Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: d4a9d6d6 by ARATA Mizuki at 2025-10-19T18:43:47+09:00 Handle implications between x86 feature flags This includes: * Multiple -msse* options can be specified * -mavx implies -msse4.2 * -mavx2 implies -mavx * -mfma implies -mavx * -mavx512f implies -mavx2 and -mfma * -mavx512{cd,er,pf} imply -mavx512f Closes #24989 Co-authored-by: sheaf <sam.derbyshire@gmail.com> - - - - - 14 changed files: - compiler/GHC/CmmToAsm/Config.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToAsm/X86/Instr.hs - compiler/GHC/Driver/Config/CmmToAsm.hs - compiler/GHC/Driver/DynFlags.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Platform.hs - docs/users_guide/9.16.1-notes.rst - docs/users_guide/using.rst - testsuite/tests/codeGen/should_gen_asm/all.T - + testsuite/tests/codeGen/should_gen_asm/mavx-should-enable-popcnt.asm - + testsuite/tests/codeGen/should_gen_asm/mavx-should-enable-popcnt.hs - + testsuite/tests/codeGen/should_gen_asm/msse-option-order.asm - + testsuite/tests/codeGen/should_gen_asm/msse-option-order.hs Changes: ===================================== compiler/GHC/CmmToAsm/Config.hs ===================================== @@ -29,9 +29,7 @@ data NCGConfig = NCGConfig , ncgRegsGraph :: !Bool , ncgAsmLinting :: !Bool -- ^ Perform ASM linting pass , ncgDoConstantFolding :: !Bool -- ^ Perform CMM constant folding - , ncgSseVersion :: Maybe SseVersion -- ^ (x86) SSE instructions - , ncgAvxEnabled :: !Bool - , ncgAvx2Enabled :: !Bool + , ncgSseAvxVersion :: Maybe SseAvxVersion -- ^ (x86) SSE and AVX instructions , ncgAvx512fEnabled :: !Bool , ncgBmiVersion :: Maybe BmiVersion -- ^ (x86) BMI instructions , ncgDumpRegAllocStages :: !Bool ===================================== compiler/GHC/CmmToAsm/X86/CodeGen.hs ===================================== @@ -104,30 +104,32 @@ is32BitPlatform = do platform <- getPlatform return $ target32Bit platform +-- These flags may be implied by other flags like -mfma or -mavx512f. +-- See Note [Implications between X86 CPU feature flags] for details. ssse3Enabled :: NatM Bool ssse3Enabled = do config <- getConfig - return (ncgSseVersion config >= Just SSSE3) + return (ncgSseAvxVersion config >= Just SSSE3) sse4_1Enabled :: NatM Bool sse4_1Enabled = do config <- getConfig - return (ncgSseVersion config >= Just SSE4) + return (ncgSseAvxVersion config >= Just SSE4) sse4_2Enabled :: NatM Bool sse4_2Enabled = do config <- getConfig - return (ncgSseVersion config >= Just SSE42) + return (ncgSseAvxVersion config >= Just SSE42) avxEnabled :: NatM Bool avxEnabled = do config <- getConfig - return (ncgAvxEnabled config) + return (ncgSseAvxVersion config >= Just AVX1) avx2Enabled :: NatM Bool avx2Enabled = do config <- getConfig - return (ncgAvx2Enabled config) + return (ncgSseAvxVersion config >= Just AVX2) cmmTopCodeGen :: RawCmmDecl ===================================== compiler/GHC/CmmToAsm/X86/Instr.hs ===================================== @@ -1121,8 +1121,8 @@ movInstr config fmt = = f plat = ncgPlatform config - avx = ncgAvxEnabled config - avx2 = ncgAvx2Enabled config + avx = ncgSseAvxVersion config >= Just AVX1 + avx2 = ncgSseAvxVersion config >= Just AVX2 avx512f = ncgAvx512fEnabled config avx_move sFmt = if isFloatScalarFormat sFmt ===================================== compiler/GHC/Driver/Config/CmmToAsm.hs ===================================== @@ -52,15 +52,18 @@ initNCGConfig dflags this_mod = NCGConfig -- operations would change the precision and final result of what -- would otherwise be the same expressions with respect to single or -- double precision IEEE floating point computations. - , ncgSseVersion = - let v | sseVersion dflags < Just SSE2 = Just SSE2 - | otherwise = sseVersion dflags + + -- ncgSseAvxVersion is set to the actual SSE/AVX version. + -- For example, -mfma does not set DynFlags's sseAvxVersion, but makes ncgSseAvxVersion >= AVX1. + -- See also Note [Implications between X86 CPU feature flags] + , ncgSseAvxVersion = + let v | isAvx2Enabled dflags = Just AVX2 -- -mavx512f does not set sseAvxVersion, but makes isAvx2Enabled true + | isAvxEnabled dflags = Just AVX1 -- -mfma does not set sseAvxVersion, but makes isAvxEnabled true + | otherwise = max (Just SSE2) (sseAvxVersion dflags) in case platformArch (targetPlatform dflags) of ArchX86_64 -> v ArchX86 -> v _ -> Nothing - , ncgAvxEnabled = isAvxEnabled dflags - , ncgAvx2Enabled = isAvx2Enabled dflags , ncgAvx512fEnabled = isAvx512fEnabled dflags , ncgDwarfEnabled = osElfTarget (platformOS (targetPlatform dflags)) && debugLevel dflags > 0 && platformArch (targetPlatform dflags) /= ArchAArch64 ===================================== compiler/GHC/Driver/DynFlags.hs ===================================== @@ -447,10 +447,8 @@ data DynFlags = DynFlags { interactivePrint :: Maybe String, -- | Machine dependent flags (-m\<blah> stuff) - sseVersion :: Maybe SseVersion, + sseAvxVersion :: Maybe SseAvxVersion, bmiVersion :: Maybe BmiVersion, - avx :: Bool, - avx2 :: Bool, avx512cd :: Bool, -- Enable AVX-512 Conflict Detection Instructions. avx512er :: Bool, -- Enable AVX-512 Exponential and Reciprocal Instructions. avx512f :: Bool, -- Enable AVX-512 instructions. @@ -731,10 +729,8 @@ defaultDynFlags mySettings = profAuto = NoProfAuto, callerCcFilters = [], interactivePrint = Nothing, - sseVersion = Nothing, + sseAvxVersion = Nothing, bmiVersion = Nothing, - avx = False, - avx2 = False, avx512cd = False, avx512er = False, avx512f = False, @@ -1548,22 +1544,28 @@ initPromotionTickContext dflags = -- SSE, AVX, FMA isSse3Enabled :: DynFlags -> Bool -isSse3Enabled dflags = sseVersion dflags >= Just SSE3 +isSse3Enabled dflags = sseAvxVersion dflags >= Just SSE3 || isAvxEnabled dflags isSsse3Enabled :: DynFlags -> Bool -isSsse3Enabled dflags = sseVersion dflags >= Just SSSE3 +isSsse3Enabled dflags = sseAvxVersion dflags >= Just SSSE3 || isAvxEnabled dflags isSse4_1Enabled :: DynFlags -> Bool -isSse4_1Enabled dflags = sseVersion dflags >= Just SSE4 +isSse4_1Enabled dflags = sseAvxVersion dflags >= Just SSE4 || isAvxEnabled dflags isSse4_2Enabled :: DynFlags -> Bool -isSse4_2Enabled dflags = sseVersion dflags >= Just SSE42 +isSse4_2Enabled dflags = sseAvxVersion dflags >= Just SSE42 || isAvxEnabled dflags isAvxEnabled :: DynFlags -> Bool -isAvxEnabled dflags = avx dflags || avx2 dflags || avx512f dflags +isAvxEnabled dflags = sseAvxVersion dflags >= Just AVX1 || (isX86 && fma dflags) || isAvx512fEnabled dflags + where + -- -mfma can be used on multiple platforms, but -mavx is x86-only + isX86 = case platformArch (targetPlatform dflags) of + ArchX86_64 -> True + ArchX86 -> True + _ -> False isAvx2Enabled :: DynFlags -> Bool -isAvx2Enabled dflags = avx2 dflags || avx512f dflags +isAvx2Enabled dflags = sseAvxVersion dflags >= Just AVX2 || isAvx512fEnabled dflags isAvx512cdEnabled :: DynFlags -> Bool isAvx512cdEnabled dflags = avx512cd dflags @@ -1572,13 +1574,49 @@ isAvx512erEnabled :: DynFlags -> Bool isAvx512erEnabled dflags = avx512er dflags isAvx512fEnabled :: DynFlags -> Bool -isAvx512fEnabled dflags = avx512f dflags +isAvx512fEnabled dflags = avx512f dflags || avx512cd dflags || avx512er dflags || avx512pf dflags isAvx512pfEnabled :: DynFlags -> Bool isAvx512pfEnabled dflags = avx512pf dflags isFmaEnabled :: DynFlags -> Bool -isFmaEnabled dflags = fma dflags +isFmaEnabled dflags = fma dflags || (isX86 && isAvx512fEnabled dflags) + where + -- -mfma is used on multiple platforms, but -mavx512f is x86-only + isX86 = case platformArch (targetPlatform dflags) of + ArchX86_64 -> True + ArchX86 -> True + _ -> False + +{- Note [Implications between X86 CPU feature flags] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Many X86 CPU feature flags (such as -mavx, -mfma or -msse4) imply other +feature flags. In particular, there are straightforward linear implication +structures: + + 1. AVX2 -> AVX -> SSE4.2 -> SSE4 -> SSSE3 -> SSE3 -> SSE2 -> SSE1 + 2. BMI2 -> BMI1 + +together with other implications such as + + 3. FMA -> AVX + 4. AVX512{CD,ED,PF} -> AVX512F -> AVX2 + + +We handle this as follows: + + A. When parsing command line options into `DynFlags`, we record: + - an `SseAvxVersion` which gives the SSE/AVX level supported in + the total order (1), + - a `BmiVersion` for (2), + - whether FMA is enabled, + - various AVX512 flags saying which AVX512 extensions are supported + + B. When converting these "raw" `DynFlags` into a `CmmConfig` for use + in code generator backends, we handle the remaining implications (3) (4), + e.g. if the user passed -mavx512f then we also set the `SseAvxVersion` + to `AVX2`. +-} -- ----------------------------------------------------------------------------- -- BMI2 ===================================== compiler/GHC/Driver/Session.hs ===================================== @@ -1684,25 +1684,28 @@ dynamic_flags_deps = [ (setDumpFlag Opt_D_dump_faststrings) ------ Machine dependent (-m<blah>) stuff --------------------------- + -- See Note [Implications between X86 CPU feature flags] , make_ord_flag defGhcFlag "msse" (noArg (\d -> - d { sseVersion = Just SSE1 })) + d { sseAvxVersion = max (Just SSE1) (sseAvxVersion d) })) , make_ord_flag defGhcFlag "msse2" (noArg (\d -> - d { sseVersion = Just SSE2 })) + d { sseAvxVersion = max (Just SSE2) (sseAvxVersion d) })) , make_ord_flag defGhcFlag "msse3" (noArg (\d -> - d { sseVersion = Just SSE3 })) + d { sseAvxVersion = max (Just SSE3) (sseAvxVersion d) })) , make_ord_flag defGhcFlag "mssse3" (noArg (\d -> - d { sseVersion = Just SSSE3 })) + d { sseAvxVersion = max (Just SSSE3) (sseAvxVersion d) })) , make_ord_flag defGhcFlag "msse4" (noArg (\d -> - d { sseVersion = Just SSE4 })) + d { sseAvxVersion = max (Just SSE4) (sseAvxVersion d) })) , make_ord_flag defGhcFlag "msse4.2" (noArg (\d -> - d { sseVersion = Just SSE42 })) + d { sseAvxVersion = max (Just SSE42) (sseAvxVersion d) })) , make_ord_flag defGhcFlag "mbmi" (noArg (\d -> - d { bmiVersion = Just BMI1 })) + d { bmiVersion = max (Just BMI1) (bmiVersion d) })) , make_ord_flag defGhcFlag "mbmi2" (noArg (\d -> d { bmiVersion = Just BMI2 })) - , make_ord_flag defGhcFlag "mavx" (noArg (\d -> d { avx = True })) - , make_ord_flag defGhcFlag "mavx2" (noArg (\d -> d { avx2 = True })) + , make_ord_flag defGhcFlag "mavx" (noArg (\d -> + d { sseAvxVersion = max (Just AVX1) (sseAvxVersion d) })) + , make_ord_flag defGhcFlag "mavx2" (noArg (\d -> + d { sseAvxVersion = max (Just AVX2) (sseAvxVersion d) })) , make_ord_flag defGhcFlag "mavx512cd" (noArg (\d -> d { avx512cd = True })) , make_ord_flag defGhcFlag "mavx512er" (noArg (\d -> ===================================== compiler/GHC/Platform.hs ===================================== @@ -32,7 +32,7 @@ module GHC.Platform , platformCConvNeedsExtension , platformHasRTSLinker , PlatformMisc(..) - , SseVersion (..) + , SseAvxVersion (..) , BmiVersion (..) , wordAlignment -- * SSE and AVX @@ -264,14 +264,16 @@ platformHasRTSLinker p = case archOS_arch (platformArchOS p) of -- Instruction sets -------------------------------------------------- --- | x86 SSE instructions -data SseVersion +-- | x86 SSE and AVX instructions +data SseAvxVersion = SSE1 | SSE2 | SSE3 | SSSE3 | SSE4 | SSE42 + | AVX1 + | AVX2 deriving (Eq, Ord) -- | x86 BMI (bit manipulation) instructions ===================================== docs/users_guide/9.16.1-notes.rst ===================================== @@ -28,6 +28,16 @@ Compiler bound to variables. The very similar pattern ``Foo{bar = Bar{baz = 42}}`` will will not yet mark ``bar`` or ``baz`` as covered. +- When multiple ``-msse*`` flags are given, the maximum version takes effect. + For example, ``-msse4.2 -msse2`` is now equivalent to ``-msse4.2``. + Previously, only the last flag took effect. + +- Some x86 architecture flags now imply other flags. + For example, :ghc-flag:`-mavx` now implies :ghc-flag:`-msse4.2`, + and :ghc-flag:`-mavx512f` now implies :ghc-flag:`-mfma` + in addition to :ghc-flag:`-mavx2`. + Refer to the users' guide for more details about each individual flag. + GHCi ~~~~ ===================================== docs/users_guide/using.rst ===================================== @@ -1594,6 +1594,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-msse4.2` + (x86 only) This flag allows the code generator (whether the :ref:`native code generator <native-code-gen>` or the :ref:`LLVM backend <llvm-code-gen>`) to emit x86_64 AVX instructions. @@ -1602,6 +1604,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-mavx` + (x86 only) This flag allows the code generator (whether the :ref:`native code generator <native-code-gen>` or the :ref:`LLVM backend <llvm-code-gen>`) to emit x86_64 AVX2 instructions. @@ -1610,6 +1614,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-mavx512f` + (x86 only) This flag allows the code generator (whether the :ref:`native code generator <native-code-gen>` or the :ref:`LLVM backend <llvm-code-gen>`) to emit x86_64 AVX512-CD instructions. @@ -1618,6 +1624,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-mavx512f` + (x86 only) This flag allows the code generator (whether the :ref:`native code generator <native-code-gen>` or the :ref:`LLVM backend <llvm-code-gen>`) to emit x86_64 AVX512-ER instructions. @@ -1626,6 +1634,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-mavx2`, :ghc-flag:`-mfma` + (x86 only) This flag allows the code generator (whether the :ref:`native code generator <native-code-gen>` or the :ref:`LLVM backend <llvm-code-gen>`) to emit x86_64 AVX512-F instructions. @@ -1634,6 +1644,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-mavx512f` + (x86 only) This flag allows the code generator (whether the :ref:`native code generator <native-code-gen>` or the :ref:`LLVM backend <llvm-code-gen>`) to emit x86_64 AVX512-PF instructions. @@ -1690,6 +1702,7 @@ Some flags only make sense for particular target platforms. :category: platform-options :since: 9.14.1 + :implies: :ghc-flag:`-msse3` (x86 only) Use the SSSE3 instruction set to implement some vector operations @@ -1701,6 +1714,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-mssse3` + (x86 only) Use the SSE4 instruction set to implement some floating point and bit operations(whether using the :ref:`native code generator <native-code-gen>` or the :ref:`LLVM backend <llvm-code-gen>`). @@ -1710,6 +1725,8 @@ Some flags only make sense for particular target platforms. :type: dynamic :category: platform-options + :implies: :ghc-flag:`-msse4` + (x86 only, added in GHC 7.4.1) Use the SSE4.2 instruction set to implement some floating point and bit operations, whether using the :ref:`native code generator <native-code-gen>` @@ -1747,6 +1764,7 @@ Some flags only make sense for particular target platforms. :default: off by default, except for Aarch64 where it's on by default. :since: 9.8.1 + :implies: (on x86) :ghc-flag:`-mavx` Use native FMA instructions to implement the fused multiply-add floating-point operations of the form ``x * y + z``. ===================================== testsuite/tests/codeGen/should_gen_asm/all.T ===================================== @@ -12,3 +12,8 @@ test('bytearray-memcpy-unroll', is_amd64_codegen, compile_grep_asm, ['hs', True, test('T18137', [when(opsys('darwin'), skip), only_ways(llvm_ways)], compile_grep_asm, ['hs', False, '-fllvm -split-sections']) test('T24941', [only_ways(['optasm'])], compile, ['-fregs-graph']) + +test('msse-option-order', [unless(arch('x86_64') or arch('i386'), skip), + when(unregisterised(), skip)], compile_grep_asm, ['hs', False, '-msse4.2 -msse2']) +test('mavx-should-enable-popcnt', [unless(arch('x86_64') or arch('i386'), skip), + when(unregisterised(), skip)], compile_grep_asm, ['hs', False, '-mavx']) ===================================== testsuite/tests/codeGen/should_gen_asm/mavx-should-enable-popcnt.asm ===================================== @@ -0,0 +1 @@ +popcnt(?![0-9]) \ No newline at end of file ===================================== testsuite/tests/codeGen/should_gen_asm/mavx-should-enable-popcnt.hs ===================================== @@ -0,0 +1,10 @@ +-- `-mavx` should imply `-msse4.2`. +-- See https://gitlab.haskell.org/ghc/ghc/-/issues/24989 +import Data.Bits + +{-# NOINLINE foo #-} +foo :: Int -> Int +foo x = 1 + popCount x + +main :: IO () +main = print (foo 42) ===================================== testsuite/tests/codeGen/should_gen_asm/msse-option-order.asm ===================================== @@ -0,0 +1 @@ +popcnt(?![0-9]) \ No newline at end of file ===================================== testsuite/tests/codeGen/should_gen_asm/msse-option-order.hs ===================================== @@ -0,0 +1,10 @@ +-- `-msse2 -msse4.2` and `-msse4.2 -msse2` should have the same effect. +-- See https://gitlab.haskell.org/ghc/ghc/-/issues/24989#note_587510 +import Data.Bits + +{-# NOINLINE foo #-} +foo :: Int -> Int +foo x = 1 + popCount x + +main :: IO () +main = print (foo 42) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/d4a9d6d6ec73b1851dec36cbf04d607e... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/d4a9d6d6ec73b1851dec36cbf04d607e... 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