Z80 constant multiplication

readme.MD

Compile the C program like gcc <location>.c -o <location>. Call the ruby program like:

ruby gen.rb <HL initial value> <multiplier>

gen.rb

def input(prompt = "")
    print prompt
    $stdin.gets.chomp
end

def log2(n)
    Math.log(n, 2)
end

def int_like(n)
    n == n.to_i
end

op, ini_reg, val = ARGV

val = val.to_i

$compiled = ""

def type(str)
    $compiled += str + "\n"
end

case op
when /^mul/
    type "LD HL, #{ini_reg}"
    # puts reg, op, val
    if int_like log2 val
        log2(val).to_i.times {
            type "ADD HL, HL"
        }
    else
        a, b = %x(c/pow2dif.exe #{val}).split(" ").map &:to_i
        
        if 2**a + 2**b == val
            b.times {
                type "ADD HL, HL"
            }
            type "LD D, H"
            type "LD E, L"
            (a - b).times {
                type "ADD HL, HL"
            }
            type "ADD HL, DE"
        elsif 2**a - 2**b == val
            (b - 1).times {
                type "ADD HL, HL"
            }
            type "LD D, H"
            type "LD E, L"
            a.times {
                type "ADD HL, HL"
            }
            type "SCF"
            type "CCF"
            type "SBC HL, DE"
        else
            lines = []
            type "LD D, H"
            type "LD E, L"
            until val == 1
                if val % 2 == 0
                    val /= 2
                    lines.push "ADD HL, HL"
                else
                    val -= 1
                    lines.push "ADD HL, DE"
                end
            end
            type lines.reverse.join "\n"
        end
    end
else
    puts "unsupported op `#{op}`"
end

puts ".nolist
#include    \"ti83plus.inc\"
#define b_call(x) bcall(x)
.list
.org    $9D93
.db    t2ByteTok, tAsmCmp
    b_call(_ClrLCDFull)
    ld    hl, 0
    ld    (curRow), hl
#{$compiled.gsub(/^/, " " * 4)}
    b_call(_DispHL)
    RET
.end
.end"

pow2dif.c

#include <stdio.h>
#include <stdlib.h>

// thanks to LegionMammal978 
// http://codegolf.stackexchange.com/users/33208/legionmammal978

int main(int argc, char *argv[]) {
    unsigned int i0, i1;
    long long num;
    if (argc < 2) {
        printf("Usage: %s number\n", argv[0]);
        return 1;
    }
    num = strtoll(argv[1], NULL, 10);
    i0 = 0;
    while (!(num & 1)) {
        num >>= 1;
        i0++;
    }
    i1 = 0;
    while (num) {
        if (!(num & 1)) {
            while (!(num & 1)) {
                num >>= 1;
                i1++;
            }
            break;
        }
        num >>= 1;
        i1++;
    }
    printf("%u %u\n", i0 + i1, i0);
}