On 31/01/13 20:30, Geoffrey Mainland wrote:
Simon, this reminds me of two other issues...
1) SSE vector values are only passed in registers on x86-64 anyway right now. MAX_REAL_FLOAT_REG and MAX_REAL_DOUBLE_REG are both #defined to 0 on x86-32 in includes/stg/MachRegs.h. Are floats and double not passed in registers on x86-32? I'm confused as to how this works. The GHC calling convention in LLVM certainly says they are passed in registers.
No, floats are not passed in registers on x86-32. I don't know about LLVM.
2) SSE support is processor and platform dependent. What is the proper way for the programmer to know what SSE primitives are available? A CPP define? If so, what should it be called?
Right now one can look at the TARGET_* and __GLASGOW_HASKELL_LLVM__ CPP macros and make a decision as to whether or not SSE primitives are available, but that's not a great solution. Also, what happens when we want to add AVX support? How do we control the inclusion of AVX support when building GHC, and how do we let the programmer know that the AVX primops/primtypes are available for use?
We #define __SSE__: http://hackage.haskell.org/trac/ghc/ticket/7554 Similar things would need to happen for AVX. Cheers, Simon