GitLab

Hannes Siebenhandl pushed to branch wip/fendor/no-code-output-constr at Glasgow Haskell Compiler / GHC

Commits:

046418ca

by fendor at 2026-06-24T16:16:50+02:00

Add 'backendSupportsInfoTableMap' backend predicate

Check whether the backend supports the `-finfo-table-map` flag and
ignore it otherwise.

61d935d3

by Matthew Pickering at 2026-06-24T16:16:50+02:00

Add failing test for `-finfo-table-map` and bytecode backend

If you compile a module using the bytecode backend, with
-finfo-table-map, then the info table map doesn't get populated for the
module.

This is because the -finfo-table-map code path is implemented mostly in
the StgToCmm phase which isn't run when creating bytecode.

Ticket #27039

7 changed files:

compiler/GHC/Driver/Backend.hs
compiler/GHC/Driver/CodeOutput.hs
compiler/GHC/Driver/Session.hs
testsuite/tests/ghci/scripts/all.T
+ testsuite/tests/ghci/scripts/bytecodeIPE.hs
+ testsuite/tests/ghci/scripts/bytecodeIPE.script
+ testsuite/tests/ghci/scripts/bytecodeIPE.stdout

Changes:

compiler/GHC/Driver/Backend.hs

@@ -99,6 +99,7 @@ module GHC.Driver.Backend
     , backendPostHscPipeline
     , backendNormalSuccessorPhase
     , backendName
 +   , backendSupportsInfoTableMap
     , backendValidityOfCImport
     , backendValidityOfCExport
@@ -680,6 +681,16 @@ backendSupportsBreakpoints = \case
    Named Bytecode -> True
    Named NoBackend   -> False
 +-- | If this flag is unset, then the driver ignores the flag @-finfo-table-map@,
 +-- since the backend doesn't support generating the info table map.
 +backendSupportsInfoTableMap :: Backend -> Bool
 +backendSupportsInfoTableMap (Named NCG)        = True
 +backendSupportsInfoTableMap (Named LLVM)       = False
 +backendSupportsInfoTableMap (Named ViaC)       = True
 +backendSupportsInfoTableMap (Named JavaScript) = False
 +backendSupportsInfoTableMap (Named Bytecode)   = False
 +backendSupportsInfoTableMap (Named NoBackend)  = True -- We are not generating code, so we ignore it any way
++
  -- | If this flag is set, then the driver forces the
  -- optimization level to 0, issuing a warning message if
  -- the command line requested a higher optimization level.

compiler/GHC/Driver/CodeOutput.hs

@@ -63,6 +63,7 @@ import GHC.Types.Unique.Supply ( UniqueTag(..) )
  import System.IO
  import Data.Set (Set)
  import qualified Data.Set as Set
 +import GHC.Plugins (panic)
  {-
  ************************************************************************

compiler/GHC/Driver/Session.hs

@@ -3903,9 +3903,9 @@ makeDynFlagsConsistent dflags
          in dflags_c
   | gopt Opt_InfoTableMap dflags
 - , LlvmCodeOutput <- backendCodeOutput (backend dflags)
 + , backendSupportsInfoTableMap (backend dflags)
      = loop (gopt_unset dflags Opt_InfoTableMap)
 -           "-finfo-table-map is incompatible with -fllvm and is disabled (See #26435)"
 +           $ "-finfo-table-map is incompatible with " ++ show (backend dflags) ++ " and is disabled (See #26435)"
   | otherwise = (dflags, mempty, mempty)
      where loc = mkGeneralSrcSpan (fsLit "when making flags consistent")

testsuite/tests/ghci/scripts/all.T

@@ -385,6 +385,14 @@ test('ListTuplePunsPpr', normal, ghci_script, ['ListTuplePunsPpr.script'])
  test('ListTuplePunsPprNoAbbrevTuple', [limit_stdout_lines(14)], ghci_script, ['ListTuplePunsPprNoAbbrevTuple.script'])
  test('T24459', normal, ghci_script, ['T24459.script'])
  test('T24632', normal, ghci_script, ['T24632.script'])
 +# bytecode backend doesn't support '-finfo-table-map' (#27039)
 +test('bytecodeIPE',
 +     [ extra_hc_opts('-finfo-table-map')
 +     , extra_files(['bytecodeIPE.hs'])
 +     , req_rts_linker
 +     , when(arch('wasm32') or arch('javascript'), skip)
 +     ],
 +     ghci_script, ['bytecodeIPE.script'])
  # Test package renaming in GHCi session
  test('GhciPackageRename',

testsuite/tests/ghci/scripts/bytecodeIPE.hs

 +module BytecodeIPE where
++
 +import Data.Maybe (isJust)
 +import GHC.InfoProv (whereFrom)
++
 +marker :: String
 +marker = id "bytecode-stub-init"
 +{-# NOINLINE marker #-}
++
 +-- `whereFrom` only succeeds if the module's IPE initializer ran.
 +probe :: IO Bool
 +probe = isJust <$> whereFrom marker

testsuite/tests/ghci/scripts/bytecodeIPE.script

	1	+:load bytecodeIPE.hs
	2	+probe

testsuite/tests/ghci/scripts/bytecodeIPE.stdout

+False