Wrong fun type in dumped Cmm
Summary
main:Main.argGenBigFun{v r3Pu}_entry() { // [R6, R5, R4, R3, R2]
{ info_tbls: [(ca7I,
label: main:Main.argGenBigFun{v r3Pu}_info
rep: HeapRep static {
Fun {arity: 59
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, False]} }
srt: Just base:GHC.Num.$fNumWord{v r1Nm}_closure)]
stack_info: arg_space: 440
}
This is an excerpt from dumped Cmm (-ddump-cmm
). What's wrong? There's no such thing as a fun_type: ArgGen
with more parameters than would fit into a small bitmap. It should be fun_type: ArgGenBig
to indicate that a large bitmap is used.
Steps to reproduce
The Cmm belongs to this function:
-- | 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 ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
Word ->
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
Compile it with -ddump-to-file -ddump-cmm -dppr-debug
.
Expected behavior
The correct fun type should be shown.
I guess that this Outputable ArgDescr
instance is to blame: https://gitlab.haskell.org/ghc/ghc/-/blob/496607fdb77baf12e2fe263104ba5d0d700eee3b/compiler/GHC/Runtime/Heap/Layout.hs#L228
Environment
- GHC version used: Close to
master