-----------------------------------------------------------------------------
module CmmOpt (
+ cmmEliminateDeadBlocks,
cmmMiniInline,
cmmMachOpFold,
cmmLoopifyForC,
#include "HsVersions.h"
-import Cmm
-import CmmExpr
+import OldCmm
import CmmUtils
import CLabel
import StaticFlags
import Unique
import FastTypes
import Outputable
+import BlockId
import Data.Bits
import Data.Word
import Data.Int
+import Data.Maybe
+import Data.List
+
+import Compiler.Hoopl hiding (Unique)
+
+-- -----------------------------------------------------------------------------
+-- Eliminates dead blocks
+
+{-
+We repeatedly expand the set of reachable blocks until we hit a
+fixpoint, and then prune any blocks that were not in this set. This is
+actually a required optimization, as dead blocks can cause problems
+for invariants in the linear register allocator (and possibly other
+places.)
+-}
+
+-- Deep fold over statements could probably be abstracted out, but it
+-- might not be worth the effort since OldCmm is moribund
+cmmEliminateDeadBlocks :: [CmmBasicBlock] -> [CmmBasicBlock]
+cmmEliminateDeadBlocks [] = []
+cmmEliminateDeadBlocks blocks@(BasicBlock base_id _:_) =
+ let -- Calculate what's reachable from what block
+ reachableMap = foldl' f emptyUFM blocks -- lazy in values
+ where f m (BasicBlock block_id stmts) = addToUFM m block_id (reachableFrom stmts)
+ reachableFrom stmts = foldl stmt [] stmts
+ where
+ stmt m CmmNop = m
+ stmt m (CmmComment _) = m
+ stmt m (CmmAssign _ e) = expr m e
+ stmt m (CmmStore e1 e2) = expr (expr m e1) e2
+ stmt m (CmmCall c _ as _ _) = f (actuals m as) c
+ where f m (CmmCallee e _) = expr m e
+ f m (CmmPrim _) = m
+ stmt m (CmmBranch b) = b:m
+ stmt m (CmmCondBranch e b) = b:(expr m e)
+ stmt m (CmmSwitch e bs) = catMaybes bs ++ expr m e
+ stmt m (CmmJump e as) = expr (actuals m as) e
+ stmt m (CmmReturn as) = actuals m as
+ actuals m as = foldl' (\m h -> expr m (hintlessCmm h)) m as
+ -- We have to do a deep fold into CmmExpr because
+ -- there may be a BlockId in the CmmBlock literal.
+ expr m (CmmLit l) = lit m l
+ expr m (CmmLoad e _) = expr m e
+ expr m (CmmReg _) = m
+ expr m (CmmMachOp _ es) = foldl' expr m es
+ expr m (CmmStackSlot _ _) = m
+ expr m (CmmRegOff _ _) = m
+ lit m (CmmBlock b) = b:m
+ lit m _ = m
+ -- go todo done
+ reachable = go [base_id] (setEmpty :: BlockSet)
+ where go [] m = m
+ go (x:xs) m
+ | setMember x m = go xs m
+ | otherwise = go (add ++ xs) (setInsert x m)
+ where add = fromMaybe (panic "cmmEliminateDeadBlocks: unknown block")
+ (lookupUFM reachableMap x)
+ in filter (\(BasicBlock block_id _) -> setMember block_id reachable) blocks
-- -----------------------------------------------------------------------------
-- The mini-inliner
{-
-This pass inlines assignments to temporaries that are used just
-once. It works as follows:
+This pass inlines assignments to temporaries. Temporaries that are
+only used once are unconditionally inlined. Temporaries that are used
+two or more times are only inlined if they are assigned a literal. It
+works as follows:
- count uses of each temporary
- - for each temporary that occurs just once:
+ - for each temporary:
- attempt to push it forward to the statement that uses it
- only push forward past assignments to other temporaries
(assumes that temporaries are single-assignment)
cmmMiniInlineStmts :: UniqFM Int -> [CmmStmt] -> [CmmStmt]
cmmMiniInlineStmts uses [] = []
cmmMiniInlineStmts uses (stmt@(CmmAssign (CmmLocal (LocalReg u _)) expr) : stmts)
- -- not used at all: just discard this assignment
+ -- not used: just discard this assignment
| Nothing <- lookupUFM uses u
= cmmMiniInlineStmts uses stmts
- -- used once: try to inline at the use site
+ -- used (literal): try to inline at all the use sites
+ | Just n <- lookupUFM uses u, isLit expr
+ =
+#ifdef NCG_DEBUG
+ trace ("nativeGen: inlining " ++ showSDoc (pprStmt stmt)) $
+#endif
+ case lookForInlineLit u expr stmts of
+ (m, stmts')
+ | n == m -> cmmMiniInlineStmts (delFromUFM uses u) stmts'
+ | otherwise ->
+ stmt : cmmMiniInlineStmts (adjustUFM (\x -> x - m) uses u) stmts'
+
+ -- used (foldable to literal): try to inline at all the use sites
+ | Just n <- lookupUFM uses u,
+ CmmMachOp op es <- expr,
+ e@(CmmLit _) <- cmmMachOpFold op es
+ =
+#ifdef NCG_DEBUG
+ trace ("nativeGen: inlining " ++ showSDoc (pprStmt stmt)) $
+#endif
+ case lookForInlineLit u e stmts of
+ (m, stmts')
+ | n == m -> cmmMiniInlineStmts (delFromUFM uses u) stmts'
+ | otherwise ->
+ stmt : cmmMiniInlineStmts (adjustUFM (\x -> x - m) uses u) stmts'
+
+ -- used once (non-literal): try to inline at the use site
| Just 1 <- lookupUFM uses u,
Just stmts' <- lookForInline u expr stmts
=
cmmMiniInlineStmts uses (stmt:stmts)
= stmt : cmmMiniInlineStmts uses stmts
-lookForInline u expr (stmt : rest)
+-- | Takes a register, a 'CmmLit' expression assigned to that
+-- register, and a list of statements. Inlines the expression at all
+-- use sites of the register. Returns the number of substituations
+-- made and the, possibly modified, list of statements.
+lookForInlineLit :: Unique -> CmmExpr -> [CmmStmt] -> (Int, [CmmStmt])
+lookForInlineLit _ _ [] = (0, [])
+lookForInlineLit u expr stmts@(stmt : rest)
+ | Just n <- lookupUFM (countUses stmt) u
+ = case lookForInlineLit u expr rest of
+ (m, stmts) -> let z = n + m
+ in z `seq` (z, inlineStmt u expr stmt : stmts)
+
+ | ok_to_skip
+ = case lookForInlineLit u expr rest of
+ (n, stmts) -> (n, stmt : stmts)
+
+ | otherwise
+ = (0, stmts)
+ where
+ -- We skip over assignments to registers, unless the register
+ -- being assigned to is the one we're inlining.
+ ok_to_skip = case stmt of
+ CmmAssign (CmmLocal r@(LocalReg u' _)) _ | u' == u -> False
+ _other -> True
+
+lookForInline u expr stmts = lookForInline' u expr regset stmts
+ where regset = foldRegsUsed extendRegSet emptyRegSet expr
+
+lookForInline' u expr regset (stmt : rest)
| Just 1 <- lookupUFM (countUses stmt) u, ok_to_inline
= Just (inlineStmt u expr stmt : rest)
| ok_to_skip
- = case lookForInline u expr rest of
+ = case lookForInline' u expr regset rest of
Nothing -> Nothing
Just stmts -> Just (stmt:stmts)
CmmCall{} -> hasNoGlobalRegs expr
_ -> True
- -- We can skip over assignments to other tempoararies, because we
- -- know that expressions aren't side-effecting and temporaries are
- -- single-assignment.
+ -- Expressions aren't side-effecting. Temporaries may or may not
+ -- be single-assignment depending on the source (the old code
+ -- generator creates single-assignment code, but hand-written Cmm
+ -- and Cmm from the new code generator is not single-assignment.)
+ -- So we do an extra check to make sure that the register being
+ -- changed is not one we were relying on. I don't know how much of a
+ -- performance hit this is (we have to create a regset for every
+ -- instruction.) -- EZY
ok_to_skip = case stmt of
CmmNop -> True
- CmmAssign (CmmLocal (LocalReg u' _)) rhs | u' /= u -> True
+ CmmComment{} -> True
+ CmmAssign (CmmLocal r@(LocalReg u' _)) rhs | u' /= u && not (r `elemRegSet` regset) -> True
CmmAssign g@(CmmGlobal _) rhs -> not (g `regUsedIn` expr)
_other -> False
inlineStmt u a (CmmStore e1 e2) = CmmStore (inlineExpr u a e1) (inlineExpr u a e2)
inlineStmt u a (CmmCall target regs es srt ret)
= CmmCall (infn target) regs es' srt ret
- where infn (CmmCallee fn cconv) = CmmCallee fn cconv
+ where infn (CmmCallee fn cconv) = CmmCallee (inlineExpr u a fn) cconv
infn (CmmPrim p) = CmmPrim p
es' = [ (CmmHinted (inlineExpr u a e) hint) | (CmmHinted e hint) <- es ]
inlineStmt u a (CmmCondBranch e d) = CmmCondBranch (inlineExpr u a e) d
MO_Add r -> CmmLit (CmmInt (x + y) r)
MO_Sub r -> CmmLit (CmmInt (x - y) r)
MO_Mul r -> CmmLit (CmmInt (x * y) r)
+ MO_U_Quot r | y /= 0 -> CmmLit (CmmInt (x_u `quot` y_u) r)
+ MO_U_Rem r | y /= 0 -> CmmLit (CmmInt (x_u `rem` y_u) r)
MO_S_Quot r | y /= 0 -> CmmLit (CmmInt (x `quot` y) r)
MO_S_Rem r | y /= 0 -> CmmLit (CmmInt (x `rem` y) r)
-- PicBaseReg from the corresponding label (or label difference).
--
cmmMachOpFold mop1 [CmmMachOp mop2 [arg1,arg2], arg3]
- | mop1 == mop2 && isAssociativeMachOp mop1
+ | mop2 `associates_with` mop1
&& not (isLit arg1) && not (isPicReg arg1)
- = cmmMachOpFold mop1 [arg1, cmmMachOpFold mop2 [arg2,arg3]]
+ = cmmMachOpFold mop2 [arg1, cmmMachOpFold mop1 [arg2,arg3]]
+ where
+ MO_Add{} `associates_with` MO_Sub{} = True
+ mop1 `associates_with` mop2 =
+ mop1 == mop2 && isAssociativeMachOp mop1
+
+-- special case: (a - b) + c ==> a + (c - b)
+cmmMachOpFold mop1@(MO_Add{}) [CmmMachOp mop2@(MO_Sub{}) [arg1,arg2], arg3]
+ | not (isLit arg1) && not (isPicReg arg1)
+ = cmmMachOpFold mop1 [arg1, cmmMachOpFold mop2 [arg3,arg2]]
-- Make a RegOff if we can
cmmMachOpFold (MO_Add _) [CmmReg reg, CmmLit (CmmInt n rep)]
= case mop of
MO_Mul rep
| Just p <- exactLog2 n ->
- CmmMachOp (MO_Shl rep) [x, CmmLit (CmmInt p rep)]
+ cmmMachOpFold (MO_Shl rep) [x, CmmLit (CmmInt p rep)]
+ MO_U_Quot rep
+ | Just p <- exactLog2 n ->
+ cmmMachOpFold (MO_U_Shr rep) [x, CmmLit (CmmInt p rep)]
MO_S_Quot rep
| Just p <- exactLog2 n,
CmmReg _ <- x -> -- We duplicate x below, hence require
-- it is a reg. FIXME: remove this restriction.
-- shift right is not the same as quot, because it rounds
- -- to minus infinity, whereasq uot rounds toward zero.
+ -- to minus infinity, whereasq quot rounds toward zero.
-- To fix this up, we add one less than the divisor to the
-- dividend if it is a negative number.
--
CmmMachOp (MO_And rep) [x1, CmmLit (CmmInt (n-1) rep)]
x3 = CmmMachOp (MO_Add rep) [x, x2]
in
- CmmMachOp (MO_S_Shr rep) [x3, CmmLit (CmmInt p rep)]
+ cmmMachOpFold (MO_S_Shr rep) [x3, CmmLit (CmmInt p rep)]
other
-> unchanged
where
-}
cmmLoopifyForC :: RawCmmTop -> RawCmmTop
-cmmLoopifyForC p@(CmmProc info entry_lbl []
+cmmLoopifyForC p@(CmmProc info entry_lbl
(ListGraph blocks@(BasicBlock top_id _ : _)))
| null info = p -- only if there's an info table, ignore case alts
| otherwise =
-- pprTrace "jump_lbl" (ppr jump_lbl <+> ppr entry_lbl) $
- CmmProc info entry_lbl [] (ListGraph blocks')
+ CmmProc info entry_lbl (ListGraph blocks')
where blocks' = [ BasicBlock id (map do_stmt stmts)
| BasicBlock id stmts <- blocks ]
projects / ghc-hetmet.git / blobdiff