add x86 prefixes and escape opcodes flowchart

soc · Aug 6, 2023 · ceffe59 · ceffe59
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diff --git a/_interfaces/x86-prefixes-and-escape-opcodes-flowchart.md b/_interfaces/x86-prefixes-and-escape-opcodes-flowchart.md
@@ -0,0 +1,87 @@
+---
+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)                           ║  |
+  ┗━━|━┛        |         ┗━━━━┛┗━━|━┛┗━━━━┛┗━━━━┛ m bits   |    ╚══════════════════════════════════════════════════╝  |
+     |          |                  |                        |                                                          |
+     '----------+------------------+------------------------+    ╔══════════════════════════════════════════════════╗  |
+                       m bits                               '--->║ 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                                            - R extends register bits
+- X extends index in SIB byte                                        - X extends index in SIB byte
+- B extends base in SIB byte                                         - B extends base in SIB byte
+                                                                     - W extends operand size
+
+
+┏━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┓                                    ┏━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┓
+┃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
+- escape bytes 0F implied (legacy map 1)                             - 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)
+
+
+┏━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┳━┯━┯━┯━┯━┯━┯━┯━┓          Notes:
+┃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┃          - letters with a dot above denote that the
+┗━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┻━┷━┷━┷━┷━┷━┷━┷━┛            prefix contains the bit in inverted form
+EVEX (4-byte prefix)                                                       - the diagram elides escape bytes D8 til DF
+- 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)
+- Ŀ selects vector length (512bit) or rounding control mode (with L)
+- Ŀ selects vector length (256bit)
+- b encodes source broadcast or rounding control (with Ŀ and L) or exception suppression
+</div>
diff --git 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>