[cfe-commits] [PATCH] Driver reengineering - first patch

[James Molloy]

Hi Jean-Daniel,

> From dicsussions at http://llvm.org/bugs/show_bug.cgi?id=4127 it was
suggested to not use target triple as an argument, but instead having
something > like 
>
> '--target=configdb-entry-alias' which would define the corresponding
triple. 
>
> Using this flag, you will be able to use --target=linux_distro directly
instead of having 2 arguments for this.
>
> What do you think about this ?

I have no issues with this. What I would say, is that this first patch
cannot yet completely replace the existing code (which is why it is
implemented as a wart on top of the existing codebase). Therefore, I'm loath
to change the operation of any non-hidden or obvious options until it is
stable.

That's why I'm using -ccc-* options at the moment. When it's stable, it's a
ten-line patch to switch these off and move over to --target, --triple or
whatever we want.

Cheers,

James

-----Original Message-----
From: Jean-Daniel Dupas [mailto:devlists at shadowlab.org] 
Sent: 18 January 2012 11:48
To: James Molloy
Cc: cfe-commits at cs.uiuc.edu
Subject: Re: [cfe-commits] [PATCH] Driver reengineering - first patch


Le 18 janv. 2012 à 12:26, James Molloy a écrit :

> Hi,
> 
> The attached patch is the first of the clang driver revamp. This patch has
> no intended functionality change unless you use the new hidden flag
> "-ccc-dynamic-driver".
> 
> This patch addresses two points brought up during the driver BoF last
> November, namely
>  * "There should be a 'driver database' of known platforms"
>    * "This should fall back for the unusual case: load from some sort of
> config file (in JSON format)"
>  * "We should be able to ship a compiler that can always act like it's
> targetting Ubuntu".
> 
> Firstly, this first patch has some limitations:
>  * It has only been fully implemented for Linux, and only tested (to
> exhaustion) on Ubuntu Natty and RHEL5.
>  * It only deals with what should be the "uncommon" case - loading JSON at
> runtime.
>  * It doesn't yet copy the target DB into the correct place in the build
or
> install dirs.
> 
> Secondly, this is what it does do:
>  * llvm.diff adds SMLoc tracking, raw MemoryBuffer input and '// ...'
style
> comment support to the JSON parser. This makes developing the target DB
> files a lot easier, and the comment support is invaluable (and means we
can
> add the copyright header).
>  * Adds an implementation of the Target Database for linux, and minix (as
> an example of a trivial platform). The database parser is completely
> implemented, and a schema is implemented and described that should be
> sufficient for everything we need, and also simple enough to grasp easily.
> This has been at the expense of some terseness in the DB definition.
> 
> The input to the target database is a JSON file. This JSON file can
include
> other files. The file consists of a list of lists. Each of those lists is
a
> "group" of objects. When queried, the targetdb will iterate over these
> groups. For each group, all objects are iterated in order. If an object
> "matches" the query criteria, its contents are added to the query result,
> and no more objects are iterated over in that group.
> 
> See lib/Driver/TargetDB_Linux.json for an example of how it works. A query
> to the target database will result in a structure containing everything
you
> should need to compile/link/assemble on the target. The format of this
> structure is derived from a tablegen file (the patch includes a new
tablegen
> backend), so there is no boilerplate if you want to add a new struct
member.
> 
> The patch has been tested by taking an indicative subset of all possible
> Clang flags (especially interesting ones such as -static, -shared, -pie,
-S
> etc) and brute force running through the entire set of combinations of
these
> flags testing the targetdb-based driver's generated command lines against
> the current one.
> 
> The new patch adds a new command flag "-ccc-target-triple" to be
> distinguished from -ccc-host-triple. (When this patch and its followups
are
> accepted and turned on by default, this will change into "-target"). This
> way we can actually (finally!) test "compile targetting X as if you were
on
> Y", which should let us increase our driver test coverage (I also added
> -ccc-linux-distro which allows you to pretend to be a specific distro, as
> this is not encoded in the triple).
> 
> Speaking of tests, the submitted patch does not have any yet. I intend to
> submit them in a later patch, as I'd like this to be at least concept
> approved before I spend an infinite amount of time writing a decent test
> set.
> 
> Heckling... commence! :-)


>From dicsussions at http://llvm.org/bugs/show_bug.cgi?id=4127 it was
suggested to not use target triple as an argument, but instead having
something like 

'--target=configdb-entry-alias' which would define the corresponding triple.


Using this flag, you will be able to use --target=linux_distro directly
instead of having 2 arguments for this.

What do you think about this ? 

-- Jean-Daniel