Fix fun_type in Cmm dump (#22760)

Fixes #22760

I've introduced a new constructor ArgGenBig. An alternative would have been to e.g. add a flag to ArgGen, but these are separate things in the RTS, too, so a new constructor seems to be a more sensible decision. Though, this requires some duplication in pattern matches.

Test

IMHO creating a test for this would be more effort than it's worth. (We're talking about debug output here and currently there's no good way to test dumped Cmm in GHC.)

I did a manual test:

module Test where

{-# NOINLINE argGenFun #-}
argGenFun ::
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
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  Word ->
  Word
argGenFun a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 a11 a12 a13 a14 a15 a16 a17 a18 a19 a20 a21 a22 a23 a24 a25 a26 a27 a28 a29 a30 a31 a32 a33 a34 a35 a36 a37 a38 a39 a40 a41 a42 a43 a44 a45 a46 a47 a48 a49 a50 a51 a52 a53 a54 a55 a56 a57 a58 =
    a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10 + a11 + a12 + a13 + a14 + a15 + a16 + a17 + a18 + a19 + a20 + a21 + a22 + a23 + a24 + a25 + a26 + a27 + a28 + a29 + a30 + a31 + a32 + a33 + a34 + a35 + a36 + a37 + a38 + a39 + a40 + a41 + a42 + a43 + a44 + a45 + a46 + a47 + a48 + a49 + a50 + a51 + a52 + a53 + a54 + a55 + a56 + a57 + a58

-- | A function with 59 arguments
--
-- A small bitmap has @64 - 6 = 58@ entries on 64bit machines. On 32bit machines
-- it's less (for obvious reasons.) I.e. this function's bitmap a large one;
-- function type is @ARG_GEN_BIG@.
{-# NOINLINE argGenBigFun #-}
argGenBigFun ::
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
  Word ->
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  Word ->
  Word
argGenBigFun a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 a11 a12 a13 a14 a15 a16 a17 a18 a19 a20 a21 a22 a23 a24 a25 a26 a27 a28 a29 a30 a31 a32 a33 a34 a35 a36 a37 a38 a39 a40 a41 a42 a43 a44 a45 a46 a47 a48 a49 a50 a51 a52 a53 a54 a55 a56 a57 a58 a59 =
    a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10 + a11 + a12 + a13 + a14 + a15 + a16 + a17 + a18 + a19 + a20 + a21 + a22 + a23 + a24 + a25 + a26 + a27 + a28 + a29 + a30 + a31 + a32 + a33 + a34 + a35 + a36 + a37 + a38 + a39 + a40 + a41 + a42 + a43 + a44 + a45 + a46 + a47 + a48 + a49 + a50 + a51 + a52 + a53 + a54 + a55 + a56 + a57 + a58 + a59

compiled with

../_build/stage1/bin/ghc -ddump-cmm -ddump-to-file -no-hs-main Test.hs

leads to these entries:

...
 Test.argGenBigFun_entry() { //  [R6, R5, R4, R3, R2]
         { info_tbls: [(cYa,
                        label: Test.argGenBigFun_info
                        rep: HeapRep static {
                               Fun {arity: 59
                                    fun_type: ArgGenBig [False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False, False,
                                                         False, False, False, False, False]} }
                        srt: Just GHC.Num.$fNumWord_closure)]
           stack_info: arg_space: 440
         }
...
 Test.argGenFun_entry() { //  [R6, R5, R4, R3, R2]
         { info_tbls: [(c19i,
                        label: Test.argGenFun_info
                        rep: HeapRep static {
                               Fun {arity: 58
                                    fun_type: ArgGen [False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False, False, False,
                                                      False, False, False, False]} }
                        srt: Just GHC.Num.$fNumWord_closure)]
           stack_info: arg_space: 432
         }
...