diff --git a/compiler/cmm/Cmm.hs b/compiler/cmm/Cmm.hs index 383ed060e08b85b9cd48df7dc3e4700978374c2d..4b18e46cdf010196affb3d0a0c3d26fa924657f2 100644 --- a/compiler/cmm/Cmm.hs +++ b/compiler/cmm/Cmm.hs @@ -174,7 +174,9 @@ data ClosureTypeInfo | ThunkInfo ClosureLayout C_SRT | ThunkSelectorInfo SelectorOffset C_SRT | ContInfo - [Maybe LocalReg] -- stack layout + [Maybe LocalReg] -- Stack layout: Just x, an item x + -- Nothing: a 1-word gap + -- Start of list is the *young* end C_SRT data CmmReturnInfo = CmmMayReturn diff --git a/compiler/cmm/CmmExpr.hs b/compiler/cmm/CmmExpr.hs index d09be34b6a943ad261435ad786cfe5b67ac37c00..e1a78a707e3f026a0a34a861cbc346520c966a8c 100644 --- a/compiler/cmm/CmmExpr.hs +++ b/compiler/cmm/CmmExpr.hs @@ -95,10 +95,26 @@ data Area deriving (Eq, Ord) data AreaId - = Old -- entry parameters, jumps, and returns share one call area at old end of stack + = Old -- See Note [Old Area] | Young BlockId deriving (Eq, Ord) +{- Note [Old Area] +~~~~~~~~~~~~~~~~~~ +There is a single call area 'Old', allocated at the extreme old +end of the stack frame (ie just younger than the return address) +which holds: + * incoming (overflow) parameters, + * outgoing (overflow) parameter to tail calls, + * outgoing (overflow) result values + * the update frame (if any) + +Its size is the max of all these requirements. On entry, the stack +pointer will point to the youngest incoming parameter, which is not +necessarily at the young end of the Old area. + +End of note -} + type SubArea = (Area, Int, Int) -- area, offset, width type SubAreaSet = FiniteMap Area [SubArea] type AreaMap = FiniteMap Area Int diff --git a/compiler/cmm/ZipCfgCmmRep.hs b/compiler/cmm/ZipCfgCmmRep.hs index d5496a7ff862dc77683ec036614cf0c5bf9948ec..27191f38c9844b336893f3ae48278a1dacdafc1a 100644 --- a/compiler/cmm/ZipCfgCmmRep.hs +++ b/compiler/cmm/ZipCfgCmmRep.hs @@ -85,18 +85,31 @@ data Last -- one -> second block etc -- Undefined outside range, and when there's a Nothing | LastCall { -- A call (native or safe foreign) - cml_target :: CmmExpr, -- never a CmmPrim to a CallishMachOp! - cml_cont :: Maybe BlockId, + cml_target :: CmmExpr, -- never a CmmPrim to a CallishMachOp! + + cml_cont :: Maybe BlockId, -- BlockId of continuation (Nothing for return or tail call) - cml_args :: ByteOff, -- byte offset for youngest outgoing arg - -- (includes update frame, which must be younger) - cml_ret_args:: ByteOff, -- byte offset for youngest incoming arg - cml_ret_off :: Maybe UpdFrameOffset} - -- stack offset for return (update frames); + + cml_args :: ByteOff, + -- Byte offset, from the *old* end of the Area associated with + -- the BlockId (if cml_cont = Nothing, then Old area), of + -- youngest outgoing arg. Set the stack pointer to this before + -- transferring control. + -- (NB: an update frame might also have been stored in the Old + -- area, but it'll be in an older part than the args.) + + cml_ret_args :: ByteOff, + -- For calls *only*, the byte offset for youngest returned value + -- This is really needed at the *return* point rather than here + -- at the call, but in practice it's convenient to record it here. + + cml_ret_off :: Maybe UpdFrameOffset + -- Stack offset for return (update frames); -- The return offset should be Nothing only if we have to create -- a new call, e.g. for a procpoint, in which case it's an invariant -- that the call does not stand for a return or a tail call, -- and the successor does not need an info table. + } data MidCallTarget -- The target of a MidUnsafeCall = ForeignTarget -- A foreign procedure