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| author | Ben Gamari <ben@smart-cactus.org> | 2023-01-22 08:11:02 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2023-01-30 05:06:26 -0500 |
| commit | 8bed166bb79445f90015757fd5baac69a7b835df (patch) | |
| tree | e0d23918d6ace41e69bc60bd7c65b953cef0138b /compiler/GHC | |
| parent | 78c07219d5dad9730bbe3ec26ad22912ff22f058 (diff) | |
| download | haskell-8bed166bb79445f90015757fd5baac69a7b835df.tar.gz | |
nativeGen: Disable asm-shortcutting on Darwin
Asm-shortcutting may produce relative references to symbols defined in
other compilation units. This is not something that MachO relocations
support (see #21972). For this reason we disable the optimisation on
Darwin. We do so without a warning since this flag is enabled by `-O2`.
Another way to address this issue would be to rather implement a
PLT-relocatable jump-table strategy. However, this would only benefit
Darwin and does not seem worth the effort.
Closes #21972.
Diffstat (limited to 'compiler/GHC')
| -rw-r--r-- | compiler/GHC/CmmToAsm.hs | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/compiler/GHC/CmmToAsm.hs b/compiler/GHC/CmmToAsm.hs index c0ac96fa79..94bdaa648b 100644 --- a/compiler/GHC/CmmToAsm.hs +++ b/compiler/GHC/CmmToAsm.hs @@ -812,6 +812,19 @@ generateJumpTables ncgImpl xs = concatMap f xs -- ----------------------------------------------------------------------------- -- Shortcut branches +-- Note [No asm-shortcutting on Darwin] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-- Asm-shortcutting may produce relative references to symbols defined in +-- other compilation units. This is not something that MachO relocations +-- support (see #21972). For this reason we disable the optimisation on Darwin. +-- We do so in the backend without a warning since this flag is enabled by +-- `-O2`. +-- +-- Another way to address this issue would be to rather implement a +-- PLT-relocatable jump-table strategy. However, this would only benefit Darwin +-- and does not seem worth the effort as this optimisation generally doesn't +-- offer terribly great benefits. + shortcutBranches :: forall statics instr jumpDest. (Outputable jumpDest) => NCGConfig @@ -822,6 +835,8 @@ shortcutBranches shortcutBranches config ncgImpl tops weights | ncgEnableShortcutting config + -- See Note [No asm-shortcutting on Darwin] + , not $ osMachOTarget $ platformOS $ ncgPlatform config = ( map (apply_mapping ncgImpl mapping) tops' , shortcutWeightMap mappingBid <$!> weights ) | otherwise |