What is the problem you face? That you want to allow passing a dynamic number of float or double arguments? I assume you are keeping it fixed at 6 still but want to allow those 6 to be either 6 floats, 6 doubles or any other combination. (Long term is anything that can be put in a xmm* register...)
Why do you want Cmm liveness on entry? Is it simply to solve the above so you can generate specialized function types instead of the universal one the LLVM backend uses? If so, have you tried just using the most general universal type? e.g., how badly is the generated code affected if you have all arguments be Doubles and then do type casts on jumps and function entries? This is the original commit I wrote for tracking STG reg liveness: 4384e146640230399b38cd62e8e5df391f72c3a7 This is the one Simon Marlow wrote to do the same but in the new code gen: c6a61235aa0baf6f9e8a41c5a771ccc7e32c23a5 I'd suggest you look at these commits and they should show you where to get the information from. (I can't remember anymore sorry). Cheers, David On 16 October 2012 03:45, Geoffrey Mainland <[email protected]> wrote: > Hi all, > > I'm working on changing GHC's calling convention to support overlapping > register classes. On x86-64 this will mean that a function can receive up to > six Float/Double arguments (any mixture) in registers. Right now only two > Double arguments can be passed in registers on x86-64, even if a function > takes zero Float arguments---the register classes for Floats and Doubles > cannot overlap even though both are passed in xmm* registers. > > This is working fine with the native back-end, but I'm not sure how to get > it working with the LLVM back-end. Right now LLVM translates a Cmm procedure > to an LLVM function of a single universal type( that is, all LLVM functions > that the LLVM back-end produces for Cmm procedures have the same type) that > takes all STG registers as arguments. A Cmm procedure call passes all the > STG registers, although the back-end takes advantage of the liveness > information attached to Cmm jumps to pass undefined values for non-live > registers. > > Now that register classes can overlap, I need to change this. Since jumps > have liveness information attached, I can simply pass the live registers. > But when translating Cmm procedures, I need to know which registers are live > on entry to the procedure. > > The slightly longer-term goal is to add support for passing SSE vectors in > registers. What I'd like to have ideally is the set of live registers *and > their Cmm types* at each procedure entry and jump. I envision having a > single STG register class, say X16, for all 128-bit-wide SSE registers, but > I'd like the Cmm type information when generating LLVM type signatures so I > can generate the appropriate LLVM types---a 128-bit-wide vector of 32-bit > integers does not have the same type as a 128-bit-wide vector of double > precision floats. > > I might be able to do without the Cmm type information by inserting > appropriate casts in the generated LLVM code, but I really need the set of > live registers on entry to a Cmm procedure. I don't see how to get this > unfortunately. Any hints? > > Thanks, > Geoff > > _______________________________________________ > Cvs-ghc mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/cvs-ghc _______________________________________________ Cvs-ghc mailing list [email protected] http://www.haskell.org/mailman/listinfo/cvs-ghc
