On 26/06/2008 Coos Haak wrote:
> Op Thu, 26 Jun 2008 01:10:21 -0500 schreef Mohan kumar:
>
> > Hi thanks for your reply,
> >
> > the puzzling question that rocks my mind is why should they
> > terminate the stack by subtracting 64 with the stack pointer(r1)
> >
> > addi r1,r11,__stackstart_pt@[EMAIL PROTECTED]
> > addi r1,r11,__stackstart_pt@[EMAIL PROTECTED]
> > addi r0,r0,0
> > stwu r0,-64(r1)
> >
> > 1. first two lines of code have defined the stack pointer(r1)
> > 2. third lines has cleared register r0.
> > 3. r1 is the stack pointer(sp) and sp is already initialised by
> > first two lines. and in the fourth line, they carry out this
> > operation on stack pointer "stwu r0,-64(r1)" Instruction does
> > the following. => Effective address(EA) r1-64
> > => EA is stored in stack pointer(r1)
> Wrong. EA is nowhere stored
Yes, it is; the calculated value of EA is loaded into r1. See here:
http://pds.twi.tudelft.nl/vakken/in1200/labcourse/instruction-set/stwu.h
tml
> > => value at the effective address is cleared to zero.
> >
> > Why should the stack pointer will now hold the address given by EA.?
> >
> > Any guess?
> No guess, EA is only used to determine the address where the value of
> r0 is to be stored.
Wrong. See link above.
--
John B
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