-- in
return (Any rep code)
- {- Case2: shift length is complex (non-immediate) -}
+ {- Case2: shift length is complex (non-immediate)
+ * y must go in %ecx.
+ * we cannot do y first *and* put its result in %ecx, because
+ %ecx might be clobbered by x.
+ * if we do y second, then x cannot be
+ in a clobbered reg. Also, we cannot clobber x's reg
+ with the instruction itself.
+ * so we can either:
+ - do y first, put its result in a fresh tmp, then copy it to %ecx later
+ - do y second and put its result into %ecx. x gets placed in a fresh
+ tmp. This is likely to be better, becuase the reg alloc can
+ eliminate this reg->reg move here (it won't eliminate the other one,
+ because the move is into the fixed %ecx).
+ -}
shift_code rep instr x y{-amount-} = do
- (x_reg, x_code) <- getNonClobberedReg x
+ x_code <- getAnyReg x
+ tmp <- getNewRegNat rep
y_code <- getAnyReg y
let
- code = x_code `appOL`
+ code = x_code tmp `appOL`
y_code ecx `snocOL`
- instr (OpReg ecx) (OpReg x_reg)
+ instr (OpReg ecx) (OpReg tmp)
-- in
- return (Fixed rep x_reg code)
+ return (Fixed rep tmp code)
--------------------
add_code :: MachRep -> CmmExpr -> CmmExpr -> NatM Register
(arg_reg, arg_code) <- getSomeReg arg
delta <- getDeltaNat
setDeltaNat (delta-arg_size)
- let code' = code `appOL` toOL [
- MOV arg_rep (OpReg arg_reg) (OpAddr (spRel 0)),
+ let code' = code `appOL` arg_code `appOL` toOL [
SUB wordRep (OpImm (ImmInt arg_size)) (OpReg rsp) ,
- DELTA (delta-arg_size)]
+ DELTA (delta-arg_size),
+ MOV arg_rep (OpReg arg_reg) (OpAddr (spRel 0))]
push_args rest code'
| otherwise = do
-- -----------------------------------------------------------------------------
-- Coercing to/from integer/floating-point...
+-- When going to integer, we truncate (round towards 0).
+
-- @coerce(Int2FP|FP2Int)@ are more complicated integer/float
-- conversions. We have to store temporaries in memory to move
-- between the integer and the floating point register sets.
coerceFP2Int from to x = do
(x_op, x_code) <- getOperand x -- ToDo: could be a safe operand
let
- opc = case from of F32 -> CVTSS2SI; F64 -> CVTSD2SI
+ opc = case from of F32 -> CVTTSS2SIQ; F64 -> CVTTSD2SIQ
code dst = x_code `snocOL` opc x_op dst
-- in
return (Any to code) -- works even if the destination rep is <I32