b)) => 0,
(Option2::Some(a), Option2::Some(b)) => 0,
(Option2::None, Option2::None) => 2,
(Option2::Other, Option2::Other) => 3,
_ => 1,
}
}
// EMIT_MIR early_otherwise_branch.opt4.EarlyOtherwiseBranch.diff
fn opt4(x: Option2<u32>, y: Option2<u32>) -> u32 {
match (x, y) {
(Option2::Some(a), Option2::Some(b)) => 0,
(Option2::None, Option2::None) => 2,
(Option2::Other, Option2::Other) => 3,
_ => 1,
}
}
@ -29,5 +52,6 @@ fn opt3(x: Option<u32>, y: Option<bool>) -> u32 {
fn main() {
opt1(None, Some(0));
opt2(None, Some(0));
opt3(None, Some(false));
opt3(Option2::None, Option2::Some(false));
opt4(Option2::None, Option2::Some(0));
}

91
tests/mir-opt/early_otherwise_branch_3_element_tuple.opt1.EarlyOtherwiseBranch.diff
View File

@ -13,17 +13,15 @@
let mut _8: isize;
let mut _9: isize;
let mut _10: isize;
let _11: u32;
let _12: u32;
let mut _11: isize;
let mut _12: isize;
let _13: u32;
+ let mut _14: isize;
+ let mut _15: bool;
+ let mut _16: isize;
+ let mut _17: bool;
let _14: u32;
let _15: u32;
scope 1 {
debug a => _11;
debug b => _12;
debug c => _13;
debug a => _13;
debug b => _14;
debug c => _15;
}
bb0: {
@ -38,60 +36,61 @@
StorageDead(_7);
StorageDead(_6);
StorageDead(_5);
_10 = discriminant((_4.0: std::option::Option<u32>));
- switchInt(move _10) -> [1: bb2, otherwise: bb1];
+ StorageLive(_14);
+ _14 = discriminant((_4.1: std::option::Option<u32>));
+ StorageLive(_15);
+ _15 = Ne(_10, move _14);
+ StorageDead(_14);
+ switchInt(move _15) -> [0: bb5, otherwise: bb1];
_12 = discriminant((_4.0: std::option::Option<u32>));
switchInt(move _12) -> [0: bb4, 1: bb2, otherwise: bb9];
}
bb1: {
+ StorageDead(_17);
+ StorageDead(_15);
_0 = const 1_u32;
- goto -> bb5;
+ goto -> bb4;
goto -> bb8;
}
bb2: {
- _9 = discriminant((_4.1: std::option::Option<u32>));
- switchInt(move _9) -> [1: bb3, otherwise: bb1];
- }
-
- bb3: {
_9 = discriminant((_4.1: std::option::Option<u32>));
switchInt(move _9) -> [1: bb3, 0: bb1, otherwise: bb9];
}
bb3: {
_8 = discriminant((_4.2: std::option::Option<u32>));
- switchInt(move _8) -> [1: bb4, otherwise: bb1];
+ switchInt(move _8) -> [1: bb3, otherwise: bb1];
switchInt(move _8) -> [1: bb6, 0: bb1, otherwise: bb9];
}
- bb4: {
+ bb3: {
StorageLive(_11);
_11 = (((_4.0: std::option::Option<u32>) as Some).0: u32);
StorageLive(_12);
_12 = (((_4.1: std::option::Option<u32>) as Some).0: u32);
bb4: {
_11 = discriminant((_4.1: std::option::Option<u32>));
switchInt(move _11) -> [0: bb5, 1: bb1, otherwise: bb9];
}
bb5: {
_10 = discriminant((_4.2: std::option::Option<u32>));
switchInt(move _10) -> [0: bb7, 1: bb1, otherwise: bb9];
}
bb6: {
StorageLive(_13);
_13 = (((_4.2: std::option::Option<u32>) as Some).0: u32);
_13 = (((_4.0: std::option::Option<u32>) as Some).0: u32);
StorageLive(_14);
_14 = (((_4.1: std::option::Option<u32>) as Some).0: u32);
StorageLive(_15);
_15 = (((_4.2: std::option::Option<u32>) as Some).0: u32);
_0 = const 0_u32;
StorageDead(_15);
StorageDead(_14);
StorageDead(_13);
StorageDead(_12);
StorageDead(_11);
- goto -> bb5;
+ goto -> bb4;
goto -> bb8;
}
- bb5: {
+ bb4: {
bb7: {
_0 = const 2_u32;
goto -> bb8;
}
bb8: {
StorageDead(_4);
return;
+ }
+
+ bb5: {
+ StorageDead(_15);
+ switchInt(_10) -> [1: bb2, otherwise: bb1];
}
bb9: {
unreachable;
}
}

138
tests/mir-opt/early_otherwise_branch_3_element_tuple.opt2.EarlyOtherwiseBranch.diff Normal file
View File

@ -0,0 +1,138 @@
- // MIR for `opt2` before EarlyOtherwiseBranch
+ // MIR for `opt2` after EarlyOtherwiseBranch
fn opt2(_1: Option2<u32>, _2: Option2<u32>, _3: Option2<u32>) -> u32 {
debug x => _1;
debug y => _2;
debug z => _3;
let mut _0: u32;
let mut _4: (Option2<u32>, Option2<u32>, Option2<u32>);
let mut _5: Option2<u32>;
let mut _6: Option2<u32>;
let mut _7: Option2<u32>;
let mut _8: isize;
let mut _9: isize;
let mut _10: isize;
let mut _11: isize;
let mut _12: isize;
let mut _13: isize;
let mut _14: isize;
let _15: u32;
let _16: u32;
let _17: u32;
+ let mut _18: isize;
+ let mut _19: bool;
scope 1 {
debug a => _15;
debug b => _16;
debug c => _17;
}
bb0: {
StorageLive(_4);
StorageLive(_5);
_5 = move _1;
StorageLive(_6);
_6 = move _2;
StorageLive(_7);
_7 = move _3;
_4 = (move _5, move _6, move _7);
StorageDead(_7);
StorageDead(_6);
StorageDead(_5);
_14 = discriminant((_4.0: Option2<u32>));
- switchInt(move _14) -> [0: bb2, 1: bb4, 2: bb6, otherwise: bb12];
+ StorageLive(_18);
+ _18 = discriminant((_4.1: Option2<u32>));
+ StorageLive(_19);
+ _19 = Ne(_14, move _18);
+ StorageDead(_18);
+ switchInt(move _19) -> [0: bb9, otherwise: bb1];
}
bb1: {
+ StorageDead(_19);
_0 = const 1_u32;
- goto -> bb11;
+ goto -> bb8;
}
bb2: {
- _9 = discriminant((_4.1: Option2<u32>));
- switchInt(move _9) -> [0: bb3, otherwise: bb1];
- }
-
- bb3: {
_8 = discriminant((_4.2: Option2<u32>));
- switchInt(move _8) -> [0: bb8, otherwise: bb1];
+ switchInt(move _8) -> [0: bb5, otherwise: bb1];
}
- bb4: {
- _11 = discriminant((_4.1: Option2<u32>));
- switchInt(move _11) -> [1: bb5, otherwise: bb1];
- }
-
- bb5: {
+ bb3: {
_10 = discriminant((_4.2: Option2<u32>));
- switchInt(move _10) -> [1: bb9, otherwise: bb1];
+ switchInt(move _10) -> [1: bb6, otherwise: bb1];
}
- bb6: {
- _13 = discriminant((_4.1: Option2<u32>));
- switchInt(move _13) -> [2: bb7, otherwise: bb1];
- }
-
- bb7: {
+ bb4: {
_12 = discriminant((_4.2: Option2<u32>));
- switchInt(move _12) -> [2: bb10, otherwise: bb1];
+ switchInt(move _12) -> [2: bb7, otherwise: bb1];
}
- bb8: {
+ bb5: {
StorageLive(_15);
_15 = (((_4.0: Option2<u32>) as Some).0: u32);
StorageLive(_16);
_16 = (((_4.1: Option2<u32>) as Some).0: u32);
StorageLive(_17);
_17 = (((_4.2: Option2<u32>) as Some).0: u32);
_0 = const 0_u32;
StorageDead(_17);
StorageDead(_16);
StorageDead(_15);
- goto -> bb11;
+ goto -> bb8;
}
- bb9: {
+ bb6: {
_0 = const 2_u32;
- goto -> bb11;
+ goto -> bb8;
}
- bb10: {
+ bb7: {
_0 = const 3_u32;
- goto -> bb11;
+ goto -> bb8;
}
- bb11: {
+ bb8: {
StorageDead(_4);
return;
}
- bb12: {
- unreachable;
+ bb9: {
+ StorageDead(_19);
+ switchInt(_14) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb1];
}
}

21
tests/mir-opt/early_otherwise_branch_3_element_tuple.rs
View File

@ -1,14 +1,35 @@
// skip-filecheck
//@ unit-test: EarlyOtherwiseBranch
//@ compile-flags: -Zmir-enable-passes=+UnreachableEnumBranching
enum Option2<T> {
Some(T),
None,
Other,
}
// FIXME: `switchInt` will have three targets after `UnreachableEnumBranching`,
// otherwise is unreachable. We can consume the UB fact to transform back to if else pattern.
// EMIT_MIR early_otherwise_branch_3_element_tuple.opt1.EarlyOtherwiseBranch.diff
fn opt1(x: Option<u32>, y: Option<u32>, z: Option<u32>) -> u32 {
match (x, y, z) {
(Some(a), Some(b), Some(c)) => 0,
(None, None, None) => 2,
_ => 1,
}
}
// EMIT_MIR early_otherwise_branch_3_element_tuple.opt2.EarlyOtherwiseBranch.diff
fn opt2(x: Option2<u32>, y: Option2<u32>, z: Option2<u32>) -> u32 {
match (x, y, z) {
(Option2::Some(a), Option2::Some(b), Option2::Some(c)) => 0,
(Option2::None, Option2::None, Option2::None) => 2,
(Option2::Other, Option2::Other, Option2::Other) => 3,
_ => 1,
}
}
fn main() {
opt1(None, Some(0), None);
opt2(Option2::None, Option2::Some(0), Option2::None);
}

1
tests/mir-opt/early_otherwise_branch_68867.rs
View File

@ -1,5 +1,6 @@
// skip-filecheck
//@ unit-test: EarlyOtherwiseBranch
//@ compile-flags: -Zmir-enable-passes=+UnreachableEnumBranching
// FIXME: This test was broken by the derefer change.

6
tests/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff
View File

@ -78,7 +78,7 @@
StorageDead(_5);
_34 = deref_copy (_4.0: &ViewportPercentageLength);
_11 = discriminant((*_34));
switchInt(move _11) -> [0: bb2, 1: bb3, 2: bb4, 3: bb5, otherwise: bb1];
switchInt(move _11) -> [0: bb2, 1: bb3, 2: bb4, 3: bb5, otherwise: bb12];
}
bb1: {
@ -213,5 +213,9 @@
bb11: {
return;
}
bb12: {
unreachable;
}
}

1
tests/mir-opt/early_otherwise_branch_noopt.rs
View File

@ -1,5 +1,6 @@
// skip-filecheck
//@ unit-test: EarlyOtherwiseBranch
//@ compile-flags: -Zmir-enable-passes=+UnreachableEnumBranching
// must not optimize as it does not follow the pattern of
// left and right hand side being the same variant

8
tests/mir-opt/early_otherwise_branch_soundness.no_deref_ptr.EarlyOtherwiseBranch.diff
View File

@ -14,7 +14,7 @@
bb0: {
_3 = discriminant(_1);
switchInt(move _3) -> [1: bb2, otherwise: bb1];
switchInt(move _3) -> [1: bb2, 0: bb1, otherwise: bb6];
}
bb1: {
@ -24,7 +24,7 @@
bb2: {
_4 = discriminant((*_2));
switchInt(move _4) -> [1: bb4, otherwise: bb3];
switchInt(move _4) -> [1: bb4, 0: bb3, otherwise: bb6];
}
bb3: {
@ -43,5 +43,9 @@
bb5: {
return;
}
bb6: {
unreachable;
}
}

8
tests/mir-opt/early_otherwise_branch_soundness.no_downcast.EarlyOtherwiseBranch.diff
View File

@ -12,13 +12,13 @@
bb0: {
_3 = discriminant((*_1));
switchInt(move _3) -> [1: bb1, otherwise: bb3];
switchInt(move _3) -> [1: bb1, 0: bb3, otherwise: bb5];
}
bb1: {
_4 = deref_copy (((*_1) as Some).0: &E<'_>);
_2 = discriminant((*_4));
switchInt(move _2) -> [1: bb2, otherwise: bb3];
switchInt(move _2) -> [1: bb2, 0: bb3, otherwise: bb5];
}
bb2: {
@ -34,5 +34,9 @@
bb4: {
return;
}
bb5: {
unreachable;
}
}

1
tests/mir-opt/early_otherwise_branch_soundness.rs
View File

@ -1,5 +1,6 @@
// skip-filecheck
//@ unit-test: EarlyOtherwiseBranch
//@ compile-flags: -Zmir-enable-passes=+UnreachableEnumBranching
// Tests various cases that the `early_otherwise_branch` opt should *not* optimize