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ULM Generator (Part 4): Fetch/Store Instructions			[TOC]
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---- VIDEO ------------------------------
https://www.youtube.com/embed/k3ubwx8tomk
-----------------------------------------

Material: Instruction Set and "hello, world!" Program
=====================================================

Here the final instruction set that was created:

---- CODE (file=session08/hello/isa.txt, fold) ---------------------------------
RRR     (OP u 8) (X u 8) (Y u 8) (Z u 8)
J26     (OP u 8) (XYZ j 24)
U16R    (OP u 8) (XY u 16) (Z u 8)


0x01    RRR
    ulm_halt(ulm_regVal(X));

0x02    RRR
    ulm_setReg(ulm_readChar() & 0xFF, X);

0x03    RRR
    ulm_printChar(ulm_regVal(X) & 0xFF);

0x04    J26
    ulm_unconditionalRelJump(XYZ);

0x05    RRR
    ulm_sub64(X, ulm_regVal(Y), Z);

0x06    J26
    ulm_conditionalRelJump(ulm_statusReg[ULM_ZF] == 0, XYZ);

0x07    J26
    ulm_conditionalRelJump(ulm_statusReg[ULM_ZF] == 1, XYZ);

0x08    U16R
    ulm_setReg(XY, Z);

0x09    RRR
    ulm_fetch64(0, X, 0, 0, ULM_ZERO_EXT, 1, Z);

0x0A    RRR
    ulm_add64(X, ulm_regVal(Y), Z);

0x0B    RRR
    ulm_mul64(ulm_regVal(X), ulm_regVal(Y), Z);
--------------------------------------------------------------------------------

And here the "hello, world!\n" program:

---- CODE (file=session08/hello/hello, fold) -----------------------------------
08 00 20 01   # addr for first char
09 01 00 02   # fetch a char
05 00 02 00
07 00 00 04   # addr for the halt instr
03 02 00 00
0A 01 01 01
04 FF FF FB   # addr for fetching a char
01 00 00 00
68 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21 0a 00
--------------------------------------------------------------------------------

Quiz
====
Build a computer and write program for it to compute the factorial $n!$
according to the following (not recursive) algorithm described by a flow chart:

---- IMAGE ---------------
session08/factorial.png
--------------------------

Use the last byte of your program for the variable $n$. Test your program with
differnet values (recall that $0! = 1$). Note that the exit code on Unix is
truncated to the least significant byte. You can use the debugger to check the
actual computed result.

Submit your description of the instruction set `isa.txt` and your program
`factorial` with `submit hpc quiz07 isa.txt factorial`.

---- VIDEO ------------------------------
https://www.youtube.com/embed/7-kGKX8Hnv0
-----------------------------------------

Browser Test for Flow Charts
============================
For me it is actually easier to generate flow charts with Tikz/Latex. The
following chart was created this way and the `dvi` output converted to a `svg`
(scaleable vector graphic). However, I was told that some browsers have problems
to display that corretly (for me it looks ok on Safarai, Google Chrome and
Firefox). So let's discuss in class if this works for us:

---- TIKZ --------------
\begin{tikzpicture}
\input{flowchart.tex}
\renewcommand\BoxWidth {
    6
}
\SetMargin{1}{1}{0}{5}

\PutStatement{0}{$\text{Address of $n$}\to u(\%1)$}
\PutStatement{1}{$u(\text{M}_1(\%1)) \to u(\%2)$}
\PutStatement{2}{$u(0\text{x}01) \to u(\%3)$}
\PutJump{3}{$u(\%2) = 0$}
\PutStatement{4}{$u(\%2) \cdot u(\%3) \bmod 2^{64} \to u(\%3)$}
\PutStatement{5}{$(u(\%2) -1)  \bmod 2^{64} \to u(\%2)$}
\PutJump{6}{}
\PutStatement{7}{$\text{halt with exit code $u(\%3)$}$}

\AddPath{0}{1}
\AddPath{1}{2}
\AddPath{2}{3}
\AddCondJumpPath{3}{7}
\AddPath{3}{4}
\AddPath{4}{5}
\AddPath{5}{6}
\AddJumpPathLeft{6}{3}

\end{tikzpicture}
------------------------