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ZealOS/docs/Demo/Asm/MulByHand.html
TomAwezome 01e13ff62d Fix codebase HTML generation.
2021-07-03 02:47:45 -04:00

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<pre style="font-family:courier;font-size:10pt">
<a name="l1"></a><span class=cF2>/*When Terry Davis was a kid with a Commodore 64,</span><span class=cF0>
<a name="l2"></a></span><span class=cF2>the 6502 chip had no multiply inst</span><span class=cF0>
<a name="l3"></a></span><span class=cF2>and this is how he had to do it, except,</span><span class=cF0>
<a name="l4"></a></span><span class=cF2>he used more regs in this example.</span><span class=cF0>
<a name="l5"></a></span><span class=cF2>*/</span><span class=cF0>
<a name="l6"></a></span><span class=cF1>asm</span><span class=cF0> {
<a name="l7"></a></span><span class=cF2>//Opcodes are slightly different to make writing the x86_64 assembler easier.</span><span class=cF0>
<a name="l8"></a></span><span class=cF2>//See </span><a href="https://www.tomawezome.github.io/ZealOS/Compiler/OpCodes.html#l1"><span class=cF4>::/Compiler/OpCodes.DD</span></a><span class=cF2>.</span><span class=cF0>
<a name="l9"></a>
<a name="l10"></a></span><span class=cF2>//You can clobber RAX,RBX,RCX,RDX,R8,R9.</span><span class=cF0> </span><span class=cF2>The compiler expects that.</span><span class=cF0>
<a name="l11"></a>
<a name="l12"></a>MUL_BY_HAND_U8_U8_TO_U16: </span><span class=cF2>//This is only for fun.</span><span class=cF0>
<a name="l13"></a></span><span class=cF2>//8bit * 8bit--&gt;16bit</span><span class=cF0>
<a name="l14"></a></span><span class=cF2>//AL*BL--&gt;AX</span><span class=cF0>
<a name="l15"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>CL</span><span class=cF0>, </span><span class=cFE>8</span><span class=cF0>
<a name="l16"></a> </span><span class=cF1>SHL</span><span class=cF0> </span><span class=cFC>AX</span><span class=cF0>, </span><span class=cFE>8</span><span class=cF0>
<a name="l17"></a>@@05: </span><span class=cF1>SHL1</span><span class=cF0> </span><span class=cFC>AX</span><span class=cF0>
<a name="l18"></a> </span><span class=cF1>JNC</span><span class=cF0> @@10
<a name="l19"></a> </span><span class=cF1>ADD</span><span class=cF0> </span><span class=cFC>AL</span><span class=cF0>, </span><span class=cFC>BL</span><span class=cF0>
<a name="l20"></a>@@10: </span><span class=cF1>DEC</span><span class=cF0> </span><span class=cFC>CL</span><span class=cF0>
<a name="l21"></a> </span><span class=cF1>JNZ</span><span class=cF0> @@05
<a name="l22"></a> </span><span class=cF1>RET</span><span class=cF0>
<a name="l23"></a>
<a name="l24"></a>_MUL_BY_HAND_U8_U8_TO_U16:: </span><span class=cF2>//C callable</span><span class=cF0>
<a name="l25"></a> </span><span class=cF1>PUSH</span><span class=cF0> </span><span class=cFC>RBP</span><span class=cF0>
<a name="l26"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RBP</span><span class=cF0>, </span><span class=cFC>RSP</span><span class=cF0>
<a name="l27"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>AL</span><span class=cF0>, </span><span class=cF1>U8</span><span class=cF0> </span><span class=cF3>SF_ARG1</span><span class=cF0>[</span><span class=cFC>RBP</span><span class=cF0>] </span><span class=cF2>//</span><a href="https://www.tomawezome.github.io/ZealOS/Kernel/KernelA.html#l714"><span class=cF4>SF_ARG1</span></a><span class=cF0>
<a name="l28"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>BL</span><span class=cF0>, </span><span class=cF1>U8</span><span class=cF0> </span><span class=cF3>SF_ARG2</span><span class=cF0>[</span><span class=cFC>RBP</span><span class=cF0>]
<a name="l29"></a> </span><span class=cF1>CALL</span><span class=cF0> MUL_BY_HAND_U8_U8_TO_U16
<a name="l30"></a> </span><span class=cF1>MOVZX</span><span class=cF0> </span><span class=cFC>RAX</span><span class=cF0>, </span><span class=cFC>AX</span><span class=cF0>
<a name="l31"></a> </span><span class=cF1>POP</span><span class=cF0> </span><span class=cFC>RBP</span><span class=cF0>
<a name="l32"></a> </span><span class=cF1>RET1</span><span class=cF0> </span><span class=cFE>16</span><span class=cF0>
<a name="l33"></a>
<a name="l34"></a>_MUL_U64_U64_TO_U128::
<a name="l35"></a></span><span class=cF2>//64bit * 64bit--&gt;128bit</span><span class=cF0>
<a name="l36"></a> </span><span class=cF1>PUSH</span><span class=cF0> </span><span class=cFC>RBP</span><span class=cF0>
<a name="l37"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RBP</span><span class=cF0>, </span><span class=cFC>RSP</span><span class=cF0>
<a name="l38"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RBX</span><span class=cF0>, </span><span class=cF9>U64</span><span class=cF0> </span><span class=cF3>SF_ARG3</span><span class=cF0>[</span><span class=cFC>RBP</span><span class=cF0>]
<a name="l39"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cFC>RAX</span><span class=cF0>, </span><span class=cF9>U64</span><span class=cF0> </span><span class=cF3>SF_ARG1</span><span class=cF0>[</span><span class=cFC>RBP</span><span class=cF0>] </span><span class=cF2>//</span><a href="https://www.tomawezome.github.io/ZealOS/Kernel/KernelA.html#l714"><span class=cF4>SF_ARG1</span></a><span class=cF0>
<a name="l40"></a> </span><span class=cF1>MUL</span><span class=cF0> </span><span class=cF9>U64</span><span class=cF0> </span><span class=cF3>SF_ARG2</span><span class=cF0>[</span><span class=cFC>RBP</span><span class=cF0>] </span><span class=cF2>//Res RDX:RAX 128bit</span><span class=cF0>
<a name="l41"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cF9>U64</span><span class=cF0> [</span><span class=cFC>RBX</span><span class=cF0>], </span><span class=cFC>RAX</span><span class=cF0>
<a name="l42"></a> </span><span class=cF1>MOV</span><span class=cF0> </span><span class=cF9>U64</span><span class=cF0> </span><span class=cFE>8</span><span class=cF0>[</span><span class=cFC>RBX</span><span class=cF0>], </span><span class=cFC>RDX</span><span class=cF0>
<a name="l43"></a> </span><span class=cF1>POP</span><span class=cF0> </span><span class=cFC>RBP</span><span class=cF0>
<a name="l44"></a> </span><span class=cF1>RET1</span><span class=cF0> </span><span class=cFE>24</span><span class=cF0>
<a name="l45"></a>};
<a name="l46"></a>
<a name="l47"></a></span><span class=cF2>//The convention is to put an underscore</span><span class=cF0>
<a name="l48"></a></span><span class=cF2>//on C callable asm routines.</span><span class=cF0>
<a name="l49"></a></span><span class=cF1>_extern</span><span class=cF0> _MUL_BY_HAND_U8_U8_TO_U16 </span><span class=cF9>U16</span><span class=cF0> MulU8(</span><span class=cF1>U8</span><span class=cF0> n1, </span><span class=cF1>U8</span><span class=cF0> n2);
<a name="l50"></a>
<a name="l51"></a></span><span class=cF1>class</span><span class=cF0> U128
<a name="l52"></a>{
<a name="l53"></a> </span><span class=cF9>U64</span><span class=cF0> lo, hi;
<a name="l54"></a>};
<a name="l55"></a>
<a name="l56"></a></span><span class=cF1>_extern</span><span class=cF0> _MUL_U64_U64_TO_U128 </span><span class=cF1>U0</span><span class=cF0> MulU64(</span><span class=cF9>I64</span><span class=cF0> n1, </span><span class=cF9>I64</span><span class=cF0> n2, U128 *_prod);
<a name="l57"></a>
<a name="l58"></a></span><span class=cF1>U0</span><span class=cF0> MulByHand()
<a name="l59"></a>{
<a name="l60"></a> U128 p;
<a name="l61"></a>
<a name="l62"></a> </span><span class=cF6>&quot;2*7 =0x%X\n&quot;</span><span class=cF0>, MulU8(</span><span class=cFE>2</span><span class=cF0>, </span><span class=cFE>7</span><span class=cF0>);
<a name="l63"></a> </span><span class=cF6>&quot;100*10=0x%X\n&quot;</span><span class=cF0>, MulU8(</span><span class=cFE>100</span><span class=cF0>, </span><span class=cFE>10</span><span class=cF0>);
<a name="l64"></a>
<a name="l65"></a> MulU64(</span><span class=cFE>0x0123456789ABCDEF</span><span class=cF0>, </span><span class=cFE>0x1000001</span><span class=cF0>, &amp;p);
<a name="l66"></a> </span><span class=cF6>&quot;0x0123466789ABCDEF*0x1000001=0x%016X%016X\n&quot;</span><span class=cF0>, p.hi, p.lo;
<a name="l67"></a>}
<a name="l68"></a>
<a name="l69"></a>MulByHand;
<a name="l70"></a>
</span></pre></body>
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