Name

NV_push_constant_bank

Name Strings

GL_NV_push_constant_bank

Contact

Vassili Nikolaev (vnikolaev 'at' nvidia.com), NVIDIA

Contributors

Piers Daniell, NVIDIA

Ashwin Lele, NVIDIA

Status

Provisional

Version

Last Modified Date: 2025-12-16

Revision: 1

Dependencies

This extension can be applied to OpenGL GLSL versions 4.60

(#version 460) and higher.

This extension is written against revision 5 of the OpenGL Shading Language

version 4.60, dated September 4, 2017.

This extension interacts with revision 43 of the GL_KHR_vulkan_glsl

extension, dated October 25, 2017.

This extension interacts with VK_KHR_push_descriptor.

Overview

This extension provides new layout qualifiers for push constant uniform

blocks that allow shaders to organize push constant data into multiple

independent memory banks and specify explicit byte offsets for block

members within those banks.

Traditional push constant blocks in GLSL/Vulkan share a single contiguous

memory region, this prevents multiple shader stages from using use push

constants with different layouts. This extension introduces the "bank"

layout qualifier to allow shaders to specify which logical bank of push

constant memory a block should reside in, and the "member_offset"

qualifier to specify the starting byte offset of the block's members

within that bank.

This is useful for:

- Allowing different pipeline stages to have non-overlapping push constant

layouts without conflicts

- Providing explicit control over memory placement for performance

optimization on specific hardware configurations

- Enabling larger effective push constant storage by utilizing multiple

banks

Example usage:

// Push constant in bank 0 at default offset

layout(push_constant) uniform PushDataA

{

mat4 modelMatrix;

};

// Push constant in bank 4 starting at byte offset 128

layout(push_constant, bank=4, member_offset=128) uniform PushDataB

{

vec4 b;

};

Mapping to SPIR-V

-----------------

For informational purposes (non-normative), the following is an

expected way for an implementation to map GLSL constructs to SPIR-V

constructs:

bank layout qualifier -> BankNV Decoration on OpVariable

member_offset layout qualifier -> MemberOffsetNV Decoration on OpVariable

The bank value specifies the logical push constant bank index.

The member_offset value specifies the byte offset within the bank.

Modifications to the OpenGL Shading Language Specification, Version 4.60

Including the following line in a shader can be used to control the

language features described in this extension:

#extension GL_NV_push_constant_bank : <behavior>

where <behavior> is as specified in section 3.3.

New preprocessor #defines are added:

#define GL_NV_push_constant_bank 1

Changes to Chapter 4 of The OpenGL Shading Language Specification, Version 4.60

Modify Section 4.4 (Layout Qualifiers)

Add to the table in section 4.4:

Layout Qualifier Qualifier Individual Block Block Allowed

Only Variable Member Interface

---------------- --------- ---------- ------ ------ ---------

bank = X uniform

(push_constant

only)

member_offset = X uniform

(push_constant

only)

Add new sub-section to Section 4.4.5, Uniform and Shader Storage Block

Layout Qualifiers

4.4.5.X Push Constant Bank Layout Qualifiers

The "bank" and "member_offset" layout qualifiers are used to control the

placement of push constant uniform blocks in memory. These qualifiers are

only valid on uniform blocks that also have the "push_constant" layout

qualifier. It is a compile-time error to use these qualifiers on blocks

without "push_constant" or on non-block declarations.

The layout qualifiers are:

layout-qualifier-id :

bank = integer-constant-expression

member_offset = integer-constant-expression

bank

----

The "bank" layout qualifier specifies which logical push constant memory

bank the uniform block should reside in. The value must be a non-negative

integer constant expression.

When "bank" is not specified, the block is placed in bank 0 (the default

push constant bank, which corresponds to the standard Vulkan push constant

range).

Different banks represent independent regions of push constant memory.

The number of available banks and the size of each bank is

implementation-dependent and can be queried through the Vulkan API.

Limits on bank indices and bank sizes are enforced at runtime by the

Vulkan driver. Valid Usage rules in the Vulkan specification define the

constraints, and validation layers will report errors when these limits

are exceeded. Shader compilation may succeed, but pipeline creation will

fail if limits are violated.

Multiple push constant blocks may use the same bank, but their memory

ranges (determined by member_offset and block size) must not overlap.

Overlapping ranges within the same bank result in undefined behavior.

Example:

// Block in default bank 0

layout(push_constant) uniform BlockA { vec4 a; };

// Block in bank 2

layout(push_constant, bank=2) uniform BlockB { vec4 b; };

// Another block in bank 2 (must not overlap with BlockB)

layout(push_constant, bank=2, member_offset=16) uniform BlockC { vec4 c; };

member_offset

-------------

The "member_offset" layout qualifier specifies the starting byte offset

within the bank where the block's members begin. The value must be a

non-negative integer constant expression representing a byte offset.

When "member_offset" is not specified, the block's members start at

byte offset 0 within the specified bank.

The member_offset value must satisfy the alignment requirements of the

block's members. Specifically:

- The offset must be a multiple of the alignment requirement of the

first member of the block

- For standard uniform block layout rules, the offset should typically

be a multiple of 16 bytes for vec4-aligned data

Limits on valid member_offset values are enforced at runtime by the

Vulkan driver. Valid Usage rules in the Vulkan specification define the

constraints, and validation layers will report errors when these limits

are exceeded. Shader compilation may succeed, but pipeline creation will

fail if limits are violated.

The member_offset qualifier specifies the base offset of the entire block

within the bank. Individual member offsets (using the standard "offset"

layout qualifier on block members) are then added relative to this base.

For example:

layout(push_constant, bank=0, member_offset=64) uniform Block

{

layout(offset=0) vec4 a; // At byte 64 in bank 0

layout(offset=16) vec4 b; // At byte 80 in bank 0

};

Example:

// Block starting at byte 0 in bank 4

layout(push_constant, bank=4) uniform BlockX { mat4 m; };

// Block starting at byte 128 in bank 4

layout(push_constant, bank=4, member_offset=128) uniform BlockY { vec4 v; };

Combined Usage

--------------

The "bank" and "member_offset" qualifiers may be used together or

independently:

// Default bank (0), default offset (0)

layout(push_constant) uniform Block1 { vec4 a; };

// Bank 3, default offset (0)

layout(push_constant, bank=3) uniform Block2 { vec4 b; };

// Default bank (0), offset 64

layout(push_constant, member_offset=64) uniform Block3 { vec4 c; };

// Bank 4, offset 128

layout(push_constant, bank=4, member_offset=128) uniform Block4 { vec4 d; };

Interactions with GL_KHR_vulkan_glsl

The "push_constant" layout qualifier is defined by GL_KHR_vulkan_glsl.

The "bank" and "member_offset" qualifiers introduced by this extension

extend the functionality of push constants as defined in GL_KHR_vulkan_glsl.

When targeting Vulkan, the bank and member_offset values are used to

determine which VkPushConstantRange the block maps to and at what

offset within that range.

Issues

None.

Revision History

Rev. Date Author Changes

---- ----------- ------ -------------------------------------------

1 16-Dec-2025 vnikolaev Initial revision.