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Auto merge of rust-lang#49947 - oli-obk:turing_complete_const_eval, r…
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…=nagisa

Don't abort const eval due to long running evals, just warn

one check-box of rust-lang#49930

r? @nagisa (rust-lang/rfcs#2344 (comment))
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bors committed Apr 15, 2018
2 parents 7360d6d + 907df8c commit 8de5353
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Showing 6 changed files with 10 additions and 18 deletions.
1 change: 0 additions & 1 deletion src/librustc/ich/impls_ty.rs
Original file line number Diff line number Diff line change
Expand Up @@ -551,7 +551,6 @@ for ::mir::interpret::EvalError<'gcx> {
InvalidPointerMath |
ReadUndefBytes |
DeadLocal |
ExecutionTimeLimitReached |
StackFrameLimitReached |
OutOfTls |
TlsOutOfBounds |
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3 changes: 0 additions & 3 deletions src/librustc/mir/interpret/error.rs
Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,6 @@ pub enum EvalErrorKind<'tcx> {
Intrinsic(String),
OverflowingMath,
InvalidChar(u128),
ExecutionTimeLimitReached,
StackFrameLimitReached,
OutOfTls,
TlsOutOfBounds,
Expand Down Expand Up @@ -188,8 +187,6 @@ impl<'tcx> Error for EvalError<'tcx> {
"mir not found",
InvalidChar(..) =>
"tried to interpret an invalid 32-bit value as a char",
ExecutionTimeLimitReached =>
"the expression was too complex to be evaluated or resulted in an infinite loop",
StackFrameLimitReached =>
"reached the configured maximum number of stack frames",
OutOfTls =>
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3 changes: 0 additions & 3 deletions src/librustc/session/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -112,8 +112,6 @@ pub struct Session {

/// The maximum number of stackframes allowed in const eval
pub const_eval_stack_frame_limit: usize,
/// The maximum number miri steps per constant
pub const_eval_step_limit: usize,

/// The metadata::creader module may inject an allocator/panic_runtime
/// dependency if it didn't already find one, and this tracks what was
Expand Down Expand Up @@ -1103,7 +1101,6 @@ pub fn build_session_(
recursion_limit: Once::new(),
type_length_limit: Once::new(),
const_eval_stack_frame_limit: 100,
const_eval_step_limit: 1_000_000,
next_node_id: OneThread::new(Cell::new(NodeId::new(1))),
injected_allocator: Once::new(),
allocator_kind: Once::new(),
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1 change: 0 additions & 1 deletion src/librustc/ty/structural_impls.rs
Original file line number Diff line number Diff line change
Expand Up @@ -509,7 +509,6 @@ impl<'a, 'tcx> Lift<'tcx> for interpret::EvalError<'a> {
Intrinsic(ref s) => Intrinsic(s.clone()),
OverflowingMath => OverflowingMath,
InvalidChar(c) => InvalidChar(c),
ExecutionTimeLimitReached => ExecutionTimeLimitReached,
StackFrameLimitReached => StackFrameLimitReached,
OutOfTls => OutOfTls,
TlsOutOfBounds => TlsOutOfBounds,
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6 changes: 3 additions & 3 deletions src/librustc_mir/interpret/eval_context.rs
Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ pub struct EvalContext<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'mir, 'tcx>> {
/// The maximum number of terminators that may be evaluated.
/// This prevents infinite loops and huge computations from freezing up const eval.
/// Remove once halting problem is solved.
pub(crate) steps_remaining: usize,
pub(crate) terminators_remaining: usize,
}

/// A stack frame.
Expand Down Expand Up @@ -195,7 +195,7 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
memory: Memory::new(tcx, memory_data),
stack: Vec::new(),
stack_limit: tcx.sess.const_eval_stack_frame_limit,
steps_remaining: tcx.sess.const_eval_step_limit,
terminators_remaining: 1_000_000,
}
}

Expand Down Expand Up @@ -538,7 +538,7 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
}

Aggregate(ref kind, ref operands) => {
self.inc_step_counter_and_check_limit(operands.len())?;
self.inc_step_counter_and_check_limit(operands.len());

let (dest, active_field_index) = match **kind {
mir::AggregateKind::Adt(adt_def, variant_index, _, active_field_index) => {
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14 changes: 7 additions & 7 deletions src/librustc_mir/interpret/step.rs
Original file line number Diff line number Diff line change
Expand Up @@ -8,12 +8,12 @@ use rustc::mir::interpret::EvalResult;
use super::{EvalContext, Machine};

impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
pub fn inc_step_counter_and_check_limit(&mut self, n: usize) -> EvalResult<'tcx> {
self.steps_remaining = self.steps_remaining.saturating_sub(n);
if self.steps_remaining > 0 {
Ok(())
} else {
err!(ExecutionTimeLimitReached)
pub fn inc_step_counter_and_check_limit(&mut self, n: usize) {
self.terminators_remaining = self.terminators_remaining.saturating_sub(n);
if self.terminators_remaining == 0 {
// FIXME(#49980): make this warning a lint
self.tcx.sess.span_warn(self.frame().span, "Constant evaluating a complex constant, this might take some time");
self.terminators_remaining = 1_000_000;
}
}

Expand All @@ -36,7 +36,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
return Ok(true);
}

self.inc_step_counter_and_check_limit(1)?;
self.inc_step_counter_and_check_limit(1);

let terminator = basic_block.terminator();
assert_eq!(old_frames, self.cur_frame());
Expand Down

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