[Git][ghc/ghc][wip/exception-propagate] 35 commits: ci: Run abi-test on test-abi label

Rodrigo Mesquita (@alt-romes) gitlab at gitlab.haskell.org
Fri Sep 27 11:18:34 UTC 2024



Rodrigo Mesquita pushed to branch wip/exception-propagate at Glasgow Haskell Compiler / GHC


Commits:
2a551cd5 by Matthew Pickering at 2024-09-24T16:33:50+05:30
ci: Run abi-test on test-abi label

- - - - -
ab4039ac by Rodrigo Mesquita at 2024-09-24T16:33:50+05:30
testsuite: Add a test for object determinism

Extends the abi_test with an object determinism check
Also includes a standalone test to be run by developers manually when
debugging issues with determinism.

- - - - -
d62c18d8 by Rodrigo Mesquita at 2024-09-24T16:33:50+05:30
determinism: Sampling uniques in the CG

To achieve object determinism, the passes processing Cmm and the rest of
the code generation pipeline musn't create new uniques which are
non-deterministic.

This commit changes occurrences of non-deterministic unique sampling
within these code generation passes by a deterministic unique sampling
strategy by propagating and threading through a deterministic
incrementing counter in them. The threading is done implicitly with
`UniqDSM` and `UniqDSMT`.

Secondly, the `DUniqSupply` used to run a `UniqDSM` must be threaded
through all passes to guarantee uniques in different passes are unique
amongst them altogether. Specifically, the same `DUniqSupply` must be
threaded through the CG Streaming pipeline, starting with Driver.Main
calling `StgToCmm.codeGen`, `cmmPipeline`, `cmmToRawCmm`, and
`codeOutput` in sequence.

To thread resources through the `Stream` abstraction, we use the `UniqDSMT`
transformer on top of `IO` as the Monad underlying the Stream. `UniqDSMT` will
thread the `DUniqSupply` through every pass applied to the `Stream`, for every
element. We use @type CgStream = Stream (UniqDSMT IO)@ for the Stream used in
code generation which that carries through the deterministic unique supply.

See Note [Deterministic Uniques in the CG]

- - - - -
3bbe4af4 by Rodrigo Mesquita at 2024-09-24T16:33:50+05:30
determinism: Cmm unique renaming pass

To achieve object determinism, we need to prevent the non-deterministic
uniques from leaking into the object code. We can do this by
deterministically renaming the non-external uniques in the Cmm groups
that are yielded right after StgToCmm.

The key to deterministic renaming is observing that the order of
declarations, instructions, and data in the Cmm groups are already
deterministic (modulo other determinism bugs), regardless of the
uniques. We traverse the Cmm AST in this deterministic order and
rename the uniques, incrementally, in the order they are found, thus
making them deterministic. This renaming is guarded by
-fobject-determinism which is disabled by default for now.

This is one of the key passes for object determinism. Read about the
overview of object determinism and a more detailed explanation of this
pass in:
* Note [Object determinism]
* Note [Renaming uniques deterministically]

Significantly closes the gap to #12935

- - - - -
8357ed50 by Rodrigo Mesquita at 2024-09-24T16:33:50+05:30
determinism: DCmmGroup vs CmmGroup

Part of our strategy in producing deterministic objects, namely,
renaming all Cmm uniques in order, depend on the object code produced
having a deterministic order (say, A_closure always comes before
B_closure).

However, the use of LabelMaps in the Cmm representation invalidated this
requirement because the LabelMaps elements would already be in a
non-deterministic order (due to the original uniques), and the renaming
in sequence wouldn't work because of that non-deterministic order.

Therefore, we now start off with lists in CmmGroup (which preserve the
original order), and convert them into LabelMaps (for performance in the
code generator) after the uniques of the list elements have been
renamed.

See Note [DCmmGroup vs CmmGroup or: Deterministic Info Tables] and #12935.

Co-authored-by: Matthew Pickering <matthewtpickering at gmail.com>

- - - - -
0e675fb8 by Rodrigo Mesquita at 2024-09-24T16:33:50+05:30
determinism: Don't print unique in pprFullName

This unique was leaking as part of the profiling description in info
tables when profiling was enabled, despite not providing information
relevant to the profile.

- - - - -
340f58b0 by Rodrigo Mesquita at 2024-09-24T16:33:50+05:30
determinism: UDFM for distinct-constructor-tables

In order to produce deterministic objects when compiling with
-distinct-constructor-tables, we also have to update the data
constructor map to be backed by a deterministic unique map (UDFM) rather
than a non-deterministic one (UniqMap).

- - - - -
282f37a0 by Rodrigo Mesquita at 2024-09-24T16:33:50+05:30
determinism: InfoTableMap uniques in generateCgIPEStub

Fixes object determinism when using -finfo-table-map

Make sure to also deterministically rename the IPE map (as per Note
[Renaming uniques deterministically]), and to use a deterministic unique
supply when creating new labels for the IPE information to guarantee
deterministic objects when IPE information is requested.

Note that the Cmm group produced in generateCgIPEStub must /not/ be
renamed because renaming uniques is not idempotent, and the references
to the previously renamed code in the IPE Cmm group would be renamed
twice and become invalid references to non-existent symbols.

We do need to det-rename the InfoTableMap that is created in the
conversion from Core to Stg. This is not a problem since that map won't
refer any already renamed names (since it was created before the
renaming).

- - - - -
7b37afc9 by Zubin Duggal at 2024-09-24T16:33:50+05:30
ci: Allow abi-test to fail.

We are not fully deterministic yet, see #12935 for work that remains to be done.

- - - - -
a63ee33a by Simon Peyton Jones at 2024-09-25T17:08:24-04:00
Add Given injectivity for built-in type families

Ticket #24845 asks (reasonably enough) that if we have
   [G] a+b ~ 0
then we also know
   [G] a ~ 0, b ~ 0
and similar injectivity-like facts for other built-in type
families.  The status quo was that we never generate evidence for
injectivity among Givens -- but it is quite reasonnable to do so.
All we need is to have /evidence/ for the new constraints

This MR implements that goal.  I also took the opportunity to
* Address #24978: refactoring UnivCo
* Fix #25248, which was a consequences of the previous formulation of UnivCo

As a result this MR touches a lot of code.  The big things are:

* Coercion constructor UnivCo now takes a [Coercion] as argument to
  express the coercions on which the UnivCo depends. A nice consequence
  is that UnivCoProvenance now has no free variables, simpler in a number
  of places.

* Coercion constructors AxiomInstCo and AxiomRuleCo are combined into
  AxiomCo.  The new AxiomCo, carries a (slightly oddly named)
  CoAxiomRule, which itself is a sum type of the various forms of
  built-in axiom.  See Note [CoAxiomRule] in GHC.Core.Coercion.Axiom

  A merit of this is that we can separate the case of open and closed
  type families, and eliminate the redundant `BranchIndex` in the former
  case.

* Much better representation for data BuiltInSynFamily, which means we
  no longer need to enumerate built-in axioms as well as built-in tycons.

* There is a massive refactor in GHC.Builtin.Types.Literals, which contains all
  the built-in axioms for type-level operations (arithmetic, append, cons etc).

  A big change is that instead of redundantly having (a) a hand-written
  matcher, and (b) a template-based "proves" function, which were hard to
  keep in sync, the two are derive from one set of human-supplied info.
  See GHC.Builtin.Types.Literals.mkRewriteAxiom, and friends.

* Significant changes in GHC.Tc.Solver.Equality to account for the new
  opportunity for Given/Given equalities.

Smaller things

* Improve pretty-printing to avoid parens around atomic coercions.

* Do proper eqType in findMatchingIrreds, not `eqTypeNoKindCheck`.
  Looks like a bug, Richard agrees.

* coercionLKind and coercionRKind are hot functions.  I refactored the
  implementation (which I had to change anyway) to increase sharing.
  See Note [coercionKind performance] in GHC.Core.Coercion

* I wrote a new Note [Finding orphan names] in GHC.Core.FVs about orphan
  names

* I improved the `is_concrete` flag in GHC.Core.Type.buildSynTyCon, to avoid
  calling tyConsOfType.  I forget exactly why I did this, but it's definitely
  better now.

* I moved some code from GHC.Tc.Types.Constraint into GHC.Tc.Types.CtLocEnv
  and I renamed the module GHC.Tc.Types.CtLocEnv to GHC.Tc.Types.CtLoc

- - - - -
dd8ef342 by Ryan Scott at 2024-09-25T17:09:01-04:00
Resolve ambiguous method-bound type variables in vanilla defaults and GND

When defining an instance of a class with a "vanilla" default, such as in the
following example (from #14266):

```hs
class A t where
  f :: forall x m. Monoid x => t m -> m
  f = <blah>

instance A []
```

We have to reckon with the fact that the type of `x` (bound by the type
signature for the `f` method) is ambiguous. If we don't deal with the ambiguity
somehow, then when we generate the following code:

```hs
instance A [] where
  f = $dmf @[] -- NB: the type of `x` is still ambiguous
```

Then the generated code will not typecheck. (Issue #25148 is a more recent
example of the same problem.)

To fix this, we bind the type variables from the method's original type
signature using `TypeAbstractions` and instantiate `$dmf` with them using
`TypeApplications`:

```hs
instance A [] where
  f @x @m = $dmf @[] @x @m -- `x` is no longer ambiguous
```

Note that we only do this for vanilla defaults and not for generic defaults
(i.e., defaults using `DefaultSignatures`). For the full details, see `Note
[Default methods in instances] (Wrinkle: Ambiguous types from vanilla method
type signatures)`.

The same problem arose in the code generated by `GeneralizedNewtypeDeriving`,
as we also fix it here using the same technique. This time, we can take
advantage of the fact that `GeneralizedNewtypeDeriving`-generated code
_already_ brings method-bound type variables into scope via `TypeAbstractions`
(after !13190), so it is very straightforward to visibly apply the type
variables on the right-hand sides of equations. See `Note [GND and ambiguity]`.

Fixes #14266. Fixes #25148.

- - - - -
0a4da5d2 by ARATA Mizuki at 2024-09-25T17:09:41-04:00
Document primitive string literals and desugaring of string literals

Fixes #17474 and #17974

Co-authored-by: Matthew Craven <5086-clyring at users.noreply.gitlab.haskell.org>

- - - - -
ad0731ad by Zubin Duggal at 2024-09-25T17:10:18-04:00
rts: Fix segfault when using non-moving GC with profiling

`nonMovingCollect()` swaps out the `static_flag` value used as a
sentinel for `gct->scavenged_static_objects`, but the subsequent call
`resetStaticObjectForProfiling()` sees the old value of `static_flag` used as
the sentinel and segfaults. So we must call `resetStaticObjectForProfiling()`
before calling `nonMovingCollect()` as otherwise it looks for the incorrect
sentinel value

Fixes #25232 and #23958

Also teach the testsuite driver about nonmoving profiling ways
and stop disabling metric collection when nonmoving GC is enabled.

- - - - -
e7a26d7a by Sylvain Henry at 2024-09-25T17:11:00-04:00
Fix interaction between fork and kqueue (#24672)

A kqueue file descriptor isn't inherited by a child created with fork.
As such we mustn't try to close this file descriptor as we would close a
random one, e.g. the one used by timerfd.

Fix #24672

- - - - -
6863503c by Simon Peyton Jones at 2024-09-25T17:11:37-04:00
Improve GHC.Tc.Solver.defaultEquality

This MR improves GHC.Tc.Solver.defaultEquality to solve #25251.

The main change is to use checkTyEqRhs to check the equality, so
that we do promotion properly.

But within that we needed a small enhancement to LC_Promote.  See
Note [Defaulting equalites] (DE4) and (DE5)

The tricky case is (alas) hard to trigger, so I have not added a
regression test.

- - - - -
97a6c6c3 by Sylvain Henry at 2024-09-25T17:12:18-04:00
JS: fix h$withCStringOnHeap helper (#25288)

strlen returns the length of the string without the \0 terminating byte,
hence CString weren't properly allocated on the heap (ending \0 byte was
missing).

- - - - -
5f7c20bc by Ben Gamari at 2024-09-26T04:14:05-04:00
base: Propagate `error` CallStack to thrown exception

Previously `errorCallWithCallStackException` failed to propagate its
`CallStack` argument, which represents the call-chain of the preceding
`error` call, to the exception that it returned. Consequently, the
call-stack of `error` calls were quite useless.

Unfortunately, this is the second time that I have fixed this but it
seems the first must have been lost in rebasing.

Fixes a bug in the implementation of CLC proposal 164
<https://github.com/haskell/core-libraries-committee/issues/164>

Fixes #24807.

- - - - -
c20d5186 by Matthew Pickering at 2024-09-26T04:14:42-04:00
driver: Fix -working-dir for foreign files

-working-dir definitely needs more serious testing, there are some easy
ways to test this.

* Modify Cabal to call ghc using -working-dir rather than changing
  directory.
* Modify the testsuite to run ghc using `-working-dir` rather than
  running GHC with cwd = temporary directory.

However this will have to wait until after 9.12.

Fixes #25150

- - - - -
88eaa7ac by Sylvain Henry at 2024-09-26T04:15:24-04:00
Enum deriving: reuse predError, succError, toEnumError

Reuse predError, succError, and toEnumError when deriving Enum instances
to avoid generating different error strings per instance. E.g. before
this patch for every instance for a type FOO we would generate a string:

  "pred{FOO}: tried to take `pred' of first tag in enumeration"#

- - - - -
e9fa1163 by Sylvain Henry at 2024-09-26T04:15:24-04:00
Enum deriving: generate better code (#16364)

Generate better code for Enum.toEnum: check both the lower and the upper
bounds at once with an unsigned comparison.

Initially I've used a type ascription with a call to 'fromIntegral',
hence the slight refactoring of nlAscribe. Using 'fromIntegral' was
problematic (too low in the module hierarchy) so 'enumIntToWord' was
introduced instead.

Combined with the previous commit, T21839c ghc/alloc decrease by 5%

Metric Decrease:
    T21839c

- - - - -
383af074 by Sylvain Henry at 2024-09-26T04:16:06-04:00
Core: add absorb rules for binary or/and (#16351)

Rules:
  x or (x and y) ==> x
  x and (x or y) ==> x

- - - - -
783c8b29 by Matthew Pickering at 2024-09-26T12:07:44-04:00
Don't compile `asBox` with -fprof-late

The `asBox` function is intended to store exactly the closure which the
user passes to it. Placing a cost centre on asBox introduces a thunk,
which violates this expectation and can change the result of using asBox
when profiling is enabled.

See #25212 for more details and ample opportunity to discuss if this is
a bug or not.

- - - - -
0967dcc7 by Matthew Pickering at 2024-09-26T12:07:44-04:00
Fix normalisation of .prof files

Fix 1: If a cost centre contained CAF then the normalisation was
corrupted, now only check if CAF is at the start of a line.

Fix 2: "no location info" contain a space, which messed up the next
normalisation logic which assumed that columns didn't have spaced in.

- - - - -
9eda1cb9 by Matthew Pickering at 2024-09-26T12:07:44-04:00
testsuite: Fix normalisation of prof_files removing newlines

These normalisation steps were collapsing lines together, which made
subsequent normalisation steps fail.

```
foo x y z
CAF x y z
qux x y z
```

was getting normalised to

```
foo x y z qux x y z
```

which means that subsequent line based filters would not work correctly.

- - - - -
2b25f9e2 by Matthew Pickering at 2024-09-26T12:07:44-04:00
packaging: Enable late-ccs for release flavour

This enables late cost centres when building profiled libraries and
subsequently greatly improves the resolution of cost centre stacks when
profiling.

This patch also introduces the `grep_prof` test modifier which is used
to apply a further filter to the .prof file before they are compared.

Fixes #21732

-------------------------
Metric Increase:
    libdir
-------------------------

- - - - -
bb030d0d by Brandon Chinn at 2024-09-26T12:08:21-04:00
Replace manual string lexing (#25158)

Metric Increase:
    MultilineStringsPerf

This commit replaces the manual string lexing logic with native Alex
lexing syntax. This aligns the lexer much closer to the Haskell Report,
making it easier to see how the implementation and spec relate. This
slightly increases memory usage when compiling multiline strings because
we now have two distinct phases: lexing the multiline string with Alex
and post-processing the string afterwards. Before, these were done at
the same time, but separating them allows us to push as much logic into
normal Alex lexing as possible.

Since multiline strings are a new feature, this regression shouldn't be
too noticeable. We can optimize this over time.

- - - - -
16742987 by Matthew Pickering at 2024-09-26T12:08:57-04:00
Revert !4655: Stop 'import "base" Prelude' removing implicit Prelude import

This behaviour is problematic for the principle reason that `import
Prelude` may not refer to the `base` package, and in which case
importing an entirely unrelated module causing your implicit prelude to
leave the scope is extremely surprising. See the added test for this
example. Discussion on #17045.

The secondary reason for reverting this patch is that "base" can't be a
wired in package any more (see #24903), so we have to remove special
logic which singles out base from the compiler.

The rule for implicit shadowing is now simply:

* If you write import Prelude (..) then you don't get an implicit prelude import
* If you write import "foobar" Prelude (..) for all pkgs foobar,
  you get an implicit import of prelude.

If you want to write a package import of Prelude, then you can enable
`NoImplicitPrelude` for the module in question to recover the behaviour
of ghc-9.2-9.10.

Fixes #17045

- - - - -
57c50f41 by Matthew Pickering at 2024-09-26T12:08:57-04:00
Rename COMPILING_BASE_PACKAGE to COMPILING_GHC_INTERNAL_PACKAGE

The COMPILING_BASE_PACKAGE macro is concerned with issues defining
symbols and using symbols in the same compilation unit. However, these
symbols now exist in ghc-internal rather than base, so we should rename
the macro accordingly.

The code is guards is likely never used as we never produce windows DLLs
but it is simpler to just perform the renaming for now.

These days there is little doubt that this macro defined in this ad-hoc
manner would be permitted to exist, but these days are not those days.

Fixes #25221

- - - - -
70764243 by Matthew Pickering at 2024-09-26T12:08:57-04:00
Preload ghc-internal rather than base

This occurence of baseUnitId was missed when moving the bulk of internal
definitions into `ghc-internal`.

We need to remove this preloading of `base` now because `base` should
not be wired in.

Towards #24903

- - - - -
12915609 by Matthew Pickering at 2024-09-26T12:08:57-04:00
Remove Data.List compat warning

There is currently a warning implemented in -Wcompat which warns you
when importing Data.List in a non-qualified manner.

```
A.hs:3:8: warning: [-Wcompat-unqualified-imports]
    To ensure compatibility with future core libraries changes
    imports to Data.List should be
    either qualified or have an explicit import list.
  |
3 | import Data.List
  |        ^^^^^^^^^
Ok, one module loaded.
```

GHC ticket: https://gitlab.haskell.org/ghc/ghc/-/issues/17244
CLC discussion: https://groups.google.com/g/haskell-core-libraries/c/q3zHLmzBa5E

This warning was implemented as part of the migration to making
Data.List monomorphic again (and to be used like Data.Set, Data.Map
etc). That doesn't seem like it happened, and I imagine that the current
CLC would require a new proposal anyway in order to do that now. It's
not clear in any case what "future core libraries changes" we are
waiting to happen before this warning can be removed.

Given the first phase of the proposal has lasted 5 years it doesn't seem
that anyone is motivated to carry the proposal to completion. It does
seem a bit unnecessary to include a warning in the compiler about
"future changes to the module" when there's no timeline or volunteer to
implement these changes.

The removal of this warning was discussed again at:
https://github.com/haskell/core-libraries-committee/issues/269

During the discussion there was no new enthusiasm to move onto the next
stages of the proposal so we are removing the warning to unblock the
reinstallable "base" project (#24903)

Fixes #24904

- - - - -
d4e4d498 by Matthew Pickering at 2024-09-26T12:08:57-04:00
Move Control.Monad.Zip into ghc-internal

mzip is wired in and therefore needs to be in ghc-internal.

Fixes #25222

Towards #24903

- - - - -
d3dacdfb by Matthew Pickering at 2024-09-26T12:08:57-04:00
Unwire the base package

This patch just removes all the functions related to wiring-in the base
package and the `-this-unit-id=base` flag from the cabal file.

After this commit "base" becomes just like any other package and the
door is opened to moving base into an external repo and releasing base
on a separate schedule to the rest of ghc.

Closes #24903

- - - - -
aa6d7374 by Matthew Pickering at 2024-09-27T11:09:01+01:00
Fix toException method for ExceptionWithContext

Fixes #25235

- - - - -
55a3c7aa by Matthew Pickering at 2024-09-27T12:15:42+01:00
Exception rethrowing

Basic changes:

* Change `catch` function to propagate exceptions using the
  WhileHandling mechanism.
* Introduce `catchNoPropagate`, which does the same as before, but
  passes an exception which can be rethrown.
* Introduce `rethrowIO` combinator, which rethrows an exception with a
  context and doesn't add a new backtrace.
* Introduce `tryWithContext` for a variant of `try` which can rethrow
  the exception with it's original context.
* onException is modified to rethrow the original error rather than
  creating a new callstack.
* Functions which rethrow in GHC.Internal.IO.Handle.FD,
  GHC.Internal.IO.Handle.Internals, GHC.Internal.IO.Handle.Text, and
  GHC.Internal.System.IO.Error are modified to not add a new callstack.

Implements CLC proposal#202 <https://github.com/haskell/core-libraries-committee/issues/202>

- - - - -
b23f019c by Rodrigo Mesquita at 2024-09-27T12:18:04+01:00
Add test for #25300

This reverts commit f781b76635390b9f8c04362638193dc1b9c2541a.

- - - - -


27 changed files:

- .gitlab-ci.yml
- .gitlab/ci.sh
- compiler/GHC/Builtin/Names.hs
- compiler/GHC/Builtin/Types/Literals.hs
- compiler/GHC/Cmm.hs
- compiler/GHC/Cmm/BlockId.hs
- compiler/GHC/Cmm/CLabel.hs
- compiler/GHC/Cmm/Dataflow.hs
- compiler/GHC/Cmm/Dataflow/Graph.hs
- compiler/GHC/Cmm/Graph.hs
- compiler/GHC/Cmm/Info.hs
- compiler/GHC/Cmm/Info/Build.hs
- compiler/GHC/Cmm/LayoutStack.hs
- compiler/GHC/Cmm/Opt.hs
- compiler/GHC/Cmm/Parser.y
- compiler/GHC/Cmm/Pipeline.hs
- compiler/GHC/Cmm/ProcPoint.hs
- compiler/GHC/Cmm/Reducibility.hs
- compiler/GHC/Cmm/Sink.hs
- compiler/GHC/Cmm/Switch.hs
- compiler/GHC/Cmm/Switch/Implement.hs
- compiler/GHC/Cmm/ThreadSanitizer.hs
- + compiler/GHC/Cmm/UniqueRenamer.hs
- compiler/GHC/CmmToAsm.hs
- compiler/GHC/CmmToAsm/AArch64/CodeGen.hs
- compiler/GHC/CmmToAsm/AArch64/Instr.hs
- compiler/GHC/CmmToAsm/BlockLayout.hs


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