Magnus pushed to branch wip/mangoiv/27556 at Glasgow Haskell Compiler / GHC

Commits:

• 0c73f75d
  by mangoiv at 2026-08-21T09:54:44+02:00

  simplifier: allow more ticks in argument position in rebuild_app
  
  In cpeApp, we were carefully asserting that all argument ticks were
  profiling ticks. This was too strict as we allow any non-floatable
  tick in that position, which is described in Note [Ticks and mandatory
  eta expansion]. When `canCollectArgsThrougTick` was introduced, the
  rules for ticks in argument positions became more lenient, for instance,
  it was not a necessary precondition for the Id to have no binding, which
  simply allowed more ticks to float to that position. The test
  demonstrates that; with optimized bytecode, a breakpoint tick appears
  and takes as argument a primop that has to be eta expanded so we move it
  out of the way.
  
  Fixes #27556
  

5 changed files:

• + changelog.d/27556
• compiler/GHC/CoreToStg/Prep.hs
• + testsuite/tests/simplCore/should_compile/T27556.hs
• + testsuite/tests/simplCore/should_compile/T27556.script
• testsuite/tests/simplCore/should_compile/all.T

Changes:

+section: compiler

+synopsis: Remove a too strict assert in coreprep

+mrs: !16558

+issues: #27556

       -- See Note [Ticks and mandatory eta expansion]

       AITick tickish

-        | tickishPlace tickish == PlaceRuntime

+        | PlaceRuntime <- tickishPlace tickish

         , req_depth > 0

-        -> assert (isProfTick tickish) $

-           rebuild_app' env as fun' floats ss (tickish:rt_ticks) req_depth

+        -> rebuild_app' env as fun' floats ss (tickish:rt_ticks) req_depth

         | otherwise

         -- See [Floating Ticks in CorePrep]

         -> rebuild_app' env as fun' (snocFloat floats (FloatTick tickish)) ss rt_ticks req_depth

+import Control.Exception

+

+main = mask $ \restore -> restore (pure ())

+

+:l T27556

 test('T27296b', [], makefile_test, ['T27296b'])

 test('T27589', [grep_errmsg(r'wombat')], compile, ['-O -ddump-simpl -dno-typeable-binds -dsuppress-uniques'])

 test('T27590', [grep_errmsg(r'wombat')], compile, ['-O -ddump-simpl -dno-typeable-binds -dsuppress-uniques'])

+test('T27556', [only_ways('ghci'), extra_hc_opts('-O -fno-unoptimized-core-for-interpreter')], ghci_script, ['T27556.script'])