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54cf3c1e
by sheaf at 2026-11-03T07:00:23-05:00
Consolidate all CPU feature handling
This commit introduces GHC.Platform.CpuFeatures which consolidates all
of the logic for implications between CPU feature flags (mainly X86):
- DynFlags now only records the set of -m<feature> flags that were
passed, as an EnumSet CpuFeature. That keeps it a simple record of
the flags the user passed, with no post-processing.
- GHC.Platform.CpuFeatures.initCpuFeatures turns this set into a
CpuFeatures value, applying all implications and the per-architecture
baseline. This is the single home for all of the feature implication
logic.
Some datatypes were reworked to better reflect the implication
structure in the types, e.g. SseAvxVersion has a strategically
placed 'FMA' boolean.
- The NCG, LLVM backend, StgToCmm, CPP defines and LLVM -mattr
flags all consult CpuFeatures, via targetCpuFeatures.
See Note [CPU features], which replaces
Note [Implications between X86 CPU feature flags].
Behaviour changes:
- x86 feature flags (-msse3, -mavx, -mavx512*, -mgfni, ...) passed
when targeting a non-x86 architecture no longer cause x86 CPP
macros (__SSE3__, __AVX512BW__, __GFNI__, ...) to be defined, nor
x86 attributes to be passed to LLVM.
- Error messages reported when required CPU features are not enabled
now print out the minimal set of flags required
(e.g. "-mavx512vl" rather than "-mavx512f -mavx512vl").
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9af64305
by Luite Stegeman at 2026-11-03T07:01:23-05:00
rts: move stack check to the start of the stg_unpack_cstring thunks
fixes a deadlock
see #27272
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a2208b21
by Simon Jakobi at 2026-11-03T07:02:05-05:00
Cmm: exclude the entry block from common block elimination
a1d8139054c had fixed #27722 only partially, because it didn't prevent
elimination of the entry block in later rounds, where the entry block is
no longer guaranteed to come first.
To close this loophole, we exclude the entry block from the CBE merge
logic. See Note [Retain entry block during common block elimination] for
details.
This also deletes a misleading comment regarding unreachable blocks: the
control-flow optimiser doesn't actually guarantee that no unreachable
blocks reach CBE.
Fixes #27722.
Assisted-by: Claude Fable 5.1
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37ad4710
by Alan Zimmerman at 2026-11-03T07:02:46-05:00
EPA: Use AnnList for GADT declarations
Continuing the process of using AnnList to capture parser layout
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f982f613
by Andrea Vezzosi at 2026-11-03T13:18:27+01:00
driver: Don't let -dynamic unset -fsplit-sections
`addWay' WayDyn` used to unset Opt_SplitSections, so -fsplit-sections was
ignored if it came before -dynamic, but worked if it came after.
The -fsplit-sections -dynamic combination has legitimate uses, e.g. an
executable can be linked dynamically against libraries and still have dead code
from its own sources to eliminate. Or the same objects could be used for both
static archives and shared objects.
The removal of Opt_SplitSections was also motivated by problems on Darwin.
It is now done in `makeDynFlagsConsistent` instead, see Note [Split sections are not
supported on Mach-O].
For consistency, we also keep Opt_SplitSections when `dynamicNow` is activated.
There is a cost of larger .dyn_o (but not .so) files and slower link times (esp.
with ld.bfd), but does not seem significant enough to warrant special casing.
Fixes #28061
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>