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Make copy/copy_nonoverlapping fn's again #86003

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merged 8 commits into from
Jun 9, 2021

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@pnkfelix pnkfelix commented Jun 4, 2021

Make copy/copy_nonoverlapping fn's again, rather than intrinsics.

This a short-term change to address issue #84297.

It effectively reverts PRs #81167 #81238 (and part of #82967), #83091, and parts of #79684.

This is preparation for reverting 81238 for short-term resolution of issue 84297.
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Some changes occurred in src/tools/clippy.

cc @rust-lang/clippy

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r? @yaahc

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 4, 2021
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pnkfelix commented Jun 4, 2021

oh wait I need a regression test too. :)

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pnkfelix commented Jun 4, 2021

r? @Mark-Simulacrum

@pnkfelix pnkfelix added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. beta-nominated Nominated for backporting to the compiler in the beta channel. labels Jun 4, 2021
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pnkfelix commented Jun 4, 2021

The job mingw-check failed! Check out the build log: (web) (plain)
Click to see the possible cause of the failure (guessed by this bot)

configure: rust.channel         := nightly
configure: rust.debug-assertions := True
configure: llvm.assertions      := True
configure: dist.missing-tools   := True
configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
configure: writing `config.toml` in current directory
configure: 
configure: run `python /checkout/x.py --help`
configure: 
---
    Checking rand v0.7.3
    Checking alloc v0.0.0 (/checkout/library/alloc)
    Checking std v0.0.0 (/checkout/library/std)
    Checking core v0.0.0 (/checkout/library/core)
error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
   |
   |
60 |             ptr::write(&mut res as *mut _, 42);


error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
   |
   |
84 |             (&mut res as *mut i32).write(42);

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0015`.
For more information about this error, try `rustc --explain E0015`.
error: could not compile `core`

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed
command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "check" "--target" "i686-pc-windows-gnu" "-Zbinary-dep-depinfo" "-j" "16" "--release" "--locked" "--color" "always" "--features" "panic-unwind backtrace compiler-builtins-c" "--manifest-path" "/checkout/library/test/Cargo.toml" "--all-targets" "-p" "test" "-p" "panic_abort" "-p" "alloc" "-p" "core" "-p" "panic_unwind" "-p" "unwind" "-p" "term" "-p" "std" "-p" "proc_macro" "--message-format" "json-render-diagnostics"
failed to run: /checkout/obj/build/bootstrap/debug/bootstrap check --target=i686-pc-windows-gnu --host=i686-pc-windows-gnu --all-targets
Build completed unsuccessfully in 0:00:31

weird, my local build+tests passed. Looking now.

Update: Oh, my local build driver script only runs x.py test on stuff under src/test/. Heh, whoops.

…pping`.

Test was added in PR rust-lang#84404.

The intent here is: The `copy`/`copy_overlapping` intrinsics are going through
some flip-flopping now of "are they intrinsics or not". We can achieve the same
effect that the test intended by using `likely`/`unlikely`.
(for the short term, that is; see issue 84297.)
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@bors r+ p=1

Mostly just reverting some stuff, including unstable const-fn-ing, but seems good.

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bors commented Jun 8, 2021

📌 Commit f08f933 has been approved by Mark-Simulacrum

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 8, 2021
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bors commented Jun 8, 2021

⌛ Testing commit f08f933 with merge 957453fc62205d24f9c5e331c4b68fe802e83797...

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bors commented Jun 8, 2021

💔 Test failed - checks-actions

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Beta backport accepted as per compiler team on Zulip

@rustbot label +beta-accepted

@rustbot rustbot added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Jun 10, 2021
bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 11, 2021
…r=dtolnay

Beta targetted Make copy/copy_nonoverlapping fn's again

beta backport of PR rust-lang#86003

to address issue rust-lang#84297
@Mark-Simulacrum Mark-Simulacrum modified the milestones: 1.54.0, 1.53.0 Jun 11, 2021
@Mark-Simulacrum Mark-Simulacrum removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Jun 11, 2021
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beta backported in #86203

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rylev commented Jun 16, 2021

@pnkfelix @Mark-Simulacrum This change led to some moderate performance regressions. I imagine performance regressions are somewhat expected going from intrinsics to function calls as it seems LLVM might have more to process now. A quick look at where the regressions are happening shows it to be mostly in codegen. Any thoughts?

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This was a stopgap measure to fix regressions; it should be fixable in the long run. I don't think it makes sense to prioritize the work too much though.

flip1995 pushed a commit to flip1995/rust that referenced this pull request Jun 17, 2021
…Mark-Simulacrum

Make copy/copy_nonoverlapping fn's again

Make copy/copy_nonoverlapping fn's again, rather than intrinsics.

This a short-term change to address issue rust-lang#84297.

It effectively reverts PRs rust-lang#81167 rust-lang#81238 (and part of rust-lang#82967), rust-lang#83091, and parts of rust-lang#79684.
bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 27, 2021
…r=RalfJung

Revert revert of constness in rust-lang#86003

Re-constify `mem::swap`, `mem::replace`, `ptr::write` which were marked as not `const` in rust-lang#86003

Once the checks pass, this should solve rust-lang#86236
bors added a commit to rust-lang-ci/rust that referenced this pull request Aug 8, 2021
Avoid using the `copy_nonoverlapping` wrapper through `mem::replace`.

This is a much simpler way to achieve the pre-rust-lang#86003 behavior of `mem::replace` not needing dynamically-sized `memcpy`s (at least before inlining), than re-doing rust-lang#81238 (which needs rust-lang#86699 or something similar).

I didn't notice it until recently, but `ptr::write` already explicitly avoided using the wrapper, while `ptr::read` just called the wrapper (and was the reason for us observing any behavior change from rust-lang#86003 in Rust-GPU).

<hr/>

The codegen test I've added fails without the change to `core::ptr::read` like this (ignore the `v0` mangling, I was using a worktree with it turned on by default, for this):
```llvm
       13: ; core::intrinsics::copy_nonoverlapping::<u8>
       14: ; Function Attrs: inlinehint nonlazybind uwtable
       15: define internal void `@_RINvNtCscK5tvALCJol_4core10intrinsics19copy_nonoverlappinghECsaS4X3EinRE8_25mem_replace_direct_memcpy(i8*` %src, i8* %dst, i64 %count) unnamed_addr #0 {
       16: start:
       17:  %0 = mul i64 %count, 1
       18:  call void `@llvm.memcpy.p0i8.p0i8.i64(i8*` align 1 %dst, i8* align 1 %src, i64 %0, i1 false)
not:17      !~~~~~~~~~~~~~~~~~~~~~                                                                     error: no match expected
       19:  ret void
       20: }
```
With the `core::ptr::read` change, `core::intrinsics::copy_nonoverlapping` doesn't get instantiated and the test passes.

<hr/>

r? `@m-ou-se` cc `@nagisa` (codegen test) `@oli-obk` / `@RalfJung` (miri diagnostic changes)
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