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| author | Ben Gamari <ben@smart-cactus.org> | 2020-04-20 11:05:06 -0400 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2020-04-22 23:14:57 -0400 |
| commit | 4b4a8b60a5b403e02117ab0a30a386664845586b (patch) | |
| tree | 9812fef655d88bf53723899b462f4f6abfbb9833 /compiler/GHC | |
| parent | c29f0fa6ee831ec8a223561312d7176ef87a7ece (diff) | |
| download | haskell-4b4a8b60a5b403e02117ab0a30a386664845586b.tar.gz | |
llvmGen: Remove -fast-llvm flag
Issue #18076 drew my attention to the undocumented `-fast-llvm` flag for
the LLVM code generator introduced in
22733532171330136d87533d523f565f2a4f102f. Speaking to Moritz about this,
the motivation for this flag was to avoid potential incompatibilities
between LLVM and the assembler/linker toolchain by making LLVM
responsible for machine-code generation.
Unfortunately, this cannot possibly work: the LLVM backend's mangler
performs a number of transforms on the assembler generated by LLVM that
are necessary for correctness. These are currently:
* mangling Haskell functions' symbol types to be `object` instead of
`function` on ELF platforms (necessary for tables-next-to-code)
* mangling AVX instructions to ensure that we don't assume alignment
(which LLVM otherwise does)
* mangling Darwin's subsections-via-symbols directives
Given that these are all necessary I don't believe that we can support
`-fast-llvm`. Let's rather remove it.
Diffstat (limited to 'compiler/GHC')
| -rw-r--r-- | compiler/GHC/Driver/Pipeline.hs | 18 | ||||
| -rw-r--r-- | compiler/GHC/Driver/Session.hs | 2 |
2 files changed, 1 insertions, 19 deletions
diff --git a/compiler/GHC/Driver/Pipeline.hs b/compiler/GHC/Driver/Pipeline.hs index f61430b475..1fc37e0662 100644 --- a/compiler/GHC/Driver/Pipeline.hs +++ b/compiler/GHC/Driver/Pipeline.hs @@ -866,20 +866,6 @@ getOutputFilename stop_phase output basename dflags next_phase maybe_location | otherwise = persistent --- | The fast LLVM Pipeline skips the mangler and assembler, --- emitting object code directly from llc. --- --- slow: opt -> llc -> .s -> mangler -> as -> .o --- fast: opt -> llc -> .o --- --- hidden flag: -ffast-llvm --- --- if keep-s-files is specified, we need to go through --- the slow pipeline (Kavon Farvardin requested this). -fastLlvmPipeline :: DynFlags -> Bool -fastLlvmPipeline dflags - = not (gopt Opt_KeepSFiles dflags) && gopt Opt_FastLlvm dflags - -- | LLVM Options. These are flags to be passed to opt and llc, to ensure -- consistency we list them in pairs, so that they form groups. llvmOptions :: DynFlags @@ -890,7 +876,6 @@ llvmOptions dflags = ,"-relocation-model=" ++ rmodel) | not (null rmodel)] ++ [("-stack-alignment=" ++ (show align) ,"-stack-alignment=" ++ (show align)) | align > 0 ] - ++ [("", "-filetype=obj") | fastLlvmPipeline dflags ] -- Additional llc flags ++ [("", "-mcpu=" ++ mcpu) | not (null mcpu) @@ -1472,8 +1457,7 @@ runPhase (RealPhase LlvmOpt) input_fn dflags runPhase (RealPhase LlvmLlc) input_fn dflags = do - next_phase <- if | fastLlvmPipeline dflags -> maybeMergeForeign - -- hidden debugging flag '-dno-llvm-mangler' to skip mangling + next_phase <- if -- hidden debugging flag '-dno-llvm-mangler' to skip mangling | gopt Opt_NoLlvmMangler dflags -> return (As False) | otherwise -> return LlvmMangle diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs index eda031652f..7efba2bcea 100644 --- a/compiler/GHC/Driver/Session.hs +++ b/compiler/GHC/Driver/Session.hs @@ -2818,8 +2818,6 @@ dynamic_flags_deps = [ (NoArg (setGeneralFlag Opt_D_faststring_stats)) , make_ord_flag defGhcFlag "dno-llvm-mangler" (NoArg (setGeneralFlag Opt_NoLlvmMangler)) -- hidden flag - , make_ord_flag defGhcFlag "fast-llvm" - (NoArg (setGeneralFlag Opt_FastLlvm)) -- hidden flag , make_ord_flag defGhcFlag "dno-typeable-binds" (NoArg (setGeneralFlag Opt_NoTypeableBinds)) , make_ord_flag defGhcFlag "ddump-debug" |