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GLSLangSpec.4.60.html
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<!DOCTYPE html>
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<div id="header">
<h1>The OpenGL<sup>®</sup> Shading Language, Version 4.60.7</h1>
<div class="details">
<span id="author" class="author">John Kessenich, Google (Editor and Author) ; Dave Baldwin and Randi Rost (Version 1.1 Authors)</span><br>
<span id="revnumber">version 4.60.7,</span>
<span id="revdate">Wed, 10 Jul 2019 20:42:58 +0000</span>
<br><span id="revremark">Git branch information not available</span>
</div>
<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#introduction">1. Introduction</a>
<ul class="sectlevel2">
<li><a href="#changes">1.1. Changes</a></li>
<li><a href="#overview">1.2. Overview</a></li>
<li><a href="#error-handling">1.3. Error Handling</a></li>
<li><a href="#typographical-conventions">1.4. Typographical Conventions</a></li>
<li><a href="#deprecation">1.5. Deprecation</a></li>
</ul>
</li>
<li><a href="#overview-of-opengl-shading">2. Overview of Shading</a>
<ul class="sectlevel2">
<li><a href="#vertex-processor">2.1. Vertex Processor</a></li>
<li><a href="#tessellation-control-processor">2.2. Tessellation Control Processor</a></li>
<li><a href="#tessellation-evaluation-processor">2.3. Tessellation Evaluation Processor</a></li>
<li><a href="#geometry-processor">2.4. Geometry Processor</a></li>
<li><a href="#fragment-processor">2.5. Fragment Processor</a></li>
<li><a href="#compute-processor">2.6. Compute Processor</a></li>
</ul>
</li>
<li><a href="#basics">3. Basics</a>
<ul class="sectlevel2">
<li><a href="#character-set">3.1. Character Set and Phases of Compilation</a></li>
<li><a href="#source-strings">3.2. Source Strings</a></li>
<li><a href="#preprocessor">3.3. Preprocessor</a></li>
<li><a href="#comments">3.4. Comments</a></li>
<li><a href="#tokens">3.5. Tokens</a></li>
<li><a href="#keywords">3.6. Keywords</a></li>
<li><a href="#identifiers">3.7. Identifiers</a></li>
<li><a href="#definitions">3.8. Definitions</a></li>
</ul>
</li>
<li><a href="#variables-and-types">4. Variables and Types</a>
<ul class="sectlevel2">
<li><a href="#basic-types">4.1. Basic Types</a></li>
<li><a href="#scoping">4.2. Scoping</a></li>
<li><a href="#storage-qualifiers">4.3. Storage Qualifiers</a></li>
<li><a href="#layout-qualifiers">4.4. Layout Qualifiers</a></li>
<li><a href="#interpolation-qualifiers">4.5. Interpolation Qualifiers</a></li>
<li><a href="#parameter-qualifiers">4.6. Parameter Qualifiers</a></li>
<li><a href="#precision-and-precision-qualifiers">4.7. Precision and Precision Qualifiers</a></li>
<li><a href="#variance-and-the-invariant-qualifier">4.8. Variance and the Invariant Qualifier</a></li>
<li><a href="#the-precise-qualifier">4.9. The Precise Qualifier</a></li>
<li><a href="#memory-qualifiers">4.10. Memory Qualifiers</a></li>
<li><a href="#specialization-constant-qualifier">4.11. Specialization-Constant Qualifier</a></li>
<li><a href="#order-of-qualification">4.12. Order and Repetition of Qualification</a></li>
<li><a href="#empty-declarations">4.13. Empty Declarations</a></li>
</ul>
</li>
<li><a href="#operators-and-expressions">5. Operators and Expressions</a>
<ul class="sectlevel2">
<li><a href="#operators">5.1. Operators</a></li>
<li><a href="#array-operations">5.2. Array Operations</a></li>
<li><a href="#function-calls">5.3. Function Calls</a></li>
<li><a href="#constructors">5.4. Constructors</a></li>
<li><a href="#vector-components">5.5. Vector and Scalar Components and Length</a></li>
<li><a href="#matrix-components">5.6. Matrix Components</a></li>
<li><a href="#structure-and-array-operations">5.7. Structure and Array Operations</a></li>
<li><a href="#assignments">5.8. Assignments</a></li>
<li><a href="#expressions">5.9. Expressions</a></li>
<li><a href="#vector-and-matrix-operations">5.10. Vector and Matrix Operations</a></li>
<li><a href="#out-of-bounds-accesses">5.11. Out-of-Bounds Accesses</a></li>
<li><a href="#specialization-constant-operations">5.12. Specialization-Constant Operations</a></li>
</ul>
</li>
<li><a href="#statements-and-structure">6. Statements and Structure</a>
<ul class="sectlevel2">
<li><a href="#function-definitions">6.1. Function Definitions</a></li>
<li><a href="#selection">6.2. Selection</a></li>
<li><a href="#iteration">6.3. Iteration</a></li>
<li><a href="#jumps">6.4. Jumps</a></li>
</ul>
</li>
<li><a href="#built-in-variables">7. Built-In Variables</a>
<ul class="sectlevel2">
<li><a href="#built-in-language-variables">7.1. Built-In Language Variables</a></li>
<li><a href="#compatibility-profile-vertex-shader-built-in-inputs">7.2. Compatibility Profile Vertex Shader Built-In Inputs</a></li>
<li><a href="#built-in-constants">7.3. Built-In Constants</a></li>
<li><a href="#built-in-uniform-state">7.4. Built-In Uniform State</a></li>
<li><a href="#redeclaring-built-in-blocks">7.5. Redeclaring Built-In Blocks</a></li>
</ul>
</li>
<li><a href="#built-in-functions">8. Built-In Functions</a>
<ul class="sectlevel2">
<li><a href="#angle-and-trigonometry-functions">8.1. Angle and Trigonometry Functions</a></li>
<li><a href="#exponential-functions">8.2. Exponential Functions</a></li>
<li><a href="#common-functions">8.3. Common Functions</a></li>
<li><a href="#floating-point-pack-and-unpack-functions">8.4. Floating-Point Pack and Unpack Functions</a></li>
<li><a href="#geometric-functions">8.5. Geometric Functions</a></li>
<li><a href="#matrix-functions">8.6. Matrix Functions</a></li>
<li><a href="#vector-relational-functions">8.7. Vector Relational Functions</a></li>
<li><a href="#integer-functions">8.8. Integer Functions</a></li>
<li><a href="#texture-functions">8.9. Texture Functions</a></li>
<li><a href="#atomic-counter-functions">8.10. Atomic Counter Functions</a></li>
<li><a href="#atomic-memory-functions">8.11. Atomic Memory Functions</a></li>
<li><a href="#image-functions">8.12. Image Functions</a></li>
<li><a href="#geometry-shader-functions">8.13. Geometry Shader Functions</a></li>
<li><a href="#fragment-processing-functions">8.14. Fragment Processing Functions</a></li>
<li><a href="#noise-functions">8.15. Noise Functions</a></li>
<li><a href="#shader-invocation-control-functions">8.16. Shader Invocation Control Functions</a></li>
<li><a href="#shader-memory-control-functions">8.17. Shader Memory Control Functions</a></li>
<li><a href="#_subpass_input_functions">8.18. Subpass-Input Functions</a></li>
<li><a href="#shader-invocation-group-functions">8.19. Shader Invocation Group Functions</a></li>
</ul>
</li>
<li><a href="#shading-language-grammar">9. Shading Language Grammar</a></li>
<li><a href="#acknowledgments">10. Acknowledgments</a></li>
<li><a href="#references">11. Normative References</a></li>
<li><a href="#_non_normative_spir_v_mappings">12. Non-Normative SPIR-V Mappings</a>
<ul class="sectlevel2">
<li><a href="#_feature_comparisons">12.1. Feature Comparisons</a></li>
<li><a href="#_mapping_from_glsl_to_spir_v">12.2. Mapping from GLSL to SPIR-V</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div style="page-break-after: always;"></div>
<div class="paragraph">
<p>Copyright © 2008-2018 The Khronos Group Inc. All Rights Reserved.</p>
</div>
<div class="paragraph">
<p>This specification is protected by copyright laws and contains material
proprietary to the Khronos Group, Inc. It or any components may not be
reproduced, republished, distributed, transmitted, displayed, broadcast,
or otherwise exploited in any manner without the express prior written
permission of Khronos Group. You may use this specification for
implementing the functionality therein, without altering or removing any
trademark, copyright or other notice from the specification, but the
receipt or possession of this specification does not convey any rights
to reproduce, disclose, or distribute its contents, or to manufacture,
use, or sell anything that it may describe, in whole or in part.</p>
</div>
<div class="paragraph">
<p>Khronos Group grants express permission to any current Promoter,
Contributor or Adopter member of Khronos to copy and redistribute
UNMODIFIED versions of this specification in any fashion, provided that
NO CHARGE is made for the specification and the latest available update
of the specification for any version of the API is used whenever
possible. Such distributed specification may be reformatted AS LONG AS
the contents of the specification are not changed in any way. The
specification may be incorporated into a product that is sold as long as
such product includes significant independent work developed by the
seller. A link to the current version of this specification on the
Khronos Group website should be included whenever possible with
specification distributions.</p>
</div>
<div class="paragraph">
<p>Khronos Group makes no, and expressly disclaims any, representations or
warranties, express or implied, regarding this specification, including,
without limitation, any implied warranties of merchantability or fitness
for a particular purpose or noninfringement of any intellectual
property. Khronos Group makes no, and expressly disclaims any,
warranties, express or implied, regarding the correctness, accuracy,
completeness, timeliness, and reliability of the specification. Under no
circumstances will the Khronos Group, or any of its Promoters,
Contributors or Members or their respective partners, officers,
directors, employees, agents, or representatives be liable for any
damages, whether direct, indirect, special or consequential damages for
lost revenues, lost profits, or otherwise, arising from or in connection
with these materials.</p>
</div>
<div class="paragraph">
<p>Khronos, Vulkan, SYCL, SPIR, WebGL, EGL, COLLADA, StreamInput, OpenVX,
OpenKCam, glTF, OpenKODE, OpenVG, OpenWF, OpenSL ES, OpenMAX, OpenMAX
AL, OpenMAX IL and OpenMAX DL are trademarks and WebCL is a
certification mark of the Khronos Group Inc. OpenCL is a trademark of
Apple Inc. and OpenGL and OpenML are registered trademarks and the
OpenGL ES and OpenGL SC logos are trademarks of Silicon Graphics
International used under license by Khronos. All other product names,
trademarks, and/or company names are used solely for identification and
belong to their respective owners.</p>
</div>
<div style="page-break-after: always;"></div>
<!-- toc disabled -->
</div>
</div>
<div class="sect1">
<h2 id="introduction">1. Introduction</h2>
<div class="sectionbody">
<div class="paragraph">
<p>This document specifies only version 4.60 of the OpenGL Shading Language (GLSL).
It requires __VERSION__ to substitute 460, and requires
<strong>#version</strong> to accept only
<code>460</code>.
If <strong>#version</strong> is declared with a smaller number, the language accepted is a
previous version of the shading language, which will be supported depending
on the version and type of context in the API.
See the <a href="#references">normative references</a> for details on what language
versions are supported.</p>
</div>
<div class="paragraph">
<p>Previous versions of the OpenGL Shading Language, as well as the OpenGL ES Shading Language,
are not strict subsets of the version specified here, particularly with
respect to precision, name-hiding rules, and treatment of interface
variables.
See the specification corresponding to a particular language version for
details specific to that version of the language.</p>
</div>
<div class="paragraph">
<p>Throughout, when generating SPIR-V for consumption by the Vulkan API
(see <a href="#references">normative references</a>), this will be said to be
<em>targeting Vulkan</em>.</p>
</div>
<div class="paragraph">
<p>While this specification and the OpenGL Specification are normative for OpenGL Shading Language, for
SPIR-V generation it is still the SPIR-V specification and the SPIR-V client
API specification that are normative for the generated SPIR-V.
See the <a href="#references">normative references</a> for further detail.</p>
</div>
<div class="paragraph">
<p>For SPIR-V generation, the SPIR-V client API specifies the commands used to
manipulate SPIR-V shaders.</p>
</div>
<div class="paragraph">
<p>Independent offline tool chains will compile GLSL down to the SPIR-V
intermediate language.
SPIR-V generation is not enabled with a <strong>#extension</strong>, <strong>#version</strong>, or a
profile.
Instead, use of GLSL for SPIR-V is determined by offline tool-chain use.
See the documentation of such tools to see how to request generation of
SPIR-V for its client API.</p>
</div>
<div class="paragraph">
<p>GLSL → SPIR-V compilers must be directed as to what SPIR-V <strong>Capabilities</strong>
are legal at run-time and give errors for GLSL feature use outside those
capabilities.
This is also true for implementation-dependent limits that can be error
checked by the front-end against built-in constants present in the GLSL
source: the front-end can be informed of such limits, and report errors when
they are exceeded.</p>
</div>
<div class="paragraph">
<p>SPIR-V features that are not controlled by a SPIR-V capability, but do have an
equivalent GLSL counterpart (stages, built-in functions, types, limits, etc.)
are only expected to work on OpenGL drivers that support the GLSL counterpart.</p>
</div>
<div class="paragraph">
<p>All references in this specification to the <a href="#references">OpenGL Specification</a> are to
the Core profile of version 4.6, unless a different profile is
specified.</p>
</div>
<div class="sect2">
<h3 id="changes">1.1. Changes</h3>
<div class="sect3">
<h4 id="_changes_from_revision_6_of_glsl_4_6">1.1.1. Changes from Revision 6 of GLSL 4.6</h4>
<div class="ulist">
<ul>
<li>
<p>Incorporated the GL_KHR_vulkan_glsl specification.</p>
</li>
<li>
<p>Add note in the introduction about presence in drivers of SPIR-V features,
as they relate to GLSL features.</p>
</li>
<li>
<p>Clarify it is same location that triggers default-uniform block matching
rules.
See <a href="#uniform-variable-layout-qualifiers">Uniform Variable Layout Qualifiers</a>.</p>
</li>
</ul>
</div>
</div>
<div class="sect3">
<h4 id="_changes_from_revision_5_of_glsl_4_6">1.1.2. Changes from Revision 5 of GLSL 4.6</h4>
<div class="ulist">
<ul>
<li>
<p>Private GLSL issue #34: Clarify/consolidate implicit conversion rules from int → uint
to be the same as explicit construction.</p>
</li>
<li>
<p>Private GLSL issue #24: Clarify that <strong>barrier</strong>() by itself is enough to synchronize
both control flow and memory accesses to <strong>shared</strong> variables and tessellation
control output variables. For other memory accesses an additional memory
barrier is still required.</p>
</li>
<li>
<p>Normatively reference IEEE-754 for definitions of floating-point formats.</p>
</li>
<li>
<p>Private GLSL issue 36: <strong>refract</strong> function on <strong>double</strong> types requires eta
argument to have type <strong>double</strong>.</p>
</li>
<li>
<p>Clarify restrictions on input variables in tessellation and geometry stages.</p>
</li>
<li>
<p>Private GLSL issue 15: Clarify the ordering of bindings for arrays of arrays.</p>
</li>
<li>
<p>Private GLSL issue 14: Uniform variables need only match at link time if they
are statically used.</p>
</li>
<li>
<p>For <strong>precise</strong> computations, the controlling expressions for
control flow and ternary operators (<strong>?:</strong>) are not included.</p>
</li>
</ul>
</div>
</div>
<div class="sect3">
<h4 id="_changes_from_revision_4_of_glsl_4_6">1.1.3. Changes from Revision 4 of GLSL 4.6</h4>
<div class="ulist">
<ul>
<li>
<p>Private bug 13012: Clarified that builtin uniform variables might only
be available in the fragment stage.</p>
</li>
<li>
<p>Private bug 13837: Ternary and sequence operators may operate on <strong>void</strong> types.</p>
</li>
<li>
<p>Clarified that errors arising from preprocessing must be returned at compile time.</p>
</li>
<li>
<p>Clarified that access to any part of a variable constitutes a static use.</p>
</li>
<li>
<p>Private GLSL issue 19: A statement is required following any label at the end of a <strong>switch</strong>.</p>
</li>
<li>
<p>Private GLSL issue 26: <strong>noise</strong> is not valid when compiling for SPIR-V.</p>
</li>
<li>
<p>Private GLSL issue 20: <strong>length</strong>() expressions returning a constant value may not
contain side effects.</p>
</li>
<li>
<p>Public OpenGL-API issue 7: Variables can be declared as both <strong>readonly</strong>
and <strong>writeonly</strong>.</p>
</li>
<li>
<p>Private GLSL issue 16: Use of constant expressions within <strong>#line</strong> directives is undefined.</p>
</li>
<li>
<p>Corrected return type of <strong>imageAtomicExchange</strong> on <strong>float</strong> images.</p>
</li>
<li>
<p>Private GLSL issue 32: Remove <strong>length</strong>() method contradiction:
Non runtime-sized arrays only support <strong>length</strong>() on explicitly
sized arrays.</p>
</li>
<li>
<p>Private GLSL issue 21: Clarified the l-value restriction on <strong>interpolateAt</strong>.</p>
</li>
<li>
<p>Private OpenGL-API issue 53: Clarified bit-width requirements for location aliasing.</p>
</li>
<li>
<p>Public GLSL issue 15: <strong>gl_in</strong> can be redeclared using unsized-array syntax.</p>
</li>
<li>
<p>Clarification of the formats needed for DEPTH_COMPONENT and
STENCIL_COMPONENT for depth/stencil textures.</p>
</li>
<li>
<p>Added image formats to the layout-qualifier table in the
<a href="#layout-qualifiers">Layout Qualifiers</a> section.</p>
</li>
</ul>
</div>
</div>
<div class="sect3">
<h4 id="_changes_from_revision_3_of_glsl_4_6">1.1.4. Changes from Revision 3 of GLSL 4.6</h4>
<div class="ulist">
<ul>
<li>
<p>Private GLSL issue 13: Fix misspelling of <strong>allInvocationsEqual</strong>().
(The one in the table was incorrectly listed as <strong>anyInvocationsEqual</strong>(),
other spellings were correct.)</p>
</li>
</ul>
</div>
</div>
<div class="sect3">
<h4 id="_summary_of_changes_from_revision_7_of_glsl_version_4_50">1.1.5. Summary of Changes from Revision 7 of GLSL Version 4.50</h4>
<div class="ulist">
<ul>
<li>
<p>Incorporated the GL_ARB_shader_atomic_counter_ops extension.</p>
</li>
<li>
<p>Incorporated the GL_ARB_shader_draw_parameters extension.</p>
</li>
<li>
<p>Incorporated the GL_ARB_shader_group_vote extension.</p>
</li>
<li>
<p>Incorporated the GL_ARB_gl_spirv extension.</p>
</li>
<li>
<p>Private Bug 16070: Allow extra semi-colons at global scope.</p>
</li>
<li>
<p>Private GLSL Issue 5: Be explicit that “fail to link” is really
“compile-time or link-time error”, for some forms of error.</p>
</li>
<li>
<p>Private GLSL Issue 7: Change <em>gl_MaxComputeUniformComponents</em> to 1024.</p>
</li>
<li>
<p>Private OpenGL API Issue 35: Require location on transparent individual
uniform variables for SPIR-V.</p>
</li>
<li>
<p>Private GLSL Issue 8: Be more clear an <strong>interpolateAt</strong>() interpolant can
be a structure member.</p>
</li>
<li>
<p>Private GLSL Issue 9: Specify how <strong>xfb_buffer</strong> interacts with a block
array: the capturing buffer increments for each block array element.</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2">
<h3 id="overview">1.2. Overview</h3>
<div class="paragraph">
<p>This document describes <em>The OpenGL Shading Language, version 4.60</em>.</p>
</div>
<div class="paragraph">
<p>Independent compilation units written in this language are called <em>shaders</em>.
A <em>program</em> is a set of shaders that are compiled and linked
together,
completely creating one or more of the programmable stages of the
API pipeline.
All the shaders for a single programmable stage must be within the same
program.
A complete set of programmable stages can be put into a single program or
the stages can be partitioned across multiple programs.
The aim of this document is to thoroughly specify the programming language.
The <a href="#references">normative references</a> will specify the API entry points
used to manipulate and communicate with programs and shaders.</p>
</div>
</div>
<div class="sect2">
<h3 id="error-handling">1.3. Error Handling</h3>
<div class="paragraph">
<p>Compilers, in general, accept programs that are ill-formed, due to the
impossibility of detecting all ill-formed programs.