I have to say that I'm not very keen. There is an annotation facility in Core, but it's easy for the notes to be discarded. So if they are conveying important info, it might easily get lost... and if not, what's it doing there in the first place. What do you expect to happen to these annotations? So just now I'm a bit sceptical. Core is a data type that I'm trying hard to keep simple. Simon | -----Original Message----- | From: Hal Daume III [mailto:hdaume@ISI.EDU] | Sent: 03 February 2003 23:24 | To: GHC Users Mailing List | Subject: ghc feature request: core notes | | I'm not sure how "generally useful" this would be, but I would find it | useful to be able to attach notes to core expressions from the Haskell | code. The idea being something along the lines of a code annotation like | a pragma. For instance, in my Haskell program I would have something | like: | | f x y = | case {-# CORE "my first note" #-} g x of | ... | | then, the core would come out with, instead of: | | case g x of ... | | we would have | | case {note "my first note"} g x of ... | | The reason I would find this useful is somewhat obscure, but the basic | idea is that I need to be able to both preprocess code and then change | core based on how it was preprocessed. I'd like to send annotations like | these out of the preprocessor so they can then be picked up later by my | core transformer. | | If this sounds like a good enough idea to go in, but no one has time to | implement it, I could do it myself (probably), but I thought I'd ask the | experts first (or if there's anything like this in there currently)... | | - Hal | | -- | Hal Daume III | | "Computer science is no more about computers | hdaume@isi.edu | than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Simon, I wasn't suggesting extending the Core datatype. Part of the Core Exp datatype is these notes. From ExternalCore.hs:
data Exp ... | Note String Exp ...
My suggestion is simply to allow pragmas to fill in these Note values. I've actually implemented it in my copy of GHC and it's a very very small addition. It requires essentially modifying slightly the parser and lexer to accept '{-# CORE' as a pragma and then to pass this value down through all the passes (typechecking, renaming, etc.). I think it's about 20 additional lines of code in all. It doesn't seem that these get thrown away anywhere in the AbsSyn -> Core piping process. I'm not sure the extend to which this de-simplifies Core. Currently these Notes are only used to store SCC information for profiling and INLINE information. - Hal -- Hal Daume III "Computer science is no more about computers | hdaume@isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume On Tue, 4 Feb 2003, Simon Peyton-Jones wrote:
I have to say that I'm not very keen. There is an annotation facility in Core, but it's easy for the notes to be discarded. So if they are conveying important info, it might easily get lost... and if not, what's it doing there in the first place. What do you expect to happen to these annotations?
So just now I'm a bit sceptical. Core is a data type that I'm trying hard to keep simple.
Simon
| -----Original Message----- | From: Hal Daume III [mailto:hdaume@ISI.EDU] | Sent: 03 February 2003 23:24 | To: GHC Users Mailing List | Subject: ghc feature request: core notes | | I'm not sure how "generally useful" this would be, but I would find it | useful to be able to attach notes to core expressions from the Haskell | code. The idea being something along the lines of a code annotation like | a pragma. For instance, in my Haskell program I would have something | like: | | f x y = | case {-# CORE "my first note" #-} g x of | ... | | then, the core would come out with, instead of: | | case g x of ... | | we would have | | case {note "my first note"} g x of ... | | The reason I would find this useful is somewhat obscure, but the basic | idea is that I need to be able to both preprocess code and then change | core based on how it was preprocessed. I'd like to send annotations like | these out of the preprocessor so they can then be picked up later by my | core transformer. | | If this sounds like a good enough idea to go in, but no one has time to | implement it, I could do it myself (probably), but I thought I'd ask the | experts first (or if there's anything like this in there currently)... | | - Hal | | -- | Hal Daume III | | "Computer science is no more about computers | hdaume@isi.edu | than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
"Hal Daume III"
I'm not sure how "generally useful" this would be, but I would find it useful to be able to attach notes to core expressions from the Haskell code. The idea being something along the lines of a code annotation like a pragma. [...]
Simon Peyton-Jones
[...] There is an annotation facility in Core, but it's easy for the notes to be discarded. So if they are conveying important info, it might easily get lost... and if not, what's it doing there in the first place. What do you expect to happen to these annotations? [...]
It seems like _scc_ is (almost) exactly what you need here. When used
for profiling, you mark subexpressions you want profiled and ghc takes
care to preserve and propagate them in a semantically meaningful way.
Any _scc_ annotations that ghc chooses to drop can be reported as
bugs :-)
I say "almost" because what the semantics used when profiling may not
be the right ones for your purposes. (I'm being vague because I don't
know your purposes.)
Naturally, you'd want to be able to use these notes independently of
profiling - which can probably be done with a little preprocessor
hackery. Assuming that the 1st argument to 'NOTE' is a literal string
in the following:
#ifdef TRACK_NOTES
#define NOTE(x,y) (_scc_ "
participants (3)
-
Alastair Reid -
Hal Daume III -
Simon Peyton-Jones