some questions about registers in nios2

[Altera_Forum]

i have some questions about registers in nios2  

1: the GP(r26)' function like PC as in X86 architecture ?   2: (r15-r8) is named Caller-Saved registers ,their function ?  3:(r16_r23),their function ?  4: when call a function, the rule of saving registers is what? between r2 to  r25 ,which should be saved ?  5: when an interrupt happen or call function , the differences between the saving registers and restore register action.

[Altera_Forum]

Hi wkongwkong, 

 Please see the "Nios II Processor Reference Handbook":  http://www.altera.com/literature/lit-nio2.jsp (http://www.altera.com/literature/lit-nio2.jsp)  Regards, --Scott

[Altera_Forum]

--- Quote Start ---  originally posted by wkongwkong@Jun 22 2006, 11:15 PM i have some questions about registers in nios2  1: the gp(r26)&#39; function like  pc as in x86 architecture ?   2: (r15-r8) is named  caller-saved  registers ,their function ?  3:(r16_r23),their function ?  4: when call a function, the rule of saving registers is what? between r2 to     r25 ,which should be saved ?  5: when an interrupt  happen or call function ,  the differences between  the saving registers  and restore register  action. <div align='right'><{post_snapback}> (index.php?act=findpost&pid=16354)  --- quote end ---    --- Quote End ---   1. I&#39;m rusty on my x86 so I&#39;m not sure of the answer to this. 2. Caller saved registers have to be saved by the calling function. So if you&#39;re writing in assembler you don&#39;t have to bother saving them. 3. They&#39;re just registers that you can do with what you will 4. When calling a function if doing it from assembler you should save the caller saved registers. If you do the call from C the compiler looks after this for you. 5. If you want to know which registers are saved for an IRQ look in the file alt_exception_entry.S in the nios2 component