High-level Cmm code and stack allocation

[Carter Schonwald]

hey Herbert,
I generally start with looking at the primops.cmm file for examples
https://github.com/ghc/ghc/blob/master/rts/PrimOps.cmm#L572-L588

otoh, the comments in cmmparse.y indicate that's not quite "kosher"? or
maybe the comments are a lie?
https://github.com/ghc/ghc/blob/master/compiler/cmm/CmmParse.y#L24-L28


On Sat, Jan 4, 2014 at 6:26 PM, Herbert Valerio Riedel <hvr at gnu.org> wrote:

> Hello,
>
> According to Note [Syntax of .cmm files],
>
> | There are two ways to write .cmm code:
> |
> |  (1) High-level Cmm code delegates the stack handling to GHC, and
> |      never explicitly mentions Sp or registers.
> |
> |  (2) Low-level Cmm manages the stack itself, and must know about
> |      calling conventions.
> |
> | Whether you want high-level or low-level Cmm is indicated by the
> | presence of an argument list on a procedure.
>
> However, while working on integer-gmp I've been noticing in
> integer-gmp/cbits/gmp-wrappers.cmm that even though all Cmm procedures
> have been converted to high-level Cmm, they still reference the 'Sp'
> register, e.g.
>
>
>     #define GMP_TAKE1_RET1(name,mp_fun)       \
>     name (W_ ws1, P_ d1)                      \
>     {                                         \
>       W_ mp_tmp1;                             \
>       W_ mp_result1;                          \
>                                               \
>     again:                                    \
>       STK_CHK_GEN_N (2 * SIZEOF_MP_INT);      \
>       MAYBE_GC(again);                        \
>                                               \
>       mp_tmp1    = Sp - 1 * SIZEOF_MP_INT;    \
>       mp_result1 = Sp - 2 * SIZEOF_MP_INT;    \
>       ...                                     \
>
>
> So is this valid high-level Cmm code? What's the proper way to allocate
> Stack (and/or Heap) memory from high-level Cmm code?
>
> Cheers,
>   hvr
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