DWARF version 5 brings a number of improvements over version 4. Quoting from
the announcement [1]:
> Version 5 incorporates improvements in many areas: better data compression,
> separation of debugging data from executable files, improved description of
> macros and source files, faster searching for symbols, improved debugging
> optimized code, as well as numerous improvements in functionality and
> performance.
On platforms where DWARF version 5 is supported (Linux, primarily), this commit
adds support for it behind a new `-Z dwarf-version=5` flag.
[1]: https://dwarfstd.org/Public_Review.php
Migrate some diagnostics from `rustc_const_eval` to `SessionDiagnostic`
I'm still trying to get the hang of this, so it doesn't migrate _all_ of `rustc_const_eval`. Working on that later.
r? `@davidtwco`
Add a `-Zdump-drop-tracking-cfg` debugging flag
This is useful for debugging drop-tracking; previously, you had to recompile
rustc from source and manually add a call to `write_graph_to_file`. This
makes the option more discoverable and configurable at runtime.
I also took the liberty of making the labels for the CFG nodes much easier to read:
previously, they looked like `id(2), local_id: 48`, now they look like
```
expr from_config (hir_id=HirId { owner: DefId(0:10 ~ default_struct_update[79f9]::foo), local_id: 2})
```
r? ``@eholk``
Rename the `--output-width` flag to `--diagnostic-width` as this appears
to be the preferred name within the compiler team.
Signed-off-by: David Wood <david.wood@huawei.com>
Rename the `--terminal-width` flag to `--output-width` as the behaviour
doesn't just apply to terminals (and so is slightly less accurate).
Signed-off-by: David Wood <david.wood@huawei.com>
Formerly `-Zterminal-width`, `--terminal-width` allows the user or build
tool to inform rustc of the width of the terminal so that diagnostics
can be truncated.
Signed-off-by: David Wood <david.wood@huawei.com>
The `rustc_lint_diagnostics` attribute is used by the diagnostic
translation/struct migration lints to identify calls where
non-translatable diagnostics or diagnostics outwith impls are being
created. Any function used in creating a diagnostic should be annotated
with this attribute so this commit adds the attribute to many more
functions.
Signed-off-by: David Wood <david.wood@huawei.com>
This is useful for debugging drop-tracking; previously, you had to recompile
rustc from source and manually add a call to `write_graph_to_file`. This
makes the option more discoverable and configurable at runtime.
I also took the liberty of making the labels for the CFG nodes much easier to read:
previously, they looked like `id(2), local_id: 48`, now they look like
```
expr from_config (hir_id=HirId { owner: DefId(0:10 ~ default_struct_update[79f9]::foo), local_id: 2})
```
Support lint expectations for `--force-warn` lints (RFC 2383)
Rustc has a `--force-warn` flag, which overrides lint level attributes and forces the diagnostics to always be warn. This means, that for lint expectations, the diagnostic can't be suppressed as usual. This also means that the expectation would not be fulfilled, even if a lint had been triggered in the expected scope.
This PR now also tracks the expectation ID in the `ForceWarn` level. I've also made some minor adjustments, to possibly catch more bugs and make the whole implementation more robust.
This will probably conflict with https://github.com/rust-lang/rust/pull/97718. That PR should ideally be reviewed and merged first. The conflict itself will be trivial to fix.
---
r? `@wesleywiser`
cc: `@flip1995` since you've helped with the initial review and also discussed this topic with me. 🙃
Follow-up of: https://github.com/rust-lang/rust/pull/87835
Issue: https://github.com/rust-lang/rust/issues/85549
Yeah, and that's it.
Integrate measureme's hardware performance counter support.
*Note: this is a companion to https://github.com/rust-lang/measureme/pull/143, and duplicates some information with it for convenience*
**(much later) EDIT**: take any numbers with a grain of salt, they may have changed since initial PR open.
## Credits
I'd like to start by thanking `@alyssais,` `@cuviper,` `@edef1c,` `@glandium,` `@jix,` `@Mark-Simulacrum,` `@m-ou-se,` `@mystor,` `@nagisa,` `@puckipedia,` and `@yorickvP,` for all of their help with testing, and valuable insight and suggestions.
Getting here wouldn't have been possible without you!
(If I've forgotten anyone please let me know, I'm going off memory here, plus some discussion logs)
## Summary
This PR adds support to `-Z self-profile` for counting hardware events such as "instructions retired" (as opposed to being limited to time measurements), using the `rdpmc` instruction on `x86_64` Linux.
While other OSes may eventually be supported, preliminary research suggests some kind of kernel extension/driver is required to enable this, whereas on Linux any user can profile (at least) their own threads.
Supporting Linux on architectures other than x86_64 should be much easier (provided the hardware supports such performance counters), and was mostly not done due to a lack of readily available test hardware.
That said, 32-bit `x86` (aka `i686`) would be almost trivial to add and test once we land the initial `x86_64` version (as all the CPU detection code can be reused).
A new flag `-Z self-profile-counter` was added, to control which of the named `measureme` counters is used, and which defaults to `wall-time`, in order to keep `-Z self-profile`'s current functionality unchanged (at least for now).
The named counters so far are:
* `wall-time`: the existing time measurement
* name chosen for consistency with `perf.rust-lang.org`
* continues to use `std::time::Instant` for a nanosecond-precision "monotonic clock"
* `instructions:u`: the hardware performance counter usually referred to as "Instructions retired"
* here "retired" (roughly) means "fully executed"
* the `:u` suffix is from the Linux `perf` tool and indicates the counter only runs while userspace code is executing, and therefore counts no kernel instructions
* *see [Caveats/Subtracting IRQs](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Subtracting-IRQs) for why this isn't entirely true and why `instructions-minus-irqs:u` should be preferred instead*
* `instructions-minus-irqs:u`: same as `instructions:u`, except the count of hardware interrupts ("IRQs" here for brevity) is subtracted
* *see [Caveats/Subtracting IRQs](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Subtracting-IRQs) for why this should be preferred over `instructions:u`*
* `instructions-minus-r0420:u`: experimental counter, same as `instructions-minus-irqs:u` but subtracting an undocumented counter (`r0420:u`) instead of IRQs
* the `rXXXX` notation is again from Linux `perf`, and indicates a "raw" counter, with a hex representation of the low-level counter configuration - this was picked because we still don't *really* know what it is
* this only exists for (future) testing and isn't included/used in any comparisons/data we've put together so far
* *see [Challenges/Zen's undocumented 420 counter](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Epilogue-Zen’s-undocumented-420-counter) for details on how this counter was found and what it does*
---
There are also some additional commits:
* ~~see [Challenges/Rebasing *shouldn't* affect the results, right?](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Rebasing-*shouldn’t*-affect-the-results,-right) for details on the changes to `rustc_parse` and `rustc_trait_section` (the latter far more dubious, and probably shouldn't be merged, or not as-is)~~
* **EDIT**: the effects of these are no long quantifiable, the PR includes reverts for them
* ~~see [Challenges/`jemalloc`: purging will commence in ten seconds](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#jemalloc-purging-will-commence-in-ten-seconds) for details on the `jemalloc` change~~
* this is also separately found in #77162, and we probably want to avoid doing it by default, ideally we'd use the runtime control API `jemalloc` offers (assuming that can stop the timer that's already running, which I'm not sure about)
* **EDIT**: until we can do this based on `-Z` flags, this commit has also been reverted
* the `proc_macro` change was to avoid randomized hashing and therefore ASLR-like effects
---
**(much later) EDIT**: take any numbers with a grain of salt, they may have changed since initial PR open.
#### Write-up / report
Because of how extensive the full report ended up being, I've kept most of it [on `hackmd.io`](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view), but for convenient access, here are all the sections (with individual links):
<sup>(someone suggested I'd make a backup, so [here it is on the wayback machine](http://web.archive.org/web/20201127164748/https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view) - I'll need to remember to update that if I have to edit the write-up)</sup>
* [**Motivation**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Motivation)
* [**Results**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Results)
* [**Overhead**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Overhead)
*Preview (see the report itself for more details):*
|Counter|Total<br>`instructions-minus-irqs:u`|Overhead from "Baseline"<br>(for all 1903881<br>counter reads)|Overhead from "Baseline"<br>(per each counter read)|
|-|-|-|-|
|Baseline|63637621286 ±6||
|`instructions:u`|63658815885 ±2| +21194599 ±8| +11|
|`instructions-minus-irqs:u`|63680307361 ±13| +42686075 ±19| +22|
|`wall-time`|63951958376 ±10275|+314337090 ±10281|+165|
* [**"Macro" noise (self time)**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#“Macro”-noise-(self-time))
*Preview (see the report itself for more details):*
|| `wall-time` (ns) | `instructions:u` | `instructions-minus-irqs:u`
-: | -: | -: | -:
`typeck` | 5478261360 ±283933373 (±~5.2%) | 17350144522 ±6392 (±~0.00004%) | 17351035832.5 ±4.5 (±~0.00000003%)
`expand_crate` | 2342096719 ±110465856 (±~4.7%) | 8263777916 ±2937 (±~0.00004%) | 8263708389 ±0 (±~0%)
`mir_borrowck` | 2216149671 ±119458444 (±~5.4%) | 8340920100 ±2794 (±~0.00003%) | 8341613983.5 ±2.5 (±~0.00000003%)
`mir_built` | 1269059734 ±91514604 (±~7.2%) | 4454959122 ±1618 (±~0.00004%) | 4455303811 ±1 (±~0.00000002%)
`resolve_crate` | 942154987.5 ±53068423.5 (±~5.6%) | 3951197709 ±39 (±~0.000001%) | 3951196865 ±0 (±~0%)
* [**"Micro" noise (individual sampling intervals)**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#“Micro”-noise-(individual-sampling-intervals))
* [**Caveats**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Caveats)
* [**Disabling ASLR**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Disabling-ASLR)
* [**Non-deterministic proc macros**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Non-deterministic-proc-macros)
* [**Subtracting IRQs**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Subtracting-IRQs)
* [**Lack of support for multiple threads**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Lack-of-support-for-multiple-threads)
* [**Challenges**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Challenges)
* [**How do we even read hardware performance counters?**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#How-do-we-even-read-hardware-performance-counters)
* [**ASLR: it's free entropy**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#ASLR-it’s-free-entropy)
* [**The serializing instruction**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#The-serializing-instruction)
* [**Getting constantly interrupted**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Getting-constantly-interrupted)
* [**AMD patented time-travel and dubbed it `SpecLockMap`<br><sup> or: "how we accidentally unlocked `rr` on AMD Zen"</sup>**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#AMD-patented-time-travel-and-dubbed-it-SpecLockMapnbspnbspnbspnbspnbspnbspnbspnbspor-“how-we-accidentally-unlocked-rr-on-AMD-Zen”)
* [**`jemalloc`: purging will commence in ten seconds**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#jemalloc-purging-will-commence-in-ten-seconds)
* [**Rebasing *shouldn't* affect the results, right?**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Rebasing-*shouldn’t*-affect-the-results,-right)
* [**Epilogue: Zen's undocumented 420 counter**](https://hackmd.io/sH315lO2RuicY-SEt7ynGA?view#Epilogue-Zen’s-undocumented-420-counter)
Adds the virtual-function-elimination unstable compiler flag and a check
that this flag is only used in combination with -Clto. LLVM can only
apply this optimization with fat LTO.
lint: add diagnostic translation migration lints
Introduce allow-by-default lints for checking whether diagnostics are written in
`SessionDiagnostic` or `AddSubdiagnostic` impls and whether diagnostics are translatable. These lints can be denied for modules once they are fully migrated to impls and translation.
These lints are intended to be temporary - once all diagnostics have been changed then we can just change the APIs we have and that will enforce these constraints thereafter.
r? `````@oli-obk`````
Fix#71363's test by adding `-Z translate-remapped-path-to-local-path=no`
The test relies on `library/std/src/error.rs` not corresponding to a local path, but remapping might still find the related local file of a remapped path. To fix the test, this PR adds a new `-Z` flag to disable finding the corresponding local path of a remapped path.
Introduce allow-by-default lints for checking whether diagnostics are
written in `SessionDiagnostic`/`AddSubdiagnostic` impls and whether
diagnostics are translatable. These lints can be denied for modules once
they are fully migrated to impls and translation.
Signed-off-by: David Wood <david.wood@huawei.com>
The test relies on library/std/src/error.rs not corresponding to a local
path, but remapping might still find the related local file of a
remapped path. To fix the test, this adds a new -Z flag to disable
finding the corresponding local path of a remapped path.
It looks like the last time had left some remaining cfg's -- which made me think
that the stage0 bump was actually successful. This brings us to a released 1.62
beta though.
Currently, the only API for creating errors from a diagnostic derive
will emit it immediately. This makes it difficult to add subdiagnostics
to diagnostics from the derive, so add `create_{err,warning}` functions
that return the diagnostic without emitting it.
Signed-off-by: David Wood <david.wood@huawei.com>
rustc_ast: Harmonize delimiter naming with `proc_macro::Delimiter`
Compiler cannot reuse `proc_macro::Delimiter` directly due to extra impls, but can at least use the same naming.
After this PR the only difference between these two enums is that `proc_macro::Delimiter::None` is turned into `token::Delimiter::Invisible`.
It's my mistake that the invisible delimiter is called `None` on stable, during the stabilization I audited the naming and wrote the docs, but missed the fact that the `None` naming gives a wrong and confusing impression about what this thing is.
cc https://github.com/rust-lang/rust/pull/96421
r? ``@nnethercote``
Make sure `-Dunused-crate-dependencies --json unused-externs` makes rustc exit with error status
This PR:
- fixes compiletest to understand unused extern notifications
- adds tests for `--json unused-externs`
- makes sure that deny-level unused externs notifications are treated as compile errors
- refactors the `emit_unused_externs` callstack to plumb through the level as an enum as a string, and adds `Level::is_error`
Update: adds `--json unused-externs-silent` with the original behaviour since Cargo needs it. Should address `@est31's` concerns.
Fixes: https://github.com/rust-lang/rust/issues/96068
Add missing `target_feature` to the list of well known cfg names
This PR adds the missing `target_feature` cfg name to the list of well known cfg names.
It was notice missing in https://github.com/rust-lang/rust/issues/96472 thanks to `@bjorn3,` the reason being that `--check-cfg=names()` automatically inherit the names passed by `--cfg` (or internal to `rustc`) and is seems that the vast majority of targets have at least one target feature leading to `target_feature` being a well known name in most target but it should always be a well known name so this PR add it unconditionally to list.
r? `@petrochenkov`
Since Cargo wants to do its own fatal error handling for unused
dependencies, add the option `--json unused-externs-silent` which
has the original behaviour of not indicating non-zero exit status for
`deny`/`forbid`-level unused dependencies.
Implement MIR opt unit tests
This implements rust-lang/compiler-team#502 .
There's not much to say here, this implementation does everything as proposed. I also added the flag to a bunch of existing tests (mostly those to which I could add it without causing huge diffs due to changes in line numbers). Summarizing the changes to test outputs:
- Every time an `MirPatch` is created, it adds a cleanup block to the body if it did not exist already. If this block is unused (as is usually the case), it usually gets removed soon after by some pass calling `SimplifyCFG` for unrelated reasons (in many cases this cycle happens quite a few times for a single body). We now run `SimplifyCFG` less often, so those blocks end up in some of our outputs. I looked at changing `MirPatch` to not do this, but that seemed too complicated for this PR. I may still do that in a follow-up.
- The `InstCombine` test had set `-C opt-level=0` in its flags and so there were no storage markers. I don't really see a good motivation for doing this, so bringing it back in line with what everything else does seems correct.
- One of the `EarlyOtherwiseBranch` tests had `UnreachableProp` running on it. Preventing that kind of thing is the goal of this feature, so this seems fine.
For the remaining tests for which this feature might be useful, we can gradually migrate them as opportunities present themselves.
In terms of documentation, I plan on submitting a PR to the rustc dev guide in the near future documenting this and other recent changes to MIR. If there's any other places to update, do let me know
r? `@nagisa`
This adds `nounused` to the set of extern flags:
`--extern nounused:core=/path/to/core/libcore.rlib`.
The effect of this flag is to suppress `unused-crate-dependencies`
warnings relating to the crate.
Remove `--extern-location` and all associated code
`--extern-location` was an experiment to investigate the best way to
generate useful diagnostics for unused dependency warnings by enabling a
build system to identify the corresponding build config.
While I did successfully use this, I've since been convinced the
alternative `--json unused-externs` mechanism is the way to go, and
there's no point in having two mechanisms with basically the same
functionality.
This effectively reverts https://github.com/rust-lang/rust/pull/72603
