User Guide for R600 Back-end — LLVM 3.6 documentation

# User Guide for R600 Back-end

## Introduction

The R600 back-end provides ISA code generation for AMD GPUs, starting with the R600 family up until the current Sea Islands (GCN Gen 2).

## Assembler

The assembler is currently a work in progress and not yet complete. Below are the currently supported features.

### SOPP Instructions

Unless otherwise mentioned, all SOPP instructions that with an operand accept a integer operand(s) only. No verification is performed on the operands, so it is up to the programmer to be familiar with the range or acceptable values.

#### s_waitcnt

s_waitcnt accepts named arguments to specify which memory counter(s) to wait for.

    // Wait for all counters to be 0
    s_waitcnt 0

    // Equivalent to s_waitcnt 0.  Counter names can also be delimited by
    // '&' or ','.
    s_waitcnt vmcnt(0) expcnt(0) lgkcmt(0)

    // Wait for vmcnt counter to be 1.
    s_waitcnt vmcnt(1)