Andrea Vezzosi pushed to branch wip/andrea/splitsections at Glasgow Haskell Compiler / GHC

Commits:

13 changed files:

Changes:

  • changelog.d/split-sections-dynamic
    1 
    +section: compiler
    2 
    +synopsis: ``-fsplit-sections`` is no longer disabled by ``-dynamic``
    3 
    +description:
    4 
    +  ``-dynamic`` used to unset ``-fsplit-sections``, but only when
    5 
    +  ``-fsplit-sections`` appeared earlier on the command line, so the flag meant
    6 
    +  different things depending on the order of the two. Both orders now split
    7 
    +  sections, as do the dynamic outputs of ``-dynamic-too``.
    8 
    +
    9 
    +  On Darwin, ``-fsplit-sections`` is now always ignored with a warning: Mach-O
    10 
    +  has poor support for split sections and instead offers
    11 
    +  ``.subsections_via_symbols``, which GHC uses where it's able to.
    12 
    +
    13 
    +mrs: !16915
    14 
    +issues: #28061

  • compiler/GHC/Driver/Downsweep.hs
    ... ... @@ -1638,10 +1638,7 @@ enableCodeGenWhen logger tmpfs staticLife dynLife unit_env mod_graph = do
    1638 1638 
                 dflags_b = foldl gopt_set dflags_a
    1639 1639 
                          $ concatMap (wayGeneralFlags platform)
    1640 1640 
                                      hostFullWays
    1641 
    -            dflags_c = foldl gopt_unset dflags_b
    1642 
    -                     $ concatMap (wayUnsetGeneralFlags platform)
    1643 
    -                                 hostFullWays
    1644 
    -        in dflags_c
    1641 
    +        in dflags_b
    1645 1642
    1646 1643 
     {- Note [-fno-code mode]
    1647 1644 
     ~~~~~~~~~~~~~~~~~~~~~~~~

  • compiler/GHC/Driver/DynFlags.hs
    ... ... @@ -1079,16 +1079,13 @@ dopt_unset dfs f = dfs{ dumpFlags = EnumSet.delete f (dumpFlags dfs) }
    1079 1079 
     -- | Test whether a 'GeneralFlag' is set
    1080 1080 
     --
    1081 1081 
     -- Note that `dynamicNow` (i.e., dynamic objects built with `-dynamic-too`)
    1082 
    --- always implicitly enables Opt_PIC, Opt_ExternalDynamicRefs, and disables
    1082 
    +-- always implicitly enables Opt_PIC and Opt_ExternalDynamicRefs.
    1083 1083 
     --
    1084 1084 
     gopt :: GeneralFlag -> DynFlags -> Bool
    1085 1085 
     gopt Opt_PIC dflags
    1086 1086 
        | dynamicNow dflags = True
    1087 1087 
     gopt Opt_ExternalDynamicRefs dflags
    1088 1088 
        | dynamicNow dflags = True
    1089 
    -   | dynamicNow dflags = True
    1090 
    -gopt Opt_SplitSections dflags
    1091 1089 
     gopt f dflags = f `EnumSet.member` generalFlags dflags
    1092 1090
    1093 1091 
     -- | Set a 'GeneralFlag'

  • compiler/GHC/Driver/Session.hs
    ... ... @@ -2985,9 +2985,7 @@ addWay' w dflags0 =
    2985 2985 
            dflags1 = dflags0 { targetWays_ = addWay w (targetWays_ dflags0) }
    2986 2986 
            dflags2 = foldr setGeneralFlag' dflags1
    2987 2987 
                            (wayGeneralFlags platform w)
    2988 
    -       dflags3 = foldr unSetGeneralFlag' dflags2
    2989 
    -                       (wayUnsetGeneralFlags platform w)
    2990 
    -   in dflags3
    2988 
    +   in dflags2
    2991 2989
    2992 2990 
     removeWayDynP :: Way -> DynP ()
    2993 2991 
     removeWayDynP w = upd (\dfs -> dfs { targetWays_ = removeWay w (targetWays_ dfs) })
    ... ... @@ -3806,6 +3804,20 @@ In the checks and fixes performed by `makeDynFlagsConsistent`, the choice
    3806 3804 
     between the two does not seem uniform. TODO: Make this choice more evident and uniform.
    3807 3805 
     -}
    3808 3806
    3807 
    +{- Note [Split sections are not supported on Darwin]
    3808 
    +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    3809 
    +On Darwin, split sections are either ignored by the backends (NCG, C) or would
    3810 
    +cause errors (LLVM, see split-sections-darwin test).
    3811 
    +
    3812 
    +The `.subsections_via_symbols` feature of Mach-O is used instead (see Note
    3813 
    +[Subsections Via Symbols]). This works on x86_64, but not yet on aarch64 (c.f
    3814 
    +#24962 #23672).
    3815 
    +
    3816 
    +`makeDynFlagsConsistent` then disables split-sections on darwin unconditionally.
    3817 
    +This is redundant on x86_64, because of the `platformHasSubsectionsViaSymbols`
    3818 
    +check, but harmless.
    3819 
    +-}
    3820 
    +
    3809 3821 
     -- | Resolve any internal inconsistencies in a set of 'DynFlags'.
    3810 3822 
     -- Returns the consistent 'DynFlags' as well as a list of warnings
    3811 3823 
     -- to report to the user, and a list of verbose info msgs.
    ... ... @@ -3835,6 +3847,13 @@ makeDynFlagsConsistent dflags
    3835 3847 
                      "since it uses subsections-via-symbols. Ignoring."
    3836 3848 
           in loop dflags' warn
    3837 3849
    3850 
    +   -- See Note [Split sections are not supported on Mach-O]
    3851 
    + | gopt Opt_SplitSections dflags
    3852 
    + , os == OSDarwin
    3853 
    +    = let dflags' = gopt_unset dflags Opt_SplitSections
    3854 
    +          warn = "-fsplit-sections is not supported on Mach-O. Ignoring."
    3855 
    +      in loop dflags' warn
    3856 
    +
    3838 3857 
        -- Via-C backend only supports unregisterised ABI. Switch to a backend
    3839 3858 
        -- supporting it if possible.
    3840 3859 
      | backendUnregisterisedAbiOnly (backend dflags) &&
    ... ... @@ -3950,10 +3969,7 @@ makeDynFlagsConsistent dflags
    3950 3969 
                 dflags_b = foldl gopt_set dflags_a
    3951 3970 
                          $ concatMap (wayGeneralFlags platform)
    3952 3971 
                                      hostFullWays
    3953 
    -            dflags_c = foldl gopt_unset dflags_b
    3954 
    -                     $ concatMap (wayUnsetGeneralFlags platform)
    3955 
    -                                 hostFullWays
    3956 
    -        in dflags_c
    3972 
    +        in dflags_b
    3957 3973
    3958 3974 
      | gopt Opt_InfoTableMap dflags
    3959 3975 
      , NotValid msg <- backendInfoTableMapValidity (backend dflags)

  • compiler/GHC/Platform/Ways.hs
    ... ... @@ -28,7 +28,6 @@ module GHC.Platform.Ways
    28 28 
        , removeWay
    29 29 
        , allowed_combination
    30 30 
        , wayGeneralFlags
    31 
    -   , wayUnsetGeneralFlags
    32 31 
        , wayOptc
    33 32 
        , wayOptcxx
    34 33 
        , wayOptl
    ... ... @@ -164,16 +163,6 @@ wayGeneralFlags platform WayProf
    164 163 
          - https://gitlab.haskell.org/ghc/ghc/-/issues/26994 -}
    165 164 
     wayGeneralFlags _ WayProf     = []
    166 165
    167 
    --- | Turn these flags off when enabling this way
    168 
    -wayUnsetGeneralFlags :: Platform -> Way -> [GeneralFlag]
    169 
    -wayUnsetGeneralFlags _ (WayCustom {}) = []
    170 
    -wayUnsetGeneralFlags _ WayThreaded = []
    171 
    -wayUnsetGeneralFlags _ WayDebug    = []
    172 
    -wayUnsetGeneralFlags _ WayDyn      = [Opt_SplitSections]
    173 
    -   -- There's no point splitting when we're going to be dynamically linking.
    174 
    -   -- Plus it breaks compilation on OSX x86.
    175 
    -wayUnsetGeneralFlags _ WayProf     = []
    176 
    -
    177 166 
     -- | Pass these options to the C compiler when enabling this way
    178 167 
     wayOptc :: Platform -> Way -> [String]
    179 168 
     wayOptc _ (WayCustom {}) = []

  • docs/users_guide/phases.rst
    ... ... @@ -1063,6 +1063,10 @@ for example).
    1063 1063 
         When linking, the linker can automatically remove all unreferenced sections
    1064 1064 
         and thus produce smaller executables.
    1065 1065
    1066 
    +    This flag is ignored on Darwin as the Mach-O object format is not suitable
    1067 
    +    for split sections. The ``.subsections_via_symbols`` directive and the
    1068 
    +    linker's ``-dead_strip`` are used where supported, regardless of this flag.
    1069 
    +
    1066 1070 
     .. ghc-flag:: -static
    1067 1071 
         :shortdesc: Use static Haskell libraries
    1068 1072 
         :type: dynamic

  • testsuite/tests/codeGen/should_gen_asm/all.T
    ... ... @@ -11,6 +11,22 @@ test('bytearray-memset-unroll', is_amd64_codegen, compile_grep_asm, ['hs', True,
    11 11 
     test('bytearray-memcpy-unroll', is_amd64_codegen, compile_grep_asm, ['hs', True, ''])
    12 12 
     test('T18137', [when(opsys('darwin'), skip), only_ways(llvm_ways)], compile_grep_asm, ['hs', False, '-fllvm -split-sections'])
    13 13
    14 
    +# -fsplit-sections used to be silently unset by -dynamic, but only when it
    15 
    +# appeared before -dynamic on the command line. Check that both orders split.
    16 
    +# Mach-O has no split sections at all, and COFF names subsections with '$'.
    17 
    +split_sections_dynamic = [
    18 
    +    unless(have_dynamic(), skip),
    19 
    +    when(opsys('darwin'), skip),
    20 
    +    when(opsys('mingw32'), skip),
    21 
    +    when(unregisterised(), skip),
    22 
    +    only_ways(['normal']),
    23 
    +]
    24 
    +
    25 
    +test('split-sections-dynamic1', split_sections_dynamic, compile_grep_asm,
    26 
    +     ['hs', False, '-fsplit-sections -dynamic'])
    27 
    +test('split-sections-dynamic2', split_sections_dynamic, compile_grep_asm,
    28 
    +     ['hs', False, '-dynamic -fsplit-sections'])
    29 
    +
    14 30 
     test('T24941', [only_ways(['optasm'])], compile, ['-fregs-graph'])
    15 31
    16 32 
     test('msse-option-order', [unless(arch('x86_64') or arch('i386'), skip),

  • testsuite/tests/codeGen/should_gen_asm/split-sections-dynamic1.asm
    1 
    +\.section\s+\.text\.SplitSectionsDyn_
    \ No newline at end of file

  • testsuite/tests/codeGen/should_gen_asm/split-sections-dynamic1.hs
    1 
    +-- -fsplit-sections before -dynamic; split-sections-dynamic2 is the other order.
    2 
    +module SplitSectionsDyn (f, g) where
    3 
    +
    4 
    +f :: Int -> Int
    5 
    +f x = x + 1
    6 
    +
    7 
    +g :: Int -> Int
    8 
    +g = (* 2)

  • testsuite/tests/codeGen/should_gen_asm/split-sections-dynamic2.asm
    1 
    +\.section\s+\.text\.SplitSectionsDyn_
    \ No newline at end of file

  • testsuite/tests/codeGen/should_gen_asm/split-sections-dynamic2.hs
    1 
    +-- -dynamic before -fsplit-sections; split-sections-dynamic1 is the other order.
    2 
    +module SplitSectionsDyn (f, g) where
    3 
    +
    4 
    +f :: Int -> Int
    5 
    +f x = x + 1
    6 
    +
    7 
    +g :: Int -> Int
    8 
    +g = (* 2)

  • testsuite/tests/llvm/should_compile/all.T
    ... ... @@ -23,3 +23,8 @@ test('T17920fail', cmm_src, compile_fail, ['-no-hs-main'])
    23 23 
     test('T25019', unless((arch('x86_64') or arch('i386')) and have_cpu_feature('sse4_2'),skip), compile, ['-msse4.2'])
    24 24 
     test('T25353', unless((arch('x86_64') or arch('i386')) and have_cpu_feature('sse4_2'),skip), compile_grep_asm, ['hs', True, '-msse4.2'])
    25 25 
     test('T25606', normal, compile, [''])
    26 
    +
    27 
    +test('split-sections-darwin',
    28 
    +     [unless(opsys('darwin'), skip),
    29 
    +      normalise_errmsg_fun(ignore_llvm_and_vortex)],
    30 
    +     compile, ['-fsplit-sections -Wno-inconsistent-flags'])

  • testsuite/tests/llvm/should_compile/split-sections-darwin.hs
    1 
    +-- -fsplit-sections must be ignored on Darwin; see
    2 
    +-- Note [Split sections are not supported on Mach-O] in GHC.Driver.Session.
    3 
    +--
    4 
    +-- Mach-O cannot name a section after a symbol, so GHC ignores -fsplit-sections
    5 
    +-- on Darwin. Without that, llvmFunSection emits ELF-style ".text.<label>" names
    6 
    +-- and LLVM rejects them. Only reproduces on AArch64/Darwin: on
    7 
    +-- x86_64/Darwin the flag is already dropped for subsections-via-symbols.
    8 
    +-- -Wno-inconsistent-flags suppresses the "Ignoring" warning, whose wording
    9 
    +-- differs between the two Darwin platforms.
    10 
    +module SplitSectionsDarwin (f) where
    11 
    +
    12 
    +f :: Int -> Int
    13 
    +f x = x + 1

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