From 311297cb006201f4706704b32c762630806c7adb Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Sat, 14 Oct 2017 23:33:27 -0700
Subject: 4066

I spent a while spelunking into the code generated by C compilers before
realizing that ignoring the order of arguments for 'cmp' instructions
clarifies everything.
---
 html/subx/011direct_addressing.cc.html   | 2 +-
 html/subx/012indirect_addressing.cc.html | 2 +-
 subx/011direct_addressing.cc             | 2 +-
 subx/012indirect_addressing.cc           | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/html/subx/011direct_addressing.cc.html b/html/subx/011direct_addressing.cc.html
index 8638ecfe..67117464 100644
--- a/html/subx/011direct_addressing.cc.html
+++ b/html/subx/011direct_addressing.cc.html
@@ -226,7 +226,7 @@ if ('onhashchange' in window) {
 <span id="L161" class="LineNr">161 </span><span class="traceContains">+run: SF=0; ZF=0; OF=0</span>
 <span id="L162" class="LineNr">162 </span>
 <span id="L163" class="LineNr">163 </span><span class="Delimiter">:(before &quot;End Single-Byte Opcodes&quot;)</span>
-<span id="L164" class="LineNr">164 </span><span class="Normal">case</span> <span class="Constant">0x39</span>: <span class="Delimiter">{</span>  <span class="Comment">// compare r32 with r/m32</span>
+<span id="L164" class="LineNr">164 </span><span class="Normal">case</span> <span class="Constant">0x39</span>: <span class="Delimiter">{</span>  <span class="Comment">// set SF if r/m32 &lt; r32</span>
 <span id="L165" class="LineNr">165 </span>  <span class="Normal">uint8_t</span> modrm = <a href='010core.cc.html#L210'>next</a><span class="Delimiter">();</span>
 <span id="L166" class="LineNr">166 </span>  <span class="Normal">uint8_t</span> reg2 = <span class="Delimiter">(</span>modrm&gt;&gt;<span class="Constant">3</span><span class="Delimiter">)</span>&amp;<span class="Constant">0x7</span><span class="Delimiter">;</span>
 <span id="L167" class="LineNr">167 </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">&quot;run&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;compare <a href='010core.cc.html#L15'>reg</a> &quot;</span> &lt;&lt; <a href='010core.cc.html#L228'>NUM</a><span class="Delimiter">(</span>reg2<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; with effective address&quot;</span> &lt;&lt; <a href='003trace.cc.html#L184'>end</a><span class="Delimiter">();</span>
diff --git a/html/subx/012indirect_addressing.cc.html b/html/subx/012indirect_addressing.cc.html
index 72211ce3..ab3650f6 100644
--- a/html/subx/012indirect_addressing.cc.html
+++ b/html/subx/012indirect_addressing.cc.html
@@ -302,7 +302,7 @@ if ('onhashchange' in window) {
 <span id="L238" class="LineNr">238 </span><span class="traceContains">+run: SF=0; ZF=0; OF=0</span>
 <span id="L239" class="LineNr">239 </span>
 <span id="L240" class="LineNr">240 </span><span class="Delimiter">:(before &quot;End Single-Byte Opcodes&quot;)</span>
-<span id="L241" class="LineNr">241 </span><span class="Normal">case</span> <span class="Constant">0x3b</span>: <span class="Delimiter">{</span>  <span class="Comment">// compare r/m32 with r32</span>
+<span id="L241" class="LineNr">241 </span><span class="Normal">case</span> <span class="Constant">0x3b</span>: <span class="Delimiter">{</span>  <span class="Comment">// set SF if r32 &lt; r/m32</span>
 <span id="L242" class="LineNr">242 </span>  <span class="Normal">uint8_t</span> modrm = <a href='010core.cc.html#L210'>next</a><span class="Delimiter">();</span>
 <span id="L243" class="LineNr">243 </span>  <span class="Normal">uint8_t</span> reg1 = <span class="Delimiter">(</span>modrm&gt;&gt;<span class="Constant">3</span><span class="Delimiter">)</span>&amp;<span class="Constant">0x7</span><span class="Delimiter">;</span>
 <span id="L244" class="LineNr">244 </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">&quot;run&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;compare effective address with <a href='010core.cc.html#L15'>reg</a> &quot;</span> &lt;&lt; <a href='010core.cc.html#L228'>NUM</a><span class="Delimiter">(</span>reg1<span class="Delimiter">)</span> &lt;&lt; <a href='003trace.cc.html#L184'>end</a><span class="Delimiter">();</span>
diff --git a/subx/011direct_addressing.cc b/subx/011direct_addressing.cc
index facc8378..a12b5541 100644
--- a/subx/011direct_addressing.cc
+++ b/subx/011direct_addressing.cc
@@ -161,7 +161,7 @@ case 0xf7: {  // xor r32 with r/m32
 +run: SF=0; ZF=0; OF=0
 
 :(before "End Single-Byte Opcodes")
-case 0x39: {  // compare r32 with r/m32
+case 0x39: {  // set SF if r/m32 < r32
   uint8_t modrm = next();
   uint8_t reg2 = (modrm>>3)&0x7;
   trace(2, "run") << "compare reg " << NUM(reg2) << " with effective address" << end();
diff --git a/subx/012indirect_addressing.cc b/subx/012indirect_addressing.cc
index 38c3d234..546df707 100644
--- a/subx/012indirect_addressing.cc
+++ b/subx/012indirect_addressing.cc
@@ -238,7 +238,7 @@ case 0x33: {  // xor r/m32 with r32
 +run: SF=0; ZF=0; OF=0
 
 :(before "End Single-Byte Opcodes")
-case 0x3b: {  // compare r/m32 with r32
+case 0x3b: {  // set SF if r32 < r/m32
   uint8_t modrm = next();
   uint8_t reg1 = (modrm>>3)&0x7;
   trace(2, "run") << "compare effective address with reg " << NUM(reg1) << end();
-- 
cgit 1.4.1-2-gfad0