diff options
Diffstat (limited to 'compiler/cmm/CmmPipeline.hs')
| -rw-r--r-- | compiler/cmm/CmmPipeline.hs | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/compiler/cmm/CmmPipeline.hs b/compiler/cmm/CmmPipeline.hs index 70ff754166..4e9a90a153 100644 --- a/compiler/cmm/CmmPipeline.hs +++ b/compiler/cmm/CmmPipeline.hs @@ -134,6 +134,8 @@ cpsTop hsc_env proc = return $ if optLevel dflags >= 1 then map (cmmCfgOptsProc splitting_proc_points) gs else gs + gs <- return (map removeUnreachableBlocksProc gs) + -- Note [unreachable blocks] dumps Opt_D_dump_cmmz_cfg "Post control-flow optimsations" gs return (cafEnv, gs) @@ -152,6 +154,8 @@ cpsTop hsc_env proc = return $ if optLevel dflags >= 1 then cmmCfgOptsProc splitting_proc_points g else g + g <- return (removeUnreachableBlocksProc g) + -- Note [unreachable blocks] dump' Opt_D_dump_cmmz_cfg "Post control-flow optimsations" g return (cafEnv, [g]) @@ -212,7 +216,15 @@ _GLOBAL_OFFSET_TABLE_, regardless of which entry point we arrived via. -} +{- Note [unreachable blocks] +The control-flow optimiser sometimes leaves unreachable blocks behind +containing junk code. If these blocks make it into the native code +generator then they trigger a register allocator panic because they +refer to undefined LocalRegs, so we must eliminate any unreachable +blocks before passing the code onwards. + +-} runUniqSM :: UniqSM a -> IO a runUniqSM m = do |