Skip to content

interpret: don't rely on ScalarPair for overflowed arithmetic #98627

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
bors merged 2 commits into from
Jul 4, 2022
Merged

interpret: don't rely on ScalarPair for overflowed arithmetic #98627

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
595dd97
interpret: don't rely on ScalarPair for overflowed arithmetic
RalfJung Jun 28, 2022
0850bad
extra assertion, extra sure
RalfJung Jul 4, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
19 changes: 17 additions & 2 deletions compiler/rustc_const_eval/src/interpret/operator.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ use rustc_middle::mir;
use rustc_middle::mir::interpret::{InterpResult, Scalar};
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_middle::ty::{self, FloatTy, Ty};
use rustc_target::abi::Abi;

use super::{ImmTy, Immediate, InterpCx, Machine, PlaceTy};

Expand All @@ -25,8 +26,22 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
"type mismatch for result of {:?}",
op,
);
let val = Immediate::ScalarPair(val.into(), Scalar::from_bool(overflowed).into());
self.write_immediate(val, dest)
if let Abi::ScalarPair(..) = dest.layout.abi {
// We can use the optimized path and avoid `place_field` (which might do
// `force_allocation`).
let pair = Immediate::ScalarPair(val.into(), Scalar::from_bool(overflowed).into());
self.write_immediate(pair, dest)?;
} else {
assert!(self.tcx.sess.opts.debugging_opts.randomize_layout);
// With randomized layout, `(int, bool)` might cease to be a `ScalarPair`, so we have to

@lcnr lcnr Jul 4, 2022

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

maybe explicitly assert that we're using -Zrandomize-layout (or however the flag is called) here?

// do a component-wise write here. This code path is slower than the above because
// `place_field` will have to `force_allocate` locals here.
let val_field = self.place_field(&dest, 0)?;
self.write_scalar(val, &val_field)?;
let overflowed_field = self.place_field(&dest, 1)?;
self.write_scalar(Scalar::from_bool(overflowed), &overflowed_field)?;
}
Ok(())
}

/// Applies the binary operation `op` to the arguments and writes the result to the
Expand Down