On Tue, Jun 22, 2010 at 2:56 PM, Basile Starynkevitch <bas...@starynkevitch.net> wrote: > On Tue, 2010-06-22 at 14:47 -0400, Jianzhou Zhao wrote: >> Hi, >> >> Is there any project for translations between GCC RTL and LLVM SSA, >> RTL -> SSA and SSA -> RTL? I am working on a project that may reuse >> existing optimization passes from LLVM and GCC. So I was wondering if >> there is a way to switch between their IR's. > > > I am not sure RTL is the best intermediate representation of GCC to > translate to or even from LLVM SSA (which I confess not knowing much). > > I would rather recommend using Gimple, see > http://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html for more, or > Gimple/SSA, inside GCC, as the intermediate representation in GCC to > handle (i.e. to translate from or to LLVM IR).
The Gimple/SSA provides a better mapping from LLVM's SSA. Is Gimple more architect-independent than RTL? The optimizations run on LLVM's SSA are almost target-independent. I am also only interested in the target-independent pass in GCC for the time being. If GCC RTL is for lower level optimizations than Gimple, I think Gimple is a better target. > > I am not sure that conversion between LLVM & GCC internal > representations is an easy task. As usual, the evil is in the details > (the source location -in the compiled *.c file- is probably very > differently represented in GCC & in LLVM). > > To manipulate GIMPLE easily, you could be tempted to use the MELT plugin > or branch, see http://gcc.gnu.org/wiki/MELT for more. > > MELT is a lispy domain specific language offering notably Gimple pattern > matching, & this precise feature of MELT will help you a lot coding a > Gimple to LLVM/SSA converter if you wanted to do that. This is cool. I will look at it. > > However, a DraggonEgg plugin exist which precisely do that GCC -> LLVM > conversion, according to my incomplete understanding (or perhaps > DraggonEgg convert Gimple to LLVM *front-end* but not middle-end > representation? I don't know!). Thanks for pointing out this DragonEgg project http://dragonegg.llvm.org/. It does the translation from Gimple to LLVM bitcode (which means SSA in my understanding). It seems that I need to find a translation for the other direction, or create a one. > > You could ask me more (e.g. here) about MELT. I am its main author. > > Regards. > > -- > Basile STARYNKEVITCH http://starynkevitch.net/Basile/ > email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359 > 8, rue de la Faiencerie, 92340 Bourg La Reine, France > *** opinions {are only mines, sont seulement les miennes} *** > > > -- Jianzhou
