From 4618092fb7ad0e062d07cf06143fd5cd8cb9595a Mon Sep 17 00:00:00 2001
From: Simon Ochsenreither <simon@ochsenreither.de>
Date: Sun, 30 Jul 2023 20:54:53 +0200
Subject: [PATCH] add x86 prefixes and escape opcodes flowchart

---
 ...6-prefixes-and-escape-opcodes-flowchart.md | 84 +++++++++++++++++++
 index.md                                      |  1 +
 2 files changed, 85 insertions(+)
 create mode 100644 _interfaces/x86-prefixes-and-escape-opcodes-flowchart.md

diff --git a/_interfaces/x86-prefixes-and-escape-opcodes-flowchart.md b/_interfaces/x86-prefixes-and-escape-opcodes-flowchart.md
new file mode 100644
index 00000000..e9cb4c3b
--- /dev/null
+++ b/_interfaces/x86-prefixes-and-escape-opcodes-flowchart.md
@@ -0,0 +1,84 @@
+---
+title:  "x86 prefixes and escape opcodes flowchart (WIP)"
+date:   2023-07-29 12:00:00 +0200
+markdeep: true
+---
+
+<div class="diagram">
+ start here
+      |
+      v
+╔═══════════════════════════════════════════════════╤══╗   ╔══════════════════════════════════════════════════════╗
+║ 1-byte instructions (legacy map 0)                │0F--->║ 2-byte instructions (legacy map 1)                   ║
+║                                                   └──╢   ║                                                      ║
+╟──────────────────────────────────────────────────────╢   ║ operand type specified      ┌──┐   ┌──┐              ║
+║                          40-4F                       ║   ║ via mandatory prefixes      │38│   │3A------------------.
+╟────────────────────────────|─────────────────────────╢   ║ - none (packed single)      └─|┘   └──┘              ║  |
+║      ┌──┐       ┌──┬──┐    |                         ║   ║ - 66   (packed double)        |                      ║  |
+║    .--62│       │66│67│    |                         ║   ║ - F2   (scalar single)        |                      ║  |
+║    | └──┘       └─|┴─|┘    |                         ║   ║ - F3   (scalar double)        |                      ║  |
+║    |              |  |     |    ┌──┬──┐              ║   ╚═══════════════════════════════|══════════════════════╝  |
+║    |              |  |     |    │C4│C5-----.         ║                                   v                         |
+║    |              |  |     |    └|─┼──┤    |         ║   ╔══════════════════════════════════════════════════════╗  |
+╟──┐ | ┌──┬──┐      |  |     |     | │D5│    |         ║   ║ 3-byte instructions (legacy map 2)                   ║  |
+║F0│ | │F2│F3│      |  |     |     | └─|┘    |         ║   ║                                                      ║  |
+╚══╧═|═╧═|╧═|╧══════|══|═════|═════|═══|═════|═════════╝   ║ operand type specified                               ║  |
+     |   |  |   ^   |  |     |^    |^  |^    |^            ║ via mandatory prefixes                               ║  |
+     |   |  |   |   |  |     ||    ||  ||    ||            ║ - none (packed single)                               ║  |
+     v   '--+---+---+--'     v|    v|  v|    v|            ║ - 66   (packed double)                               ║  |
+  ┏━━━━┓                  ┏━━━|┓┏━━━|┓┏━|━━┓┏━|━━┓         ║ - F2   (scalar single)                               ║  |
+  ┃EVEX┃                  ┃REX1┃┃VEX3┃┃REX2┃┃VEX2┃         ║ - F3   (scalar double)                               ║  |
+  ┗━━━━┛                  ┗━━━━┛┗━━━━┛┗━━━━┛┗━━━━┛         ╚══════════════════════════════════════════════════════╝  |
+                                                                                                                     |
+                                                           ╔══════════════════════════════════════════════════════╗  |
+                                                           ║ 3-byte instructions (legacy map 3)                   ║<-+
+                                                           ║                                                      ║
+                                                           ║ operand type specified                               ║
+                                                           ║ via mandatory prefixes                               ║
+                                                           ║ - none (packed single)                               ║
+                                                           ║ - 66   (packed double)                               ║
+                                                           ║ - F2   (scalar single)                               ║
+                                                           ║ - F3   (scalar double)                               ║
+                                                           ╚══════════════════════════════════════════════════════╝
+</div>
+
+<div class="diagram">
+┏━┯━┯━┯━┯━┯━┯━┯━┓                                                    ┏━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┓
+┃0 1 0 0 W R X B┃                                                    ┃1 1 0 1 0 1 0 1┃M R X B W R X B┃
+┗━┷━┷━┷━┷━┷━┷━┷━┛                                                    ┗━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┛
+REX (1-byte prefix                                                   REX (2-byte prefix)
+- W extends operand size                                             - M selects legacy map 0 or legacy map 1
+- R extends register bits                                            - W extends operand size
+- X extends index in SIB byte                                        - R extends register bits
+- B extends base in SIB byte                                         - X extends index in SIB byte
+                                                                     - B extends base in SIB byte
+
+
+┏━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┓                                    ┏━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┓
+┃1 1 0 0 0 1 0 1┃Ṙ ⩒ ⩒ ⩒ ⩒ L p p┃                                    ┃1 1 0 0 0 1 0 0┃Ṙ Ẋ Ḃ m m m m m┃W ⩒ ⩒ ⩒ ⩒ L p p┃
+┗━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┛                                    ┗━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┛
+VEX (2-byte prefix)                                                  VEX (3-byte prefix)
+- R extends register bits                                            - R extends register bits
+- v encodes additional source register                               - X extends index in SIB byte
+- L selects vector length (0: 128bit | 1: 256bit)                    - B extends base in SIB byte
+- p encodes mandatory prefixes                                       - m encodes escape bytes (1: 0F | 2: 0F38 | 3: 0F3A)
+  (0: none | 1: 66 | 2: F2 | 3: F3)                                  - W extends operand size
+                                                                     - v encodes additional source register
+                                                                     - L selects vector length (0: 128bit, 1: 256bit)                
+                                                                     - p encodes mandatory prefixes
+                                                                       (0: none | 1: 66 | 2: F2 | 3: F3)
+
+
+┏━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┓
+┃0 1 1 0 0 0 1 0┃Ṙ Ẋ Ḃ Ṙ B m m m┃W ⩒ ⩒ ⩒ ⩒ Ẋ p p┃z Ŀ L b ⩒ a a a┃
+┗━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┛
+EVEX (4-byte prefix)
+- R extends register bits
+- X extends index in SIB byte
+- B extends base in SIB byte
+- m encodes escape bytes (1: 0F | 2: 0F38 | 3: 0F3A)
+- W extends operand size
+- v encodes additional source register
+- p encodes mandatory prefixes (0: none | 1: 66 | 2: F2 | 3: F3)
+- z selects merge mode (0: zero | 1: merge)
+</div>
diff --git a/index.md b/index.md
index bb5e4d7c..c8ed1a63 100644
--- a/index.md
+++ b/index.md
@@ -187,6 +187,7 @@ navigation: true
   <tr>
     <th class="table-topic">Interfaces</th>
     <td>
+      <div><a href="interfaces/x86-prefixes-and-escape-opcodes-flowchart" class="compact">x86 prefix & escape flowchart</a></div>
       <div><a href="interfaces/improving-the-xfce-settings-ui" class="compact">Improving the XFCE Settings UI</a></div>
     </td>
     <td>