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<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="Comment">//: operating directly on a register</span>
<span id="L2" class="LineNr"> 2 </span>
<span id="L3" class="LineNr"> 3 </span><span class="Delimiter">:(scenario add_r32_to_r32)</span>
<span id="L4" class="LineNr"> 4 </span><span class="Special">% Reg[0].i = 0x10;</span>
<span id="L5" class="LineNr"> 5 </span><span class="Special">% Reg[3].i = 1;</span>
<span id="L6" class="LineNr"> 6 </span><span class="Comment"># op ModR/M SIB displacement immediate</span>
<span id="L7" class="LineNr"> 7 </span> <span class="PreProc">0</span><span class="Constant">1</span> d8 <span class="Comment"># add EBX (reg 3) to EAX (reg 0)</span>
<span id="L8" class="LineNr"> 8 </span><span class="traceContains">+run: add <a href='010core.cc.html#L15'>reg</a> 3 to effective address</span>
<span id="L9" class="LineNr"> 9 </span><span class="traceContains">+run: effective address is <a href='010core.cc.html#L15'>reg</a> 0</span>
<span id="L10" class="LineNr">10 </span><span class="traceContains">+run: storing 0x00000011</span>
<span id="L11" class="LineNr">11 </span>
<span id="L12" class="LineNr">12 </span><span class="Delimiter">:(before "End Single-Byte Opcodes")</span>
<span id="L13" class="LineNr">13 </span><span class="Normal">case</span> <span class="Constant">0x01</span>: <span class="Delimiter">{</span> <span class="Comment">// add r32 to r/m32</span>
<span id="L14" class="LineNr">14 </span> <span class="Normal">uint8_t</span> modrm = <a href='010core.cc.html#L202'>next</a><span class="Delimiter">();</span>
<span id="L15" class="LineNr">15 </span> <span class="Normal">uint8_t</span> arg2 = <span class="Delimiter">(</span>modrm>><span class="Constant">3</span><span class="Delimiter">)</span>&<span class="Constant">0x7</span><span class="Delimiter">;</span>
<span id="L16" class="LineNr">16 </span> <a href='003trace.cc.html#L160'>trace</a><span class="Delimiter">(</span><span class="Constant">2</span><span class="Delimiter">,</span> <span class="Constant">"run"</span><span class="Delimiter">)</span> << <span class="Constant">"add <a href='010core.cc.html#L15'>reg</a> "</span> << <a href='010core.cc.html#L220'>NUM</a><span class="Delimiter">(</span>arg2<span class="Delimiter">)</span> << <span class="Constant">" to effective address"</span> << <a href='003trace.cc.html#L184'>end</a><span class="Delimiter">();</span>
<span id="L17" class="LineNr">17 </span> <span class="Normal">int32_t</span>* arg1 = <a href='011direct_addressing.cc.html#L26'>effective_address</a><span class="Delimiter">(</span>modrm<span class="Delimiter">);</span>
<span id="L18" class="LineNr">18 </span> <a href='010core.cc.html#L39'>BINARY_ARITHMETIC_OP</a><span class="Delimiter">(</span>+<span class="Delimiter">,</span> *arg1<span class="Delimiter">,</span> Reg[arg2]<span class="Delimiter">.</span><a href='010core.cc.html#L16'>i</a><span class="Delimiter">);</span>
<span id="L19" class="LineNr">19 </span> <span class="Identifier">break</span><span class="Delimiter">;</span>
<span id="L20" class="LineNr">20 </span><span class="Delimiter">}</span>
<span id="L21" class="LineNr">21 </span>
<span id="L22" class="LineNr">22 </span><span class="Delimiter">:(code)</span>
<span id="L23" class="LineNr">23 </span><span class="Comment">// Implement tables 2-2 and 2-3 in the Intel manual, Volume 2.</span>
<span id="L24" class="LineNr">24 </span><span class="Comment">// We return a pointer so that instructions can write to multiple bytes in</span>
<span id="L25" class="LineNr">25 </span><span class="Comment">// 'Mem' at once.</span>
<span id="L26" class="LineNr">26 </span><span class="Normal">int32_t</span>* <a href='011direct_addressing.cc.html#L26'>effective_address</a><span class="Delimiter">(</span><span class="Normal">uint8_t</span> modrm<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L27" class="LineNr">27 </span> <span class="Normal">uint8_t</span> mod = <span class="Delimiter">(</span>modrm>><span class="Constant">6</span><span class="Delimiter">);</span>
<span id="L28" class="LineNr">28 </span> <span class="Comment">// ignore middle 3 'reg opcode' bits</span>
<span id="L29" class="LineNr">29 </span> <span class="Normal">uint8_t</span> rm = modrm & <span class="Constant">0x7</span><span class="Delimiter">;</span>
<span id="L30" class="LineNr">30 </span> <span class="Normal">int32_t</span>* result = <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L31" class="LineNr">31 </span> <span class="Normal">switch</span> <span class="Delimiter">(</span>mod<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L32" class="LineNr">32 </span> <span class="Normal">case</span> <span class="Constant">3</span>:
<span id="L33" class="LineNr">33 </span> <span class="Conceal">¦</span> <span class="Comment">// mod 3 is just register direct addressing</span>
<span id="L34" class="LineNr">34 </span> <span class="Conceal">¦</span> <a href='003trace.cc.html#L160'>trace</a><span class="Delimiter">(</span><span class="Constant">2</span><span class="Delimiter">,</span> <span class="Constant">"run"</span><span class="Delimiter">)</span> << <span class="Constant">"effective address is <a href='010core.cc.html#L15'>reg</a> "</span> << <a href='010core.cc.html#L220'>NUM</a><span class="Delimiter">(</span>rm<span class="Delimiter">)</span> << <a href='003trace.cc.html#L184'>end</a><span class="Delimiter">();</span>
<span id="L35" class="LineNr">35 </span> <span class="Conceal">¦</span> result = &Reg[rm]<span class="Delimiter">.</span><a href='010core.cc.html#L16'>i</a><span class="Delimiter">;</span>
<span id="L36" class="LineNr">36 </span> <span class="Conceal">¦</span> <span class="Identifier">break</span><span class="Delimiter">;</span>
<span id="L37" class="LineNr">37 </span> <span class="Comment">// End Mod Special-cases</span>
<span id="L38" class="LineNr">38 </span> <span class="Normal">default</span>:
<span id="L39" class="LineNr">39 </span> <span class="Conceal">¦</span> cerr << <span class="Constant">"unrecognized mod bits: "</span> << <a href='010core.cc.html#L220'>NUM</a><span class="Delimiter">(</span>mod<span class="Delimiter">)</span> << <span class="cSpecial">'\n'</span><span class="Delimiter">;</span>
<span id="L40" class="LineNr">40 </span> <span class="Conceal">¦</span> exit<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
<span id="L41" class="LineNr">41 </span> <span class="Delimiter">}</span>
<span id="L42" class="LineNr">42 </span> <span class="Identifier">return</span> result<span class="Delimiter">;</span>
<span id="L43" class="LineNr">43 </span><span class="Delimiter">}</span>
<span id="L44" class="LineNr">44 </span>
<span id="L45" class="LineNr">45 </span><span class="SalientComment">//:: subtract</span>
<span id="L46" class="LineNr">46 </span>
<span id="L47" class="LineNr">47 </span><span class="Delimiter">:(scenario subtract_r32_from_r32)</span>
<span id="L48" class="LineNr">48 </span><span class="Special">% Reg[0].i = 10;</span>
<span id="L49" class="LineNr">49 </span><span class="Special">% Reg[3].i = 1;</span>
<span id="L50" class="LineNr">50 </span><span class="Comment"># op ModR/M SIB displacement immediate</span>
<span id="L51" class="LineNr">51 </span> <span class="Constant">29</span> d8 <span class="Comment"># subtract EBX (reg 3) from EAX (reg 0)</span>
<span id="L52" class="LineNr">52 </span><span class="traceContains">+run: subtract <a href='010core.cc.html#L15'>reg</a> 3 from effective address</span>
<span id="L53" class="LineNr">53 </span><span class="traceContains">+run: effective address is <a href='010core.cc.html#L15'>reg</a> 0</span>
<span id="L54" class="LineNr">54 </span><span class="traceContains">+run: storing 0x00000009</span>
<span id="L55" class="LineNr">55 </span>
<span id="L56" class="LineNr">56 </span><span class="Delimiter">:(before "End Single-Byte Opcodes")</span>
<span id="L57" class="LineNr">57 </span><span class="Normal">case</span> <span class="Constant">0x29</span>: <span class="Delimiter">{</span> <span class="Comment">// subtract r32 from r/m32</span>
<span id="L58" class="LineNr">58 </span> <span class="Normal">uint8_t</span> modrm = <a href='010core.cc.html#L202'>next</a><span class="Delimiter">();</span>
<span id="L59" class="LineNr">59 </span> <span class="Normal">uint8_t</span> arg2 = <span class="Delimiter">(</span>modrm>><span class="Constant">3</span><span class="Delimiter">)</span>&<span class="Constant">0x7</span><span class="Delimiter">;</span>
<span id="L60" class="LineNr">60 </span> <a href='003trace.cc.html#L160'>trace</a><span class="Delimiter">(</span><span class="Constant">2</span><span class="Delimiter">,</span> <span class="Constant">"run"</span><span class="Delimiter">)</span> << <span class="Constant">"subtract <a href='010core.cc.html#L15'>reg</a> "</span> << <a href='010core.cc.html#L220'>NUM</a><span class="Delimiter">(</span>arg2<span class="Delimiter">)</span> << <span class="Constant">" from effective address"</span> << <a href='003trace.cc.html#L184'>end</a><span class="Delimiter">();</span>
<span id="L61" class="LineNr">61 </span> <span class="Normal">int32_t</span>* arg1 = <a href='011direct_addressing.cc.html#L26'>effective_address</a><span class="Delimiter">(</span>modrm<span class="Delimiter">);</span>
<span id="L62" class="LineNr">62 </span> <a href='010core.cc.html#L39'>BINARY_ARITHMETIC_OP</a><span class="Delimiter">(</span>-<span class="Delimiter">,</span> *arg1<span class="Delimiter">,</span> Reg[arg2]<span class="Delimiter">.</span><a href='010core.cc.html#L16'>i</a><span class="Delimiter">);</span>
<span id="L63" class="LineNr">63 </span> <span class="Identifier">break</span><span class="Delimiter">;</span>
<span id="L64" class="LineNr">64 </span><span class="Delimiter">}</span>
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