[Git][ghc/ghc][master] LLVM backend: Pass the +evex512 attribute to LLVM 18+ if -mavx512f is set

12 Nov 2025


      Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
b22777d4 by ARATA Mizuki at 2025-11-11T11:49:44-05:00
LLVM backend: Pass the +evex512 attribute to LLVM 18+ if -mavx512f is set

The newer LLVM requires the +evex512 attribute to enable use of ZMM registers.
LLVM exhibits a backward-compatible behavior if the cpu is `x86-64`, but not if `penryn`.
Therefore, on macOS, where the cpu is set to `penryn`, we need to explicitly pass +evex512.

Fixes #26410

- - - - -


7 changed files:

- compiler/GHC/Driver/Pipeline/Execute.hs
- + testsuite/tests/simd/should_run/T26410_ffi.hs
- + testsuite/tests/simd/should_run/T26410_ffi.stdout
- + testsuite/tests/simd/should_run/T26410_ffi_c.c
- + testsuite/tests/simd/should_run/T26410_prim.hs
- + testsuite/tests/simd/should_run/T26410_prim.stdout
- testsuite/tests/simd/should_run/all.T


Changes:

=====================================
compiler/GHC/Driver/Pipeline/Execute.hs
=====================================
@@ -42,6 +42,7 @@ import GHC.Utils.Logger
 import GHC.Utils.TmpFs
 import GHC.Platform
 import Data.List (intercalate, isInfixOf)
+import qualified Data.List.NonEmpty as NE
 import GHC.Unit.Env
 import GHC.Utils.Error
 import Data.Maybe
@@ -69,6 +70,7 @@ import GHC.Platform.Ways
 import GHC.Runtime.Loader (initializePlugins)
 import GHC.Driver.LlvmConfigCache (readLlvmConfigCache)
 import GHC.CmmToLlvm.Config (LlvmTarget (..), LlvmConfig (..))
+import GHC.CmmToLlvm.Version.Type (LlvmVersion (..))
 import {-# SOURCE #-} GHC.Driver.Pipeline (compileForeign, compileEmptyStub)
 import GHC.Settings
 import System.IO
@@ -229,8 +231,9 @@ runLlvmLlcPhase pipe_env hsc_env input_fn = do
           1 -> "-O1"
           _ -> "-O2"
 
-        defaultOptions = map GHC.SysTools.Option . concatMap words . snd
-                         $ unzip (llvmOptions llvm_config dflags)
+    llvm_version <- figureLlvmVersion logger dflags
+    let defaultOptions = map GHC.SysTools.Option . concatMap words . snd
+                         $ unzip (llvmOptions llvm_config llvm_version dflags)
         optFlag = if null (getOpts dflags opt_lc)
                   then map GHC.SysTools.Option $ words llvmOpts
                   else []
@@ -265,8 +268,9 @@ runLlvmOptPhase pipe_env hsc_env input_fn = do
                     Nothing -> panic ("runPhase LlvmOpt: llvm-passes file "
                                       ++ "is missing passes for level "
                                       ++ show optIdx)
-        defaultOptions = map GHC.SysTools.Option . concat . fmap words . fst
-                         $ unzip (llvmOptions llvm_config dflags)
+    llvm_version <- figureLlvmVersion logger dflags
+    let defaultOptions = map GHC.SysTools.Option . concat . fmap words . fst
+                         $ unzip (llvmOptions llvm_config llvm_version dflags)
 
         -- don't specify anything if user has specified commands. We do this
         -- for opt but not llc since opt is very specifically for optimisation
@@ -964,9 +968,10 @@ getOutputFilename logger tmpfs stop_phase output basename dflags next_phase mayb
 -- | 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 :: LlvmConfig
+            -> Maybe LlvmVersion
             -> DynFlags
             -> [(String, String)]  -- ^ pairs of (opt, llc) arguments
-llvmOptions llvm_config dflags =
+llvmOptions llvm_config llvm_version dflags =
        [("-relocation-model=" ++ rmodel
         ,"-relocation-model=" ++ rmodel) | not (null rmodel)]
 
@@ -1006,6 +1011,10 @@ llvmOptions llvm_config dflags =
               ++ ["+sse2"    | isSse2Enabled platform   ]
               ++ ["+sse"     | isSseEnabled platform    ]
               ++ ["+avx512f" | isAvx512fEnabled dflags  ]
+              ++ ["+evex512" | isAvx512fEnabled dflags
+                             , maybe False (>= LlvmVersion (18 NE.:| [])) llvm_version ]
+                   -- +evex512 is recognized by LLVM 18 or newer and needed on macOS (#26410).
+                   -- It may become deprecated in a future LLVM version, though.
               ++ ["+avx2"    | isAvx2Enabled dflags     ]
               ++ ["+avx"     | isAvxEnabled dflags      ]
               ++ ["+avx512cd"| isAvx512cdEnabled dflags ]


=====================================
testsuite/tests/simd/should_run/T26410_ffi.hs
=====================================
@@ -0,0 +1,40 @@
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE UnboxedTuples #-}
+{-# LANGUAGE UnliftedFFITypes #-}
+import GHC.Exts
+import GHC.Int
+
+foreign import ccall unsafe "minInt64X8"
+  minInt64X8# :: Int64X8# -> Int64X8# -> Int64X8#
+
+data Int64X8 = Int64X8# Int64X8#
+
+minInt64X8 :: Int64X8 -> Int64X8 -> Int64X8
+minInt64X8 (Int64X8# a) (Int64X8# b) = Int64X8# (minInt64X8# a b)
+{-# NOINLINE minInt64X8 #-}
+
+broadcastInt64X8 :: Int64 -> Int64X8
+broadcastInt64X8 (I64# x) = Int64X8# (broadcastInt64X8# x)
+
+packInt64X8 :: (Int64, Int64, Int64, Int64, Int64, Int64, Int64, Int64) -> Int64X8
+packInt64X8 (I64# x0, I64# x1, I64# x2, I64# x3, I64# x4, I64# x5, I64# x6, I64# x7) = Int64X8# (packInt64X8# (# x0, x1, x2, x3, x4, x5, x6, x7 #))
+
+unpackInt64X8 :: Int64X8 -> (Int64, Int64, Int64, Int64, Int64, Int64, Int64, Int64)
+unpackInt64X8 (Int64X8# a) = case unpackInt64X8# a of
+  (# x0, x1, x2, x3, x4, x5, x6, x7 #) -> (I64# x0, I64# x1, I64# x2, I64# x3, I64# x4, I64# x5, I64# x6, I64# x7)
+
+-- You can check the assembly code for this function to see if ZMM registers are used
+plusInt64X8 :: Int64X8 -> Int64X8 -> Int64X8
+plusInt64X8 (Int64X8# a) (Int64X8# b) = Int64X8# (plusInt64X8# a b)
+
+main :: IO ()
+main = do
+  let a = broadcastInt64X8 3
+      b = packInt64X8 (1, 2, 3, 4, 5, 6, 7, 8)
+      c = minInt64X8 a b
+  print $ unpackInt64X8 c
+  let d = packInt64X8 (-1, -2, -3, -4, -5, -6, -7, -8)
+      e = broadcastInt64X8 (-3)
+      f = minInt64X8 d e
+  print $ unpackInt64X8 f
+  print $ unpackInt64X8 (plusInt64X8 a b)


=====================================
testsuite/tests/simd/should_run/T26410_ffi.stdout
=====================================
@@ -0,0 +1,3 @@
+(1,2,3,3,3,3,3,3)
+(-3,-3,-3,-4,-5,-6,-7,-8)
+(4,5,6,7,8,9,10,11)


=====================================
testsuite/tests/simd/should_run/T26410_ffi_c.c
=====================================
@@ -0,0 +1,6 @@
+#include <x86intrin.h>
+
+__m512i minInt64X8(__m512i a, __m512i b)
+{
+    return _mm512_min_epi64(a, b);
+}


=====================================
testsuite/tests/simd/should_run/T26410_prim.hs
=====================================
@@ -0,0 +1,38 @@
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE UnboxedTuples #-}
+{-# LANGUAGE UnliftedFFITypes #-}
+import GHC.Exts
+import GHC.Int
+import GHC.Prim (minInt64X8#)
+
+data Int64X8 = Int64X8# Int64X8#
+
+minInt64X8 :: Int64X8 -> Int64X8 -> Int64X8
+minInt64X8 (Int64X8# a) (Int64X8# b) = Int64X8# (minInt64X8# a b)
+{-# NOINLINE minInt64X8 #-}
+
+broadcastInt64X8 :: Int64 -> Int64X8
+broadcastInt64X8 (I64# x) = Int64X8# (broadcastInt64X8# x)
+
+packInt64X8 :: (Int64, Int64, Int64, Int64, Int64, Int64, Int64, Int64) -> Int64X8
+packInt64X8 (I64# x0, I64# x1, I64# x2, I64# x3, I64# x4, I64# x5, I64# x6, I64# x7) = Int64X8# (packInt64X8# (# x0, x1, x2, x3, x4, x5, x6, x7 #))
+
+unpackInt64X8 :: Int64X8 -> (Int64, Int64, Int64, Int64, Int64, Int64, Int64, Int64)
+unpackInt64X8 (Int64X8# a) = case unpackInt64X8# a of
+  (# x0, x1, x2, x3, x4, x5, x6, x7 #) -> (I64# x0, I64# x1, I64# x2, I64# x3, I64# x4, I64# x5, I64# x6, I64# x7)
+
+-- You can check the assembly code for this function to see if ZMM registers are used
+plusInt64X8 :: Int64X8 -> Int64X8 -> Int64X8
+plusInt64X8 (Int64X8# a) (Int64X8# b) = Int64X8# (plusInt64X8# a b)
+
+main :: IO ()
+main = do
+  let a = broadcastInt64X8 3
+      b = packInt64X8 (1, 2, 3, 4, 5, 6, 7, 8)
+      c = minInt64X8 a b
+  print $ unpackInt64X8 c
+  let d = packInt64X8 (-1, -2, -3, -4, -5, -6, -7, -8)
+      e = broadcastInt64X8 (-3)
+      f = minInt64X8 d e
+  print $ unpackInt64X8 f
+  print $ unpackInt64X8 (plusInt64X8 a b)


=====================================
testsuite/tests/simd/should_run/T26410_prim.stdout
=====================================
@@ -0,0 +1,3 @@
+(1,2,3,3,3,3,3,3)
+(-3,-3,-3,-4,-5,-6,-7,-8)
+(4,5,6,7,8,9,10,11)


=====================================
testsuite/tests/simd/should_run/all.T
=====================================
@@ -164,3 +164,19 @@ test('T25062_V64'
 test('T25169', [], compile_and_run, [''])
 test('T25455', [], compile_and_run, [''])
 test('T25486', [], compile_and_run, [''])
+
+test('T26410_ffi'
+    , [ only_ways(llvm_ways) # SIMD NCG TODO: support 512-bit wide vectors
+      , unless(arch('x86_64') and have_cpu_feature('avx512f'), skip)
+      , extra_hc_opts('-mavx512f -optc -mavx512f -optlc -mcpu=penryn')
+      ]
+    , compile_and_run if have_cpu_feature('avx512f') else compile
+    , ['T26410_ffi_c.c'])
+
+test('T26410_prim'
+    , [ only_ways(llvm_ways) # SIMD NCG TODO: support 512-bit wide vectors
+      , unless(arch('x86_64') and have_cpu_feature('avx512f'), skip)
+      , extra_hc_opts('-mavx512f -optlc -mcpu=penryn')
+      ]
+    , compile_and_run if have_cpu_feature('avx512f') else compile
+    , [''])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b22777d4b7182f40a31eb430fa27f5fb...

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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b22777d4b7182f40a31eb430fa27f5fb...
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