#7443: Generated C code under -prof -fprof-auto -fprof-cafs very slow to compile
-----------------------------+----------------------------------------------
Reporter: orenbenkiki | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.2 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Blockedby:
Blocking: | Related:
-----------------------------+----------------------------------------------
Some background: This is C code generated when I turned on profiling with
-fprof-auto -fprof-cafs, on Haskell code that contains a large amount of
injected TemplateHaskell code. GHC takes several minutes to compile this
on its side; but for some reason it emits the attached C code, which (if
compiled with -O) takes "forever" to compile. At least, I killed it after
consuming 3 hours of CPU and occupying 9GB of RAM.
I also opened a GCC bug for this; but a cursory look seems to indicate
this C code is trying to build a linked list in memory, which it seems
should be doable in a much more straightforward way. In fact since the
list of CAFs will not change in run-time, it should be possible to
initialize it in compile time as:
ENTRY entry_0[1] = { ..., link = NULL };
ENTRY entry_1[1] = { ..., link = entry_0 };
...
head = entry_n;
And this is before wondering why not use an array of entries instead of a
linked list in the 1st place. That said, I am just guessing here, I have
no understanding of what is really going on, other than the fact I was
forced to add {-# OPTIONS_GHC -optc -O0 #-} to the offending file.
Attached is a tgz file containing the generated C code (plus a version
which is post-CPP, so you can just try to compile it in various ways on
systems without GHC installed).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7443>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
