diff options
Diffstat (limited to 'compiler/GHC/CmmToAsm.hs')
| -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 |