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Testing out updating fork to rust base #1

Merged
merged 264 commits into from
May 24, 2020

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csmoe and others added 30 commits May 5, 2020 23:35
…igation

Given code like `v[&field].boo();` where `field: String` and
`.boo(&mut self)`, typeck will have decided that `v` is accessed using
`Index`, but when `boo` adds a new `mut` obligation,
`convert_place_op_to_mutable` is called. When this happens, for *some
reason* the arguments' dereference adjustments are completely ignored
causing an error saying that `IndexMut` is not satisfied:

```
error[E0596]: cannot borrow data in an index of `Indexable` as mutable
  --> src/main.rs:30:5
   |
30 |     v[&field].boo();
   |     ^^^^^^^^^ cannot borrow as mutable
   |
   = help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `Indexable`
```

This is not true, but by changing `try_overloaded_place_op` to retry
when given `Needs::MutPlace` without passing the argument types, the
example successfully compiles.

I believe there might be more appropriate ways to deal with this.
This stabilizes process_set_argv0 targeting 1.45.0. It has been
useful in practice and seems useful as-is.

The equivalent feature could be implemented for Windows, but as far as I
know nobody has. That can be done separately.

Tracking issue: #66510
WSL1 does not support `fcntl`-based lock and will always report success,
therefore creating a race condition when multiple rustc processes are
modifying shared data such as `search-index.js`. WSL1 does however
support `flock`.

`flock` is supported by all unix-like platforms. The only caveat is that
Linux 2.6.11 or earlier does not support `flock` on NFS mounts, but as
the minimum supported Linux version is 2.6.18, it is not an issue.

Fixes #72157
…g an error.

This way the hir is "valid" and we can remove one more call to
`opt_node_id_to_hir_id` but an error is still emitted.

This is another partial fix for #71104
NRVO optimizes away the locals whose alignment is tested. I don't think
this affects the purpose of the test.
I introduced this mistake in 175976e
and I can't quite remember what the reasoning was back then. I think I
modeled it on `apply_constructor`, not realizing there was an important
difference in the order in which fields were stored.
Using a more error-oriented approache to `Option`.
JohnTitor and others added 10 commits May 23, 2020 17:53
Replace obligation construction with deref_steps()

1. Use `probe()` to avoid unwanted binding committing during `deref_steps()`.
2. Fixes #59819 again by using `deref_steps()`, make the code cleaner. And if we want to suggest multiple dereferences (like: `consider dereferencing the borrow: "****a"`) in the future, this change will make it easier to achieve.
add warning sign to UB examples

Just to make it less likely that people miss the fact that these are examples for how to *not* do it.
Impl Ord for proc_macro::LineColumn

```rust
impl Ord for LineColumn {...}
impl PartialOrd for LineColumn {...}
```

for https://doc.rust-lang.org/nightly/proc_macro/struct.LineColumn.html.

The ordering is the natural one you would get by writing one line after another, where we compare line first, then compare columns within the same line.
Correct small typo: 'not' -> 'note'
Rollup of 5 pull requests

Successful merges:

 - #72292 (Replace obligation construction with deref_steps())
 - #72431 (add warning sign to UB examples)
 - #72446 (Impl Ord for proc_macro::LineColumn)
 - #72492 (Add some regression tests)
 - #72496 (Correct small typo: 'not' -> 'note')

Failed merges:

r? @ghost
@null-sleep
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Author

@arora-aman @ChrisPardy @Azhng @jenniferwills @roxelo Doth me thy honor of approving this PR.

@ChrisPardy ChrisPardy self-requested a review May 24, 2020 00:28
@null-sleep null-sleep merged this pull request into sexxi-goose:master May 24, 2020
sexxi-bot pushed a commit that referenced this pull request May 31, 2020
…ing opaque return type

Go from

```
error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
  --> file8.rs:22:5
   |
22 | /     move || {
23 | |         *dest = g.get();
24 | |     }
   | |_____^
   |
note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the function body at 18:1...
  --> file8.rs:18:1
   |
18 | / fn bat<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
19 | | where
20 | |     G: Get<T>
21 | | {
...  |
24 | |     }
25 | | }
   | |_^
note: ...so that the types are compatible
  --> file8.rs:22:5
   |
22 | /     move || { //~ ERROR cannot infer an appropriate lifetime
23 | |         *dest = g.get();
24 | |     }
   | |_____^
   = note: expected  `&mut T`
              found  `&mut T`
note: but, the lifetime must be valid for the lifetime `'a` as defined on the function body at 18:8...
  --> file8.rs:18:8
   |
18 | fn bat<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
   |        ^^
note: ...so that return value is valid for the call
  --> file8.rs:18:45
   |
18 | fn bat<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
   |                                             ^^^^^^^^^^^^^^^^^^^^^^^
```

to

```
error[E0621]: explicit lifetime required in the type of `dest`
  --> file8.rs:18:45
   |
18 | fn bat<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
   |                                  ------     ^^^^^^^^^^^^^^^^^^^^^^^ lifetime `'a` required
   |                                  |
   |                                  help: add explicit lifetime `'a` to the type of `dest`: `&'a mut T`
   ```
sexxi-bot pushed a commit that referenced this pull request Jun 19, 2020
sexxi-bot pushed a commit that referenced this pull request Sep 13, 2020
* Fix `const-display.rs` XPATH queries

* Add `issue_76501.rs` test file

* Rename issue_76501.rs to issue-76501.rs
arora-aman pushed a commit that referenced this pull request Oct 28, 2020
Fixes rust-lang#836

Benchmark #1: simple-raytracer/raytracer_cg_clif
  Time (mean ± σ):      9.250 s ±  0.056 s    [User: 9.213 s, System: 0.015 s]
  Range (min … max):    9.151 s …  9.348 s    20 runs

Benchmark #2: simple-raytracer/raytracer_cg_clif_cold_separated
  Time (mean ± σ):      9.179 s ±  0.101 s    [User: 9.141 s, System: 0.016 s]
  Range (min … max):    9.070 s …  9.473 s    20 runs

Summary
  'simple-raytracer/raytracer_cg_clif_cold_separated' ran
    1.01 ± 0.01 times faster than 'simple-raytracer/raytracer_cg_clif'
arora-aman pushed a commit that referenced this pull request Oct 28, 2020
`stride == 1` case can be computed more efficiently through `-p (mod
a)`. That, then translates to a nice and short sequence of LLVM
instructions:

    %address = ptrtoint i8* %p to i64
    %negptr = sub i64 0, %address
    %offset = and i64 %negptr, %a_minus_one

And produces pretty much ideal code-gen when this function is used in
isolation.

Typical use of this function will, however, involve use of
the result to offset a pointer, i.e.

    %aligned = getelementptr inbounds i8, i8* %p, i64 %offset

This still looks very good, but LLVM does not really translate that to
what would be considered ideal machine code (on any target). For example
that's the codegen we obtain for an unknown alignment:

    ; x86_64
    dec     rsi
    mov     rax, rdi
    neg     rax
    and     rax, rsi
    add     rax, rdi

In particular negating a pointer is not something that’s going to be
optimised for in the design of CISC architectures like x86_64. They
are much better at offsetting pointers. And so we’d love to utilize this
ability and produce code that's more like this:

    ; x86_64
    lea     rax, [rsi + rdi - 1]
    neg     rsi
    and     rax, rsi

To achieve this we need to give LLVM an opportunity to apply its
various peep-hole optimisations that it does during DAG selection. In
particular, the `and` instruction appears to be a major inhibitor here.
We cannot, sadly, get rid of this load-bearing operation, but we can
reorder operations such that LLVM has more to work with around this
instruction.

One such ordering is proposed in rust-lang#75579 and results in LLVM IR that
looks broadly like this:

    ; using add enables `lea` and similar CISCisms
    %offset_ptr = add i64 %address, %a_minus_one
    %mask = sub i64 0, %a
    %masked = and i64 %offset_ptr, %mask
    ; can be folded with `gepi` that may follow
    %offset = sub i64 %masked, %address

…and generates the intended x86_64 machine code. One might also wonder
how the increased amount of code would impact a RISC target. Turns out
not much:

    ; aarch64 previous                 ; aarch64 new
    sub     x8, x1, #1                 add     x8, x1, x0
    neg     x9, x0                     sub     x8, x8, #1
    and     x8, x9, x8                 neg     x9, x1
    add     x0, x0, x8                 and     x0, x8, x9

    (and similarly for ppc, sparc, mips, riscv, etc)

The only target that seems to do worse is… wasm32.

Onto actual measurements – the best way to evaluate snippets like these
is to use llvm-mca. Much like Aarch64 assembly would allow to suspect,
there isn’t any performance difference to be found. Both snippets
execute in same number of cycles for the CPUs I tried. On x86_64,
we get throughput improvement of >50%, however!
arora-aman pushed a commit that referenced this pull request Oct 28, 2020
Benchmark #1: ./raytracer_cg_clif_pre
  Time (mean ± σ):      8.251 s ±  0.021 s    [User: 8.245 s, System: 0.005 s]
  Range (min … max):    8.225 s …  8.292 s    10 runs

Benchmark #2: ./raytracer_cg_clif_post
  Time (mean ± σ):      8.206 s ±  0.043 s    [User: 8.199 s, System: 0.007 s]
  Range (min … max):    8.168 s …  8.279 s    10 runs
arora-aman pushed a commit that referenced this pull request Oct 28, 2020
…-Simulacrum

Optimise align_offset for stride=1 further

`stride == 1` case can be computed more efficiently through `-p (mod
a)`. That, then translates to a nice and short sequence of LLVM
instructions:

    %address = ptrtoint i8* %p to i64
    %negptr = sub i64 0, %address
    %offset = and i64 %negptr, %a_minus_one

And produces pretty much ideal code-gen when this function is used in
isolation.

Typical use of this function will, however, involve use of
the result to offset a pointer, i.e.

    %aligned = getelementptr inbounds i8, i8* %p, i64 %offset

This still looks very good, but LLVM does not really translate that to
what would be considered ideal machine code (on any target). For example
that's the codegen we obtain for an unknown alignment:

    ; x86_64
    dec     rsi
    mov     rax, rdi
    neg     rax
    and     rax, rsi
    add     rax, rdi

In particular negating a pointer is not something that’s going to be
optimised for in the design of CISC architectures like x86_64. They
are much better at offsetting pointers. And so we’d love to utilize this
ability and produce code that's more like this:

    ; x86_64
    lea     rax, [rsi + rdi - 1]
    neg     rsi
    and     rax, rsi

To achieve this we need to give LLVM an opportunity to apply its
various peep-hole optimisations that it does during DAG selection. In
particular, the `and` instruction appears to be a major inhibitor here.
We cannot, sadly, get rid of this load-bearing operation, but we can
reorder operations such that LLVM has more to work with around this
instruction.

One such ordering is proposed in rust-lang#75579 and results in LLVM IR that
looks broadly like this:

    ; using add enables `lea` and similar CISCisms
    %offset_ptr = add i64 %address, %a_minus_one
    %mask = sub i64 0, %a
    %masked = and i64 %offset_ptr, %mask
    ; can be folded with `gepi` that may follow
    %offset = sub i64 %masked, %address

…and generates the intended x86_64 machine code.
One might also wonder how the increased amount of code would impact a
RISC target. Turns out not much:

    ; aarch64 previous                 ; aarch64 new
    sub     x8, x1, #1                 add     x8, x1, x0
    neg     x9, x0                     sub     x8, x8, #1
    and     x8, x9, x8                 neg     x9, x1
    add     x0, x0, x8                 and     x0, x8, x9

    (and similarly for ppc, sparc, mips, riscv, etc)

The only target that seems to do worse is… wasm32.

Onto actual measurements – the best way to evaluate snipets like these
is to use llvm-mca. Much like Aarch64 assembly would allow to suspect,
there isn’t any performance difference to be found. Both snippets
execute in same number of cycles for the CPUs I tried. On x86_64,
we get throughput improvement of >50%!

Fixes rust-lang#75579
sexxi-bot pushed a commit that referenced this pull request Nov 12, 2020
Before:

```
2:rustc INFO rustc_interface::passes Pre-codegen
2:rustcTy interner             total           ty lt ct all
2:rustc    Adt               :   1078 81.3%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Array             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Slice             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
2:rustc    RawPtr            :      2  0.2%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Ref               :      4  0.3%,  0.1%   0.1%  0.0%  0.0%
2:rustc    FnDef             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    FnPtr             :     76  5.7%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Placeholder       :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Generator         :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    GeneratorWitness  :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Dynamic           :      3  0.2%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Closure           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Tuple             :     13  1.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Bound             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Param             :    146 11.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Infer             :      2  0.2%,  0.1%   0.0%  0.0%  0.0%
2:rustc    Projection        :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Opaque            :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Foreign           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc                  total   1326         0.2%   0.1%  0.0%  0.0%
2:rustcInternalSubsts interner: rust-lang#437
2:rustcRegion interner: rust-lang#355
2:rustcStability interner: #1
2:rustcConst Stability interner: #0
2:rustcAllocation interner: #0
2:rustcLayout interner: #0
```

After:

```
 INFO rustc_interface::passes Post-codegen
Ty interner             total           ty lt ct all
    Adt               :   1078 81.3%,  0.0%   0.0%  0.0%  0.0%
    Array             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
    Slice             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
    RawPtr            :      2  0.2%,  0.0%   0.0%  0.0%  0.0%
    Ref               :      4  0.3%,  0.1%   0.1%  0.0%  0.0%
    FnDef             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    FnPtr             :     76  5.7%,  0.0%   0.0%  0.0%  0.0%
    Placeholder       :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Generator         :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    GeneratorWitness  :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Dynamic           :      3  0.2%,  0.0%   0.0%  0.0%  0.0%
    Closure           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Tuple             :     13  1.0%,  0.0%   0.0%  0.0%  0.0%
    Bound             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Param             :    146 11.0%,  0.0%   0.0%  0.0%  0.0%
    Infer             :      2  0.2%,  0.1%   0.0%  0.0%  0.0%
    Projection        :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Opaque            :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Foreign           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
                  total   1326         0.2%   0.1%  0.0%  0.0%
InternalSubsts interner: rust-lang#437
Region interner: rust-lang#355
Stability interner: #1
Const Stability interner: #0
Allocation interner: #0
Layout interner: #0
```
sexxi-bot pushed a commit that referenced this pull request Nov 12, 2020
Don't print thread ids and names in `tracing` logs

Before:

```
2:rustc INFO rustc_interface::passes Pre-codegen
2:rustcTy interner             total           ty lt ct all
2:rustc    Adt               :   1078 81.3%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Array             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Slice             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
2:rustc    RawPtr            :      2  0.2%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Ref               :      4  0.3%,  0.1%   0.1%  0.0%  0.0%
2:rustc    FnDef             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    FnPtr             :     76  5.7%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Placeholder       :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Generator         :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    GeneratorWitness  :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Dynamic           :      3  0.2%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Closure           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Tuple             :     13  1.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Bound             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Param             :    146 11.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Infer             :      2  0.2%,  0.1%   0.0%  0.0%  0.0%
2:rustc    Projection        :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Opaque            :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Foreign           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc                  total   1326         0.2%   0.1%  0.0%  0.0%
2:rustcInternalSubsts interner: rust-lang#437
2:rustcRegion interner: rust-lang#355
2:rustcStability interner: #1
2:rustcConst Stability interner: #0
2:rustcAllocation interner: #0
2:rustcLayout interner: #0
```

After:

```
 INFO rustc_interface::passes Post-codegen
Ty interner             total           ty lt ct all
    Adt               :   1078 81.3%,  0.0%   0.0%  0.0%  0.0%
    Array             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
    Slice             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
    RawPtr            :      2  0.2%,  0.0%   0.0%  0.0%  0.0%
    Ref               :      4  0.3%,  0.1%   0.1%  0.0%  0.0%
    FnDef             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    FnPtr             :     76  5.7%,  0.0%   0.0%  0.0%  0.0%
    Placeholder       :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Generator         :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    GeneratorWitness  :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Dynamic           :      3  0.2%,  0.0%   0.0%  0.0%  0.0%
    Closure           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Tuple             :     13  1.0%,  0.0%   0.0%  0.0%  0.0%
    Bound             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Param             :    146 11.0%,  0.0%   0.0%  0.0%  0.0%
    Infer             :      2  0.2%,  0.1%   0.0%  0.0%  0.0%
    Projection        :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Opaque            :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
    Foreign           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
                  total   1326         0.2%   0.1%  0.0%  0.0%
InternalSubsts interner: rust-lang#437
Region interner: rust-lang#355
Stability interner: #1
Const Stability interner: #0
Allocation interner: #0
Layout interner: #0
```

Closes rust-lang#78931
r? ``@oli-obk``
roxelo pushed a commit that referenced this pull request Nov 30, 2020
```
Benchmark #1: ./raytracer_cg_clif_pre
  Time (mean ± σ):      9.553 s ±  0.129 s    [User: 9.543 s, System: 0.008 s]
  Range (min … max):    9.438 s …  9.837 s    10 runs

Benchmark #2: ./raytracer_cg_clif_post
  Time (mean ± σ):      9.463 s ±  0.055 s    [User: 9.452 s, System: 0.008 s]
  Range (min … max):    9.387 s …  9.518 s    10 runs

Summary
  './raytracer_cg_clif_post' ran
    1.01 ± 0.01 times faster than './raytracer_cg_clif_pre'
```
roxelo pushed a commit that referenced this pull request Nov 30, 2020
Don't run `resolve_vars_if_possible` in `normalize_erasing_regions`

Neither `@eddyb` nor I could figure out what this was for. I changed it to `assert_eq!(normalized_value, infcx.resolve_vars_if_possible(&normalized_value));` and it passed the UI test suite.

<details><summary>

Outdated, I figured out the issue - `needs_infer()` needs to come _after_ erasing the lifetimes

</summary>

Strangely, if I change it to `assert!(!normalized_value.needs_infer())` it panics almost immediately:

```
query stack during panic:
#0 [normalize_generic_arg_after_erasing_regions] normalizing `<str::IsWhitespace as str::pattern::Pattern>::Searcher`
#1 [needs_drop_raw] computing whether `str::iter::Split<str::IsWhitespace>` needs drop
#2 [mir_built] building MIR for `str::<impl str>::split_whitespace`
#3 [unsafety_check_result] unsafety-checking `str::<impl str>::split_whitespace`
#4 [mir_const] processing MIR for `str::<impl str>::split_whitespace`
#5 [mir_promoted] processing `str::<impl str>::split_whitespace`
#6 [mir_borrowck] borrow-checking `str::<impl str>::split_whitespace`
#7 [analysis] running analysis passes on this crate
end of query stack
```

I'm not entirely sure what's going on - maybe the two disagree?

</details>

For context, this came up while reviewing rust-lang#77467 (cc `@lcnr).`

Possibly this needs a crater run?

r? `@nikomatsakis`
cc `@matthewjasper`
sexxi-bot pushed a commit that referenced this pull request Feb 13, 2021
HWAddressSanitizer support

#  Motivation
Compared to regular ASan, HWASan has a [smaller overhead](https://source.android.com/devices/tech/debug/hwasan). The difference in practice is that HWASan'ed code is more usable, e.g. Android device compiled with HWASan can be used as a daily driver.

# Example
```
fn main() {
    let xs = vec![0, 1, 2, 3];
    let _y = unsafe { *xs.as_ptr().offset(4) };
}
```
```
==223==ERROR: HWAddressSanitizer: tag-mismatch on address 0xefdeffff0050 at pc 0xaaaad00b3468
READ of size 4 at 0xefdeffff0050 tags: e5/00 (ptr/mem) in thread T0
    #0 0xaaaad00b3464  (/root/main+0x53464)
    #1 0xaaaad00b39b4  (/root/main+0x539b4)
    #2 0xaaaad00b3dd0  (/root/main+0x53dd0)
    #3 0xaaaad00b61dc  (/root/main+0x561dc)
    #4 0xaaaad00c0574  (/root/main+0x60574)
    #5 0xaaaad00b6290  (/root/main+0x56290)
    #6 0xaaaad00b6170  (/root/main+0x56170)
    #7 0xaaaad00b3578  (/root/main+0x53578)
    #8 0xffff81345e70  (/lib64/libc.so.6+0x20e70)
    #9 0xaaaad0096310  (/root/main+0x36310)

[0xefdeffff0040,0xefdeffff0060) is a small allocated heap chunk; size: 32 offset: 16
0xefdeffff0050 is located 0 bytes to the right of 16-byte region [0xefdeffff0040,0xefdeffff0050)
allocated here:
    #0 0xaaaad009bcdc  (/root/main+0x3bcdc)
    #1 0xaaaad00b1eb0  (/root/main+0x51eb0)
    #2 0xaaaad00b20d4  (/root/main+0x520d4)
    #3 0xaaaad00b2800  (/root/main+0x52800)
    #4 0xaaaad00b1cf4  (/root/main+0x51cf4)
    #5 0xaaaad00b33d4  (/root/main+0x533d4)
    #6 0xaaaad00b39b4  (/root/main+0x539b4)
    #7 0xaaaad00b61dc  (/root/main+0x561dc)
    #8 0xaaaad00b3578  (/root/main+0x53578)
    #9 0xaaaad0096310  (/root/main+0x36310)

Thread: T0 0xeffe00002000 stack: [0xffffc0590000,0xffffc0d90000) sz: 8388608 tls: [0xffff81521020,0xffff815217d0)
Memory tags around the buggy address (one tag corresponds to 16 bytes):
  0xfefcefffef80: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffef90: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefa0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefb0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefc0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefd0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefe0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffeff0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
=>0xfefceffff000: a2  a2  05  00  e5 [00] 00  00  00  00  00  00  00  00  00  00
  0xfefceffff010: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff020: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff030: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff040: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff050: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff060: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff070: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff080: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
Tags for short granules around the buggy address (one tag corresponds to 16 bytes):
  0xfefcefffeff0: ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
=>0xfefceffff000: ..  ..  c5  ..  .. [..] ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
  0xfefceffff010: ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
See https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html#short-granules for a description of short granule tags
Registers where the failure occurred (pc 0xaaaad00b3468):
    x0  e500efdeffff0050  x1  0000000000000004  x2  0000ffffc0d8f5a0  x3  0200efff00000000
    x4  0000ffffc0d8f4c0  x5  000000000000004f  x6  00000ffffc0d8f36  x7  0000efff00000000
    x8  e500efdeffff0050  x9  0200efff00000000  x10 0000000000000000  x11 0200efff00000000
    x12 0200effe000006b0  x13 0200effe000006b0  x14 0000000000000008  x15 00000000c00000cf
    x16 0000aaaad00a0afc  x17 0000000000000003  x18 0000000000000001  x19 0000ffffc0d8f718
    x20 ba00ffffc0d8f7a0  x21 0000aaaad00962e0  x22 0000000000000000  x23 0000000000000000
    x24 0000000000000000  x25 0000000000000000  x26 0000000000000000  x27 0000000000000000
    x28 0000000000000000  x29 0000ffffc0d8f650  x30 0000aaaad00b3468
```

# Comments/Caveats
* HWASan is only supported on arm64.
* I'm not sure if I should add a feature gate or piggyback on the existing one for sanitizers.
* HWASan requires `-C target-feature=+tagged-globals`. That flag should probably be set transparently to the user. Not sure how to go about that.

# TODO
* Need more tests.
* Update documentation.
* Fix symbolization.
* Integrate with CI
sexxi-bot pushed a commit that referenced this pull request Mar 8, 2021
bypass auto_da_alloc for metadata files

This saves about 0.7% when rerunning the UI test suite. I.e. when the metadata files exist and will be overwritten. No improvements expected for a clean build. So it might show up in incr-patched perf results.
```
regular rename:

Benchmark #1: touch src/tools/compiletest/src/main.rs ; RUSTC_WRAPPER="" schedtool -B -e ./x.py test src/test/ui
  Time (mean ± σ):     47.305 s ±  0.170 s    [User: 1631.540 s, System: 412.648 s]
  Range (min … max):   47.125 s … 47.856 s    20 runs

non-durable rename:

Benchmark #1: touch src/tools/compiletest/src/main.rs ; RUSTC_WRAPPER="" schedtool -B -e ./x.py test src/test/ui
  Time (mean ± σ):     46.930 s ±  0.064 s    [User: 1634.344 s, System: 396.038 s]
  Range (min … max):   46.759 s … 47.043 s    20 runs
```

There are more places that trigger auto_da_alloc behavior by overwriting existing files with O_TRUNC, but those are much harder to locate because `O_TRUNC` is set on `open()` but the writeback is triggered on `close()`. The latter is the part which shows up in profiles.
sexxi-bot pushed a commit that referenced this pull request May 11, 2021
…nt, r=Mark-Simulacrum

Show nicer error when an 'unstable fingerprints' error occurs

An example of the error produced by this PR:

```
error: internal compiler error: encountered incremental compilation error with evaluate_obligation(9f2ad55260c30262-c36667639674ad83)
  |
  = help: This is a known issue with the compiler. Run `cargo clean -p syn` or `cargo clean` to allow your project to compile
  = note: Please follow the instructions below to create a bug report with the provided information

thread 'rustc' panicked at 'Found unstable fingerprints for evaluate_obligation(9f2ad55260c30262-c36667639674ad83): Ok(EvaluatedToOk)', /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:595:9
stack backtrace:
   0: rust_begin_unwind
             at /home/aaron/repos/rust/library/std/src/panicking.rs:493:5
   1: std::panicking::begin_panic_fmt
             at /home/aaron/repos/rust/library/std/src/panicking.rs:435:5
   2: rustc_query_system::query::plumbing::incremental_verify_ich
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:595:9
   3: rustc_query_system::query::plumbing::load_from_disk_and_cache_in_memory
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:557:9
   4: rustc_query_system::query::plumbing::try_execute_query::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:473:21
   5: core::option::Option<T>::map
             at /home/aaron/repos/rust/library/core/src/option.rs:487:29
   6: rustc_query_system::query::plumbing::try_execute_query::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:471:13
   7: stacker::maybe_grow
             at /home/aaron/.cargo/registry/src/github.com-1ecc6299db9ec823/stacker-0.1.12/src/lib.rs:55:9
   8: rustc_data_structures::stack::ensure_sufficient_stack
             at /home/aaron/repos/rust/compiler/rustc_data_structures/src/stack.rs:16:5
   9: <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::start_query::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_impl/src/plumbing.rs:169:17
  10: rustc_middle::ty::context::tls::enter_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:50
  11: rustc_middle::ty::context::tls::set_tlv
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1720:9
  12: rustc_middle::ty::context::tls::enter_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:9
  13: <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::start_query::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_impl/src/plumbing.rs:168:13
  14: rustc_middle::ty::context::tls::with_related_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1780:13
  15: rustc_middle::ty::context::tls::with_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:40
  16: rustc_middle::ty::context::tls::with_context_opt
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1753:22
  17: rustc_middle::ty::context::tls::with_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:9
  18: rustc_middle::ty::context::tls::with_related_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1777:9
  19: <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::start_query
             at /home/aaron/repos/rust/compiler/rustc_query_impl/src/plumbing.rs:157:9
  20: rustc_query_system::query::plumbing::try_execute_query
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:469:22
  21: rustc_query_system::query::plumbing::get_query_impl
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:674:5
  22: rustc_query_system::query::plumbing::get_query
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:785:9
  23: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::evaluate_obligation
             at /home/aaron/repos/rust/compiler/rustc_query_impl/src/plumbing.rs:603:17
  24: rustc_middle::ty::query::TyCtxtAt::evaluate_obligation
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/query/mod.rs:204:17
  25: rustc_middle::ty::query::<impl rustc_middle::ty::context::TyCtxt>::evaluate_obligation
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/query/mod.rs:185:17
  26: <rustc_infer::infer::InferCtxt as rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt>::evaluate_obligation
             at /home/aaron/repos/rust/compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs:72:9
  27: <rustc_infer::infer::InferCtxt as rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt>::evaluate_obligation_no_overflow
             at /home/aaron/repos/rust/compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs:82:15
  28: <rustc_infer::infer::InferCtxt as rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt>::predicate_must_hold_modulo_regions
             at /home/aaron/repos/rust/compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs:58:9
  29: rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions
             at /home/aaron/repos/rust/compiler/rustc_trait_selection/src/traits/mod.rs:146:18
  30: rustc_ty_utils::common_traits::is_item_raw::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_ty_utils/src/common_traits.rs:33:9
  31: rustc_infer::infer::InferCtxtBuilder::enter
             at /home/aaron/repos/rust/compiler/rustc_infer/src/infer/mod.rs:582:9
  32: rustc_ty_utils::common_traits::is_item_raw
             at /home/aaron/repos/rust/compiler/rustc_ty_utils/src/common_traits.rs:32:5
  33: rustc_query_system::query::config::QueryVtable<CTX,K,V>::compute
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/config.rs:44:9
  34: rustc_query_system::query::plumbing::load_from_disk_and_cache_in_memory::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:544:67
  35: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/dep_graph/mod.rs:77:46
  36: rustc_middle::ty::context::tls::enter_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:50
  37: rustc_middle::ty::context::tls::set_tlv
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1720:9
  38: rustc_middle::ty::context::tls::enter_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:9
  39: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/dep_graph/mod.rs:77:13
  40: rustc_middle::ty::context::tls::with_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:40
  41: rustc_middle::ty::context::tls::with_context_opt
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1753:22
  42: rustc_middle::ty::context::tls::with_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:9
  43: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
             at /home/aaron/repos/rust/compiler/rustc_middle/src/dep_graph/mod.rs:74:9
  44: rustc_query_system::dep_graph::graph::DepGraph<K>::with_ignore
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/dep_graph/graph.rs:167:9
  45: rustc_query_system::query::plumbing::load_from_disk_and_cache_in_memory
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:544:22
  46: rustc_query_system::query::plumbing::try_execute_query::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:473:21
  47: core::option::Option<T>::map
             at /home/aaron/repos/rust/library/core/src/option.rs:487:29
  48: rustc_query_system::query::plumbing::try_execute_query::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:471:13
  49: stacker::maybe_grow
             at /home/aaron/.cargo/registry/src/github.com-1ecc6299db9ec823/stacker-0.1.12/src/lib.rs:55:9
  50: rustc_data_structures::stack::ensure_sufficient_stack
             at /home/aaron/repos/rust/compiler/rustc_data_structures/src/stack.rs:16:5
  51: <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::start_query::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_impl/src/plumbing.rs:169:17
  52: rustc_middle::ty::context::tls::enter_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:50
  53: rustc_middle::ty::context::tls::set_tlv
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1720:9
  54: rustc_middle::ty::context::tls::enter_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:9
  55: <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::start_query::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_impl/src/plumbing.rs:168:13
  56: rustc_middle::ty::context::tls::with_related_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1780:13
  57: rustc_middle::ty::context::tls::with_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:40
  58: rustc_middle::ty::context::tls::with_context_opt
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1753:22
  59: rustc_middle::ty::context::tls::with_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:9
  60: rustc_middle::ty::context::tls::with_related_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1777:9
  61: <rustc_query_impl::plumbing::QueryCtxt as rustc_query_system::query::QueryContext>::start_query
             at /home/aaron/repos/rust/compiler/rustc_query_impl/src/plumbing.rs:157:9
  62: rustc_query_system::query::plumbing::try_execute_query
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:469:22
  63: rustc_query_system::query::plumbing::get_query_impl
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:674:5
  64: rustc_query_system::query::plumbing::get_query
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/query/plumbing.rs:785:9
  65: rustc_middle::ty::query::TyCtxtAt::is_unpin_raw
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/query/mod.rs:204:17
  66: rustc_middle::ty::util::<impl rustc_middle::ty::TyS>::is_unpin
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/util.rs:727:38
  67: rustc_middle::ty::layout::<impl rustc_target::abi::TyAndLayoutMethods<C> for &rustc_middle::ty::TyS>::pointee_info_at
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/layout.rs:2341:32
  68: rustc_target::abi::TyAndLayout<Ty>::pointee_info_at
             at /home/aaron/repos/rust/compiler/rustc_target/src/abi/mod.rs:1164:9
  69: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::new_internal::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/layout.rs:2781:36
  70: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::new_internal::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/layout.rs:2840:17
  71: rustc_target::abi::call::ArgAbi<Ty>::new
             at /home/aaron/repos/rust/compiler/rustc_target/src/abi/call/mod.rs:457:53
  72: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::new_internal::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/layout.rs:2838:27
  73: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::new_internal::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/layout.rs:2870:32
  74: core::iter::adapters::map::map_fold::{{closure}}
             at /home/aaron/repos/rust/library/core/src/iter/adapters/map.rs:82:28
  75: <core::iter::adapters::enumerate::Enumerate<I> as core::iter::traits::iterator::Iterator>::fold::enumerate::{{closure}}
             at /home/aaron/repos/rust/library/core/src/iter/adapters/enumerate.rs:104:27
  76: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
             at /home/aaron/repos/rust/library/core/src/ops/function.rs:269:13
  77: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
             at /home/aaron/repos/rust/library/core/src/ops/function.rs:269:13
  78: core::iter::adapters::map::map_fold::{{closure}}
             at /home/aaron/repos/rust/library/core/src/iter/adapters/map.rs:82:21
  79: core::iter::traits::iterator::Iterator::fold
             at /home/aaron/repos/rust/library/core/src/iter/traits/iterator.rs:2146:21
  80: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
             at /home/aaron/repos/rust/library/core/src/iter/adapters/map.rs:122:9
  81: <core::iter::adapters::cloned::Cloned<I> as core::iter::traits::iterator::Iterator>::fold
             at /home/aaron/repos/rust/library/core/src/iter/adapters/cloned.rs:58:9
  82: <core::iter::adapters::chain::Chain<A,B> as core::iter::traits::iterator::Iterator>::fold
             at /home/aaron/repos/rust/library/core/src/iter/adapters/chain.rs:119:19
  83: <core::iter::adapters::chain::Chain<A,B> as core::iter::traits::iterator::Iterator>::fold
             at /home/aaron/repos/rust/library/core/src/iter/adapters/chain.rs:119:19
  84: <core::iter::adapters::enumerate::Enumerate<I> as core::iter::traits::iterator::Iterator>::fold
             at /home/aaron/repos/rust/library/core/src/iter/adapters/enumerate.rs:110:9
  85: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
             at /home/aaron/repos/rust/library/core/src/iter/adapters/map.rs:122:9
  86: core::iter::traits::iterator::Iterator::for_each
             at /home/aaron/repos/rust/library/core/src/iter/traits/iterator.rs:776:9
  87: <alloc::vec::Vec<T,A> as alloc::vec::spec_extend::SpecExtend<T,I>>::spec_extend
             at /home/aaron/repos/rust/library/alloc/src/vec/spec_extend.rs:40:17
  88: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter
             at /home/aaron/repos/rust/library/alloc/src/vec/spec_from_iter_nested.rs:56:9
  89: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
             at /home/aaron/repos/rust/library/alloc/src/vec/spec_from_iter.rs:36:9
  90: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
             at /home/aaron/repos/rust/library/alloc/src/vec/mod.rs:2448:9
  91: core::iter::traits::iterator::Iterator::collect
             at /home/aaron/repos/rust/library/core/src/iter/traits/iterator.rs:1788:9
  92: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::new_internal
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/layout.rs:2864:19
  93: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::of_instance
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/layout.rs:2670:9
  94: rustc_codegen_llvm::mono_item::<impl rustc_codegen_ssa::traits::declare::PreDefineMethods for rustc_codegen_llvm::context::CodegenCx>::predefine_fn
             at /home/aaron/repos/rust/compiler/rustc_codegen_llvm/src/mono_item.rs:57:22
  95: <rustc_middle::mir::mono::MonoItem as rustc_codegen_ssa::mono_item::MonoItemExt>::predefine
             at /home/aaron/repos/rust/compiler/rustc_codegen_ssa/src/mono_item.rs:76:17
  96: rustc_codegen_llvm::base::compile_codegen_unit::module_codegen
             at /home/aaron/repos/rust/compiler/rustc_codegen_llvm/src/base.rs:122:17
  97: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/dep_graph/graph.rs:235:62
  98: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/dep_graph/mod.rs:77:46
  99: rustc_middle::ty::context::tls::enter_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:50
 100: rustc_middle::ty::context::tls::set_tlv
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1720:9
 101: rustc_middle::ty::context::tls::enter_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:9
 102: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/dep_graph/mod.rs:77:13
 103: rustc_middle::ty::context::tls::with_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:40
 104: rustc_middle::ty::context::tls::with_context_opt
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1753:22
 105: rustc_middle::ty::context::tls::with_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1764:9
 106: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
             at /home/aaron/repos/rust/compiler/rustc_middle/src/dep_graph/mod.rs:74:9
 107: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/dep_graph/graph.rs:235:26
 108: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
             at /home/aaron/repos/rust/compiler/rustc_query_system/src/dep_graph/graph.rs:205:9
 109: rustc_codegen_llvm::base::compile_codegen_unit
             at /home/aaron/repos/rust/compiler/rustc_codegen_llvm/src/base.rs:103:9
 110: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::ExtraBackendMethods>::compile_codegen_unit
             at /home/aaron/repos/rust/compiler/rustc_codegen_llvm/src/lib.rs:109:9
 111: rustc_codegen_ssa::base::codegen_crate
             at /home/aaron/repos/rust/compiler/rustc_codegen_ssa/src/base.rs:655:38
 112: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
             at /home/aaron/repos/rust/compiler/rustc_codegen_llvm/src/lib.rs:270:18
 113: rustc_interface::passes::start_codegen::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/passes.rs:1021:9
 114: rustc_data_structures::profiling::VerboseTimingGuard::run
             at /home/aaron/repos/rust/compiler/rustc_data_structures/src/profiling.rs:573:9
 115: rustc_session::utils::<impl rustc_session::session::Session>::time
             at /home/aaron/repos/rust/compiler/rustc_session/src/utils.rs:16:9
 116: rustc_interface::passes::start_codegen
             at /home/aaron/repos/rust/compiler/rustc_interface/src/passes.rs:1020:19
 117: rustc_interface::queries::Queries::ongoing_codegen::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/queries.rs:296:20
 118: rustc_interface::passes::QueryContext::enter::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/passes.rs:755:42
 119: rustc_middle::ty::context::tls::enter_context::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:50
 120: rustc_middle::ty::context::tls::set_tlv
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1720:9
 121: rustc_middle::ty::context::tls::enter_context
             at /home/aaron/repos/rust/compiler/rustc_middle/src/ty/context.rs:1736:9
 122: rustc_interface::passes::QueryContext::enter
             at /home/aaron/repos/rust/compiler/rustc_interface/src/passes.rs:755:9
 123: rustc_interface::queries::Queries::ongoing_codegen::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/queries.rs:287:13
 124: rustc_interface::queries::Query<T>::compute
             at /home/aaron/repos/rust/compiler/rustc_interface/src/queries.rs:40:28
 125: rustc_interface::queries::Queries::ongoing_codegen
             at /home/aaron/repos/rust/compiler/rustc_interface/src/queries.rs:285:9
 126: rustc_driver::run_compiler::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_driver/src/lib.rs:442:13
 127: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
             at /home/aaron/repos/rust/compiler/rustc_interface/src/queries.rs:428:19
 128: rustc_driver::run_compiler::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_driver/src/lib.rs:337:22
 129: rustc_interface::interface::create_compiler_and_run::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/interface.rs:208:13
 130: rustc_span::with_source_map
             at /home/aaron/repos/rust/compiler/rustc_span/src/lib.rs:788:5
 131: rustc_interface::interface::create_compiler_and_run
             at /home/aaron/repos/rust/compiler/rustc_interface/src/interface.rs:202:5
 132: rustc_interface::interface::run_compiler::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/interface.rs:224:12
 133: rustc_interface::util::setup_callbacks_and_run_in_thread_pool_with_globals::{{closure}}::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/util.rs:155:13
 134: scoped_tls::ScopedKey<T>::set
             at /home/aaron/.cargo/registry/src/github.com-1ecc6299db9ec823/scoped-tls-1.0.0/src/lib.rs:137:9
 135: rustc_span::with_session_globals
             at /home/aaron/repos/rust/compiler/rustc_span/src/lib.rs:105:5
 136: rustc_interface::util::setup_callbacks_and_run_in_thread_pool_with_globals::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/util.rs:153:9
 137: rustc_interface::util::scoped_thread::{{closure}}
             at /home/aaron/repos/rust/compiler/rustc_interface/src/util.rs:128:24
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.54.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: -C opt-level=3 -C embed-bitcode=no -C incremental --crate-type lib

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `quote::Tokens: std::marker::Unpin`
#1 [is_unpin_raw] computing whether `quote::Tokens` is `Unpin`
end of query stack
error: aborting due to previous error

error: could not compile `syn`

To learn more, run the command again with --verbose.
```

I've left in the panic and ICE following the pretty error, so that we still have all of the debug information available in a bug report.

This message can be reproduced by cloning the repository `https://github.com/Aaron1011/syn-crash`, and running the following shell script (with a `rustup override` set in the directory):

```
set -xe
cargo clean -p syn
cargo clean --release -p syn

git checkout minimize
cargo build --release -j 1

git checkout minimize-change
cargo build --release -j 1
```

r? ``@Mark-Simulacrum``
sexxi-bot pushed a commit that referenced this pull request May 15, 2021
str::is_char_boundary - slight optimization

Current `str::is_char_boundary` implementation emits slightly more instructions, because it includes an additional branch for `index == s.len()`
```rust
pub fn is_char_boundary(s: &str, index: usize) -> bool {
    if index == 0 || index == s.len() {
        return true;
    }
    match s.as_bytes().get(index) {
        None => false,
        Some(&b) => (b as i8) >= -0x40,
    }
}
```
Just changing the place of `index == s.len()` merges it with `index < s.len()` from `s.as_bytes().get(index)`
```rust
pub fn is_char_boundary2(s: &str, index: usize) -> bool {
    if index == 0 {
        return true;
    }

    match s.as_bytes().get(index) {
        // For some reason, LLVM likes this comparison here more
        None => index == s.len(),
        // This is bit magic equivalent to: b < 128 || b >= 192
        Some(&b) => (b as i8) >= -0x40,
    }
}
```
This one has better codegen on every platform, except powerpc
<details><summary>x86 codegen</summary>
<p>

```nasm
example::is_char_boundary:
        mov     al, 1
        test    rdx, rdx
        je      .LBB0_5
        cmp     rsi, rdx
        je      .LBB0_5
        cmp     rsi, rdx
        jbe     .LBB0_3
        cmp     byte ptr [rdi + rdx], -65
        setg    al
.LBB0_5:
        ret
.LBB0_3:
        xor     eax, eax
        ret

example::is_char_boundary2:
        test    rdx, rdx
        je      .LBB1_1
        cmp     rsi, rdx
        jbe     .LBB1_4
        cmp     byte ptr [rdi + rdx], -65
        setg    al
        ret
.LBB1_1:  ; technically this branch is the same as LBB1_4
        mov     al, 1
        ret
.LBB1_4:
        sete    al
        ret
 ```
</p>
</details>

<details><summary>aarch64 codegen</summary>
<p>

```as
example::is_char_boundary:
        mov     x8, x0
        mov     w0, #1
        cbz     x2, .LBB0_4
        cmp     x1, x2
        b.eq    .LBB0_4
        b.ls    .LBB0_5
        ldrsb   w8, [x8, x2]
        cmn     w8, rust-lang#65
        cset    w0, gt
.LBB0_4:
        ret
.LBB0_5:
        mov     w0, wzr
        ret

example::is_char_boundary2:
        cbz     x2, .LBB1_3
        cmp     x1, x2
        b.ls    .LBB1_4
        ldrsb   w8, [x0, x2]
        cmn     w8, rust-lang#65
        cset    w0, gt
        ret
.LBB1_3:
        mov     w0, #1
        ret
.LBB1_4:
        cset    w0, eq
        ret
```

</p>
</details>

<details><summary>riscv64gc codegen</summary>
<p>

example::is_char_boundary:
        seqz    a3, a2
        xor     a4, a1, a2
        seqz    a4, a4
        or      a4, a4, a3
        addi    a3, zero, 1
        bnez    a4, .LBB0_3
        bgeu    a2, a1, .LBB0_4
        add     a0, a0, a2
        lb      a0, 0(a0)
        addi    a1, zero, -65
        slt     a3, a1, a0
.LBB0_3:
        mv      a0, a3
        ret
.LBB0_4:
        mv      a0, zero
        ret

example::is_char_boundary2:
        beqz    a2, .LBB1_3
        bgeu    a2, a1, .LBB1_4
        add     a0, a0, a2
        lb      a0, 0(a0)
        addi    a1, zero, -65
        slt     a0, a1, a0
        ret
.LBB1_3:
        addi    a0, zero, 1
        ret
.LBB1_4:
        xor     a0, a1, a2
        seqz    a0, a0
        ret

</p>
</details>

[Link to godbolt](https://godbolt.org/z/K8avEz8Gr)

`@rustbot` label: A-codegen
arora-aman pushed a commit that referenced this pull request Aug 25, 2021
Otherwise, we can get into a situation where you have
a subtype obligation `#1 <: #2` pending, #1 is constrained
by `check_casts`, but #2` is unaffected.

Co-authored-by: Niko Matsakis <[email protected]>
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