On 02/01/2013 08:47 AM, Simon Marlow wrote:
On 01/02/13 08:19, Geoffrey Mainland wrote:
On 02/01/2013 08:03 AM, Simon Marlow wrote:
On 31/01/13 20:30, Geoffrey Mainland wrote:
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.
If I invoke ghc with -msse on a Win32 box then __SSE__ will be 1, but that doesn't mean I will be able to use SSE primops due to the stack alignment issue on that platform.
I guess we should not allow -msse with -fllvm on Win32. Or perhaps not -msse at all.
Hm, OK, but that would also means external C files could not be compiled with -msse when using the LLVM back-end on Win32 since we pass the flags through to the C compiler, right?
Also, the decision as to whether or not SSE primops will be available at all needs to be made when GHC is itself built. How should we expose that knob?
Why does it need to be decided at build time? Isn't it dependent on -msse on x86-32, and always available on x86-64?
The primops would need to be compiled in to GHC for -msse to be able expose them. In general, how would we make the set of primops and primtypes a function of dynflags? It's my understanding that this isn't possible right now. Or is it? And what about GHC.PrimopWrappers?
As an aside, what's the proper way for me to test the ARM cross-compilation support? I'm afraid my patches may break things there.
You could follow the instructions for building an RPi cross-compiler here:
http://hackage.haskell.org/trac/ghc/wiki/Building/Preparation/RaspberryPi
it should be fairly smooth.
Thanks! Geoff