GitLab

Alan Zimmerman pushed to branch wip/az/ghc-cpp at Glasgow Haskell Compiler / GHC

Commits:

fe6ed8d9

by Sylvain Henry at 2025-04-24T18:04:12-04:00

Doc: add doc for JS interruptible calling convention (#24444)

6111c5e4

by Ben Gamari at 2025-04-24T18:04:53-04:00

compiler: Ensure that Panic.Plain.assertPanic' provides callstack

In 36cddd2ce1a3bc62ea8a1307d8bc6006d54109cf @alt-romes removed CallStack
output from `GHC.Utils.Panic.Plain.assertPanic'`. While this output is
redundant due to the exception backtrace proposal, we may be
bootstrapping with a compiler which does not yet include this machinery.
Reintroduce the output for now.

Fixes #25898.

217caad1

by Matthew Pickering at 2025-04-25T18:58:42+01:00

Implement Explicit Level Imports for Template Haskell

This commit introduces the `ExplicitLevelImports` and
`ImplicitStagePersistence` language extensions as proposed in GHC
Proposal #682.

Key Features
------------

- `ExplicitLevelImports` adds two new import modifiers - `splice` and
`quote` - allowing precise control over the level at which imported
identifiers are available
- `ImplicitStagePersistence` (enabled by default) preserves existing
path-based cross-stage persistence behavior
- `NoImplicitStagePersistence` disables implicit cross-stage
persistence, requiring explicit level imports

Benefits
--------

- Improved compilation performance by reducing unnecessary code generation
- Enhanced IDE experience with faster feedback in `-fno-code` mode
- Better dependency tracking by distinguishing compile-time and runtime dependencies
- Foundation for future cross-compilation improvements

This implementation enables the separation of modules needed at
compile-time from those needed at runtime, allowing for more efficient
compilation pipelines and clearer code organization in projects using
Template Haskell.

Implementation Notes
--------------------

The level which a name is availble at is stored in the 'GRE', in the normal
GlobalRdrEnv. The function `greLevels` returns the levels which a specific GRE
is imported at. The level information for a 'Name' is computed by `getCurrentAndBindLevel`.
The level validity is checked by `checkCrossLevelLifting`.

Instances are checked by `checkWellLevelledDFun`, which computes the level an
instance by calling `checkWellLevelledInstanceWhat`, which sees what is
available at by looking at the module graph.

Modifications to downsweep
--------------------------

Code generation is now only enabled for modules which are needed at
compile time.
See the Note [-fno-code mode] for more information.

Uniform error messages for level errors
---------------------------------------

All error messages to do with levels are now reported uniformly using
the `TcRnBadlyStaged` constructor.

Error messages are uniformly reported in terms of levels.

0 - top-level
1 - quote level
-1 - splice level

The only level hard-coded into the compiler is the top-level in
GHC.Types.ThLevelIndex.topLevelIndex.

Uniformly refer to levels and stages
------------------------------------

There was much confusion about levels vs stages in the compiler.
A level is a semantic concept, used by the typechecker to ensure a
program can be evaluated in a well-staged manner.

A stage is an operational construct, program evaluation proceeds in
stages.

Deprecate -Wbadly-staged-types
------------------------------

`-Wbadly-staged-types` is deprecated in favour of `-Wbadly-levelled-types`.

Lift derivation changed
-----------------------

Derived lift instances will now not generate code with expression
quotations.

Before:

```
data A = A Int deriving Lift

=>
lift (A x) = [| A $(lift x) |]
```

After:

```
lift (A x) = conE 'A `appE` (lift x)
```

This is because if you attempt to derive `Lift` in a module where
`NoImplicitStagePersistence` is enabled, you would get an infinite loop
where a constructor was attempted to be persisted using the instance you
are currently defining.

GHC API Changes
---------------

The ModuleGraph now contains additional information about the type of
the edges (normal, quote or splice) between modules. This is abstracted
using the `ModuleGraphEdge` data type.

Fixes #25828

-------------------------
Metric Increase:
MultiLayerModulesTH_Make
-------------------------

7641a74a

by Simon Peyton Jones at 2025-04-26T22:05:19-04:00

Get a decent MatchContext for pattern synonym bindings

In particular when we have a pattern binding
    K p1 .. pn = rhs
where K is a pattern synonym.  (It might be nested.)

This small MR fixes #25995.  It's a tiny fix, to an error message,
removing an always-dubious `unkSkol`.

The bug report was in the context of horde-ad, a big program,
and I didn't manage to make a small repro case quickly. I decided
not to bother further.

cd6cd9d3

by Alan Zimmerman at 2025-04-27T09:42:33+01:00

GHC-CPP: first rough proof of concept

Processes

     #define FOO
     #ifdef FOO
     x = 1
     #endif

Into

    [ITcppIgnored [L loc ITcppDefine]
    ,ITcppIgnored [L loc ITcppIfdef]
    ,ITvarid "x"
    ,ITequal
    ,ITinteger (IL {il_text = SourceText "1", il_neg = False, il_value = 1})
    ,ITcppIgnored [L loc ITcppEndif]
    ,ITeof]

In time, ITcppIgnored will be pushed into a comment

42fbb8d8

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Tidy up before re-visiting the continuation mechanic

406d80a0

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Switch preprocessor to continuation passing style

Proof of concept, needs tidying up

479e2847
by Alan Zimmerman at 2025-04-27T09:42:37+01:00
```
Small cleanup
```
7c8d33f0
by Alan Zimmerman at 2025-04-27T09:42:37+01:00
```
Get rid of some cruft
```

987dc05b

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Starting to integrate.

Need to get the pragma recognised and set

8c1b61a9

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Make cppTokens extend to end of line, and process CPP comments

d520ffa6
by Alan Zimmerman at 2025-04-27T09:42:37+01:00
```
Remove unused ITcppDefined
```

2a402d8a

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Allow spaces between # and keyword for preprocessor directive

5ac9db4b

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Process CPP continuation lines

They are emited as separate ITcppContinue tokens.
Perhaps the processing should be more like a comment, and keep on
going to the end.
BUT, the last line needs to be slurped as a whole.

d6c6f169

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Accumulate CPP continuations, process when ready

Can be simplified further, we only need one CPP token

c39d12e1

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Simplify Lexer interface. Only ITcpp

We transfer directive lines through it, then parse them from scratch
in the preprocessor.

e1b6dc62

by Alan Zimmerman at 2025-04-27T09:42:37+01:00

Deal with directive on last line, with no trailing \n

bd137110
by Alan Zimmerman at 2025-04-27T09:42:37+01:00
```
Start parsing and processing the directives
```
b4e92dac
by Alan Zimmerman at 2025-04-27T09:42:37+01:00
```
Prepare for processing include files
```

1ad6ec4e

by Alan Zimmerman at 2025-04-27T09:43:51+01:00

Move PpState into PreProcess

And initParserState, initPragState too

e7ec1320

by Alan Zimmerman at 2025-04-27T09:43:53+01:00

Process nested include files

Also move PpState out of Lexer.x, so it is easy to evolve it in a ghci
session, loading utils/check-cpp/Main.hs

2a02f630
by Alan Zimmerman at 2025-04-27T09:43:53+01:00
```
Split into separate files
```

f9c13601

by Alan Zimmerman at 2025-04-27T09:43:53+01:00

Starting on expression parser.

But it hangs. Time for Text.Parsec.Expr

5d21a660

by Alan Zimmerman at 2025-04-27T09:43:53+01:00

Start integrating the ghc-cpp work

From https://github.com/alanz/ghc-cpp

f17c82b8
by Alan Zimmerman at 2025-04-27T09:43:54+01:00
```
WIP
```
2b7e8616
by Alan Zimmerman at 2025-04-27T09:44:33+01:00
```
Fixup after rebase
```
2bad789d
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
WIP
```
446f656e
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
Fixup after rebase, including all tests pass
```
a36ba3a6
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
Change pragma usage to GHC_CPP from GhcCPP
```
2227185e
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
Some comments
```
ebbefb31
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
Reformat
```
a76f409b
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
Delete unused file
```
75f1b629
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
Rename module Parse to ParsePP
```
914c8ed2
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
Clarify naming in the parser
```

f79218ae

by Alan Zimmerman at 2025-04-27T09:44:36+01:00

WIP. Switching to alex/happy to be able to work in-tree

Since Parsec is not available

1201a517

by Alan Zimmerman at 2025-04-27T09:44:36+01:00

Layering is now correct

- GHC lexer, emits CPP tokens
- accumulated in Preprocessor state
- Lexed by CPP lexer, CPP command extracted, tokens concated with
  spaces (to get rid of token pasting via comments)
- if directive lexed and parsed by CPP lexer/parser, and evaluated

2fdf808f

by Alan Zimmerman at 2025-04-27T09:44:36+01:00

First example working

Loading Example1.hs into ghci, getting the right results

```
{-# LANGUAGE GHC_CPP #-}
module Example1 where

y = 3

x =
  "hello"
  "bye now"

foo = putStrLn x
```

7b56ff52

by Alan Zimmerman at 2025-04-27T09:44:36+01:00

Rebase, and all tests pass except whitespace for generated parser

0be8ae74
by Alan Zimmerman at 2025-04-27T09:44:36+01:00
```
More plumbing. Ready for testing tomorrow.
```

da4c51eb

by Alan Zimmerman at 2025-04-27T09:44:36+01:00

Proress. Renamed module State from Types

And at first blush it seems to handle preprocessor scopes properly.

22065fab

by Alan Zimmerman at 2025-04-27T09:45:37+01:00

Insert basic GHC version macros into parser

__GLASGOW_HASKELL__
__GLASGOW_HASKELL_FULL_VERSION__
__GLASGOW_HASKELL_PATCHLEVEL1__
__GLASGOW_HASKELL_PATCHLEVEL2__

fc538156
by Alan Zimmerman at 2025-04-27T09:45:43+01:00
```
Re-sync check-cpp for easy ghci work
```
6f4b8e0a
by Alan Zimmerman at 2025-04-27T09:45:43+01:00
```
Get rid of warnings
```

e8a868b4

by Alan Zimmerman at 2025-04-27T09:45:43+01:00

Rework macro processing, in check-cpp

Macros kept at the top level, looked up via name, multiple arity
versions per name can be stored

da7b4bd7

by Alan Zimmerman at 2025-04-27T09:45:43+01:00

WIP. Can crack arguments for #define

Next step it to crack out args in an expansion

2cb5187f
by Alan Zimmerman at 2025-04-27T09:45:43+01:00
```
WIP on arg parsing.
```
fd6219ba
by Alan Zimmerman at 2025-04-27T09:45:43+01:00
```
Progress. Still screwing up nested parens.
```
a185cf05
by Alan Zimmerman at 2025-04-27T09:45:43+01:00
```
Seems to work, but has redundant code
```
add511d8
by Alan Zimmerman at 2025-04-27T09:45:43+01:00
```
Remove redundant code
```
92e3fb7b
by Alan Zimmerman at 2025-04-27T09:45:44+01:00
```
Reformat
```

053762fa

by Alan Zimmerman at 2025-04-27T09:45:44+01:00

Expand args, single pass

Still need to repeat until fixpoint

d6ba6e1c
by Alan Zimmerman at 2025-04-27T09:45:44+01:00
```
Fixed point expansion
```
998a3449
by Alan Zimmerman at 2025-04-27T09:45:44+01:00
```
Sync the playground to compiler
```

49229bdb

by Alan Zimmerman at 2025-04-27T09:45:44+01:00

Working on dumping the GHC_CPP result

But We need to keep the BufSpan in a comment

4af70371

by Alan Zimmerman at 2025-04-27T09:45:44+01:00

Keep BufSpan in queued comments in GHC.Parser.Lexer

74c76e32

by Alan Zimmerman at 2025-04-27T09:45:44+01:00

Getting close to being able to print the combined tokens

showing what is in and what is out

73131f6b

by Alan Zimmerman at 2025-04-27T09:45:44+01:00

First implementation of dumpGhcCpp.

Example output

First dumps all macros in the state, then the source, showing which
lines are in and which are out

------------------------------

- |#define FOO(A,B) A + B
- |#define FOO(A,B,C) A + B + C
- |#if FOO(1,FOO(3,4)) == 8
- |-- a comment
  |x = 1
- |#else
- |x = 5
- |#endif

6486091b
by Alan Zimmerman at 2025-04-27T09:45:44+01:00
```
Clean up a bit
```
0e0b1812
by Alan Zimmerman at 2025-04-27T09:45:44+01:00
```
Add -ddump-ghc-cpp option and a test based on it
```

e6567926

by Alan Zimmerman at 2025-04-27T09:45:44+01:00

Restore Lexer.x rules, we need them for continuation lines

39204055

by Alan Zimmerman at 2025-04-27T09:45:44+01:00

Lexer.x: trying to sort out the span for continuations

- We need to match on \n at the end of the line
- We cannot simply back up for it

ee2ff3f9

by Alan Zimmerman at 2025-04-27T09:46:38+01:00

Inserts predefined macros. But does not dump properly

Because the cpp tokens have a trailing newline

112c7c67

by Alan Zimmerman at 2025-04-27T09:46:40+01:00

Remove unnecessary LExer rules

We *need* the ones that explicitly match to the end of the line.

ed24feed

by Alan Zimmerman at 2025-04-27T09:46:40+01:00

Generate correct span for ITcpp

Dump now works, except we do not render trailing `\` for continuation
lines. This is good enough for use in test output.

7f963a43
by Alan Zimmerman at 2025-04-27T09:46:40+01:00
```
Reduce duplication in lexer
```
8d543de7
by Alan Zimmerman at 2025-04-27T09:46:40+01:00
```
Tweaks
```

aaa0c03e

by Alan Zimmerman at 2025-04-27T09:46:40+01:00

Insert min_version predefined macros into state

The mechanism now works. Still need to flesh out the full set.

06342391

by Alan Zimmerman at 2025-04-27T09:46:40+01:00

Trying my alternative pragma syntax.

It works, but dumpGhcCpp is broken, I suspect from the ITcpp token
span update.

0e507bdb

by Alan Zimmerman at 2025-04-27T09:46:40+01:00

Pragma extraction now works, with both CPP and GHC_CPP

For the following

    {-# LANGUAGE CPP #-}
    #if __GLASGOW_HASKELL__ >= 913
    {-# LANGUAGE GHC_CPP #-}
    #endif

We will enable GHC_CPP only

057bdfdb
by Alan Zimmerman at 2025-04-27T09:46:40+01:00
```
Remove some tracing
```
d1c11ee8
by Alan Zimmerman at 2025-04-27T09:46:40+01:00
```
Fix test exes for changes
```

36192a2e

by Alan Zimmerman at 2025-04-27T09:46:40+01:00

For GHC_CPP tests, normalise config-time-based macros

1570daca
by Alan Zimmerman at 2025-04-27T09:46:40+01:00
```
WIP
```
72a9d4de
by Alan Zimmerman at 2025-04-27T09:46:40+01:00
```
WIP again. What is wrong?
```
f6f73963
by Alan Zimmerman at 2025-04-27T09:46:40+01:00
```
Revert to dynflags for normal not pragma lexing
```
ddabab27
by Alan Zimmerman at 2025-04-27T09:46:41+01:00
```
Working on getting check-exact to work properly
```
db52fe62
by Alan Zimmerman at 2025-04-27T09:46:41+01:00
```
Passes CppCommentPlacement test
```

d4f4516c