Simon Peyton Jones pushed to branch wip/T26315 at Glasgow Haskell Compiler / GHC
Commits:
79816cc4 by Rodrigo Mesquita at 2025-09-02T12:19:59-04:00
cleanup: Move dehydrateCgBreakInfo to Stg2Bc
This no longer has anything to do with Core.
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53da94ff by Rodrigo Mesquita at 2025-09-02T12:19:59-04:00
rts/Disassembler: Fix spacing of BRK_FUN
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08c0cf85 by Rodrigo Mesquita at 2025-09-02T12:19:59-04:00
debugger: Fix bciPtr in Step-out
We need to use `BCO_NEXT` to move bciPtr to ix=1, because ix=0 points to
the instruction itself!
I do not understand how this didn't crash before.
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e7e021fa by Rodrigo Mesquita at 2025-09-02T12:19:59-04:00
debugger: Allow BRK_FUNs to head case continuation BCOs
When we start executing a BCO, we may want to yield to the scheduler:
this may be triggered by a heap/stack check, context switch, or a
breakpoint. To yield, we need to put the stack in a state such that
when execution is resumed we are back to where we yielded from.
Previously, a BKR_FUN could only head a function BCO because we only
knew how to construct a valid stack for yielding from one -- simply add
`apply_interp_info` + the BCO to resume executing. This is valid because
the stack at the start of run_BCO is headed by that BCO's arguments.
However, in case continuation BCOs (as per Note [Case continuation BCOs]),
we couldn't easily reconstruct a valid stack that could be resumed
because we dropped too soon the stack frames regarding the value
returned (stg_ret) and received (stg_ctoi) by that continuation.
This is especially tricky because of the variable type and size return
frames (e.g. pointer ret_p/ctoi_R1p vs a tuple ret_t/ctoi_t2).
The trick to being able to yield from a BRK_FUN at the start of a case
cont BCO is to stop removing the ret frame headers eagerly and instead
keep them until the BCO starts executing. The new layout at the start of
a case cont. BCO is described by the new Note [Stack layout when entering run_BCO].
Now, we keep the ret_* and ctoi_* frames when entering run_BCO.
A BRK_FUN is then executed if found, and the stack is yielded as-is with
the preserved ret and ctoi frames.
Then, a case cont BCO's instructions always SLIDE off the headers of the
ret and ctoi frames, in StgToByteCode.doCase, turning a stack like
| .... |
+---------------+
| fv2 |
+---------------+
| fv1 |
+---------------+
| BCO |
+---------------+
| stg_ctoi_ret_ |
+---------------+
| retval |
+---------------+
| stg_ret_..... |
+---------------+
into
| .... |
+---------------+
| fv2 |
+---------------+
| fv1 |
+---------------+
| retval |
+---------------+
for the remainder of the BCO.
Moreover, this more uniform approach of keeping the ret and ctoi frames
means we need less ad-hoc logic concerning the variable size of
ret_tuple vs ret_p/np frames in the code generator and interpreter:
Always keep the return to cont. stack intact at the start of run_BCO,
and the statically generated instructions will take care of adjusting
it.
Unlocks BRK_FUNs at the start of case cont. BCOs which will enable a
better user-facing step-out (#26042) which is free of the bugs the
current BRK_ALTS implementation suffers from (namely, using BRK_FUN
rather than BRK_ALTS in a case cont. means we'll never accidentally end
up in a breakpoint "deeper" than the continuation, because we stop at
the case cont itself rather than on the first breakpoint we evaluate
after it).
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ade3c1e6 by Rodrigo Mesquita at 2025-09-02T12:19:59-04:00
BRK_FUN with InternalBreakLocs for code-generation time breakpoints
At the start of a case continuation BCO, place a BRK_FUN.
This BRK_FUN uses the new "internal breakpoint location" -- allowing us
to come up with a valid source location for this breakpoint that is not associated with a source-level tick.
For case continuation BCOs, we use the last tick seen before it as the
source location. The reasoning is described in Note [Debugger: Stepout internal break locs].
Note how T26042c, which was broken because it displayed the incorrect
behavior of the previous step out when we'd end up at a deeper level
than the one from which we initiated step-out, is now fixed.
As of this commit, BRK_ALTS is now dead code and is thus dropped.
Note [Debugger: Stepout internal break locs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Step-out tells the interpreter to run until the current function
returns to where it was called from, and stop there.
This is achieved by enabling the BRK_FUN found on the first RET_BCO
frame on the stack (See [Note Debugger: Step-out]).
Case continuation BCOs (which select an alternative branch) must
therefore be headed by a BRK_FUN. An example:
f x = case g x of <--- end up here
1 -> ...
2 -> ...
g y = ... <--- step out from here
- `g` will return a value to the case continuation BCO in `f`
- The case continuation BCO will receive the value returned from g
- Match on it and push the alternative continuation for that branch
- And then enter that alternative.
If we step-out of `g`, the first RET_BCO on the stack is the case
continuation of `f` -- execution should stop at its start, before
selecting an alternative. (One might ask, "why not enable the breakpoint
in the alternative instead?", because the alternative continuation is
only pushed to the stack *after* it is selected by the case cont. BCO)
However, the case cont. BCO is not associated with any source-level
tick, it is merely the glue code which selects alternatives which do
have source level ticks. Therefore, we have to come up at code
generation time with a breakpoint location ('InternalBreakLoc') to
display to the user when it is stopped there.
Our solution is to use the last tick seen just before reaching the case
continuation. This is robust because a case continuation will thus
always have a relevant breakpoint location:
- The source location will be the last source-relevant expression
executed before the continuation is pushed
- So the source location will point to the thing you've just stepped
out of
- Doing :step-local from there will put you on the selected
alternative (which at the source level may also be the e.g. next
line in a do-block)
Examples, using angle brackets (<<...>>) to denote the breakpoint span:
f x = case <<g x>> {- step in here -} of
1 -> ...
2 -> ...>
g y = <<...>> <--- step out from here
...
f x = <
2025-07-29 10:50:36.560949 UTC 160,161c160 < PUSH_L 0 < SLIDE 1 2
SLIDE 1 1
164,165d162 < PUSH_L 0 < SLIDE 1 1 175,176c172 < PUSH_L 0 < SLIDE 1 2 ---
SLIDE 1 1
179,180d174 < PUSH_L 0 < SLIDE 1 1 206,207d199 < PUSH_L 0 < SLIDE 1 1 210,211d201 < PUSH_L 0 < SLIDE 1 1 214,215d203 < PUSH_L 0 < SLIDE 1 1 218,219d205 < PUSH_L 0 < SLIDE 1 1 222,223d207 < PUSH_L 0 < SLIDE 1 1 ... 600,601c566 < PUSH_L 0 < SLIDE 1 2 ---
SLIDE 1 1
604,605d568
< PUSH_L 0
< SLIDE 1 1
632,633d594
< PUSH_L 0
< SLIDE 1 1
636,637d596
< PUSH_L 0
< SLIDE 1 1
640,641d598
< PUSH_L 0
< SLIDE 1 1
644,645d600
< PUSH_L 0
< SLIDE 1 1
648,649d602
< PUSH_L 0
< SLIDE 1 1
652,653d604
< PUSH_L 0
< SLIDE 1 1
656,657d606
< PUSH_L 0
< SLIDE 1 1
660,661d608
< PUSH_L 0
< SLIDE 1 1
664,665d610
< PUSH_L 0
< SLIDE 1 1
```
I also compiled lib:Cabal to bytecode and counted the number of bytecode
lines with `find dist-newstyle -name "*.dump-BCOs" -exec wc {} +`:
with unoptimized core:
1190689 lines (before) - 1172891 lines (now)
= 17798 less redundant instructions (-1.5% lines)
with optimized core:
1924818 lines (before) - 1864836 lines (now)
= 59982 less redundant instructions (-3.1% lines)
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8b2c72c0 by L0neGamer at 2025-09-04T06:32:03-04:00
Add Control.Monad.thenM and Control.Applicative.thenA
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39e1b7cb by Teo Camarasu at 2025-09-04T06:32:46-04:00
ghc-internal: invert dependency of GHC.Internal.TH.Syntax on Data.Data
This means that Data.Data no longer blocks building TH.Syntax, which
allows greater parallelism in our builds.
We move the Data.Data.Data instances to Data.Data. Quasi depends on
Data.Data for one of its methods, so,
we split the Quasi/Q, etc definition out of GHC.Internal.TH.Syntax
into its own module. This has the added benefit of splitting up this
quite large module.
Previously TH.Syntax was a bottleneck when compiling ghc-internal. Now
it is less of a bottle-neck and is also slightly quicker to
compile (since it no longer contains these instances) at the cost of
making Data.Data slightly more expensive to compile.
TH.Lift which depends on TH.Syntax can also compile quicker and no
longer blocks ghc-internal finishing to compile.
Resolves #26217
-------------------------
Metric Decrease:
MultiLayerModulesTH_OneShot
T13253
T21839c
T24471
Metric Increase:
T12227
-------------------------
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bdf82fd2 by Teo Camarasu at 2025-09-04T06:32:46-04:00
compiler: delete unused names in Builtins.Names.TH
returnQ and bindQ are no longer used in the compiler.
There was also a very old comment that referred to them that I have modernized
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41a448e5 by Ben Gamari at 2025-09-04T19:21:43-04:00
hadrian: Pass lib & include directories to ghc `Setup configure`
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46bb9a79 by Ben Gamari at 2025-09-04T19:21:44-04:00
rts/IPE: Fix compilation when zstd is enabled
This was broken by the refactoring undertaken in
c80dd91c0bf6ac034f0c592f16c548b9408a8481.
Closes #26312.
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138a6e34 by sheaf at 2025-09-04T19:22:46-04:00
Make mkCast assertion a bit clearer
This commit changes the assertion message that gets printed when one
calls mkCast with a coercion whose kind does not match the type of the
inner expression. I always found the assertion message a bit confusing,
as it didn't clearly state what exactly was the error.
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9d626be1 by sheaf at 2025-09-04T19:22:46-04:00
Simplifier/rules: fix mistakes in Notes & comments
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a71f55a3 by Simon Peyton Jones at 2025-09-05T09:40:41+01:00
Solve forall-constraints via an implication, again
In this earlier commit:
commit 953fd8f1dc080f1c56e3a60b4b7157456949be29
Author: Simon Peyton Jones