GitLab

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

Commits:

b4a6c9df

by mangoiv at 2026-09-02T14:27:21+02:00

simplifier: remove a bogus `assert` in `rebuild_app'` in `GHC.CoreToStg.Prep.cpeApp`.

Prior to this commit
    commit 08bc245be70d95801bc1138804ed1de9474fbdc0
    Author: sheaf <sam.derbyshire@gmail.com>
    Date:   Sat Feb 28 16:30:43 2026 +0100

    Clean up join points, casts & ticks

    This commit shores up the logic dealing with casts and ticks occurring
    in between a join point binding and a jump

any `PlaceRuntime` ticks we observed were profiling ticks, even though that
isn't necessary.
The more liberal rules in the above commit allow e.g. breakpoint ticks
(which are valid PlaceRuntime ticks) to legitimately appear in an argument
position.

Fixes #27556

6 changed files:

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

Changes:

changelog.d/27556

 +section: compiler
 +synopsis: Remove a too strict assert in coreprep; fixes a bug where debug builds
 +    of GHC would fail to compile correctly optimized programs.
 +mrs: !16558
 +issues: #27556

compiler/GHC/CoreToStg/Prep.hs

@@ -1260,10 +1260,9 @@ cpeApp top_env expr
        -- 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

compiler/GHC/Types/Tickish.hs

@@ -13,7 +13,6 @@ module GHC.Types.Tickish (
    mkNoCount,
    mkNoScope,
    tickishIsCode,
 -  isProfTick,
    TickishPlacement(..),
    tickishPlace,
    tickishContains,
@@ -545,10 +544,6 @@ tickishIsCode ProfNote{}   = True
  tickishIsCode Breakpoint{} = True
  tickishIsCode HpcTick{}    = True
 -isProfTick :: GenTickish pass -> Bool
 -isProfTick ProfNote{} = True
 -isProfTick _          = False
+-
  -- | Governs the kind of expression that the tick gets placed on when
  -- annotating for example using @mkTick@. If we find that we want to
  -- put a tickish on an expression ruled out here, we try to float it

testsuite/tests/simplCore/should_compile/T27556.hs

 +import Control.Exception
++
 +main = mask $ \restore -> restore (pure ())
++

testsuite/tests/simplCore/should_compile/T27556.script

+:l T27556

testsuite/tests/simplCore/should_compile/all.T

@@ -611,3 +611,4 @@ test('T27296', [], makefile_test, ['T27296'])
  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'])