-
e8d1a0d6
by Bernhard M. Wiedemann at 2026-08-10T21:31:23-04:00
driver: Link object files in a deterministic order
The object files handed to the linker come from the HomePackageTable,
which is ordered by the order in which modules finished compiling. With
-j1 that is the build plan order, with -jN it is whatever the scheduler
produced, so the same sources can link to different (but equivalent)
binaries.
The order reaches the output: .text and .rodata contributions are
concatenated in link order, so e.g. building the hdav executable of the
DAV package twice, once with -j1 and once with -j4, yields two binaries
that differ in ~100kB of section contents.
Sort the home modules by module before collecting their linkables,
guarded under `Opt_ObjectDeterminism` .
Fixes #27612
Signed-off-by: Bernhard M. Wiedemann <bwiedemann@suse.de>
-
556db2f3
by sheaf at 2026-08-10T21:32:06-04:00
Reduce SpecConstr threshold in GHC.Tc.Solver.Rewrite
As remarked in #27628, this module currently sits on a knife's edge: if
the body of 'simplifyArgsWorker' is made even a tiny bit smaller, then
SpecConstr suddenly kicks in and causes disastrous reboxing of the
LiftingContext argument.
To make this less likely to happen, this commit lowers the SpecConstr
threshold.
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d9c3e8a6
by sheaf at 2026-08-10T22:10:21-04:00
Allow rewriting in RuntimeReps for newtype ConPats
This commit implements PHASE 2 of the FixedRuntimeRep plan described in
Note [The Concrete mechanism] in GHC.Tc.Utils.Concrete for newtype
constructor patterns.
In short, GHC now accepts programs of the form
f (MkN x) = ...
in which the argument 'x' of the newtype constructor pattern 'MkN x'
has a representation that is not syntactically concrete, e.g. it can be
'Id IntRep' reducing to 'IntRep'. See T20363{,b,c} for examples.
There are two main parts to the implementation:
1. Typechecking, in GHC.Tc.Gen.Pat.tcDataConPat.
See Note [Typechecking newtype constructor patterns] in GHC.Tc.Gen.Pat.
2. Desugaring. We restructure the code for desugaring pattern matches
by allowing the scrutinised match variable to be casted. This allows
us to accumulate coercions and avoids creating binders at intermediate
types tha don't have a fixed RuntimeRep.
See the revamped Note [Match Ids] in GHC.HsToCore.Monad.
Fixes #20363
-------------------------
Metric Increase:
InstanceMatching
-------------------------
-
b33992b6
by Wolfgang Jeltsch at 2026-08-10T22:10:22-04:00
Add support for textual output of bytecode file content
-
35823b6f
by sheaf at 2026-08-10T22:10:27-04:00
Avoid wasteful allocations in mkTyConAppCo
The idiom "traverse isReflCo_maybe" followed by "map fst" used in
'GHC.Core.Coercion.mkTyConAppCo' was allocating a lot of waste.
This commit uses 'GHC.Data.Unboxed.traverseMaybeUB' to avoid all these
unnecessary intermediate allocations.
In a quick microbenchmark for 'mkTyConAppCo', this change resulted in:
- refl case (all argument coercions are reflexive):
- -60% runtime
- -80% allocations
- non-refl case:
- from 0% to -12% runtime (depending on which argument is non-refl)
- from 0% to -70% allocations ( -- '' -- )
Fixes #27648
-------------------------
Metric Decrease:
FamAppCachePerf
SimplCastPerf
T12425
T15703
T26426
T3064
T9872b_defer
T9872d
T5321Fun
T9020
T9630
-------------------------