blob: a279469c62f91e3962080db7f270d5332e3347f4 [file] [log] [blame]
Name Strings
Kedarnath Thangudu, NVIDIA Corporation (kthangudu 'at'
Pat Brown, NVIDIA
Shipping in NVIDIA release 367.XX drivers and up.
Last Modified Date: October 15, 2014
NVIDIA Revision: 1
OpenGL Extension #488
This extension is written against the OpenGL 4.5 (Compatibility Profile)
This extension is written against version 4.50 (revision 3) of the OpenGL
Shading Language Specification.
This extension requires ARB_gpu_shader_fp64 or NV_gpu_program_fp64.
This extension interacts with NV_shader_buffer_store, NV_gpu_shader5,
ARB_shader_storage_buffer_object, and ARB_compute_shader.
This extension interacts with NV_gpu_program5.
This extension provides GLSL built-in functions and assembly opcodes
allowing shaders to perform atomic read-modify-write operations to buffer
or shared memory with double-precision floating-point components. The set
of atomic operations provided by this extension is limited to adds and
exchanges. Providing atomic add support allows shaders to atomically
accumulate the sum of double-precision floating-point values into buffer
memory across multiple (possibly concurrent) shader invocations.
This extension provides GLSL support for atomics targeting double-precision
floating-point pointers (if NV_gpu_shader5 is supported).
Additionally, assembly opcodes for these operations are also provided if
NV_gpu_program5 is supported.
New Procedures and Functions
New Tokens
Additions to the OpenGL 4.5 (Compatibility Profile) Specification
Additions to the AGL/GLX/WGL Specifications
GLX Protocol
Modifications to the OpenGL Shading Language Specification, Version 4.50
(revision 3)
Including the following line in a shader can be used to control the
language features described in this extension:
#extension GL_NV_shader_atomic_float64 : <behavior>
where <behavior> is as specified in section 3.3.
New preprocessor #defines are added to the OpenGL Shading Language:
#define GL_NV_shader_atomic_float64 1
Modify Section 8.11, Atomic Memory Functions (p. 172)
(add to "atomicAdd" table cell, p. 173)
double atomicAdd(coherent inout double mem, double data)
(add to "atomicExchange" table cell, p. 173)
double atomicExchange(coherent inout double mem, double data)
Dependencies on NV_shader_buffer_store, NV_gpu_shader5,
ARB_shader_storage_buffer_object, and ARB_compute_shader
If NV_shader_buffer_store and NV_gpu_shader5 are supported, the following
functions should be added to the "Section 8.Y, Shader Memory Functions"
language in the NV_shader_buffer_store specification:
double atomicAdd(double *address, double data);
double atomicExchange(double *address, double data);
If ARB_shader_storage_buffer_object or ARB_compute_shader are supported,
make similar edits to the functions documented in the
ARB_shader_storage_buffer object extension.
These functions are available if and only if GL_NV_shader_atomic_float64 is
enabled via the "#extension" directive.
Dependencies on NV_gpu_program5
If NV_gpu_program5 is supported and "OPTION NV_shader_atomic_float64" is
specified in an assembly program, "F64" should be allowed as a storage
modifier to the ATOM instruction for the atomic operations "ADD" and
(Add to "Section 2.X.6, Program Options" of the NV_gpu_program4 extension,
as extended by NV_gpu_program5:)
+ Double-precision Floating-Point Atomic Operations (NV_shader_atomic_float64)
If a program specifies the "NV_shader_atomic_float64" option, it may use
"F64" storage modifier with the "ATOM" opcode to perform atomic double-
precision floating-point add or exchange operations.
(Add to the table in "Section 2.X.8.Z, ATOM" in NV_gpu_program5:)
atomic storage
modifier modifiers operation
-------- ----------------------- ---------------------------------
ADD U32, S32, U64, F32, F64 compute a sum
F16X2, F16X4
EXCH U32, S32, U64, F32, F64 exchange memory with operand
F16X2, F16X4
Storage modifier U64 is provided by NV_shader_atomic_int64
Storage modifier F32 is provided by NV_shader_atomic_float
Storage modifiers F16X2 and F16X4 are provided by NV_shader_atomic_fp16_vector
New State
New Implementation Dependent State
(1) What double-precision floating-point targets are supported for
atomic operations?
RESOLVED: This extension only supports atomic operations on double-
precision floating-point buffer memory. Atomic operation on double-
precision texture memory are not supported since OpenGL provides
no pixel/texture formats with double-precision components.
(2) What atomic operations should we support for double-precision
floating-point targets?
RESOLVED: Double-precision floating-point atomic addition is the main
functionality targeted by this extension. We provide exchanges because
the operation needs no special hardware support.
We chose not to provide support for bitwise operations (AND/OR/XOR);
it's possible to support these by casting a pointer or aliasing an image
if required. Minimum, maximum, and compare-and-swap make sense, but the
underlying atomic hardware targeted by this extension does not support
floating-point comparisons.
Revision History
Revision 1
- Internal revisions.