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Re: [f-cpu] new cjump instruction



hi all,

nico wrote:

On Fri, 11 Apr 2003 11:16:04 -0600
ben franchuk <bfranchuk@jetnet.ab.ca> wrote:

nico wrote:

I propose a new cjump to enable 0 cost jump.

cjump (R1,#imm12, cond)
{
if (cond(R1))
{
PC = (PC & 0x0FFF) | #imm12; }
else
{
PC++;
}

}

PC lsb is just replaced by the 12 bit constant, that's lightning
fast. No cycle could be lost by reading register bank.

What do you think of it ?

Try using it with real code and you will see the problem.
hint: page boundry is random.:(

?? That's a compiler problem. So ?

huh, i don't think that it's a good answer ....

on top of that, this technique poses new problems in FC0's pipeline.
sure, addresses are computed fast, but what about their validation,
their fetch, their lookup in the buffers ......

Ben.

YG

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