writing a new Machine Description file (e.g cortex-a57.md) in gcc

Hi Linaro Toolchain Group,

I am new to gcc development. I am trying to write a new md file describing pipeline information for a processor. Please suggest some good reference document for understanding machine description file.

Few questions from cortex-a53.md file:

For first integer pipeline following is defined - (define_cpu_unit "cortex_a53_slot0" "cortex_a53")

Is name cortex_a53_slot0 is a keyword or it is any general string? Is there any convention in choosing names for cpu units? If ‘cortex_a53_slot0’ a general string, how assembler knows it is first integer pipeline?

How these *.md files are used? When they are compiled and how they are used? How to verify an md file for a processor is written correctly or not? How to test it? What other design consideration must be kept in mind while writing a new md file?

Thanks.

with regards, Virendra Kumar Pathak