[Git][ghc/ghc][wip/andreask/spec_changelog] Document -fmax-forced-spec-args=⟨n⟩ in the 9.12 changelog.

[Andreas Klebinger (@AndreasK)]

Andreas Klebinger pushed to branch wip/andreask/spec_changelog at Glasgow Haskell Compiler / GHC


Commits:
e2d2645c by Andreas Klebinger at 2024-12-03T18:11:04+01:00
Document -fmax-forced-spec-args=⟨n⟩ in the 9.12 changelog.

Fixes #25544

- - - - -


1 changed file:

- docs/users_guide/9.12.1-notes.rst


Changes:

=====================================
docs/users_guide/9.12.1-notes.rst
=====================================
@@ -131,6 +131,15 @@ Compiler
   specialization rules was added. It was actually added ghc-9.10.1 already but
   mistakenly not mentioned in the 9.10.1 changelog.
 
+- A new flag :ghc-flag:`-fmax-forced-spec-args=⟨n⟩` has been added. When a function
+  with a SPEC argument is specialized GHC now checks the number of arguments the
+  resulting function takes.
+  If the specialized version takes less than `max-forced-spec-args` arguments it is
+  specialized. Otherwise GHC will not specialize the function and emit a warning.
+
+  This avoids edge cases where a SPEC keyword could result in functions being
+  specialized to large static data resulting in functions with thousands of arguments.
+
 - Fixed a bug that caused GHC to panic when using the aarch64 ncg and -fregs-graph
   on certain programs. (#24941)
 



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/e2d2645c01d45149420bb07987b1634e577adc04

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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/e2d2645c01d45149420bb07987b1634e577adc04
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