| Commit message (Collapse) | Author | Age | Files | Lines |
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`DsMeta.rep_sig` used to skip over `FixSig` entirely, which had the
effect of causing local fixity declarations to be dropped when quoted
in Template Haskell. But there is no good reason for this state of
affairs, as the code in `DsMeta.repFixD` (which handles top-level
fixity declarations) handles local fixity declarations just fine.
This patch factors out the necessary parts of `repFixD` so that they
can be used in `rep_sig` as well.
There was one minor complication: the fixity signatures for class
methods in each `HsGroup` were stored both in `FixSig`s _and_ the
list of `LFixitySig`s for top-level fixity signatures, so I needed
to take action to prevent fixity signatures for class methods being
converted to `Dec`s twice. I tweaked `RnSource.add` to avoid putting
these fixity signatures in two places and added
`Note [Top-level fixity signatures in an HsGroup]` in `GHC.Hs.Decls`
to explain the new design.
Fixes #17608. Bumps the Haddock submodule.
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We used to check `GrdVec`s arising from multiple clauses and guards in
isolation. That resulted in a split between `pmCheck` and
`pmCheckGuards`, the implementations of which were similar, but subtly
different in detail. Also the throttling mechanism described in
`Note [Countering exponential blowup]` ultimately got quite complicated
because it had to cater for both checking functions.
This patch realises that pattern match checking doesn't just consider
single guarded RHSs, but that it's always a whole set of clauses, each
of which can have multiple guarded RHSs in turn. We do so by
translating a list of `Match`es to a `GrdTree`:
```haskell
data GrdTree
= Rhs !RhsInfo
| Guard !PmGrd !GrdTree -- captures lef-to-right match semantics
| Sequence !GrdTree !GrdTree -- captures top-to-bottom match semantics
| Empty -- For -XEmptyCase, neutral element of Sequence
```
Then we have a function `checkGrdTree` that matches a given `GrdTree`
against an incoming set of values, represented by `Deltas`:
```haskell
checkGrdTree :: GrdTree -> Deltas -> CheckResult
...
```
Throttling is isolated to the `Sequence` case and becomes as easy as one
would expect: When the union of uncovered values becomes too big, just
return the original incoming `Deltas` instead (which is always a
superset of the union, thus a sound approximation).
The returned `CheckResult` contains two things:
1. The set of values that were not covered by any of the clauses, for
exhaustivity warnings.
2. The `AnnotatedTree` that enriches the syntactic structure of the
input program with divergence and inaccessibility information.
This is `AnnotatedTree`:
```haskell
data AnnotatedTree
= AccessibleRhs !RhsInfo
| InaccessibleRhs !RhsInfo
| MayDiverge !AnnotatedTree
| SequenceAnn !AnnotatedTree !AnnotatedTree
| EmptyAnn
```
Crucially, `MayDiverge` asserts that the tree may force diverging
values, so not all of its wrapped clauses can be redundant.
While the set of uncovered values can be used to generate the missing
equations for warning messages, redundant and proper inaccessible
equations can be extracted from `AnnotatedTree` by
`redundantAndInaccessibleRhss`.
For this to work properly, the interface to the Oracle had to change.
There's only `addPmCts` now, which takes a bag of `PmCt`s. There's a
whole bunch of `PmCt` variants to replace the different oracle functions
from before.
The new `AnnotatedTree` structure allows for more accurate warning
reporting (as evidenced by a number of changes spread throughout GHC's
code base), thus we fix #17465.
Fixes #17646 on the go.
Metric Decrease:
T11822
T9233
PmSeriesS
haddock.compiler
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Stack squeezing is done on context switch, not on GC or stack overflow.
Fix the documentation.
Fixes #17685
[ci skip]
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This changes GHC's treatment of so-called Naughty Quantification
Candidates to issue errors, instead of zapping to Any.
Close #16775.
No new test cases, because existing ones cover this well.
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This patch implements overloaded quotation brackets which generalise the
desugaring of all quotation forms in terms of a new minimal interface.
The main change is that a quotation, for example, [e| 5 |], will now
have type `Quote m => m Exp` rather than `Q Exp`. The `Quote` typeclass
contains a single method for generating new names which is used when
desugaring binding structures.
The return type of functions from the `Lift` type class, `lift` and `liftTyped` have
been restricted to `forall m . Quote m => m Exp` rather than returning a
result in a Q monad.
More details about the feature can be read in the GHC proposal.
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0246-overloaded-bracket.rst
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The old flag, `-xn`, was quite cryptic. Here we add `--nonmoving-gc` in
addition.
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We use two tricks, as suggested here [1]:
* Use microtype to try to reduce the incidence of underfull boxes
* Bump up \hbadness to eliminate the warnings
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This patch implements GHC Proposal #176:
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0176-scc-parsing.rst
Before the change:
1 / 2 / 2 = 0.25
1 / {-# SCC "name" #-} 2 / 2 = 1.0
After the change:
1 / 2 / 2 = 0.25
1 / {-# SCC "name" #-} 2 / 2 = parse error
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This relied on deriveUnique, which was far too subtle to be safely
applied. Thankfully the instance doesn't appear to be used so let's just
drop it.
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This patch implements a part of GHC Proposal #229 that covers five
operators:
* the bang operator (!)
* the tilde operator (~)
* the at operator (@)
* the dollar operator ($)
* the double dollar operator ($$)
Based on surrounding whitespace, these operators are disambiguated into
bang patterns, lazy patterns, strictness annotations, type
applications, splices, and typed splices.
This patch doesn't cover the (-) operator or the -Woperator-whitespace
warning, which are left as future work.
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In #17270 we have the pattern-match checker emit incorrect warnings. The
reason for that behavior is ultimately an inconsistency in whether we
treat TH splices as written by the user (`FromSource :: Origin`) or as
generated code (`Generated`). This was first reported in #14838.
The current solution is to TH splices as `Generated` by default and only
treat them as `FromSource` when the user requests so
(-fenable-th-splice-warnings). There are multiple reasons for opt-in
rather than opt-out:
* It's not clear that the user that compiles a splice is the author of the code
that produces the warning. Think of the situation where she just splices in
code from a third-party library that produces incomplete pattern matches.
In this scenario, the user isn't even able to fix that warning.
* Gathering information for producing the warnings (pattern-match check
warnings in particular) is costly. There's no point in doing so if the user
is not interested in those warnings.
Fixes #17270, but not #14838, because the proper solution needs a GHC
proposal extending the TH AST syntax.
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This exposes a set of interfaces from the GHC API for configuring
EventLogWriters. These can be used by consumers like
[ghc-eventlog-socket](https://github.com/bgamari/ghc-eventlog-socket).
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Adopts the language suggested by @JakobBruenker.
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See #16180.
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Otherwise this fails on Windows.
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!1906 left some loose ends in regards to Template Haskell's treatment
of unary tuples. This patch ends to tie up those loose ends:
* In addition to having `TupleT 1` produce unary tuples, `TupE [exp]`
and `TupP [pat]` also now produce unary tuples.
* I have added various special cases in GHC's pretty-printers to
ensure that explicit 1-tuples are printed using the `Unit` type.
See `testsuite/tests/th/T17380`.
* The GHC 8.10.1 release notes entry has been tidied up a little.
Fixes #16881. Fixes #17371. Fixes #17380.
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Currently, the description of CPP extension is given in the section of
command-line options.
Therefore, it is a little difficult to understand that it is a language
extension.
This commit explicitly adds a description for it.
[skip ci]
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For many years the linker would simply map all of its memory with
PROT_READ|PROT_WRITE|PROT_EXEC. However operating systems have been
becoming increasingly reluctant to accept this practice (e.g. #17353
and #12657) and for good reason: writable code is ripe for exploitation.
Consequently mmapForLinker now maps its memory with
PROT_READ|PROT_WRITE. After the linker has finished filling/relocating
the mapping it must then call mmapForLinkerMarkExecutable on the
sections of the mapping which contain executable code.
Moreover, to make all of this possible it was necessary to redesign the
m32 allocator. First, we gave (in an earlier commit) each ObjectCode its
own m32_allocator. This was necessary since code loading and symbol
resolution/relocation are currently interleaved, meaning that it is not
possible to enforce W^X when symbols from different objects reside in
the same page.
We then redesigned the m32 allocator to take advantage of the fact that
all of the pages allocated with the allocator die at the same time
(namely, when the owning ObjectCode is unloaded). This makes a number of
things simpler (e.g. no more page reference counting; the interface
provided by the allocator for freeing is simpler). See
Note [M32 Allocator] for details.
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Sets `MiscFlags.disableDelayedOsMemoryReturn`.
See the added `Note [MADV_FREE and MADV_DONTNEED]` for details.
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This updates the following:
* Add description for ImportQualifiedPost extension
* Add description for ghci command name resolution
* Fix markdown warnings
[skip ci]
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[skip ci]
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This was removed in b538476be3706264620c072e6e436debf9e0d3e4, but
without it the compare-flags.py script fails. This adds it back and
marks it as deprecated, with a notice that it is slated for removal.
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This fixes a hadrian `build docs` failure
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`:steplocal` enables only breakpoints in the current top-level binding.
When a normal breakpoint is hit, then the module name and the break id from the `BRK_FUN` byte code
allow us to access the corresponding entry in a ModBreak table. From this entry we then get the SrcSpan
(see compiler/main/InteractiveEval.hs:bindLocalsAtBreakpoint).
With this source-span we can then determine the current top-level binding, needed for the steplocal command.
However, if we break at an exception or at an error, we don't have an BRK_FUN byte-code, so we don't have any source information.
The function `bindLocalsAtBreakpoint` creates an `UnhelpfulSpan`, which doesn't allow us to determine the current top-level binding.
To avoid a `panic`, we have to check for `UnhelpfulSpan` in the function `ghc/GHCi/UI.hs:stepLocalCmd`.
Hence a :steplocal command after a break-on-exception or a break-on-error is not possible.
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This introduces a concurrent mark & sweep garbage collector to manage the old
generation. The concurrent nature of this collector typically results in
significantly reduced maximum and mean pause times in applications with large
working sets.
Due to the large and intricate nature of the change I have opted to
preserve the fully-buildable history, including merge commits, which is
described in the "Branch overview" section below.
Collector design
================
The full design of the collector implemented here is described in detail
in a technical note
> B. Gamari. "A Concurrent Garbage Collector For the Glasgow Haskell
> Compiler" (2018)
This document can be requested from @bgamari.
The basic heap structure used in this design is heavily inspired by
> K. Ueno & A. Ohori. "A fully concurrent garbage collector for
> functional programs on multicore processors." /ACM SIGPLAN Notices/
> Vol. 51. No. 9 (presented at ICFP 2016)
This design is intended to allow both marking and sweeping
concurrent to execution of a multi-core mutator. Unlike the Ueno design,
which requires no global synchronization pauses, the collector
introduced here requires a stop-the-world pause at the beginning and end
of the mark phase.
To avoid heap fragmentation, the allocator consists of a number of
fixed-size /sub-allocators/. Each of these sub-allocators allocators into
its own set of /segments/, themselves allocated from the block
allocator. Each segment is broken into a set of fixed-size allocation
blocks (which back allocations) in addition to a bitmap (used to track
the liveness of blocks) and some additional metadata (used also used
to track liveness).
This heap structure enables collection via mark-and-sweep, which can be
performed concurrently via a snapshot-at-the-beginning scheme (although
concurrent collection is not implemented in this patch).
Implementation structure
========================
The majority of the collector is implemented in a handful of files:
* `rts/Nonmoving.c` is the heart of the beast. It implements the entry-point
to the nonmoving collector (`nonmoving_collect`), as well as the allocator
(`nonmoving_allocate`) and a number of utilities for manipulating the heap.
* `rts/NonmovingMark.c` implements the mark queue functionality, update
remembered set, and mark loop.
* `rts/NonmovingSweep.c` implements the sweep loop.
* `rts/NonmovingScav.c` implements the logic necessary to scavenge the
nonmoving heap.
Branch overview
===============
```
* wip/gc/opt-pause:
| A variety of small optimisations to further reduce pause times.
|
* wip/gc/compact-nfdata:
| Introduce support for compact regions into the non-moving
|\ collector
| \
| \
| | * wip/gc/segment-header-to-bdescr:
| | | Another optimization that we are considering, pushing
| | | some segment metadata into the segment descriptor for
| | | the sake of locality during mark
| | |
| * | wip/gc/shortcutting:
| | | Support for indirection shortcutting and the selector optimization
| | | in the non-moving heap.
| | |
* | | wip/gc/docs:
| |/ Work on implementation documentation.
| /
|/
* wip/gc/everything:
| A roll-up of everything below.
|\
| \
| |\
| | \
| | * wip/gc/optimize:
| | | A variety of optimizations, primarily to the mark loop.
| | | Some of these are microoptimizations but a few are quite
| | | significant. In particular, the prefetch patches have
| | | produced a nontrivial improvement in mark performance.
| | |
| | * wip/gc/aging:
| | | Enable support for aging in major collections.
| | |
| * | wip/gc/test:
| | | Fix up the testsuite to more or less pass.
| | |
* | | wip/gc/instrumentation:
| | | A variety of runtime instrumentation including statistics
| | / support, the nonmoving census, and eventlog support.
| |/
| /
|/
* wip/gc/nonmoving-concurrent:
| The concurrent write barriers.
|
* wip/gc/nonmoving-nonconcurrent:
| The nonmoving collector without the write barriers necessary
| for concurrent collection.
|
* wip/gc/preparation:
| A merge of the various preparatory patches that aren't directly
| implementing the GC.
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* GHC HEAD
.
.
.
```
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This flag will enable the use of a non-moving oldest generation.
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Previously -ddump-stg would dump pre and post-unarise STGs. Now we have
a new flag for post-unarise STG and -ddump-stg only dumps coreToStg
output.
STG dump flags after this commit:
- -ddump-stg: Dumps CoreToStg output
- -ddump-stg-unarised: Unarise output
- -ddump-stg-final: STG right before code gen (includes CSE and lambda
lifting)
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Fixes #17382.
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With this change it is possible to reconstruct the timing portion of a
`.prof` file after the fact. By logging the stacks at each time point
a more precise executation trace of the program can be observed rather
than all identical cost centres being identified in the report.
There are two new events:
1. `EVENT_PROF_BEGIN` - emitted at the start of profiling to communicate
the tick interval
2. `EVENT_PROF_SAMPLE_COST_CENTRE` - emitted on each tick to communicate the
current call stack.
Fixes #17322
|
