Simon Marlow wrote:
Joe Buehler wrote:
What is the purpose of RESERVED_C_STACK_BYTES? Are stg routines
expecting a free area of that size at *top* of stack? I need to
make sure
that I have saved the registers at the correct end of the stack
frame created
in StgRun. It is difficult to tell from the existing hppa code
what exactly
was intended.
I had the same problem. I think you can define USE_MINIINTERPRETER
(in rts/Makefile:STANDARD_OPTS or as build.mk:SRC_CC_OPTS) and that
will get around StgCRun/Return. The problem I had was finding out
where everything was supposed to go: I needed to see the actual C
compiler output to make sure things were safe. In the end I gave up--
Windows-native RTS is unregisterised for now because CL cannot create
Explicit Register Variables or use the 'register' storage class for
global variables (both are used in includes/Regs.h).
The reserved area is used for spilling in STG code. Typically the
area above the C stack pointer is assumed to be available for
scratch space during any basic block. I'm not familiar with HPPA
though, it may have different conventions.
Maybe I have this reversed--I asked about this before now:
StgCRun.c:StgRun:
"movl %%esp, %%eax\n\t"
"addl %4, %%eax\n\t"
that %4 there is the argument RESERVED_C_STACK_BYTES--i.e., instead
of moving the saved-stack-pointer _down_ the stack (subl to where the
stack would grow) it moves up the stack (addl back up into the
stack). This would save memory (RESERVED_C_STACK_BYTES is defined in
Constants.h as (2048 * SIZEOF_LONG)) but only if it is already known
that the stack space above was used by the GHC program. The point
being that knowing what is controlling the stack you are using--GHC
or the C compiler--would help. Am I way off here?
Thanks,
Pete
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