On Fri, 4 Apr 2008, Michael Eager wrote: > Xilinx has a PowerPC 405 processor with an attached > single precision floating point processor. I have a > patch which supports this FP unit, but want to clean > it up a bit before submitting it.
What do you propose as the function call and return ABI when this is in use? At present we (32-bit GNU/Linux and EABI) have a hard-float ABI (TARGET_HARD_FLOAT && TARGET_FPRS), which relies on 64-bit FPRs to be able to pass double (so isn't usable if this processor only has 32-bit FPRs), and a soft-float ABI, also used on E500, passing floating point types in GPRs (32 bits of each GPR, not using the E500 high parts). Are you going to use the soft-float ABI and take the performance cost of doing so, or do you propose a hybrid ABI passing float in FPRs and double in GPRs? If you propose the latter then you should work with the Power.org ABI working group on defining the ABI properly. (Whatever you do, you may wish to consider how to define flags relating to the ABI separately from those relating to code generation.) -- Joseph S. Myers [EMAIL PROTECTED]
