Oh, that's a pretty cool idea !
Thanks for the tip!
Sebastien
</offtopic> :-)
On Fri, Feb 26, 2010 at 12:38 PM, Frieder Ferlemann <
frieder.ferlem...@web.de> wrote:
> Hi Sébastien,
>
> Am 26.02.2010 10:02, schrieb Sébastien Lorquet:
> > probably off topic, sorry, but what I miss in the 8051 port is a 16
> > bit-stack pointer in xdata mode :(
>
> Would swapping out contents of the 8051 hardware stack to
> xdata memory help?
>
> Appending untested sample code that tries to implement this.
> (expect some bugs in that code)
>
> You'd have to call _stackadjust at strategic places in your code.
> (eventually you can patch the function genCall in sdcc/sdcc/src/mcs51/gen.c
> to additionally emit an lcall __stackadjust (well, probably not a good
> idea))
>
> Compile with: sdcc --std-sdcc99 -c stackadjust.c
>
> Occasionally swapping in and out is probably cheaper than
> always emulating a 16 bit-stack pointer in xdata mode.
>
> Greetings,
> Frieder
>
>
>
>
>
> /*-----8<--------------stackadjust.c----------------------------------*/
> /* GPL+LE */
>
> #include <8052.h>
>
> #define STACK_SWAP_WATERMARK 0x18
> #define STACK_SWAP_SIZE 0x10
> #define STACK_SWAP_HYSTERESIS 0x08
>
> unsigned char __xdata stack_swap_area[0x200];
> unsigned char __xdata * __data stack_swap_ptr = stack_swap_area;
>
> /* defined in crtstart.asm */
> extern __idata unsigned char* _start__stack;
>
> /* inlineable helper functions *similar* to memcpy */
> static void inline memcpy_xi (__xdata unsigned char* dst, __idata unsigned
> char* src, unsigned char size)
> {
> do
> {
> *dst++ = *src++;
> } while( --size );
> }
> static void inline memcpy_ix (__idata unsigned char* dst, __xdata unsigned
> char* src, unsigned char size)
> {
> do
> {
> *dst++ = *src++;
> } while( --size );
> }
> static void inline memcpy_ii (__idata unsigned char* dst, __idata unsigned
> char* src, unsigned char size)
> {
> do
> {
> *dst++ = *src++;
> } while( --size );
> }
> static void inline memcpy_ii_topdown (__idata unsigned char* dst, __idata
> unsigned char* src, unsigned char size)
> {
> src += size;
> dst += size;
> do
> {
> *--dst = *--src;
> } while( --size );
> }
>
>
> /* Untested! Just something that could be used as a start for an
> implementation in assembler
> * Checks whether the 8051 hardware stack is above or below a watermark
> * and then eventually swaps content to/from xdata memory
> */
> void _stackadjust (void)
> {
> if (SP >= (unsigned char)((unsigned char)&_start__stack +
> STACK_SWAP_WATERMARK + STACK_SWAP_HYSTERESIS/2))
> {
> /* 8051 hardware stack was too large */
> __critical
> {
> // copying to external memory
> memcpy_xi (stack_swap_ptr, (unsigned char __idata
> *)&_start__stack, STACK_SWAP_SIZE );
> stack_swap_ptr += STACK_SWAP_SIZE;
>
> // moving contents of stack
> memcpy_ii ( (unsigned char __idata *)&_start__stack,
> (unsigned char __idata *)&_start__stack +
> STACK_SWAP_SIZE,
> (unsigned char)(SP - (unsigned char)&_start__stack -
> STACK_SWAP_SIZE));
>
> SP -= STACK_SWAP_SIZE;
> }
> } else if ( SP <= (unsigned char)((unsigned char)&_start__stack +
> STACK_SWAP_WATERMARK - STACK_SWAP_HYSTERESIS/2) &&
> stack_swap_ptr != stack_swap_area )
> {
> __critical
> {
> SP += STACK_SWAP_SIZE;
>
> // copying contents
> memcpy_ii_topdown ( (unsigned char __idata *)&_start__stack +
> STACK_SWAP_SIZE,
> (unsigned char __idata *)&_start__stack,
> (SP - (unsigned char)&_start__stack -
> STACK_SWAP_SIZE));
>
> // copying from external memory
> memcpy_ix ((unsigned char __idata *)&_start__stack,
> stack_swap_ptr, STACK_SWAP_SIZE );
> stack_swap_ptr -= STACK_SWAP_SIZE;
> }
> }
> }
>
>
>
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