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Merged
merged 1 commit into from
Apr 2, 2018

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scottmcm
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@scottmcm scottmcm commented Apr 2, 2018

Hi @clarcharr! I went to add these, but realized it would conflict with your change, so decided to offer them to you to include in your PR to upstream. If you'd rather I instead wait and submit a separate PR once yours merges, I'm happy to do that too; just let me know.

(I've never actually made a pr-to-a-pr before, so hopefully I did this right...)

@clarfonthey
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Sounds good to me! Thanks. :)

@clarfonthey clarfonthey merged commit eda3ee5 into clarfonthey:wrapping Apr 2, 2018
clarfonthey pushed a commit that referenced this pull request Apr 15, 2018
Building for x86_64-unknown-linux-musl currently results in an executable lacking debug information for musl libc itself. If you request a backtrace in GDB while control flow is within musl – including sycalls made by musl – the result looks like:

#0  0x0000000000434b46 in __cp_end ()
#1  0x0000000000432dbd in __syscall_cp_c ()
#2  0x0000000000000000 in ?? ()

i.e. not very helpful. Adding --enable-debug resolves this, and --enable-optimize re-enables optimisations which default to off given the previous flag.
clarfonthey pushed a commit that referenced this pull request Apr 15, 2018
Add --enable-debug flag to musl CI build script

Building for x86_64-unknown-linux-musl currently results in an executable lacking debug information for musl libc itself. If you request a backtrace in GDB while control flow is within musl – including sycalls made by musl – the result looks like:

```
#0  0x0000000000434b46 in __cp_end ()
#1  0x0000000000432dbd in __syscall_cp_c ()
#2  0x0000000000000000 in ?? ()
```

i.e. not very helpful. Adding --enable-debug resolves this, and --enable-optimize re-enables optimisations which default to off given the previous flag.
clarfonthey pushed a commit that referenced this pull request May 5, 2018
clarfonthey pushed a commit that referenced this pull request May 19, 2018
There is a hot path through `opt_normalize_projection_type`:
- `try_start` does a cache lookup (#1).
- The result is a `NormalizedTy`.
- There are no unresolved type vars, so we call `complete`.
- `complete` does *another* cache lookup (#2), then calls
  `SnapshotMap::insert`.
- `insert` does *another* cache lookup (rust-lang#3), inserting the same value
  that's already in the cache.

This patch optimizes this hot path by introducing `complete_normalized`,
for use when the value is known in advance to be a `NormalizedTy`. It
always avoids lookup #2. Furthermore, if the `NormalizedTy`'s
obligations are empty (the common case), we know that lookup rust-lang#3 would be
a no-op, so we avoid it, while inserting a Noop into the `SnapshotMap`'s
undo log.
clarfonthey pushed a commit that referenced this pull request Jun 6, 2018
When encountering an unexisting method for a given trait where an
associated function has the same name, suggest using the appropriate
syntax, instead of using `help` text.

When only one candidate is found, do not call it "candidate #1", just
call it "the candidate".
clarfonthey pushed a commit that referenced this pull request Jun 6, 2018
Tweak output on E0599 for assoc fn used as method

 - Use suggestion instead of `help` when possible
 - Add primary span label
 - Remove incorrect `help` suggestion using incorrect syntax
 - Do not refer to only one possible candidate as `candidate #1`, refer to it as `the candidate`
clarfonthey pushed a commit that referenced this pull request Jan 15, 2019
clarfonthey pushed a commit that referenced this pull request Sep 19, 2020
* Fix `const-display.rs` XPATH queries

* Add `issue_76501.rs` test file

* Rename issue_76501.rs to issue-76501.rs
clarfonthey pushed a commit that referenced this pull request Dec 20, 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'
```
clarfonthey pushed a commit that referenced this pull request Dec 20, 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`
rust-lang#3 [unsafety_check_result] unsafety-checking `str::<impl str>::split_whitespace`
rust-lang#4 [mir_const] processing MIR for `str::<impl str>::split_whitespace`
rust-lang#5 [mir_promoted] processing `str::<impl str>::split_whitespace`
rust-lang#6 [mir_borrowck] borrow-checking `str::<impl str>::split_whitespace`
rust-lang#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`
clarfonthey pushed a commit that referenced this pull request Aug 26, 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 <niko@alum.mit.edu>
clarfonthey pushed a commit that referenced this pull request May 19, 2022
author Preston From <prestonfrom@gmail.com> 1645164142 -0600
committer Preston From <prestonfrom@gmail.com> 1650005351 -0600
clarfonthey pushed a commit that referenced this pull request May 27, 2022
author Preston From <prestonfrom@gmail.com> 1645164142 -0600
committer Preston From <prestonfrom@gmail.com> 1650005351 -0600
clarfonthey pushed a commit that referenced this pull request Jan 4, 2023
Speed up tidy

This can be reviewed commit by commit since they contain separate optimizations.

```
# master
$ taskset -c 0-5 hyperfine './x test tidy'
Benchmark #1: ./x test tidy
  Time (mean ± σ):      4.857 s ±  0.064 s    [User: 12.967 s, System: 2.014 s]
  Range (min … max):    4.779 s …  4.997 s    10 runs

# PR
$ taskset -c 0-5 hyperfine './x test tidy'
Benchmark #1: ./x test tidy
  Time (mean ± σ):      3.672 s ±  0.035 s    [User: 10.524 s, System: 2.029 s]
  Range (min … max):    3.610 s …  3.725 s    10 runs
```
clarfonthey pushed a commit that referenced this pull request Jan 4, 2023
…aces, r=jyn514

Only deduplicate stack traces for good path bugs

Fixes rust-lang#106267

Restores backtraces for `bug!` and `delay_span_bug` after rust-lang#106056. Only `delay_good_path_bug` needed its backtraces to be deduplicated, since it spits out the backtrace where it was created when it's being emitted.

Before:

```
error: internal compiler error: /home/ubuntu/rust2/compiler/rustc_middle/src/ty/relate.rs:638:13: var types encountered in super_relate_consts: Const { ty: usize, kind: Infer(Var(_#0c)) } Const { ty: usize, kind: Param(N/#1) }

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 1.68.0-dev running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `<impl at /home/ubuntu/test.rs:7:1: 7:34>::trigger`
#1 [typeck_item_bodies] type-checking all item bodies
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors
```

Hmm... that's a little bare.

After:

```
error: internal compiler error: /home/ubuntu/rust2/compiler/rustc_middle/src/ty/relate.rs:638:13: var types encountered in super_relate_consts: Const { ty: usize, kind: Infer(Var(_#0c)) } Const { ty: usize, kind: Param(N/#1) }

thread 'rustc' panicked at 'Box<dyn Any>', /home/ubuntu/rust2/compiler/rustc_errors/src/lib.rs:1599:9
stack backtrace:
   0:     0x7ffb5b41bdd1 - std::backtrace_rs::backtrace::libunwind::trace::h26056f81198c6594
                               at /home/ubuntu/rust2/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7ffb5b41bdd1 - std::backtrace_rs::backtrace::trace_unsynchronized::hacfb345a0c6d5bb1
                               at /home/ubuntu/rust2/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7ffb5b41bdd1 - std::sys_common::backtrace::_print_fmt::h18ea6016ac8030f3
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7ffb5b41bdd1 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he35dde201d0c2d09
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7ffb5b4a0308 - core::fmt::write::h094ad263467a053c
                               at /home/ubuntu/rust2/library/core/src/fmt/mod.rs:1208:17
   5:     0x7ffb5b43caf1 - std::io::Write::write_fmt::hd47b4e2324b4d9b7
                               at /home/ubuntu/rust2/library/std/src/io/mod.rs:1682:15
   6:     0x7ffb5b41bbfa - std::sys_common::backtrace::_print::h43044162653a17fc
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7ffb5b41bbfa - std::sys_common::backtrace::print::hc8605da258fa5aeb
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7ffb5b3ffb87 - std::panicking::default_hook::{{closure}}::h9e37f23f75122a15
   9:     0x7ffb5b3ff97b - std::panicking::default_hook::h602873a063f84da2
                               at /home/ubuntu/rust2/library/std/src/panicking.rs:286:9
  10:     0x7ffb5be192b2 - <alloc[48d7b30605060536]::boxed::Box<dyn for<'a, 'b> core[672e3947e150d6c6]::ops::function::Fn<(&'a core[672e3947e150d6c6]::panic::panic_info::PanicInfo<'b>,), Output = ()> + core[672e3947e150d6c6]::marker::Send + core[672e3947e150d6c6]::marker::Sync> as core[672e3947e150d6c6]::ops::function::Fn<(&core[672e3947e150d6c6]::panic::panic_info::PanicInfo,)>>::call
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:2002:9
  11:     0x7ffb5be192b2 - rustc_driver[f5b6d32d8905ecdd]::DEFAULT_HOOK::{closure#0}::{closure#0}
                               at /home/ubuntu/rust2/compiler/rustc_driver/src/lib.rs:1204:17
  12:     0x7ffb5b4000d3 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hfd13333ca953ae8e
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:2002:9
  13:     0x7ffb5b4000d3 - std::panicking::rust_panic_with_hook::h45753e10264ebe7e
                               at /home/ubuntu/rust2/library/std/src/panicking.rs:692:13
  14:     0x7ffb5e8b3a63 - std[3330b4673efabfce]::panicking::begin_panic::<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>::{closure#0}

[... FRAMES INTENTIONALLY OMITTED BECAUSE GITHUB GOT ANGRY ...]

 186:     0x7ffb5bea5554 - <std[3330b4673efabfce]::thread::Builder>::spawn_unchecked_::<rustc_interface[947706ead88047d0]::util::run_in_thread_pool_with_globals<rustc_interface[947706ead88047d0]::interface::run_compiler<core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>, rustc_driver[f5b6d32d8905ecdd]::run_compiler::{closure#1}>::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#1}
                               at /home/ubuntu/rust2/library/std/src/thread/mod.rs:549:30
 187:     0x7ffb5bea5554 - <<std[3330b4673efabfce]::thread::Builder>::spawn_unchecked_<rustc_interface[947706ead88047d0]::util::run_in_thread_pool_with_globals<rustc_interface[947706ead88047d0]::interface::run_compiler<core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>, rustc_driver[f5b6d32d8905ecdd]::run_compiler::{closure#1}>::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#1} as core[672e3947e150d6c6]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
                               at /home/ubuntu/rust2/library/core/src/ops/function.rs:250:5
 188:     0x7ffb5b433968 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::he8b26fc22c6f51ec
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:1988:9
 189:     0x7ffb5b433968 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h5cf9cbe75a8c3ddc
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:1988:9
 190:     0x7ffb5b41199c - std::sys::unix::thread::Thread::new::thread_start::h2d6dd4455e97d031
                               at /home/ubuntu/rust2/library/std/src/sys/unix/thread.rs:108:17
 191:     0x7ffb5441b609 - start_thread
 192:     0x7ffb5b282133 - clone
 193:                0x0 - <unknown>

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 1.68.0-dev running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `<impl at /home/ubuntu/test.rs:7:1: 7:34>::trigger`
#1 [typeck_item_bodies] type-checking all item bodies
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0601`.
```
clarfonthey pushed a commit that referenced this pull request May 30, 2023
Fixes rust-lang#111510 and complements rust-lang#106547 by adding support for encoding
type parameters and also by transforming trait objects' traits into
their identities before emitting type checks.
clarfonthey pushed a commit that referenced this pull request May 30, 2023
CFI: Fix encode_ty: unexpected Param(B/#1)

Fixes rust-lang#111510 and complements rust-lang#106547 by adding support for encoding type parameters and also by transforming trait objects' traits into their identities before emitting type checks.
clarfonthey pushed a commit that referenced this pull request Jun 7, 2023
…iler-errors

Use `load`+`store` instead of `memcpy` for small integer arrays

I was inspired by rust-lang#98892 to see whether, rather than making `mem::swap` do something smart in the library, we could update MIR assignments like `*_1 = *_2` to do something smarter than `memcpy` for sufficiently-small types that doing it inline is going to be better than a `memcpy` call in assembly anyway.  After all, special code may help `mem::swap`, but if the "obvious" MIR can just result in the correct thing that helps everything -- other code like `mem::replace`, people doing it manually, and just passing around by value in general -- as well as makes MIR inlining happier since it doesn't need to deal with all the complicated library code if it just sees a couple assignments.

LLVM will turn the short, known-length `memcpy`s into direct instructions in the backend, but that's too late for it to be able to remove `alloca`s.  In general, replacing `memcpy`s with typed instructions is hard in the middle-end -- even for `memcpy.inline` where it knows it won't be a function call -- is hard [due to poison propagation issues](https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/memcpy.20vs.20load-store.20for.20MIR.20assignments/near/360376712).  So because we know more about the type invariants -- these are typed copies -- rustc can emit something more specific, allowing LLVM to `mem2reg` away the `alloca`s in some situations.

rust-lang#52051 previously did something like this in the library for `mem::swap`, but it ended up regressing during enabling mir inlining (rust-lang@cbbf06b), so this has been suboptimal on stable for ≈5 releases now.

The code in this PR is narrowly targeted at just integer arrays in LLVM, but works via a new method on the [`LayoutTypeMethods`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_codegen_ssa/traits/trait.LayoutTypeMethods.html) trait, so specific backends based on cg_ssa can enable this for more situations over time, as we find them.  I don't want to try to bite off too much in this PR, though.  (Transparent newtypes and simple things like the 3×usize `String` would be obvious candidates for a follow-up.)

Codegen demonstrations: <https://llvm.godbolt.org/z/fK8hT9aqv>

Before:
```llvm
define void `@swap_rgb48_old(ptr` noalias nocapture noundef align 2 dereferenceable(6) %x, ptr noalias nocapture noundef align 2 dereferenceable(6) %y) unnamed_addr #1 {
  %a.i = alloca [3 x i16], align 2
  call void `@llvm.lifetime.start.p0(i64` 6, ptr nonnull %a.i)
  call void `@llvm.memcpy.p0.p0.i64(ptr` noundef nonnull align 2 dereferenceable(6) %a.i, ptr noundef nonnull align 2 dereferenceable(6) %x, i64 6, i1 false)
  tail call void `@llvm.memcpy.p0.p0.i64(ptr` noundef nonnull align 2 dereferenceable(6) %x, ptr noundef nonnull align 2 dereferenceable(6) %y, i64 6, i1 false)
  call void `@llvm.memcpy.p0.p0.i64(ptr` noundef nonnull align 2 dereferenceable(6) %y, ptr noundef nonnull align 2 dereferenceable(6) %a.i, i64 6, i1 false)
  call void `@llvm.lifetime.end.p0(i64` 6, ptr nonnull %a.i)
  ret void
}
```
Note it going to stack:
```nasm
swap_rgb48_old:                         # `@swap_rgb48_old`
        movzx   eax, word ptr [rdi + 4]
        mov     word ptr [rsp - 4], ax
        mov     eax, dword ptr [rdi]
        mov     dword ptr [rsp - 8], eax
        movzx   eax, word ptr [rsi + 4]
        mov     word ptr [rdi + 4], ax
        mov     eax, dword ptr [rsi]
        mov     dword ptr [rdi], eax
        movzx   eax, word ptr [rsp - 4]
        mov     word ptr [rsi + 4], ax
        mov     eax, dword ptr [rsp - 8]
        mov     dword ptr [rsi], eax
        ret
```

Now:
```llvm
define void `@swap_rgb48(ptr` noalias nocapture noundef align 2 dereferenceable(6) %x, ptr noalias nocapture noundef align 2 dereferenceable(6) %y) unnamed_addr #0 {
start:
  %0 = load <3 x i16>, ptr %x, align 2
  %1 = load <3 x i16>, ptr %y, align 2
  store <3 x i16> %1, ptr %x, align 2
  store <3 x i16> %0, ptr %y, align 2
  ret void
}
```
still lowers to `dword`+`word` operations, but has no stack traffic:
```nasm
swap_rgb48:                             # `@swap_rgb48`
        mov     eax, dword ptr [rdi]
        movzx   ecx, word ptr [rdi + 4]
        movzx   edx, word ptr [rsi + 4]
        mov     r8d, dword ptr [rsi]
        mov     dword ptr [rdi], r8d
        mov     word ptr [rdi + 4], dx
        mov     word ptr [rsi + 4], cx
        mov     dword ptr [rsi], eax
        ret
```

And as a demonstration that this isn't just `mem::swap`, a `mem::replace` on a small array (since replace doesn't use swap since rust-lang#83022), which used to be `memcpy`s in LLVM changes in IR
```llvm
define void `@replace_short_array(ptr` noalias nocapture noundef sret([3 x i32]) dereferenceable(12) %0, ptr noalias noundef align 4 dereferenceable(12) %r, ptr noalias nocapture noundef readonly dereferenceable(12) %v) unnamed_addr #0 {
start:
  %1 = load <3 x i32>, ptr %r, align 4
  store <3 x i32> %1, ptr %0, align 4
  %2 = load <3 x i32>, ptr %v, align 4
  store <3 x i32> %2, ptr %r, align 4
  ret void
}
```
but that lowers to reasonable `dword`+`qword` instructions still
```nasm
replace_short_array:                    # `@replace_short_array`
        mov     rax, rdi
        mov     rcx, qword ptr [rsi]
        mov     edi, dword ptr [rsi + 8]
        mov     dword ptr [rax + 8], edi
        mov     qword ptr [rax], rcx
        mov     rcx, qword ptr [rdx]
        mov     edx, dword ptr [rdx + 8]
        mov     dword ptr [rsi + 8], edx
        mov     qword ptr [rsi], rcx
        ret
```
clarfonthey pushed a commit that referenced this pull request Sep 7, 2023
…=xFrednet

Fix tuple_array_conversions lint on nightly

```
changelog: ICE: [`tuple_array_conversions`]: Don't expect array length to always be usize
```

tl;dr: changed [`Const::eval_target_usize`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_middle/src/ty/consts.rs#L359) to [`Consts::try_eval_target_usize`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_middle/src/ty/consts.rs#L327) to get rid of ICE.

I have encountered a problem with clippy: it caught ICE when working with a codebase that uses a lot of nightly features.
Here's a (stripped) ICE info:

```
error: internal compiler error: /rustc/5c6a7e71cd66705c31c9af94077901a220f0870c/compiler/rustc_middle/src/ty/consts.rs:361:32: expected usize, got Const { ty: usize, kind: N/#1 }

thread 'rustc' panicked at /rustc/5c6a7e71cd66705c31c9af94077901a220f0870c/compiler/rustc_errors/src/lib.rs:1635:9:
Box<dyn Any>
stack backtrace:
...
  16:        0x110b9c590 - rustc_middle[449edf845976488d]::util::bug::bug_fmt
  17:        0x102f76ae0 - clippy_lints[71754038dd04c2d2]::tuple_array_conversions::all_bindings_are_for_conv
...
```

I don't really know what's going on low-level-wise, but seems like this lin assumed that the length of the array can always be treated as `usize`, and *I assume* this doesn't play well with `feat(generic_const_exprs)`.

I wasn't able to build a minimal reproducible example, but locally this fix does resolve the issue.
clarfonthey pushed a commit that referenced this pull request Sep 30, 2023
Make `TyKind::Adt`'s `Debug` impl be more pretty

Currently `{:?}` on `Ty` for a `TyKind::Adt` would print as `Adt(Foo, [])`. This PR changes it to be `Foo` when there are no generics or `Foo<T>`/`Foo<T, U>` when there _are_ generics. Example from debug log:
`├─0ms DEBUG rustc_hir_analysis::astconv return=Bar<T/#0, U/#1>`

I should have done this in my initial PR for a prettier TyKind: Debug impl but I thought I would need to be accessing generics_of to figure out where in the "path" the generics would have to go??? but no, adts literally only have a single place the generics can go (on the end). Feel a bit silly about this :)

r? `@oli-obk`
clarfonthey pushed a commit that referenced this pull request May 19, 2024
…r=Mark-Simulacrum

lldb-formatters: Use StdSliceSyntheticProvider for &str

&str has associated summary provider which correctly displays string values in debugger, but while working on rust-lang#124458 I've noticed that a &str inside an enum displays a blob of memory until a 0 is reached (as a c-string) which makes a very bizarre experience when debugging

However there is already StdSliceSyntheticProvider which we use for other slices. This PR enables the same synthetic provider to be used for &str, however the summary provider is still fixed to return the string value

I've added a test `debuginfo/strings-and-strs.rs` which prior to this PR would output the following in LLDB:
```
* thread #1, name = 'a', stop reason = breakpoint 1.1
    frame #0: 0x0000555555556383 a`strings_and_strs::main::h1d2b5f9227b8767d at strings-and-strs.rs:47:5
   44  	    let plain_str = "Hello";
   45  	    let str_in_struct = Foo { inner: "Hello" };
   46  	    let str_in_tuple = ("Hello", "World");
-> 47  	    zzz(); // #break
   48  	}
   49
   50  	fn zzz() {
(lldb) frame var
(alloc::string::String) plain_string = "Hello" {
  vec = size=5 {
    [0] = 'H'
    [1] = 'e'
    [2] = 'l'
    [3] = 'l'
    [4] = 'o'
  }
}
(&str) plain_str = "Hello" {
  data_ptr = 0x0000555555557263 "HelloWorld\U00000001gdb_load_rust_pretty_printers.py"
  length = 5
}
(strings_and_strs::Foo) str_in_struct = {
  inner = "Hello" {
    data_ptr = 0x0000555555557263 "HelloWorld\U00000001gdb_load_rust_pretty_printers.py"
    length = 5
  }
}
((&str, &str)) str_in_tuple = {
  0 = "Hello" {
    data_ptr = 0x0000555555557263 "HelloWorld\U00000001gdb_load_rust_pretty_printers.py"
    length = 5
  }
  1 = "World" {
    data_ptr = 0x0000555555557268 "World\U00000001gdb_load_rust_pretty_printers.py"
    length = 5
  }
}
```
After this PR it would look the following way:

```
* thread #1, name = 'a', stop reason = breakpoint 1.1
    frame #0: 0x0000555555556383 a`strings_and_strs::main::h1d2b5f9227b8767d at strings-and-strs.rs:47:5
   44  	    let plain_str = "Hello";
   45  	    let str_in_struct = Foo { inner: "Hello" };
   46  	    let str_in_tuple = ("Hello", "World");
-> 47  	    zzz(); // #break
   48  	}
   49
   50  	fn zzz() {
(lldb) frame var
(alloc::string::String) plain_string = "Hello" {
  vec = size=5 {
    [0] = 'H'
    [1] = 'e'
    [2] = 'l'
    [3] = 'l'
    [4] = 'o'
  }
}
(&str) plain_str = "Hello" {
  [0] = 'H'
  [1] = 'e'
  [2] = 'l'
  [3] = 'l'
  [4] = 'o'
}
(strings_and_strs::Foo) str_in_struct = {
  inner = "Hello" {
    [0] = 'H'
    [1] = 'e'
    [2] = 'l'
    [3] = 'l'
    [4] = 'o'
  }
}
((&str, &str)) str_in_tuple = {
  0 = "Hello" {
    [0] = 'H'
    [1] = 'e'
    [2] = 'l'
    [3] = 'l'
    [4] = 'o'
  }
  1 = "World" {
    [0] = 'W'
    [1] = 'o'
    [2] = 'r'
    [3] = 'l'
    [4] = 'd'
  }
}
```
clarfonthey pushed a commit that referenced this pull request Aug 5, 2024
…res, r=oli-obk

Tell users not to file a bug when using internal library features

Actually fixes rust-lang#97501. I don't think we should suppress the suggestion to add `#![feature(..)]`, though I guess I could be convinced otherwise.

r? `@Nilstrieb` cc `@RalfJung`

Didn't add a test b/c I don't think we test this for lang features either, but I can confirm it does work.

```
warning: the feature `core_intrinsics` is internal to the compiler or standard library
 --> /home/michael/test.rs:1:12
  |
1 | #![feature(core_intrinsics)]
  |            ^^^^^^^^^^^^^^^
  |
  = note: using it is strongly discouraged
  = note: `#[warn(internal_features)]` on by default

thread 'rustc' panicked at compiler/rustc_mir_transform/src/validate.rs:94:25:
broken MIR in Item(DefId(0:6 ~ test[42db]::{impl#0}::add)) (after phase change to runtime-optimized) at bb0[0]:
Cannot perform arithmetic Add on type WrapInt8
stack backtrace:
   0: begin_panic_handler
             at ./library/std/src/panicking.rs:665:5
   1: panic_fmt
             at ./library/core/src/panicking.rs:74:14
   2: fail<alloc::string::String>
             at ./compiler/rustc_mir_transform/src/validate.rs:146:9
   3: run_pass
             at ./compiler/rustc_mir_transform/src/validate.rs:94:13
   4: validate_body
             at ./compiler/rustc_mir_transform/src/pass_manager.rs:193:5
   5: run_passes_inner
             at ./compiler/rustc_mir_transform/src/pass_manager.rs:176:13
   6: rustc_mir_transform::pass_manager::run_passes
             at ./compiler/rustc_mir_transform/src/pass_manager.rs:87:5
   7: run_optimization_passes
             at ./compiler/rustc_mir_transform/src/lib.rs:561:5
   8: inner_optimized_mir
             at ./compiler/rustc_mir_transform/src/lib.rs:667:5
   9: optimized_mir
             at ./compiler/rustc_mir_transform/src/lib.rs:630:21
  10: {closure#0}
             at ./compiler/rustc_query_impl/src/plumbing.rs:285:13
      [... omitted 22 frames ...]
  11: query_get_at<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
             at ./compiler/rustc_middle/src/query/plumbing.rs:145:17
  12: instance_mir
  13: collect_items_of_instance
             at ./compiler/rustc_monomorphize/src/collector.rs:1203:16
  14: {closure#0}
             at ./compiler/rustc_monomorphize/src/collector.rs:447:17
  15: maybe_grow<(), rustc_monomorphize::collector::collect_items_rec::{closure_env#0}>
             at /home/michael/.cargo/registry/src/index.crates.io-6f17d22bba15001f/stacker-0.1.15/src/lib.rs:55:9
  16: ensure_sufficient_stack<(), rustc_monomorphize::collector::collect_items_rec::{closure_env#0}>
             at ./compiler/rustc_data_structures/src/stack.rs:17:5
  17: collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:446:13
  18: collect_items_rec
             at ./compiler/rustc_monomorphize/src/collector.rs:526:13
  19: {closure#0}
             at ./compiler/rustc_monomorphize/src/collector.rs:1597:17
  20: {closure#0}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:182:34
  21: call_once<(), rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure#0}::{closure#0}::{closure_env#0}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>
             at ./library/core/src/panic/unwind_safe.rs:272:9
  22: do_call<core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure#0}::{closure#0}::{closure_env#0}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>, ()>
             at ./library/std/src/panicking.rs:557:40
  23: try<(), core::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure#0}::{closure#0}::{closure_env#0}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>>
             at ./library/std/src/panicking.rs:521:19
  24: run<(), rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure#0}::{closure#1}::{closure_env#0}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:28:9
  25: {closure#1}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:186:21
  26: {closure#0}<rustc_middle::mir::mono::MonoItem, rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure#0}::{closure_env#1}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>
             at ./library/core/src/iter/traits/iterator.rs:815:29
  27: fold<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global, (), core::iter::traits::iterator::Iterator::for_each::call::{closure_env#0}<rustc_middle::mir::mono::MonoItem, rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure#0}::{closure_env#1}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>>
             at ./library/alloc/src/vec/into_iter.rs:317:25
  28: for_each<alloc::vec::into_iter::IntoIter<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure#0}::{closure_env#1}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>
             at ./library/core/src/iter/traits/iterator.rs:818:9
  29: {closure#0}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:185:17
  30: parallel_guard<(), rustc_data_structures::sync::parallel::enabled::par_for_each_in::{closure_env#0}<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:44:15
  31: par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem, alloc::alloc::Global>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure_env#0}>
             at ./compiler/rustc_data_structures/src/sync/parallel.rs:178:9
  32: {closure#1}
             at ./compiler/rustc_monomorphize/src/collector.rs:1595:13
  33: run<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure_env#1}>
             at ./compiler/rustc_data_structures/src/profiling.rs:754:9
  34: time<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure_env#1}>
             at ./compiler/rustc_session/src/utils.rs:16:9
  35: collect_crate_mono_items
             at ./compiler/rustc_monomorphize/src/collector.rs:1594:9
  36: collect_and_partition_mono_items
             at ./compiler/rustc_monomorphize/src/partitioning.rs:1124:30
  37: {closure#0}
             at ./compiler/rustc_query_impl/src/plumbing.rs:281:9
      [... omitted 22 frames ...]
  38: query_get_at<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 24]>>>
             at ./compiler/rustc_middle/src/query/plumbing.rs:145:17
  39: collect_and_partition_mono_items
             at ./compiler/rustc_middle/src/query/plumbing.rs:423:31
  40: collect_and_partition_mono_items
             at ./compiler/rustc_middle/src/query/plumbing.rs:414:17
  41: codegen_crate<rustc_codegen_llvm::LlvmCodegenBackend>
             at ./compiler/rustc_codegen_ssa/src/base.rs:596:25
  42: codegen_crate
             at ./compiler/rustc_codegen_llvm/src/lib.rs:361:18
  43: {closure#0}
             at ./compiler/rustc_interface/src/passes.rs:1027:9
  44: run<alloc::boxed::Box<dyn core::any::Any, alloc::alloc::Global>, rustc_interface::passes::start_codegen::{closure_env#0}>
             at ./compiler/rustc_data_structures/src/profiling.rs:754:9
  45: time<alloc::boxed::Box<dyn core::any::Any, alloc::alloc::Global>, rustc_interface::passes::start_codegen::{closure_env#0}>
             at ./compiler/rustc_session/src/utils.rs:16:9
  46: start_codegen
             at ./compiler/rustc_interface/src/passes.rs:1026:19
  47: codegen_and_build_linker
             at ./compiler/rustc_interface/src/queries.rs:128:31
  48: {closure#6}
             at ./compiler/rustc_driver_impl/src/lib.rs:451:25
  49: {closure#1}<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure_env#6}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_middle/src/ty/context.rs:1336:37
  50: {closure#0}<rustc_middle::ty::context::{impl#19}::enter::{closure_env#1}<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure_env#6}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_middle/src/ty/context/tls.rs:82:9
  51: try_with<core::cell::Cell<*const ()>, rustc_middle::ty::context::tls::enter_context::{closure_env#0}<rustc_middle::ty::context::{impl#19}::enter::{closure_env#1}<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure_env#6}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
             at ./library/std/src/thread/local.rs:283:12
  52: with<core::cell::Cell<*const ()>, rustc_middle::ty::context::tls::enter_context::{closure_env#0}<rustc_middle::ty::context::{impl#19}::enter::{closure_env#1}<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure_env#6}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
             at ./library/std/src/thread/local.rs:260:9
  53: enter_context<rustc_middle::ty::context::{impl#19}::enter::{closure_env#1}<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure_env#6}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_middle/src/ty/context/tls.rs:79:5
  54: enter<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure_env#6}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_middle/src/ty/context.rs:1336:9
  55: <rustc_interface::queries::QueryResult<&rustc_middle::ty::context::GlobalCtxt>>::enter::<core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#6}>
             at ./compiler/rustc_interface/src/queries.rs:64:9
  56: {closure#1}
             at ./compiler/rustc_driver_impl/src/lib.rs:450:13
  57: enter<rustc_driver_impl::run_compiler::{closure#0}::{closure_env#1}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_interface/src/queries.rs:209:19
  58: {closure#0}
             at ./compiler/rustc_driver_impl/src/lib.rs:388:22
  59: {closure#1}<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure_env#0}>
             at ./compiler/rustc_interface/src/interface.rs:502:27
  60: {closure#0}<rustc_interface::interface::run_compiler::{closure_env#1}<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure_env#0}>, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_interface/src/util.rs:154:13
  61: {closure#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure_env#0}>, core::result::Result<(), rustc_span::ErrorGuaranteed>>, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_interface/src/util.rs:106:21
  62: set<rustc_span::SessionGlobals, rustc_interface::util::run_in_thread_with_globals::{closure#0}::{closure#0}::{closure_env#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure_env#0}>, core::result::Result<(), rustc_span::ErrorGuaranteed>>, core::result::Result<(), rustc_span::ErrorGuaranteed>>, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             at /home/michael/.cargo/registry/src/index.crates.io-6f17d22bba15001f/scoped-tls-1.0.1/src/lib.rs:137:9
  63: create_session_globals_then<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::util::run_in_thread_with_globals::{closure#0}::{closure#0}::{closure_env#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure_env#0}>, core::result::Result<(), rustc_span::ErrorGuaranteed>>, core::result::Result<(), rustc_span::ErrorGuaranteed>>>
             at ./compiler/rustc_span/src/lib.rs:134:5
  64: {closure#0}<rustc_interface::util::run_in_thread_pool_with_globals::{closure_env#0}<rustc_interface::interface::run_compiler::{closure_env#1}<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure_env#0}>, core::result::Result<(), rustc_span::ErrorGuaranteed>>, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             at ./compiler/rustc_interface/src/util.rs:105:17
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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

note: using internal features is not supported and expected to cause internal compiler errors when used incorrectly

note: rustc 1.82.0-dev running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [optimized_mir] optimizing MIR for `<impl at /home/michael/test.rs:9:1: 9:32>::add`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
```
clarfonthey pushed a commit that referenced this pull request Sep 23, 2024
better implementation of signed div_floor/ceil

Tracking issue for signed `div_floor`/`div_ceil`: rust-lang#88581.

This PR improves the implementation of those two functions by adding a better branchless algorithm. Side-by-side comparison of `i32::div_floor` on x86-64:

```asm
div_floor_new:                               div_floor_old:
        push    rax                                  push    rax
        test    esi, esi                             test    esi, esi
        je      .LBB0_3                              je      .LBB1_6
        mov     eax, esi                             mov     eax, esi
        not     eax                                  not     eax
        lea     ecx, [rdi - 2147483648]              lea     ecx, [rdi - 2147483648]
        or      ecx, eax                             or      ecx, eax
        je      .LBB0_2                              je      .LBB1_7
        mov     eax, edi                             mov     eax, edi
        cdq                                          cdq
        idiv    esi                                  idiv    esi
        xor     esi, edi                             test    edx, edx
        sar     esi, 31                              setg    cl
        test    edx, edx                             test    esi, esi
        cmove   esi, edx                             sets    dil
        add     eax, esi                             test    dil, cl
        pop     rcx                                  jne     .LBB1_4
        ret                                          test    edx, edx
.LBB0_3:                                             setns   cl
        lea     rdi, [rip + .L__unnamed_1]           test    esi, esi
        call    qword ptr [rip + panic...]          setle   dl
.LBB0_2:                                             or      dl, cl
        lea     rdi, [rip + .L__unnamed_1]           jne     .LBB1_5
        call    qword ptr [rip + panic...]   .LBB1_4:
                                                     dec     eax
                                             .LBB1_5:
                                                     pop     rcx
                                                     ret
                                             .LBB1_6:
                                                     lea     rdi, [rip + .L__unnamed_2]
                                                     call    qword ptr [rip + panic...]
                                             .LBB1_7:
                                                     lea     rdi, [rip + .L__unnamed_2]
                                                     call    qword ptr [rip + panic...]
```

And on Aarch64:

```asm
_div_floor_new:                                   _div_floor_old:
        stp     x29, x30, [sp, #-16]!                     stp     x29, x30, [sp, #-16]!
        mov     x29, sp                                   mov     x29, sp
        cbz     w1, LBB0_4                                cbz     w1, LBB1_9
        mov     w8, #-2147483648                          mov     x8, x0
        cmp     w0, w8                                    mov     w9, #-2147483648
        b.ne    LBB0_3                                    cmp     w0, w9
        cmn     w1, #1                                    b.ne    LBB1_3
        b.eq    LBB0_5                                    cmn     w1, #1
LBB0_3:                                                   b.eq    LBB1_10
        sdiv    w8, w0, w1                        LBB1_3:
        msub    w9, w8, w1, w0                            sdiv    w0, w8, w1
        eor     w10, w1, w0                               msub    w8, w0, w1, w8
        asr     w10, w10, rust-lang#31                             tbz     w1, rust-lang#31, LBB1_5
        cmp     w9, #0                                    cmp     w8, #0
        csel    w9, wzr, w10, eq                          b.gt    LBB1_7
        add     w0, w9, w8                        LBB1_5:
        ldp     x29, x30, [sp], rust-lang#16                       cmp     w1, #1
        ret                                               b.lt    LBB1_8
LBB0_4:                                                   tbz     w8, rust-lang#31, LBB1_8
        adrp    x0, l___unnamed_1@PAGE            LBB1_7:
        add     x0, x0, l___unnamed_1@PAGEOFF             sub     w0, w0, #1
        bl      panic...                          LBB1_8:
LBB0_5:                                                   ldp     x29, x30, [sp], rust-lang#16
        adrp    x0, l___unnamed_1@PAGE                    ret
        add     x0, x0, l___unnamed_1@PAGEOFF     LBB1_9:
        bl      panic...                                  adrp    x0, l___unnamed_2@PAGE
                                                          add     x0, x0, l___unnamed_2@PAGEOFF
                                                          bl      panic...
                                                  LBB1_10:
                                                          adrp    x0, l___unnamed_2@PAGE
                                                          add     x0, x0, l___unnamed_2@PAGEOFF
                                                          bl      panic...
```
clarfonthey pushed a commit that referenced this pull request Oct 26, 2024
…raheemdev

Optimize `Box::default` and `Arc::default` to construct more types in place

Both the `Arc` and `Box` `Default` impls currently call `T::default()` before allocating, and then moving the resulting `T` into the allocation.

Most `Default` impls are trivial, which should in theory allow
LLVM to construct `T: Default` directly in the `Box` allocation when calling
`<Box<T>>::default()`.

However, the allocation may fail, which necessitates calling `T`'s destructor if it has one.
If the destructor is non-trivial, then LLVM has a hard time proving that it's
sound to elide, which makes it construct `T` on the stack first, and then copy it into the allocation.

Change both of these impls to allocate first, and then call `T::default` into the uninitialized allocation, so that LLVM doesn't have to prove that it's sound to elide the destructor/initial stack copy.

For example, given the following Rust code:

```rust
#[derive(Default, Clone)]
struct Foo {
    x: Vec<u8>,
    z: String,
    y: Vec<u8>,
}

#[no_mangle]
pub fn src() -> Box<Foo> {
    Box::default()
}
```

<details open>
<summary>Before this PR:</summary>

```llvm
`@__rust_no_alloc_shim_is_unstable` = external global i8

; drop_in_place() generated in case the allocation fails

; core::ptr::drop_in_place<playground::Foo>
; Function Attrs: nounwind nonlazybind uwtable
define internal fastcc void `@"_ZN4core3ptr36drop_in_place$LT$playground..Foo$GT$17hff376aece491233bE"(ptr` noalias nocapture noundef readonly align 8 dereferenceable(72) %_1) unnamed_addr #0 personality ptr `@rust_eh_personality` {
start:
  %_1.val = load i64, ptr %_1, align 8
  %0 = icmp eq i64 %_1.val, 0
  br i1 %0, label %bb6, label %"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i"

"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i": ; preds = %start
  %1 = getelementptr inbounds i8, ptr %_1, i64 8
  %_1.val6 = load ptr, ptr %1, align 8, !nonnull !3, !noundef !3
  tail call void `@__rust_dealloc(ptr` noundef nonnull %_1.val6, i64 noundef %_1.val, i64 noundef 1) rust-lang#8
  br label %bb6

bb6:                                              ; preds = %"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i", %start
  %2 = getelementptr inbounds i8, ptr %_1, i64 24
  %.val9 = load i64, ptr %2, align 8
  %3 = icmp eq i64 %.val9, 0
  br i1 %3, label %bb5, label %"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i.i11"

"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i.i11": ; preds = %bb6
  %4 = getelementptr inbounds i8, ptr %_1, i64 32
  %.val10 = load ptr, ptr %4, align 8, !nonnull !3, !noundef !3
  tail call void `@__rust_dealloc(ptr` noundef nonnull %.val10, i64 noundef %.val9, i64 noundef 1) rust-lang#8
  br label %bb5

bb5:                                              ; preds = %"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i.i11", %bb6
  %5 = getelementptr inbounds i8, ptr %_1, i64 48
  %.val4 = load i64, ptr %5, align 8
  %6 = icmp eq i64 %.val4, 0
  br i1 %6, label %"_ZN4core3ptr46drop_in_place$LT$alloc..vec..Vec$LT$u8$GT$$GT$17hb5ca95423e113cf7E.exit16", label %"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i15"

"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i15": ; preds = %bb5
  %7 = getelementptr inbounds i8, ptr %_1, i64 56
  %.val5 = load ptr, ptr %7, align 8, !nonnull !3, !noundef !3
  tail call void `@__rust_dealloc(ptr` noundef nonnull %.val5, i64 noundef %.val4, i64 noundef 1) rust-lang#8
  br label %"_ZN4core3ptr46drop_in_place$LT$alloc..vec..Vec$LT$u8$GT$$GT$17hb5ca95423e113cf7E.exit16"

"_ZN4core3ptr46drop_in_place$LT$alloc..vec..Vec$LT$u8$GT$$GT$17hb5ca95423e113cf7E.exit16": ; preds = %bb5, %"_ZN63_$LT$alloc..alloc..Global$u20$as$u20$core..alloc..Allocator$GT$10deallocate17heaa87468709346b1E.exit.i.i.i4.i15"
  ret void
}

; Function Attrs: nonlazybind uwtable
define noalias noundef nonnull align 8 ptr `@src()` unnamed_addr #1 personality ptr `@rust_eh_personality` {
start:

; alloca to place `Foo` in.
  %_1 = alloca [72 x i8], align 8
  call void `@llvm.lifetime.start.p0(i64` 72, ptr nonnull %_1)
  store i64 0, ptr %_1, align 8
  %_2.sroa.4.0._1.sroa_idx = getelementptr inbounds i8, ptr %_1, i64 8
  store ptr inttoptr (i64 1 to ptr), ptr %_2.sroa.4.0._1.sroa_idx, align 8
  %_2.sroa.5.0._1.sroa_idx = getelementptr inbounds i8, ptr %_1, i64 16
  %_3.sroa.4.0..sroa_idx = getelementptr inbounds i8, ptr %_1, i64 32
  call void `@llvm.memset.p0.i64(ptr` noundef nonnull align 8 dereferenceable(16) %_2.sroa.5.0._1.sroa_idx, i8 0, i64 16, i1 false)
  store ptr inttoptr (i64 1 to ptr), ptr %_3.sroa.4.0..sroa_idx, align 8
  %_3.sroa.5.0..sroa_idx = getelementptr inbounds i8, ptr %_1, i64 40
  %_4.sroa.4.0..sroa_idx = getelementptr inbounds i8, ptr %_1, i64 56
  call void `@llvm.memset.p0.i64(ptr` noundef nonnull align 8 dereferenceable(16) %_3.sroa.5.0..sroa_idx, i8 0, i64 16, i1 false)
  store ptr inttoptr (i64 1 to ptr), ptr %_4.sroa.4.0..sroa_idx, align 8
  %_4.sroa.5.0..sroa_idx = getelementptr inbounds i8, ptr %_1, i64 64
  store i64 0, ptr %_4.sroa.5.0..sroa_idx, align 8
  %0 = load volatile i8, ptr `@__rust_no_alloc_shim_is_unstable,` align 1, !noalias !4
  %_0.i.i.i = tail call noalias noundef align 8 dereferenceable_or_null(72) ptr `@__rust_alloc(i64` noundef 72, i64 noundef 8) rust-lang#8, !noalias !4
  %1 = icmp eq ptr %_0.i.i.i, null
  br i1 %1, label %bb2.i, label %"_ZN5alloc5boxed12Box$LT$T$GT$3new17h0864de14f863a27aE.exit"

bb2.i:                                            ; preds = %start
; invoke alloc::alloc::handle_alloc_error
  invoke void `@_ZN5alloc5alloc18handle_alloc_error17h98142d0d8d74161bE(i64` noundef 8, i64 noundef 72) rust-lang#9
          to label %.noexc unwind label %cleanup.i

.noexc:                                           ; preds = %bb2.i
  unreachable

cleanup.i:                                        ; preds = %bb2.i
  %2 = landingpad { ptr, i32 }
          cleanup
; call core::ptr::drop_in_place<playground::Foo>
  call fastcc void `@"_ZN4core3ptr36drop_in_place$LT$playground..Foo$GT$17hff376aece491233bE"(ptr` noalias noundef nonnull align 8 dereferenceable(72) %_1) rust-lang#10
  resume { ptr, i32 } %2

"_ZN5alloc5boxed12Box$LT$T$GT$3new17h0864de14f863a27aE.exit": ; preds = %start

; Copy from stack to heap if allocation is successful
  call void `@llvm.memcpy.p0.p0.i64(ptr` noundef nonnull align 8 dereferenceable(72) %_0.i.i.i, ptr noundef nonnull align 8 dereferenceable(72) %_1, i64 72, i1 false)
  call void `@llvm.lifetime.end.p0(i64` 72, ptr nonnull %_1)
  ret ptr %_0.i.i.i
}

```
</details>

<details>
<summary>After this PR</summary>

```llvm
; Notice how there's no `drop_in_place()` generated as well

define noalias noundef nonnull align 8 ptr `@src()` unnamed_addr #0 personality ptr `@rust_eh_personality` {
start:
; no stack allocation

  %0 = load volatile i8, ptr `@__rust_no_alloc_shim_is_unstable,` align 1
  %_0.i.i.i.i.i = tail call noalias noundef align 8 dereferenceable_or_null(72) ptr `@__rust_alloc(i64` noundef 72, i64 noundef 8) rust-lang#5
  %1 = icmp eq ptr %_0.i.i.i.i.i, null
  br i1 %1, label %bb3.i, label %"_ZN5alloc5boxed16Box$LT$T$C$A$GT$13new_uninit_in17h80d6355ef4b73ea3E.exit"

bb3.i:                                            ; preds = %start
; call alloc::alloc::handle_alloc_error
  tail call void `@_ZN5alloc5alloc18handle_alloc_error17h98142d0d8d74161bE(i64` noundef 8, i64 noundef 72) rust-lang#6
  unreachable

"_ZN5alloc5boxed16Box$LT$T$C$A$GT$13new_uninit_in17h80d6355ef4b73ea3E.exit": ; preds = %start
; construct `Foo` directly into the allocation if successful

  store i64 0, ptr %_0.i.i.i.i.i, align 8
  %_8.sroa.4.0._1.sroa_idx = getelementptr inbounds i8, ptr %_0.i.i.i.i.i, i64 8
  store ptr inttoptr (i64 1 to ptr), ptr %_8.sroa.4.0._1.sroa_idx, align 8
  %_8.sroa.5.0._1.sroa_idx = getelementptr inbounds i8, ptr %_0.i.i.i.i.i, i64 16
  %_8.sroa.7.0._1.sroa_idx = getelementptr inbounds i8, ptr %_0.i.i.i.i.i, i64 32
  tail call void `@llvm.memset.p0.i64(ptr` noundef nonnull align 8 dereferenceable(16) %_8.sroa.5.0._1.sroa_idx, i8 0, i64 16, i1 false)
  store ptr inttoptr (i64 1 to ptr), ptr %_8.sroa.7.0._1.sroa_idx, align 8
  %_8.sroa.8.0._1.sroa_idx = getelementptr inbounds i8, ptr %_0.i.i.i.i.i, i64 40
  %_8.sroa.10.0._1.sroa_idx = getelementptr inbounds i8, ptr %_0.i.i.i.i.i, i64 56
  tail call void `@llvm.memset.p0.i64(ptr` noundef nonnull align 8 dereferenceable(16) %_8.sroa.8.0._1.sroa_idx, i8 0, i64 16, i1 false)
  store ptr inttoptr (i64 1 to ptr), ptr %_8.sroa.10.0._1.sroa_idx, align 8
  %_8.sroa.11.0._1.sroa_idx = getelementptr inbounds i8, ptr %_0.i.i.i.i.i, i64 64
  store i64 0, ptr %_8.sroa.11.0._1.sroa_idx, align 8
  ret ptr %_0.i.i.i.i.i
}
```

</details>
clarfonthey pushed a commit that referenced this pull request Oct 26, 2024
…Kobzol

shave 150ms off bootstrap

This starts `git` commands inside `GitInfo`and the submodule updates in parallel. Git should already perform internal locking in cases where it needs to serialize a modification.

```
OLD
Benchmark #1: ./x check core
  Time (mean ± σ):     608.7 ms ±   4.4 ms    [User: 368.3 ms, System: 455.1 ms]
  Range (min … max):   602.3 ms … 618.8 ms    10 runs

NEW
Benchmark #1: ./x check core
  Time (mean ± σ):     462.8 ms ±   2.6 ms    [User: 350.2 ms, System: 485.1 ms]
  Range (min … max):   457.5 ms … 465.6 ms    10 runs
```

This should help with the rust-analyzer setup which issues many individual `./x check` calls. There's more that could be done but these were the lowest-hanging fruits that I saw.
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2 participants