# SPARC V9 ISA Reference

Reference documentation for the SPARC V9 instruction set as implemented in ReviveSparc.

## Overview

The SPARC V9 architecture is a 64-bit RISC ISA developed by Sun Microsystems and standardized by SPARC International. ReviveSparc implements the full SPARC V9 specification, including the VIS (Visual Instruction Set) extensions.

### Key Features

- 64-bit integer and floating-point registers
- 32 general-purpose registers (register windowed)
- 32 floating-point registers (quad-precision capable)
- Delayed branching with annulment
- Register windowing with 8 global + up to 32 windowed registers
- Precise exceptions and multiple trap levels

## Instruction Set Categories

### Integer Instructions

```
ADD      Add                  ADDcc    Add and modify CC
AND      And                  ANDcc    And and modify CC
OR       Or                   ORcc     Or and modify CC
XOR      Exclusive Or         XORcc    Exclusive Or and modify CC
SUB      Subtract             SUBcc    Subtract and modify CC
MULX     Multiply Extended    UDIVX    Unsigned Divide Extended
SDIVX    Signed Divide Extended
SLL      Shift Left Logical   SRL      Shift Right Logical
SRA      Shift Right Arithmetic
```

### Load/Store Instructions

```
LDUB     Load Unsigned Byte
LDSB     Load Signed Byte
LDUH     Load Unsigned Halfword
LDSH     Load Signed Halfword
LDW      Load Word
LDX      Load Doubleword
STB      Store Byte
STH      Store Halfword
STW      Store Word
STX      Store Doubleword
LDF      Load Floating-point
LDDF     Load Double Floating-point
STF      Store Floating-point
STDF     Store Double Floating-point
```

### Branch Instructions

```
Bcc      Branch on Condition
BPcc     Branch on Condition (Predicted)
BPr      Branch on Register
CALL     Call and Link
RETT     Return from Trap
JMPL     Jump and Link
RETURN   Return from Subroutine
```

### Floating-Point Instructions

```
FADDs    FP Add (single)
FADDd    FP Add (double)
FSUBs    FP Subtract (single)
FSUBd    FP Subtract (double)
FMULs    FP Multiply (single)
FMULd    FP Multiply (double)
FDIVs    FP Divide (single)
FDIVd    FP Divide (double)
FSQRTs   FP Square Root (single)
FSQRTd   FP Square Root (double)
F CMPs   FP Compare (single)
F CMPd   FP Compare (double)
```

### VIS Instructions

```
FPACK16  Pack 16-bit
FPACK32  Pack 32-bit
FALIGNDATA  Align Data
FEXPAND  Expand
FMUL8x16  Multiply 8-bit by 16-bit
FMUL8x16AU  Multiply 8-bit by 16-bit (unsigned)
FMUL8x16AL  Multiply 8-bit by 16-bit (unsigned)
FMUL8SUx16  Multiply 8-bit Signed by 16-bit Unsigned
FMUL8ULx16  Multiply 8-bit Unsigned by 16-bit Unsigned
FMULD8SUx16  Multiply Double 8-bit Signed by 16-bit Unsigned
FMULD8ULx16  Multiply Double 8-bit Unsigned by 16-bit Unsigned
```

## Register Windows

SPARC V9 uses register windows to optimize function call performance:

- **8 global registers** (%g0 through %g7, where %g0 is always zero)
- **Up to 32 register windows**, each containing 16 registers
- Each window provides: 8 incoming (%i0-%i7), 8 local (%l0-%l7), 8 outgoing (%o0-%o7) — with overlap between adjacent windows
- The number of windows is implementation-dependent

## Privileged Registers

| Register | Description |
|----------|-------------|
| TPC      | Trap PC (1-4) |
| TNPC     | Trap Next PC (1-4) |
| TSTATE   | Trap State (1-4) |
| TT       | Trap Type (1-4) |
| TBA      | Trap Base Address |
| PSTATE   | Processor State |
| TL       | Trap Level |
| PIL      | Processor Interrupt Level |
| CWP      | Current Window Pointer |
| CANSAVE  | Cleanable Windows |
| CANRESTORE | Restorable Windows |

## Trap Types

| TT Value | Trap Name | Description |
|----------|-----------|-------------|
| 0x01     | instruction_access_exception | Memory access fault |
| 0x03     | instruction_access_error | Hardware error |
| 0x04     | illegal_instruction | Unimplemented instruction |
| 0x05     | privileged_operation | Trap in user mode |
| 0x06     | fp_disabled | FPU not enabled |
| 0x08     | clean_window | Register window spill needed |
| 0x09     | division_by_zero | Integer divide by zero |
| 0x20-0x2f | interrupt_vector | External interrupts |
| 0x60-0x7f | software_trap | `ta` instruction traps |
| 0x80     | data_access_exception | Data memory access fault |
| 0x82     | data_access_error | Data memory hardware error |