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|
module CmmBrokenBlock (
BrokenBlock(..),
BlockEntryInfo(..),
FinalStmt(..),
breakBlock,
cmmBlockFromBrokenBlock,
blocksToBlockEnv,
) where
#include "HsVersions.h"
import Cmm
import CLabel
import Maybes
import Panic
import Unique
import UniqFM
-----------------------------------------------------------------------------
-- Data structures
-----------------------------------------------------------------------------
-- |Similar to a 'CmmBlock' with a little extra information
-- to help the CPS analysis.
data BrokenBlock
= BrokenBlock {
brokenBlockId :: BlockId, -- ^ The block's label like a 'CmmBasicBlock'
brokenBlockEntry :: BlockEntryInfo,
-- ^ Ways this block can be entered
brokenBlockStmts :: [CmmStmt],
-- ^ Body like a CmmBasicBlock
-- (but without the last statement)
brokenBlockTargets :: [BlockId],
-- ^ Blocks that this block could
-- branch to one either by conditional
-- branches or via the last statement
brokenBlockExit :: FinalStmt
-- ^ The final statement of the block
}
-- | How a block could be entered
data BlockEntryInfo
= FunctionEntry -- ^ Block is the beginning of a function
CLabel -- ^ The function name
CmmFormals -- ^ Aguments to function
| ContinuationEntry -- ^ Return point of a function call
CmmFormals -- ^ return values (argument to continuation)
| ControlEntry -- ^ Any other kind of block.
-- Only entered due to control flow.
-- TODO: Consider adding ProcPointEntry
-- no return values, but some live might end up as
-- params or possibly in the frame
-- | Final statement in a 'BlokenBlock'.
-- Constructors and arguments match those in 'Cmm',
-- but are restricted to branches, returns, jumps, calls and switches
data FinalStmt
= FinalBranch -- ^ Same as 'CmmBranch'
BlockId -- ^ Target must be a ControlEntry
| FinalReturn -- ^ Same as 'CmmReturn'
CmmActuals -- ^ Return values
| FinalJump -- ^ Same as 'CmmJump'
CmmExpr -- ^ The function to call
CmmActuals -- ^ Arguments of the call
| FinalCall -- ^ Same as 'CmmForeignCall'
-- followed by 'CmmGoto'
BlockId -- ^ Target of the 'CmmGoto'
-- (must be a 'ContinuationEntry')
CmmCallTarget -- ^ The function to call
CmmFormals -- ^ Results from call
-- (redundant with ContinuationEntry)
CmmActuals -- ^ Arguments to call
(Maybe [GlobalReg]) -- ^ registers that must be saved (TODO)
| FinalSwitch -- ^ Same as a 'CmmSwitch'
CmmExpr -- ^ Scrutinee (zero based)
[Maybe BlockId] -- ^ Targets
-----------------------------------------------------------------------------
-- Operations for broken blocks
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- | Takes a 'CmmBasicBlock' and breaks it up into a list of 'BrokenBlock'
-- by splitting on each 'CmmCall' in the 'CmmBasicBlock'.
breakBlock ::
[Unique] -- ^ An infinite list of uniques
-- to create names of the new blocks with
-> CmmBasicBlock -- ^ Input block to break apart
-> BlockEntryInfo -- ^ Info for the first created 'BrokenBlock'
-> [BrokenBlock]
breakBlock uniques (BasicBlock ident stmts) entry =
breakBlock' uniques ident entry [] [] stmts
where
breakBlock' uniques current_id entry exits accum_stmts stmts =
case stmts of
[] -> panic "block doesn't end in jump, goto, return or switch"
[CmmJump target arguments] ->
[BrokenBlock current_id entry accum_stmts
exits
(FinalJump target arguments)]
[CmmReturn arguments] ->
[BrokenBlock current_id entry accum_stmts
exits
(FinalReturn arguments)]
[CmmBranch target] ->
[BrokenBlock current_id entry accum_stmts
(target:exits)
(FinalBranch target)]
[CmmSwitch expr targets] ->
[BrokenBlock current_id entry accum_stmts
(mapMaybe id targets ++ exits)
(FinalSwitch expr targets)]
(CmmJump _ _:_) -> panic "jump in middle of block"
(CmmReturn _:_) -> panic "return in middle of block"
(CmmBranch _:_) -> panic "branch in middle of block"
(CmmSwitch _ _:_) -> panic "switch in middle of block"
-- Detect this special case to remain an inverse of
-- 'cmmBlockFromBrokenBlock'
[CmmCall target results arguments saves,
CmmBranch next_id] -> [block]
where
block = do_call current_id entry accum_stmts exits next_id
target results arguments saves
(CmmCall target results arguments saves:stmts) -> block : rest
where
next_id = BlockId $ head uniques
block = do_call current_id entry accum_stmts exits next_id
target results arguments saves
rest = breakBlock' (tail uniques) next_id
(ContinuationEntry results) [] [] stmts
(s:stmts) ->
breakBlock' uniques current_id entry
(cond_branch_target s++exits)
(accum_stmts++[s])
stmts
do_call current_id entry accum_stmts exits next_id
target results arguments saves =
BrokenBlock current_id entry accum_stmts (next_id:exits)
(FinalCall next_id target results arguments saves)
cond_branch_target (CmmCondBranch _ target) = [target]
cond_branch_target _ = []
-----------------------------------------------------------------------------
-- | Convert from a BrokenBlock back to an equivalent CmmBasicBlock
-- Needed by liveness analysis
cmmBlockFromBrokenBlock :: BrokenBlock -> CmmBasicBlock
cmmBlockFromBrokenBlock (BrokenBlock ident _ stmts _ exit) =
BasicBlock ident (stmts++exit_stmt)
where
exit_stmt =
case exit of
FinalBranch target -> [CmmBranch target]
FinalReturn arguments -> [CmmReturn arguments]
FinalJump target arguments -> [CmmJump target arguments]
FinalSwitch expr targets -> [CmmSwitch expr targets]
FinalCall branch_target call_target results arguments saves ->
[CmmCall call_target results arguments saves,
CmmBranch branch_target]
-----------------------------------------------------------------------------
-- | Build a mapping so we can lookup a 'BrokenBlock' by its 'BlockId'
blocksToBlockEnv :: [BrokenBlock] -> BlockEnv BrokenBlock
blocksToBlockEnv blocks = listToUFM $ map (\b -> (brokenBlockId b, b)) blocks
|
