[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 12 commits: Clarify -XGADTs enables existential quantification

Marge Bot (@marge-bot) gitlab at gitlab.haskell.org
Tue Jun 18 13:37:38 UTC 2024 


Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC


Commits:
2cf22b7e by sheaf at 2024-06-18T09:36:40-04:00
Clarify -XGADTs enables existential quantification

Even though -XGADTs does not turn on -XExistentialQuantification,
it does allow the user of existential quantification syntax, without
needing to use GADT-style syntax.

Fixes #20865

- - - - -
77c04b4f by David Binder at 2024-06-18T09:36:44-04:00
Add RTS flag --read-tix-file (GHC Proposal 612)

This commit introduces the RTS flag `--read-tix-file=<yes|no>` which
controls whether a preexisting .tix file is read in at the beginning
of a program run. The default is currently `--read-tix-file=yes` but
will change to `--read-tix-file=no` in a future release of GHC. For
this reason, whenever a .tix file is read in a warning is emitted to
stderr. This warning can be silenced by explicitly passing the
`--read-tix-file=yes` option. Details can be found in the GHC proposal
cited below.

Users can query whether this flag has been used with the help of the
module `GHC.RTS.Flags`. A new field `readTixFile` was added to the
record `HpcFlags`.

These changes have been discussed and approved in
- GHC proposal 612: https://github.com/ghc-proposals/ghc-proposals/pull/612
- CLC proposal 276: https://github.com/haskell/core-libraries-committee/issues/276

- - - - -
2516d7ae by Fendor at 2024-06-18T09:36:44-04:00
Improve sharing of duplicated values in `ModIface`, fixes #24723

As a `ModIface` often contains duplicated values that are not
necessarily shared, we improve sharing by serialising the `ModIface`
to an in-memory byte array. Serialisation uses deduplication tables, and
deserialisation implicitly shares duplicated values.

This helps reducing the peak memory usage while compiling in
`--make` mode. The peak memory usage is especially smaller when
generating interface files with core expressions
(`-fwrite-if-simplified-core`).

On agda, this reduces the peak memory usage:

* `2.2 GB` to `1.9 GB` for a ghci session.

On `lib:Cabal`, we report:

* `570 MB` to `500 MB` for a ghci session
* `790 MB` to `667 MB` for compiling `lib:Cabal` with ghc

There is a small impact on execution time, around 2% on the agda code
base.

- - - - -
bfd23255 by Fendor at 2024-06-18T09:36:44-04:00
Avoid unneccessarily re-serialising the `ModIface`

To reduce memory usage of `ModIface`, we serialise `ModIface` to an
in-memory byte array, which implicitly shares duplicated values.

This serialised byte array can be reused to avoid work when we actually
write the `ModIface` to disk.
We introduce a new field to `ModIface` which allows us to save the byte
array, and write it direclty to disk if the `ModIface` wasn't changed
after the initial serialisation.

This requires us to change absolute offsets, for example to jump to the
deduplication table for `Name` or `FastString` with relative offsets, as
the deduplication byte array doesn't contain header information, such as
fingerprints.
To allow us to dump the binary blob to disk, we need to replace all
absolute offsets with relative ones.

We introduce additional helpers for `ModIface` binary serialisation, which
construct relocatable binary blobs. We say the binary blob is relocatable,
if the binary representation can be moved and does not contain any
absolute offsets.

Further, we introduce new primitives for `Binary` that allow to create
relocatable binaries, such as `forwardGetRel` and `forwardPutRel`.

-------------------------
Metric Decrease:
    MultiLayerModulesDefsGhcWithCore
Metric Increase:
    MultiComponentModules
    MultiLayerModules
    T10421
    T12150
    T12234
    T12425
    T13035
    T13253-spj
    T13701
    T13719
    T14697
    T15703
    T16875
    T18698b
    T18140
    T18304
    T18698a
    T18730
    T18923
    T20049
    T24582
    T5837
    T6048
    T9198
    T9961
    mhu-perf
-------------------------

These metric increases may look bad, but they are all completely benign,
we simply allocate 1 MB per module for `shareIface`. As this allocation
is quite quick, it has a negligible impact on run-time performance.
In fact, the performance difference wasn't measurable on my local
machine. Reducing the size of the pre-allocated 1 MB buffer avoids these
test failures, but also requires us to reallocate the buffer if the
interface file is too big. These reallocations *did* have an impact on
performance, which is why I have opted to accept all these metric
increases, as the number of allocated bytes is merely a guidance.

This 1MB allocation increase causes a lot of tests to fail that
generally have a low allocation number. E.g., increasing from 40MB to
41MB is a 2.5% increase.
In particular, the tests T12150, T13253-spj, T18140, T18304, T18698a,
T18923, T20049, T24582, T5837, T6048, and T9961 only fail on i386-darwin
job, where the number of allocated bytes seems to be lower than in other
jobs.
The tests T16875 and T18698b fail on i386-linux for the same reason.

- - - - -
5dd66072 by Andreas Klebinger at 2024-06-18T09:36:45-04:00
Improve documentation of @Any@ type.

In particular mention possible uses for non-lifted types.

Fixes #23100.

- - - - -
8ec19242 by Jakob Bruenker at 2024-06-18T09:36:46-04:00
Update user guide to indicate support for 64-tuples

- - - - -
b98668d9 by Andreas Klebinger at 2024-06-18T09:36:47-04:00
lint notes: Add more info to notes.stdout

When fixing a note reference CI fails with a somewhat confusing diff.
See #21123. This commit adds a line to the output file being compared
which hopefully makes it clear this is the list of broken refs, not all
refs.

Fixes #21123

- - - - -
3adb1384 by Jakob Bruenker at 2024-06-18T09:36:48-04:00
docs: Update mention of ($) type in user guide

Fixes #24909

- - - - -
dd2a0226 by Jan Hrček at 2024-06-18T09:36:55-04:00
Remove duplicate Anno instances

- - - - -
416c59e4 by Sven Tennie at 2024-06-18T09:36:55-04:00
AArch64: Delete unused RegNos

This has the additional benefit of getting rid of the -1 encoding (real
registers start at 0.)

- - - - -
daf7b443 by Sjoerd Visscher at 2024-06-18T09:36:58-04:00
Bump stm submodule to current master

- - - - -
7a0f02bc by Cheng Shao at 2024-06-18T09:36:59-04:00
testsuite: bump T17572 timeout on wasm32

- - - - -


30 changed files:

- compiler/GHC.hs
- compiler/GHC/Builtin/Types.hs
- compiler/GHC/CmmToAsm/AArch64/Instr.hs
- compiler/GHC/Hs.hs
- compiler/GHC/Hs/Decls.hs
- compiler/GHC/Hs/Expr.hs
- compiler/GHC/Iface/Binary.hs
- compiler/GHC/Iface/Ext/Binary.hs
- compiler/GHC/Iface/Ext/Fields.hs
- compiler/GHC/Iface/Load.hs
- compiler/GHC/Iface/Make.hs
- compiler/GHC/Iface/Recomp.hs
- compiler/GHC/Iface/Rename.hs
- compiler/GHC/Tc/Errors/Hole.hs
- compiler/GHC/Tc/Gen/Splice.hs
- compiler/GHC/Tc/Utils/Backpack.hs
- compiler/GHC/Unit/Module/ModIface.hs
- compiler/GHC/Utils/Binary.hs
- docs/users_guide/9.12.1-notes.rst
- docs/users_guide/bugs.rst
- docs/users_guide/exts/gadt.rst
- docs/users_guide/exts/representation_polymorphism.rst
- docs/users_guide/profiling.rst
- docs/users_guide/runtime_control.rst
- libraries/base/changelog.md
- libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc
- libraries/ghc-internal/src/GHC/Internal/Unsafe/Coerce.hs
- libraries/ghc-prim/GHC/Types.hs
- libraries/stm
- linters/lint-notes/Main.hs


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/35de8a60fdf5fcd285de56ebaa290e3f87bad4fd...7a0f02bc7a2884986dd6cb5231255f94348addf7

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