llvm/docs/AMDGPU/gfx8_waitcnt.rst
Dmitry Preobrazhensky 9c0dcead36 [AMDGPU][MC][DOC] Updated AMD GPU assembler description.
Summary of changes:
- Updated to reflect recent changes in assembler;
- Minor bugfixing and improvements.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372857 91177308-0d34-0410-b5e6-96231b3b80d8
2019-09-25 12:38:35 +00:00

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.. _amdgpu_synid8_waitcnt:
waitcnt
===========================
Counts of outstanding instructions to wait for.
The bits of this operand have the following meaning:
===== ================================================ ============
Bits Description Value Range
===== ================================================ ============
3:0 VM_CNT: vector memory operations count. 0..15
6:4 EXP_CNT: export count. 0..7
11:8 LGKM_CNT: LDS, GDS, Constant and Message count. 0..15
===== ================================================ ============
This operand may be specified as one of the following:
* An :ref:`integer_number<amdgpu_synid_integer_number>` or an :ref:`absolute_expression<amdgpu_synid_absolute_expression>`. The value must be in the range 0..0xFFFF.
* A combination of *vmcnt*, *expcnt*, *lgkmcnt* and other values described below.
====================== ======================================================================
Syntax Description
====================== ======================================================================
vmcnt(<*N*>) A VM_CNT value. *N* must not exceed the largest VM_CNT value.
expcnt(<*N*>) An EXP_CNT value. *N* must not exceed the largest EXP_CNT value.
lgkmcnt(<*N*>) An LGKM_CNT value. *N* must not exceed the largest LGKM_CNT value.
vmcnt_sat(<*N*>) A VM_CNT value computed as min(*N*, the largest VM_CNT value).
expcnt_sat(<*N*>) An EXP_CNT value computed as min(*N*, the largest EXP_CNT value).
lgkmcnt_sat(<*N*>) An LGKM_CNT value computed as min(*N*, the largest LGKM_CNT value).
====================== ======================================================================
These values may be specified in any order. Spaces, ampersands and commas may be used as optional separators.
*N* is either an
:ref:`integer number<amdgpu_synid_integer_number>` or an
:ref:`absolute expression<amdgpu_synid_absolute_expression>`.
Examples:
.. parsed-literal::
vm_cnt = 1
exp_cnt = 2
lgkm_cnt = 3
cnt = vm_cnt | (exp_cnt << 4) | (lgkm_cnt << 8)
s_waitcnt cnt
s_waitcnt 1 | (2 << 4) | (3 << 8) // the same as above
s_waitcnt vmcnt(1) expcnt(2) lgkmcnt(3) // the same as above
s_waitcnt vmcnt(vm_cnt) expcnt(exp_cnt) lgkmcnt(lgkm_cnt) // the same as above
s_waitcnt vmcnt(1)
s_waitcnt expcnt(2) lgkmcnt(3)
s_waitcnt vmcnt(1), expcnt(2), lgkmcnt(3)
s_waitcnt vmcnt(1) & lgkmcnt_sat(100) & expcnt(2)