Helpful hints for the homework

circuit Class tutorial

The tutorial is here: circuit_tutorial.pdf

ECE511 Instrutcion Set Reference

The reference manual is here: ece511-isa.pdf

Using objdump

Homework2 onwards, when you do make in the sim directory, among other things, you'll get an executable called objdump. You can use it to disassemble binaries that you run on the simulator. For example, to look at the assembly code for lzw, in the sim directory, type

./objdump ../apps/lzw/mipsver > lzw.s

You can then open lzw.s in a text editor.

Command line simulator

When you do make small.out in the apps/lzw directory, the following command is run:

../../sim/pipelined-model mipsver 800

The simulator executable is called pipelined-model, and the lzw binary is called mipsver. Also, if you look in the 'apps' directory, you'll find a few other spec benchmarks (gcc, bzip2, parser, mcf). The binaries for all benchmarks are called mipsver. Most spec benchmarks need some command line parameters. Gcc, for example, needs a .c file that it can compile. The makefile for each benchmark gives it the necessary command-line parameters. When you do make in the gcc directory, for example, the following command is executed:

../../sim/pipelined-model mipsver data/tiny.in -o tiny.s

More benchmarks

You are encouraged to experiment with other benchmarks (apart from lzw) in the sim/apps directory

gcc: type make tiny.out for a short input
     type make small.out for a longer input

bzip2: type make small.out for a short input
       type make med.out for a longer input

mcf: type make test.out for a short input
     type make small.out for a longer input
     Both inputs take some time to run

parser: type make super-small.out for a super-short input
        type make test.out for a short input
        type make smred.out for a short input
        All three take some time to run

Debugging the simulator

There are three ways you can go about this:

Use the debug flag while running the simulator
If you execute lzw as given below (in the apps/lzw directory):

../../sim/pipelined-model -debug 0xffff mipsver 800

the simulator will print some useful information, which you can use to debug.
Different values of the debug flag will cause different amounts of debug information to be printed


        -debug    Use bit mask, mask[31:0], to turn on debugging output:
                        A default setting of all zeroes gives no ouput
                0.      Debug info for instruction fetch stage
                1.      Debug info for decoder stage
                2.      Debug info for register renaming state
                3.      Debug info for scoreboard stage
                4.      Debug info for the rob stage
                5.      Debug info for register file stage
                6.      Debug info for execution stage
                7.      Show current and retirement RATs
                8.      Show register renamer free list
                9.      Show scoreboard fifo destination regs
                10.     Show ROB destination regs
                11.     Show store addresses and data
                12.     Show load addresses and data
                13.     Print architectural dest reg and data for each retiring instruction
                14.     Debug info for caches
        -debug_delay         Wait until this cycle n before displaying debug info

        Example of using debug mask with full debug info:
                Debug mask = 111111111111111 in binary or 0x7fff in hex
                pipelined-model -debug 0x7fff mipsver 5
        Example of just turning on debug info for instruction fetch:
                pipelined-model -debug 1 mipsver 5

Use gdb
The simulator binary pipelined-model can be loaded in gdb, since by default it is compiled with the -g flag. There's an easy-to-use GUI wrapper for gdb, called ddd. Students who're not familiar with gdb may find it useful. To run ddd with the simulator binary, type
```
ddd pipelined-model &
```
Use printf()
Debugging by printf() is very useful, and faster than using gdb.

Compiling your own programs with the simulator

Step1

The tarball contains a version of gnu binutils for the simulator