-ddump-rules does not list all rules in effect

Hi,

the attached code has a function breakOn which calls "break (c==)" from Bytestring. That function has a rewrite rule, rewriting it to "breakChar c". I’d expect "ghc -ddump-rules" to tell me that this function was called, but that is not the case:

$ ghc -O -ddump-rules --make breakOn.hs 
[1 of 1] Compiling Main             ( breakOn.hs, breakOn.o )

==================== Transformation rules ====================
Local rules

Imported rules



==================== Top-level specialisations ====================


Linking breakOn ...

But in fact, the rule does fire, as this excert from "ghc -ddump-inlinings" shows:

Considering inlining
    bytestring-0.9.1.4:Data.ByteString.Char8.breakChar{v r3m} [gid] active: False
                                                                    arg infos [False]
                                                                    interesting continuation BoringCtxt
                                                                    is value: True
                                                                    is cheap: True
                                                                    guidance IF_ARGS 2 [0 0] 4 6
                                                                    ANSWER = NO

}}}

Trac metadata

Trac field	Value
Version	6.10.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added Tbug Trac import labels

Attached file breakOn.hs ($406).

samle code

Cale on IRC told me about "-ddump-simple-stats", which does list the rule in question:

$ ghc -O  -ddump-simpl-stats --make breakOn.hs
[1 of 1] Compiling Main             ( breakOn.hs, breakOn.o )

==================== FloatOut stats: ====================
0 Lets floated to top level; 0 Lets floated elsewhere; from 0 Lambda groups



==================== FloatOut stats: ====================
4 Lets floated to top level; 0 Lets floated elsewhere; from 1 Lambda groups



==================== Grand total simplifier statistics ====================
Total ticks:     1147

223 PreInlineUnconditionally
305 PostInlineUnconditionally
131 UnfoldingDone
15 RuleFired
    2 0# +# x#
    2 ByteString pack/packAddress
    1 ByteString specialise break (x==)
    2 int2Word#
    2 int2Word2Int
    2 narrow8Word#
    2 ord#
    2 word2Int#
39 LetFloatFromLet
1 EtaReduction
340 BetaReduction
93 KnownBranch
11 SimplifierDone


Linking breakOn ...

I guess I mis-understnad the meaning of -ddump-rules. Either close this bug, or keep it open as a reminder to extend the documentation of "-ddump-rules" in "man ghc" a bit.

Right. -ddump-rules shows precisely the rules defined in this module, not rules imported from elsewhere. I've changed the displayed headings to:

Local rules for local Ids

Local rules for imported Ids

The user manual already mentions -ddump-simpl-stats here: http://www.haskell.org/ghc/docs/latest/html/users_guide/rewrite-rules.html#id540463. I've clarified the explanation for ddump-rules, and added a cross reference to this section from the flag section http://www.haskell.org/ghc/docs/latest/html/users_guide/options-debugging.html.

I hope that'll help anyway. Patch coming.

Simon

mentioned in commit 23bc35d6

closed

Here's the patch

Tue Dec  8 02:55:56 PST 2009  simonpj@microsoft.com
  * Improve dumping for rules, and documentation of same
  Ignore-this: 4b09e56f953d130d5cb2807cf9da7303
  
  Inspired by Trac #3703

    M ./compiler/simplCore/SimplCore.lhs -2 +2
    M ./docs/users_guide/debugging.xml -2 +3
    M ./docs/users_guide/glasgow_exts.xml -3 +6

Simon

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

added Pnormal label