Add sub_ptr on pointers (the usize version of offset_from) by scottmcm · Pull Request #95837 · rust-lang/rust (original) (raw)
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Status: Awaiting review from the assignee but also interested parties.
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Like we have add/sub which are the usize version of offset, this adds the usize equivalent of offset_from. Like how .add(d) replaced a whole bunch of .offset(d as isize), you can see from the changes here that it's fairly common that code actually knows the order between the pointers and wants a usize, not an isize.
As a bonus, this can do sub nuw+udiv exact, rather than sub+sdiv exact, which can be optimized slightly better because it doesn't have to worry about negatives. That's why the slice iterators weren't using offset_from, though I haven't updated that code in this PR because slices are so perf-critical that I'll do it as its own change.
This is an intrinsic, like offset_from, so that it can eventually be allowed in CTFE. It also allows checking the extra safety condition -- see the test confirming that CTFE catches it if you pass the pointers in the wrong order.
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
and removed S-waiting-on-review
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This was referenced
May 12, 2022
celinval added a commit to celinval/kani-dev that referenced this pull request
celinval added a commit to model-checking/kani that referenced this pull request
- Update rust toolchain to 2022-05-17
Status: Compilation succeeds but regression fails due to new intrinsic.
Relevant changes:
- Implement new intrinsic ptr_offset_from_unsigned
This new intrinsic is used in many different places in the standard library and it was failing some tests for vectors.
- Apply suggestions from code review
Co-authored-by: Adrian Palacios 73246657+adpaco-aws@users.noreply.github.com
- Address PR comments
- Fix order of checks.
- Improve error message.
- Add comments to the new tests.
Co-authored-by: Adrian Palacios 73246657+adpaco-aws@users.noreply.github.com
bors added a commit to rust-lang-ci/rust that referenced this pull request
…, r=Mark-Simulacrum
Add a codegen test for slice::from_ptr_range
I noticed back in rust-lang#95579 that this didn't optimize as well as it should.
It's better now, after rust-lang#95837 changed the code in from_ptr_range and llvm/llvm-project#54824 was fixed in LLVM 15.
So here's a test to keep it generating the good version.