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OSMX64 is a 64-bit multi-core SoC architecture designed to be fast, efficient, and low-cost.
## Registers
Registers store data which can be accessed at any time. These include special registers for
| Name | Size | Purpose |
| ---------- | -------- | ----------------------------------- |
| `x0` | 64 bits | Read-only, always `0` |
| `x1`-`x15` | 64 bits | General purpose, read-write |
| `f0`-`f7` | 32 bits | IEEE 754 single-precision number |
| `d0`-`d7` | 64 bits | IEEE 754 double-precision number |
| `v0`-`v7` | 512 bits | SIMD vector data |
| `pc` | 64 bits | Program counter, `0` on startup |
| `sp` | 64 bits | Stack pointer |
| `fp` | 64 bits | Frame pointer |
| `ptp` | 64 bits | Page tree pointer |
### Internal Registers
Only accessed by the CPU for certain instructions. Cannot be directly read/written.
| Name | Size | Purpose |
| ----- | ------- | --------------------------- |
| `rp` | 64 bits | Return pointer for branches |
| `ins` | 64 bits | Current instruction at `pc` |
## Instructions
### Bitwise Instructions
Bitwise logic operations can write to all registers except `v0`-`v7`, `x0` and `pc`. Can read from all registers except `v0`-`v7`.
| Mnemonic | Effect |
| -------------------------------- | ---------------------- |
| `and` dst: r, reg: r, val: r/imm | `dst` = `dst` & `val` |
| `or` dst: r, reg: r, val: r/imm | `dst` = `dst` \| `val` |
| `xor` dst: r, reg: r, val: r/imm | `dst` = `dst` ^ `val` |
#### Example
```
/* Set x1 to 5 */
mov x1, #5
/* Ands x1 (which equals 5) with 1 */
and x1, #1
/* x1 now equals 1 */
```
### Data Movement Instructions
| Mnemonic | Effect
| ------------------------------------- | ---------------------------------- |
| `mov` dst: r, src: r/imm | `dst` = `src` |
| `stb` src: r, [dst: m, offset: r/imm] | 1-byte write to memory at `dst` |
| `stw` src: r, [dst: m, offset: r/imm] | 2-byte write to memory at `dst` |
| `std` src: r, [dst: m, offset: r/imm] | 4-byte write to memory at `dst` |
| `stq` src: r, [dst: m, offset: r/imm] | 8-byte write to memory at `dst` |
| `ltb` dst: r, [src: m, offset: r/imm] | 1-byte read from memory at `src` |
| `ltw` dst: r, [src: m, offset: r/imm] | 2-byte read from memory at `src` |
| `ltd` dst: r, [src: m, offset: r/imm] | 4-byte read from memory at `src` |
| `ltq` dst: r, [src: m, offset: r/imm] | 8-byte read from memory at `src` |
#### Example
```
/* Set x1 to 7 */
mov x1, #7
/* Write to memory pointed by sp */
stq x1, [sp]
/* Write to memory pointed by sp + 8 */
stq x1, [sp, #8]
/* Write to memory pointed by sp + x2 */
mov x2, #16
stq x1, [sp, x2]
```
### Arithmetic Instructions
Arithmetic operations can write to all registers except `v0`-`v7`, `x0` and `pc`. Can read from all registers except `v0`-`v7`.
| Mnemonic | Effect |
| ------------------------------------ | --------------------- |
| `add` dst: r, reg: r, val: r/imm | `dst` = `dst` + `val` |
| `sub` dst: r, reg: r, val: r/imm | `dst` = `dst` - `val` |
| `mul` dst: r, reg: r, val: r/imm | `dst` = `dst` * `val` |
| `div` dst: r, reg: r, val: r/imm | `dst` = `dst` / `val` |
| `inc` dst: r | `dst` = `dst` + `1` |
| `dec` dst: r | `dst` = `dst` - `1` |
#### Example
```
/* Set x1 to 5 */
mov x1, #5
/* Increment x1 */
inc x1
/* x1 now equals 6 */
```
### Control Flow Instructions
Control flow instructions are used to control which instructions the CPU executes, allowing for the concept of procedures and conditional execution.
| Mnemonic | Effect |
| -------------------------------------- | ----------------------------------------------- |
| `hlt` | Execution halted |
| `br` dst: r/m/imm | `pc` = `dst` |
| `brl` dst: r/m/imm | `rp` = `pc` + size of opcode, then `pc` = `dst` |
| `bret` | `pc` = `rp` |
| `beq` a: r/m, b: r/m/imm, dst: r/m/imm | Iff `a` = `b`, `pc` = `dst` |
| `bne` a: r/m, b: r/m/imm, dst: r/m/imm | Iff `a` != `b`, `pc` = `dst` |
| `blt` a: r/m, b: r/m/imm, dst: r/m/imm | Iff `a` < `b`, `pc` = `dst` |
| `bgt` a: r/m, b: r/m/imm, dst: r/m/imm | Iff `a` > `b`, `pc` = `dst` |
| `ble` a: r/m, b: r/m/imm, dst: r/m/imm | Iff `a` <= `b`, `pc` = `dst` |
| `bge` a: r/m, b: r/m/imm, dst: r/m/imm | Iff `a` >= `b`, `pc` = `dst` |
#### Example
```
/* Subtract x2 from x1 */
sub x1, x1, x2
beq x1, #0, zero
mov x1, #2
zero:
mov x1, #3
/* Iff x1 - x2 = 0, x1 equals 3 */
/* Iff x1 - x1 != 0, x1 equals 2 */
```
Copyright (c) 2024 Quinn Stephens and Ian Marco Moffett.
All rights reserved.
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