Commit ce8ae482 authored by Simon Peyton Jones's avatar Simon Peyton Jones

Comments only

parent 246183c6
......@@ -30,31 +30,51 @@ import Prelude hiding (succ)
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
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
cml_args :: ByteOff,
-- Byte offset, from the *old* end of the Area associated with
-- the Label (if cml_cont = Nothing, then Old area), of
......@@ -78,7 +98,9 @@ data CmmNode e x where
-- 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
......@@ -89,8 +111,8 @@ data CmmNode e x where
{- Note [Foreign calls]
A MidForeign call is used for *unsafe* foreign calls;
a LastForeign call is used for *safe* foreign calls.
A CmmUnsafeForeignCall is used for *unsafe* foreign calls;
a CmmForeignCall call is used for *safe* foreign calls.
Unsafe ones are easy: think of them as a "fat machine instruction".
In particular, they do *not* kill all live registers (there was a bit
of code in GHC that conservatively assumed otherwise.)
More notes (May 11)
In CmmNode, consider spliting CmmCall into two: call and jump
Notes on new codegen (Aug 10)
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