-- CmmNode type for representation using Hoopl graphs.
{-# LANGUAGE GADTs #-}
+
+{-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
+#if __GLASGOW_HASKELL__ >= 701
+-- GHC 7.0.1 improved incomplete pattern warnings with GADTs
+{-# OPTIONS_GHC -fwarn-incomplete-patterns #-}
+#endif
+
module CmmNode
( CmmNode(..)
, UpdFrameOffset, Convention(..), ForeignConvention(..), ForeignTarget(..)
- , mapExp, mapExpDeep, foldExp, foldExpDeep
+ , mapExp, mapExpDeep, wrapRecExp, foldExp, foldExpDeep, wrapRecExpf
)
where
data CmmNode e x where
CmmEntry :: Label -> CmmNode C O
+
CmmComment :: FastString -> CmmNode O O
+
CmmAssign :: CmmReg -> CmmExpr -> CmmNode O O -- Assign to register
+
CmmStore :: CmmExpr -> CmmExpr -> CmmNode O O -- Assign to memory location. Size is
-- given by cmmExprType of the rhs.
+
CmmUnsafeForeignCall :: -- An unsafe foreign call; see Note [Foreign calls]
+ -- Like a "fat machine instruction"; can occur
+ -- in the middle of a block
ForeignTarget -> -- call target
CmmFormals -> -- zero or more results
CmmActuals -> -- zero or more arguments
CmmNode O O
+ -- Semantics: kills only result regs; all other regs (both GlobalReg
+ -- and LocalReg) are preserved. But there is a current
+ -- bug for what can be put in arguments, see
+ -- Note [Register Parameter Passing]
+
CmmBranch :: Label -> CmmNode O C -- Goto another block in the same procedure
+
CmmCondBranch :: { -- conditional branch
cml_pred :: CmmExpr,
cml_true, cml_false :: Label
} -> CmmNode O C
+
CmmSwitch :: CmmExpr -> [Maybe Label] -> CmmNode O C -- Table branch
-- The scrutinee is zero-based;
-- zero -> first block
-- one -> second block etc
-- Undefined outside range, and when there's a Nothing
- CmmCall :: { -- A call (native or safe foreign)
+
+ CmmCall :: { -- A native call or tail call
cml_target :: CmmExpr, -- never a CmmPrim to a CallishMachOp!
cml_cont :: Maybe Label,
-- Label of continuation (Nothing for return or tail call)
+-- ToDO: add this:
+-- cml_args_regs :: [GlobalReg],
+-- It says which GlobalRegs are live for the parameters at the
+-- moment of the call. Later stages can use this to give liveness
+-- everywhere, which in turn guides register allocation.
+-- It is the companion of cml_args; cml_args says which stack words
+-- hold parameters, while cml_arg_regs says which global regs hold parameters.
+-- But do note [Register parameter passing]
+
cml_args :: ByteOff,
-- Byte offset, from the *old* end of the Area associated with
-- the Label (if cml_cont = Nothing, then Old area), of
-- cml_ret_off are treated as live, even if the sequel of
-- the call goes into a loop.
} -> CmmNode O C
+
CmmForeignCall :: { -- A safe foreign call; see Note [Foreign calls]
+ -- Always the last node of a block
tgt :: ForeignTarget, -- call target and convention
res :: CmmFormals, -- zero or more results
- args :: CmmActuals, -- zero or more arguments
+ args :: CmmActuals, -- zero or more arguments; see Note [Register parameter passing]
succ :: Label, -- Label of continuation
updfr :: UpdFrameOffset, -- where the update frame is (for building infotable)
intrbl:: Bool -- whether or not the call is interruptible
{- Note [Foreign calls]
~~~~~~~~~~~~~~~~~~~~~~~
-A MidForeign call is used for *unsafe* foreign calls;
-a LastForeign call is used for *safe* foreign calls.
-Unsafe ones are easy: think of them as a "fat machine instruction".
+A CmmUnsafeForeignCall is used for *unsafe* foreign calls;
+a CmmForeignCall call is used for *safe* foreign calls.
+
+Unsafe ones are mostly easy: think of them as a "fat machine
+instruction". In particular, they do *not* kill all live registers,
+just the registers they return to (there was a bit of code in GHC that
+conservatively assumed otherwise.) However, see [Register parameter passing].
Safe ones are trickier. A safe foreign call
r = f(x)
Note that a safe foreign call needs an info table.
-}
+{- Note [Register parameter passing]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+On certain architectures, some registers are utilized for parameter
+passing in the C calling convention. For example, in x86-64 Linux
+convention, rdi, rsi, rdx and rcx (as well as r8 and r9) may be used for
+argument passing. These are registers R3-R6, which our generated
+code may also be using; as a result, it's necessary to save these
+values before doing a foreign call. This is done during initial
+code generation in callerSaveVolatileRegs in StgCmmUtils.hs. However,
+one result of doing this is that the contents of these registers
+may mysteriously change if referenced inside the arguments. This
+is dangerous, so you'll need to disable inlining much in the same
+way is done in cmm/CmmOpt.hs currently. We should fix this!
+-}
+
---------------------------------------------
-- Eq instance of CmmNode
-- It is a shame GHC cannot infer it by itself :(
instance NonLocal CmmNode where
entryLabel (CmmEntry l) = l
- -- entryLabel _ = error "CmmNode.entryLabel"
successors (CmmBranch l) = [l]
successors (CmmCondBranch {cml_true=t, cml_false=f}) = [f, t] -- meets layout constraint
successors (CmmSwitch _ ls) = catMaybes ls
successors (CmmCall {cml_cont=l}) = maybeToList l
successors (CmmForeignCall {succ=l}) = [l]
- -- successors _ = error "CmmNode.successors"
instance HooplNode CmmNode where
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