BCO entry code - parameter passing on RISC

[Wolfgang Thaller]

After a day of running gdb in parallel on my MacOS X and Linux [quite 
annoying because of different keyboard layouts ;-) ], I've come to the 
following conclusion:

The entry code for BCOs expects all parameters to be on the stack, but 
on non-x86 machines, the stg_ap_*_ret pass parameters to it in 
registers (as for function objects). This leads to frequent crashes in 
GHCi on PowerPC, but not on Intel.

My first attempt at fixing this (by making stg_BCO_entry push the 
parameters onto the stack) is attached below, but I'm not committing it 
as I'm not sure it's the right way to do it. Are the stg_ap_*_ret 
functions the only places where a BCO is entered? It might be a nicer 
solution to modify GenApply to pass parameters to BCOs on the stack.

Cheers,

Wolfgang



Index: ghc/rts/StgMiscClosures.hc
===================================================================
RCS file: /home/cvs/root/fptools/ghc/rts/StgMiscClosures.hc,v
retrieving revision 1.82
diff -r1.82 StgMiscClosures.hc
240a241,262
 >
 > #ifndef NO_ARG_REGS
 >   {
 >     StgBCO *bco = (StgBCO*) R1.p;
 >     int size = BCO_BITMAP_SIZE(bco);
 >
 >     if(size > MAX_REAL_VANILLA_REG-1)
 >     	size = MAX_REAL_VANILLA_REG-1;
 >     Sp -= size;
 >
 >     switch(size)
 >     {
 >     case 7: Sp[6] = R8.w;
 >     case 6: Sp[5] = R7.w;
 >     case 5: Sp[4] = R6.w;
 >     case 4: Sp[3] = R5.w;
 >     case 3: Sp[2] = R4.w;
 >     case 2: Sp[1] = R3.w;
 >     case 1: Sp[0] = R2.w;
 >     }
 >   }
 > #endif