waitcnt — LLVM 8 documentation

# waitcnt

Counts of outstanding instructions to wait for.

The bits of this operand have the following meaning:

> Bits | Description
> --- | ---
> 3:0 | VM_CNT: vector memory operations count.
> 6:4 | EXP_CNT: export count.
> 11:8 | LGKM_CNT: LDS, GDS, Constant and Message count.

This operand may be specified as a positive 16-bit integer_number or as a combination of the following symbolic helpers:

> Syntax | Description
> --- | ---
> vmcnt(<N>) | VM_CNT value. N must not exceed the largest VM_CNT value.
> expcnt(<N>) | EXP_CNT value. N must not exceed the largest EXP_CNT value.
> lgkmcnt(<N>) | LGKM_CNT value. N must not exceed the largest LGKM_CNT value.
> vmcnt_sat(<N>) | VM_CNT value computed as min(N, the largest VM_CNT value).
> expcnt_sat(<N>) | EXP_CNT value computed as min(N, the largest EXP_CNT value).
> lgkmcnt_sat(<N>) | LGKM_CNT value computed as min(N, the largest LGKM_CNT value).

These helpers may be specified in any order. Ampersands and commas may be used as optional separators.

N is either an integer number or an absolute expression.

Examples:

    s_waitcnt 0
    s_waitcnt vmcnt(1)
    s_waitcnt expcnt(2) lgkmcnt(3)
    s_waitcnt vmcnt(1) expcnt(2) lgkmcnt(3)
    s_waitcnt vmcnt(1), expcnt(2), lgkmcnt(3)
    s_waitcnt vmcnt(1) & lgkmcnt_sat(100) & expcnt(2)