nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2025-06-04 19:29:07 +00:00
Code Issues Packages Projects Releases Wiki Activity

Make overflow flag propagation conditional

Browse Source
This commit is contained in:
Jannis Christopher Köhl 2022-10-15 19:24:02 +02:00
parent 1dde908fae
commit be9013f02b
3 changed files with 69 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
compiler/rustc_mir_transform/src/dataflow_const_prop.rs
View File

@ -7,7 +7,7 @@ use rustc_mir_dataflow::value_analysis::{
Map, ProjElem, State, ValueAnalysis, ValueOrPlace, ValueOrPlaceOrRef,
};
use rustc_mir_dataflow::{lattice::FlatSet, Analysis, ResultsVisitor, SwitchIntEdgeEffects};
use rustc_span::DUMMY_SP;
use rustc_span::{sym, DUMMY_SP};
use crate::MirPass;
@ -38,6 +38,7 @@ struct ConstAnalysis<'tcx> {
tcx: TyCtxt<'tcx>,
ecx: InterpCx<'tcx, 'tcx, DummyMachine>,
param_env: ty::ParamEnv<'tcx>,
propagate_overflow: bool,
}
impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'tcx> {
@ -72,7 +73,11 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'tcx> {
});
if value_target.is_some() || overflow_target.is_some() {
let (val, overflow) = self.binary_op(state, *op, left, right);
let (val, mut overflow) = self.binary_op(state, *op, left, right);
if !self.propagate_overflow {
overflow = FlatSet::Top;
}
if let Some(value_target) = value_target {
state.assign_idx(value_target, ValueOrPlaceOrRef::Value(val), self.map());
@ -202,11 +207,20 @@ impl<'tcx> std::fmt::Debug for ScalarTy<'tcx> {
impl<'tcx> ConstAnalysis<'tcx> {
pub fn new(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, map: Map) -> Self {
// It can happen that overflow will be detected even though overflow checks are disabled.
// This is caused by inlining functions that have #[rustc_inherit_overflow_checks]. Such
// overflows must not be propagated if `-C overflow-checks=off`. Also, if the function we
// are optimizing here has #[rustc_inherit_overflow_checks], the overflow checks may
// actually not be triggered by the consuming crate, so we have to ignore them too.
// Related to https://github.com/rust-lang/rust/issues/35310.
let propagate_overflow = tcx.sess.overflow_checks()
&& !tcx.has_attr(body.source.def_id(), sym::rustc_inherit_overflow_checks);
Self {
map,
tcx,
ecx: InterpCx::new(tcx, DUMMY_SP, ty::ParamEnv::empty(), DummyMachine),
param_env: tcx.param_env(body.source.def_id()),
propagate_overflow,
}
}

45
src/test/mir-opt/dataflow-const-prop/inherit_overflow_checks_use.main.DataflowConstProp.diff Normal file
View File

@ -0,0 +1,45 @@
- // MIR for `main` before DataflowConstProp
+ // MIR for `main` after DataflowConstProp
fn main() -> () {
let mut _0: (); // return place in scope 0 at $DIR/inherit_overflow_checks_use.rs:+0:11: +0:11
let mut _1: u8; // in scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
let mut _2: u8; // in scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
let mut _3: u8; // in scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
scope 1 {
}
scope 2 (inlined <u8 as Add>::add) { // at $DIR/inherit_overflow_checks_use.rs:7:13: 7:47
debug self => _2; // in scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
debug other => _3; // in scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
let mut _4: u8; // in scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
let mut _5: u8; // in scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
let mut _6: (u8, bool); // in scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
}
bb0: {
StorageLive(_1); // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
StorageLive(_2); // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
_2 = const u8::MAX; // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
StorageLive(_3); // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
_3 = const 1_u8; // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
StorageLive(_4); // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
_4 = const u8::MAX; // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
StorageLive(_5); // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
_5 = const 1_u8; // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
_6 = CheckedAdd(const u8::MAX, const 1_u8); // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
assert(!move (_6.1: bool), "attempt to compute `{} + {}`, which would overflow", const u8::MAX, const 1_u8) -> bb1; // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
}
bb1: {
- _1 = move (_6.0: u8); // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
+ _1 = const 0_u8; // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
StorageDead(_5); // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
StorageDead(_4); // scope 2 at $SRC_DIR/core/src/ops/arith.rs:LL:COL
StorageDead(_3); // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
StorageDead(_2); // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:13: +3:47
StorageDead(_1); // scope 0 at $DIR/inherit_overflow_checks_use.rs:+3:47: +3:48
nop; // scope 0 at $DIR/inherit_overflow_checks_use.rs:+0:11: +4:2
return; // scope 0 at $DIR/inherit_overflow_checks_use.rs:+4:2: +4:2
}
}

8
src/test/mir-opt/dataflow-const-prop/inherit_overflow_checks_use.rs Normal file
View File

@ -0,0 +1,8 @@
// compile-flags: -C overflow-checks=off
// EMIT_MIR inherit_overflow_checks_use.main.DataflowConstProp.diff
fn main() {
// After inlining, this will contain a `CheckedBinaryOp`. The overflow
// must be ignored by the constant propagation to avoid triggering a panic.
let _ = <u8 as std::ops::Add>::add(255, 1);
}