- 1. Name
- 2. Synopsis
- 3. Description
- 4. Command Line Options
- 5. Divergence from and extensions to GLSL specifications
glslc [--help]
glslc [--show-limits]
glslc [-c|-S|-E]
[-x ...] [-std=standard]
[ ... options for resource bindings ... ]
[-fhlsl-offsets]
[-fhlsl-functionality1]
[-fentry-point=<name>]
[-fauto-map-locations]
[-flimit=...]
[-flimit-file <resource-limits-file>]
[-fshader-stage=...]
[--target-env=...]
[-g]
[-O0|-Os]
[-Idirectory...]
[-Dmacroname[=value]...]
[-w] [-Werror]
[-o outfile]
shader...
glslc accepts both GLSL/HLSL source and SPIR-V assembly files as inputs.
glslc provides three ways to specify the shader stage of a GLSL source file:
-fshader-stage=<stage>, #pragma shader_stage(<stage>), and file extension.
The -fshader-stage= option overrides #pragma shader_stage(), which overrides
the file extension.
Shader stages can be specified by naming a file with an appropriate extension
as shown in the following table. -fshader-stage= and #pragma shader_stage(),
on the other hand, enable you to specify shader stages from the command line
and within the source file. Possible stages for them are also listed in
the following table. Details about -fshader-stage= can be found in
its own section.
| Shader Stage | Shader File Extension | <stage> |
|---|---|---|
vertex |
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fragment |
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tesselation control |
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tesselation evaluation |
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|
geometry |
|
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compute |
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#pragma shader_stage() relies on the #pragma preprocessor directive; thus,
the token inside shader_stage() is not subject to preprocessor macro
expansion. It must be exactly one of the stages in the above table.
#pragma shader_stage() behaves as follows:
-
The first
#pragma shader_stage()directive in a translation unit must precede any non-preprocessor tokens. -
If there is more than one
#pragma shader_stage()directive in the same translation unit, all thestages specified must be the same. Otherwise, glslc will issue an error.
SPIR-V assembly input files should follow the
syntax
defined in the SPIRV-Tools
project and have the .spvasm extension. Command line options treat SPIR-V
assembly files differently; some may ignore them, e.g., -E,
-S, and some may even treat them not as SPIR-V assembly
files, e.g., -fshader-stage=.
If a name is specified via -o, the output file will be given that name.
Otherwise,
-
If a compilation stage selection option is given (
-Sor-c), there will be one output file generated per input shader file. The generated output file will end with a file extension that matches the compilation stage, which is.spvasmfor-Sand.spvfor-c. The name will depend on the original file’s name and extension.-
If the input file has a shader stage selection extension, the output file will be named as by appending the file extension for the compilation stage to the input file’s name. E.g.,
glslc -c foo.vertwill generatefoo.vert.spv, andglslc -s bar.fragwill generatebar.frag.spvasm. -
Otherwise, the output file will be named as by replacing the input file’s file extension, if any, with the file extension for the compilation stage. E.g.,
glslc -c foowill generatefoo.spv, andglslc -s bar.glslwill generatebar.spvasm.
-
-
If no compilation stage is selected, the output file will be named
a.spv.
--show-limits shows default resource limits for shader compilation. The syntax
is the same as accepted by -flimit= and for the contents of the file specified
by -flimit-file.
-flimit=<resource-limits> lets you specify resource limits.
The argument should be a sequence of limit name, integer value pairs. Tokens
should be separated by whitespace. If the same limit is specified several
times, only the last setting takes effect.
Use --show-limits to show the default values, and example syntax.
This option affects all compiled shaders.
-flimit-file <resource-limits-file> lets you specify resource limits in a file.
The syntax of the file contents is the same as the argument to -flimit= and
the output of --show-limits. This option accepts Glslang resource configuration
files, e.g. as emitted by glslangValidator -c.
This option affects all compiled shaders.
-fshader-stage=<stage> lets you specify the shader stage for one or more
inputs from the command line.
Possible values for <stage> are listed in the Shader Stage Selection table.
-fshader-stage= behaves as follows:
-
-fshader-stage=sets the shader stage for subsequent input files. It does not affect the stages of any preceding inputs on the command line. -
When supplying more than one
-fshader-stage=argument, the most recent argument preceding an input file applies. -
A shader file not ending with known shader file extensions must have a
-fshader-stage=argument ahead of it to specify its stage. -
If there is a
-fshader-stage=before a file in which there is a#pragma shader_stage()directive, the directive is ignored and the-fshader-stage=argument is used instead. -
If there is a
-fshader-stage=before a file with a known shader file extension, the file extension is ignored and the-fshader-stage=argument is used instead.
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Caution
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-fshader-stage= overrides file extension; that means it should not
be used together with SPIR-V assembly files because glslc will treat the given
SPIR-V assembly files as GLSL source code of the given shader stage. If you
need to supply both SPIR-V assembly files and -fshader-stage= on the same
command line, please put SPIR-V assembly files ahead of the first
-fshader-stage=, since -fshader-stage= only affects the treatment of
subsequent files.
|
-std=<value> lets you specify a shader version and profile on the command
line. <value> can be any valid concatenation of a GLSL version number and
profile, e.g., 310es, 450core, etc. The profile can be omitted as allowed by
GLSL, e.g., 450.
-std= behaves as follows:
-
-std=affects the version of all GLSL inputs passed toglslc. -
-std=is ignored for HLSL inputs. -
-std=overwrites#versiondirectives in all input shaders, including those preceding the argument. -
If a
-std=argument specifies a different version from a#versiondirective in an input file,glslcwill issue a warning. -
If multiple
-std=arguments are specified on the command line, only the last one takes effect.
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Caution
|
-std= does not affect the #version directive in the preprocessed
output. That is, when -std= specifies a version different from the shader
source code, the #version directive in preprocessed output will still be the
one in the source code. But -std= does affect the behavior of #line
directives in the preprocessed output. Behavior of #line directives will
follow the version specified by -std=.
|
--target-env=<value> lets you specify a target environment on the command line.
This affects the generation of warnings and errors. The <value> can be one of
the following:
-
vulkan: create SPIR-V under Vulkan 1.0 semantics. -
vulkan1.0: create SPIR-V under Vulkan 1.0 semantics. -
vulkan1.1: create SPIR-V under Vulkan 1.1 semantics. -
opengl: create SPIR-V under OpenGL 4.5 semantics. -
opengl4.5: create SPIR-V under OpenGL 4.5 semantics. -
opengl_compat: create SPIR-V under OpenGL semantics, including compatibility profile functions.
Generated code uses SPIR-V 1.0, except that code compiled for Vulkan 1.1 uses SPIR-V 1.3.
If this option is not specified, a default of vulkan1.0 is used.
-x lets you specify the language of the input shader files. Valid languages
are glsl and hlsl. If the file extension is hlsl then the default language
is HLSL. Otherwise the default is 'glsl'.
Note: HLSL compilation will use HLSL packing (offset) rules for variables that are vertex shader outputs, and inputs and outputs of both geometry and pixel shaders.
-c tells the glslc compiler to run the preprocessing and compiling stage.
Each input shader file results in a SPIR-V binary file; these SPIR-V binary
files are named by the rules in the Output File Naming
section.
-E tells the glslc compiler to run only the preprocessing stage. It overrides
-c and -S. Preprocessed output is written to standard output, while
preprocessing errors are written to standard error. If multiple input shader
files are given, their preprocessed output are all written to standard output,
in the order specified on the command line.
glslc will do nothing for SPIR-V assembly files with this option.
-S tells the glslc compiler to run the preprocessing, compiling, and then
disassembling stage. It overrides -c. Each input shader file results in a
SPIR-V assembly file; these SPIR-V assembly files are named by the rules in the
Output File Naming section.
glslc will do nothing for SPIR-V assembly files with this option.
-Dmacroname[=[value]] lets you define a preprocessor macro before input shader
files are preprocessed. If value is omitted, the macro is defined with an
empty value.
Requests that the compiler place source-level debug information into the object code, such as identifier names and line numbers.
This option restrains -O from turning on the strip-debug-info optimization
pass.
|
Note
|
Currently this option has no effect. Full functionality depends on glslang support for generating debug info. |
-O specifies which optimization level to use:
-
-O0means "no optimization". This level generates the most debuggable code. -
-Omeans the default optimization level for better performance. -
-Osenables optimizations to reduce code size.
-mfmt=<format> selects output format for compilation output in SPIR-V binary
code form. Supported options are listed in the
binary output format options table. This
option is only valid to be used when the compilation output is SPIR-V binary
code. Specifying any options listed below when the output is not SPIR-V binary
code, like disassembly (with -S specified), text (with -M, -MM or -E
specified) will trigger an error.
| Format option | Description |
|---|---|
bin |
Output SPIR-V binary code as a sequence of binary 32-bitwords in host native endianness. This is the default format for SPIR-V binary compilation output. |
num |
Output SPIR-V binary code as a text file containing a list of
comma-separated hex numbers. |
c |
Output SPIR-V binary code as a text file containing C-style |
Use HLSL packing rules instead of GLSL rules when determining offsets of members of blocks. This option is always on when compiling for HLSL.
Enable extension SPV_GOOGLE_hlsl_functionality1, and instructs the compiler
to:
-
Annotate HLSL semantic string decorations on interface objects
-
Explicitly record the association of a UAV resource with its companion counter buffer.
This option can also be spelled with an underscore: -fhlsl_functionality1.
-fentry-point=<name> lets you specify the entry point name. This is only
significant for HLSL compilation. The default is "main".
For GLSL compilation, option -fauto-map-locations directs the compiler to automatically
assign location numbers to user-defined stage input and output variables if not explicitly
specified by the shader source.
For HLSL compilation, this option is on by default.
Client APIs normally require adjacent stages to agree on their I/O interface. The compiler only sees one stage at a time, so it is strongly recommended that you avoid relying on this option to assign locations.
Instead, an explicit binding number should be specified in the shader source, as follows:
-
In a GLSL shader, use a
locationlayout qualifier:
layout(location = 1) in vec4 x;
-
In an HLSL shader, use a
vk::locationattribute:
[[vk::location(1)]] float4 FooShader(
[[vk::location(0)]] float4 a,
[[vk::location(2)]] float4 b) : COLOR0 {
return a + b;
}
-w suppresses all warning output from glslc. Any warning that would have
been generated is silently ignored.
-M generates make dependencies. It outputs a rule suitable for make
describing the dependencies of the input file. Instead of outputting the result
of preprocessing, the preprocessor outputs one make rule containing the
SPIR-V object file name for that source file, a colon, and the names of all the
included files.
Unless specified explicitly (with -MT), the SPIR-V object file name in the
generated make rules follows the rules of Output File
Naming as in -c compilation stage.
Specifying -M implies -E, and suppresses warnings with an implicit -w.
By default the output will be written to stdout, unless -MF or -o is
specified.
The dependency info file name can be specified by -o and -MF options. When
both are specified, -o option is ignored.
Specifying multiple input files is valid when the make rules are written to
stdout, which means neither -MF nor -o is specified. When -o or -MF is
specified, only one input file is allowed.
-MM is an alias for -M.
E.g., glslc -M main.vert will dump main.vert.spv: main.vert <other included
files> to stdout. More examples are listed in
Dependency Generation Examples
-MD tells the glslc compiler to both compile the source and generate make
dependencies. Dependencies are written to a file whose name is determined as
follows: If option -MF is specified, use its argument. Otherwise, use the
filename formed by appending .d to the name of the file containing
compilation results.
Specifying multiple input files is valid when neither -MF nor -o is
specified. When -o or -MF is specified, only one input file is allowed.
E.g., glslc -c -MD main.vert will generate main.vert.spv as the SPIR-V
object file and main.vert.spv.d as the dependency info file. More examples
are listed in Dependency Generation Examples
-MF lets you specify the dependency info file name when used with -M or
-MD. This option is invalid when used with multiple input files.
E.g., glslc -c -MD main.vert -MF dep_info will generate main.vert.spv as
the SPIR-V object file and dep_info as the dependency info file.
-MT lets you specify the target of the rule emitted by dependency generation
when used with -M or -MD. This option is invalid when used with multiple
input files.
E.g., glslc -M main.vert -MT target will dump following dependency info to
stdout: target: main.vert <other dependent files>.
| Command Line Input | Compilation Output File | Dependency Output File | Dependency Info |
|---|---|---|---|
glslc -M main.vert |
<NA> |
<Stdout> |
main.vert.spv: main.vert |
glslc -M a.vert b.vert |
<NA> |
<Stdout> |
a.vert.spv: a.vert |
<NA> |
<Stdout> |
b.vert.spv: b.vert |
|
glslc -M main.vert -o dep_info |
<NA> |
dep_info |
main.vert.spv: main.vert |
glslc -M main.vert -MF dep_info |
<NA> |
dep_info |
main.vert.spv: main.vert |
glslc -M main.vert -MT target |
<NA> |
<Stdout> |
target: main.vert |
glslc -MD main.vert |
a.spv |
main.vert.spv.d |
main.vert.spv: main.vert |
glslc -c -MD main.vert |
main.vert.spv |
main.vert.spv.d |
main.vert.spv: main.vert |
glslc -c -MD a.vert b.vert |
a.vert.spv |
a.vert.spv.d |
a.vert.spv: a.vert |
b.vert.spv |
b.vert.spv.d |
b.vert.spv: b.vert |
|
glslc -S -MD main.vert |
main.vert.spvasm |
main.vert.spvasm.d |
main.vert.spvasm: main.vert |
glslc -c -MD main.vert -MF dep_info |
main.vert.spv |
dep_info |
main.vert.spv: main.vert |
glslc -c -MD main.vert -o obj |
obj |
obj.d |
obj: main.vert |
glslc -c -MD main.vert -o obj -MF dep_info -MT target |
obj |
dep_info |
target: main.vert |
Option -fauto-bind-uniforms directs the compiler to automatically assign
binding numbers to uniform variables, when an explicit binding is not
specified in the shader source.
An explicit binding number can be specified in the shader source by using
a binding layout qualifier. For example:
layout(binding = 12) uniform texture2D;
Option -fhlsl-iomap directs the compiler to use HLSL register
assignments as binding values.
Option -fimage-binding-base [stage] base sets the lowest automatically
assigned binding for images. If a stage is specified, only affects the specified
stage.
For HLSL, sets one less than the base.
Option -fsampler-binding-base [stage] base sets the lowest automatically
assigned binding for samplers. If a stage is specified, only affects the specified
stage.
For HLSL, sets one less than the base.
Option -ftexture-binding-base [stage] base sets the lowest automatically
assigned binding for textures. If a stage is specified, only affects the specified
stage.
For HLSL, sets one less than the base.
Option -fubo-binding-base [stage] base sets the lowest automatically
assigned binding for Uniform Buffer Objects (GLSL) or Cbuffers (HLSL).
If a stage is specified, only affects the specified stage.
For HLSL, sets one less than the base.
Option -fcbuffer-binding-base [stage] base is the same as
-fubo-binding-base [stage] base.
Option -fssbo-binding-base [stage] base sets the lowest automatically
assigned binding for Shader Storage Buffer Objects (GLSL).
If a stage is specified, only affects the specified stage.
This only affects GLSL compilation.
Option -fuav-binding-base [stage] base sets one less than the lowest
automatically assigned binding for Unordered Access Views (UAV).
If a stage is specified, only affects the specified stage.
This only affects HLSL compilation.
Option -fresource-set-binding [stage] <reg0> <set0> <binding0> sets
the descriptor set and binding for an HLSL resource, by register name.
To specify settings for more registers, append their triples consisting
of register name, descriptor set, and binding.
Example:
# For a texture in register t1, use set 1 binding 0. # For a texture in register t2, use set 1 binding 3 glslc -x hlsl foo.frag -fresource-set-binding t1 1 0 t2 1 3
If a stage is specified, only affects the specified stage.
# Same as the previous example, but the settings only apply # to fragment (pixel) shaders. glslc -x hlsl foo.frag -fresource-set-binding frag t1 1 0 t2 1 3
This section describes how the glslc compiler extends the syntax for the #line
directive and the __FILE__ macro. By default, the glslc compiler enables
the GL_GOOGLE_cpp_style_line_directive extension. It will generate this
extended syntax in the preprocessed output (obtained via the -E option).
|
Warning
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This section is still evolving. Expect changes. |
GLSL specifications have a notion of source strings.
The source for a single shader is an array of strings of characters from the character set. A single shader is made from the concatenation of these strings.
With the above notion, the second parameter to the #line directive should
be a constant integer expressions representing the source string number. Also
the __FILE__ macro will "substitute a decimal integer constant that says
which source string number is currently being processed."
The glslc compiler implements the standard #line and __FILE__ syntax. It
also provides an extension, GL_GOOGLE_cpp_style_line_directive, to allow
source filenames to be used instead of integer source string indices.
Specifically, the #line directive can have, after macro substitution, one of
the following three forms:
#line line-number
#line line-number integer-source-string-index
#line line-number "source-filename"where source-filename can be any combinations of characters except double
quotation marks. (Note that according to the GLSL specification, "there are
no escape sequences or other uses of the backslash beyond use as the
line-continuation character".)
And if source-filename-based #line is used, the __FILE__ macro expands to
a string whose contents are the filename quoted with double quotation marks.
The filename is dertermined as the last of
-
The filename given to the glslc compiler,
-
The filename argument of the most recent
#linedirective, if any.
The glslc compiler extends GLSL with the include syntax by turning on the
GL_GOOGLE_include_directive extension. It will preprocess and substitute
#include directives properly with the following behaviors.
|
Warning
|
This section is still evolving. Expect changes. |
If #include directives are used in a shader, there will be an #extension
GL_GOOGLE_include_directive : enable line generated into the preprocessed
output.
The GL_GOOGLE_cpp_style_line_directive extension is implicitly turned on by
the GL_GOOGLE_include_directive extension.
The file argument to #include must be enclosed in double quotes. It must be a
relative path, using whatever path separator the OS supports. However, the last
path element — the name of the file itself — must not contain either '/' or
'\', regardless of which path separator is used. This will not be flagged as an
error but will instead trigger undefined behavior. For example, let’s say there
is a file named f\ilename.vert on a Unix OS. It is not possible to craft a
#include that includes that file.
Furthermore, it is not possible to escape any characters in a #include
directive, so the file argument cannot contain any special characters that need
escaping in C.
The file argument is a relative path that is matched first against the including
file’s own directory and then against all -I arguments in order of their
appearance on the command line. If the file cannot be found, glslc aborts
with an error.