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get rid of ShaderCompileStep

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Use addSystemCommand to run glslc now. See the example.
This commit is contained in:
Robin Voetter
2024-09-04 23:40:43 +02:00
parent 976dbfbcca
commit 9ee4cf349f
2 changed files with 15 additions and 272 deletions
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31
README.md
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@@ -355,31 +355,30 @@ For some times (such as those from Google Games Platform) no default is known, b
### Shader compilation
vulkan-zig provides functionality to help compile shaders to SPIR-V using glslc. It can be used from build.zig as follows:
Shaders should be compiled by invoking a shader compiler via the build system. For example:
```zig
const vkgen = @import("vulkan_zig");
pub fn build(b: *Builder) void {
...
const shader_comp = vkgen.ShaderCompileStep.create(
builder,
&[_][]const u8{"glslc", "--target-env=vulkan1.2"},
"-o",
);
shader_comp.add("shader_frag", "path/to/shader.frag", .{});
shader_comp.add("shader_vert", "path/to/shader.vert", .{});
exe.addModule("shaders", shader_comp.getModule());
const vert_cmd = b.addSystemCommand(&.{
"glslc",
"--target-env=vulkan1.2",
"-o"
});
const vert_spv = vert_cmd.addOutputFileArg("vert.spv");
vert_cmd.addFileArg(b.path("shaders/triangle.vert"));
exe.root_module.addAnonymousImport("vertex_shader", .{
.root_source_file = vert_spv
});
...
}
```
Upon compilation, glslc is invoked to compile each shader, and the result is placed within `zig-cache`. All shaders which are compiled using a particular `ShaderCompileStep` are imported in a single Zig file using `@embedFile`, and this file can be added to an executable as a module using `addModule`. To slightly improve compile times, shader compilation is cached; as long as a shader's source and its compile commands stay the same, the shader is not recompiled. The SPIR-V code for any particular shader is aligned to that of a 32-bit integer as follows, as required by vkCreateShaderModule:
Note that SPIR-V must be 32-bit aligned when fed to Vulkan. The easiest way to do this is to dereference the shader's bytecode and manually align it as follows:
```zig
pub const ${name} align(@alignOf(u32)) = @embedFile("${path}").*;
const vert_spv align(@alignOf(u32)) = @embedFile("vertex_shader").*;
```
See [build.zig](build.zig) for a working example.
See [examples/build.zig](examples/build.zig) for a working example.
## Limitations

256
src/build_integration.zig
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@@ -1,256 +0,0 @@
const std = @import("std");
const Build = std.Build;
/// Utility functionality to help with compiling shaders from build.zig.
/// Invokes a shader compile command (e.g., glslc ...) for each shader
/// added via `addShader`.
pub const ShaderCompileStep = struct {
/// The directory within the zig-cache directory that is used to store
/// shader artifacts.
pub const cache_dir = "shaders";
/// This structure contains additional options that pertain to specific shaders only.
pub const ShaderOptions = struct {
/// Additional arguments that should be passed to the shader compiler.
args: []const []const u8 = &.{},
/// Paths of additional files that should be watched for changes to
/// trigger recompilation.
watched_files: []const []const u8 = &.{},
/// To ensure that if compilation options change, the shader is recompiled
/// properly.
fn hash(self: ShaderOptions, b: *Build, hasher: anytype) !void {
for (self.args) |arg| {
hasher.update(arg);
}
for (self.watched_files) |file_path| {
const full_path = b.build_root.join(b.allocator, &.{file_path}) catch unreachable;
const source = std.fs.cwd().readFileAlloc(
b.allocator,
full_path,
std.math.maxInt(usize),
) catch |err| switch (err) {
error.FileNotFound => {
std.log.err("could not open file '{s}'", .{file_path});
return error.FileNotFound;
},
else => |e| return e,
};
hasher.update(source);
}
}
};
/// Structure representing a shader to be compiled.
const Shader = struct {
/// The name of the shader in the generated file.
/// Must be unique for all shaders added to this ShaderCompileStep.
name: []const u8,
/// The path to the shader, relative to the current build root.
source_path: []const u8,
/// The final hash of the shader
hash: [64]u8,
/// Miscellaneous options to pass when compiling the shader.
options: ShaderOptions,
};
const CompileCommand = union(enum) {
real_path: []const u8,
lazy_path: Build.LazyPath,
pub fn getPath(self: CompileCommand, b: *Build) []const u8 {
return switch (self) {
.real_path => |path| path,
.lazy_path => |lazy_path| lazy_path.getPath(b),
};
}
};
step: Build.Step,
/// The command and args to invoke the shader compiler.
compile_command: CompileCommand,
compile_command_args: []const []const u8,
/// The compiler flag used to specify the output path, `-o` most of the time
output_flag: []u8,
/// List of shaders that are to be compiled.
shaders: std.ArrayList(Shader),
/// The main Zig file that contains all the shaders. Each shader is included as
/// `pub const ${name} align(@alignOf(u32))= @embedFile("${path").*;`
generated_file: Build.GeneratedFile,
/// Create a ShaderCompileStep for `builder`. When this step is invoked by the build
/// system, `<compile_command...> <shader_source> <output_flag> <path>` is invoked for each shader.
/// For example, if one calls this with `create(b, "glslc", "-o")` and then
/// `c.addShader("vertex", "vertex.glsl", .{})`, the command will be `glslc vertex.glsl -o <path>`
pub fn create(
builder: *Build,
compile_command: CompileCommand,
compile_command_args: []const []const u8,
output_flag: []const u8,
) *ShaderCompileStep {
const self = builder.allocator.create(ShaderCompileStep) catch unreachable;
self.* = .{
.step = Build.Step.init(.{
.id = .custom,
.name = "shaders",
.owner = builder,
.makeFn = make,
}),
.compile_command = compile_command,
.compile_command_args = builder.dupeStrings(compile_command_args),
.output_flag = builder.dupe(output_flag),
.shaders = std.ArrayList(Shader).init(builder.allocator),
.generated_file = undefined,
};
self.generated_file = .{ .step = &self.step };
return self;
}
/// Returns the shaders module with name.
pub fn getModule(self: *ShaderCompileStep) *Build.Module {
return self.step.owner.createModule(.{
.root_source_file = self.getSource(),
});
}
/// Returns the file source for the generated shader resource code.
pub fn getSource(self: *ShaderCompileStep) Build.LazyPath {
return .{ .generated = .{ .file = &self.generated_file } };
}
/// Add a shader to be compiled. `src` is shader source path, relative to the project root.
/// Returns the full path where the compiled binary will be stored upon successful compilation.
/// This path can then be used to include the binary into an executable, for example by passing it
/// to @embedFile via an additional generated file.
pub fn add(self: *ShaderCompileStep, name: []const u8, src: []const u8, options: ShaderOptions) void {
const b = self.step.owner;
const full_source_path = b.build_root.join(b.allocator, &.{src}) catch unreachable;
self.shaders.append(.{
.name = name,
.source_path = full_source_path,
.hash = undefined,
.options = options,
}) catch unreachable;
}
/// Create a hash of a shader's source contents.
fn hashShaderToFileName(self: *ShaderCompileStep, shader: Shader) ![64]u8 {
const b = self.step.owner;
const source = std.fs.cwd().readFileAlloc(
b.allocator,
shader.source_path,
std.math.maxInt(usize),
) catch |err| switch (err) {
error.FileNotFound => {
std.log.err("could not open shader '{s}'", .{shader.source_path});
return error.FileNotFound;
},
else => |e| return e,
};
var hasher = std.crypto.hash.blake2.Blake2b384.init(.{});
// Random bytes to make ShaderCompileStep unique. Refresh with new random
// bytes when the implementation is changed in a non-backwards-compatible way.
hasher.update("Pw7Z*9Q8r!fLY8&!");
// Make sure that there is no cache hit if the shader's source has changed.
hasher.update(source);
// Not only the shader source must be the same to ensure uniqueness -
// the compilation options must be the same as well!
try shader.options.hash(b, &hasher);
// And the compile command, too.
hasher.update(self.compile_command.getPath(b));
for (self.compile_command_args) |cmd| {
hasher.update(cmd);
}
return digest(&hasher);
}
/// Create a base-64 hash digest from a hasher, which we can use as file name.
fn digest(hasher: anytype) [64]u8 {
var hash_digest: [48]u8 = undefined;
hasher.final(&hash_digest);
var hash: [64]u8 = undefined;
_ = std.fs.base64_encoder.encode(&hash, &hash_digest);
return hash;
}
/// Internal build function.
fn make(step: *Build.Step, options: Build.Step.MakeOptions) !void {
_ = options;
const b = step.owner;
const self: *ShaderCompileStep = @fieldParentPtr("step", step);
const cwd = std.fs.cwd();
var cmd = std.ArrayList([]const u8).init(b.allocator);
try cmd.append(self.compile_command.getPath(b));
try cmd.appendSlice(self.compile_command_args);
const base_cmd_len = cmd.items.len;
var shaders_file_contents = std.ArrayList(u8).init(b.allocator);
const shaders_out = shaders_file_contents.writer();
const shaders_dir = try b.cache_root.join(
b.allocator,
&.{cache_dir},
);
try cwd.makePath(shaders_dir);
for (self.shaders.items) |*shader| {
shader.hash = try self.hashShaderToFileName(shader.*);
const shader_out_path = try std.fs.path.join(b.allocator, &.{
shaders_dir,
&shader.hash,
});
// This path must be relative to the shaders zig file - which is in the same directory
try shaders_out.print("pub const {s} align(@alignOf(u32)) = @embedFile(\"{s}\").*;\n", .{
shader.name,
&shader.hash,
});
// If we have a cache hit, we can save some compile time by not invoking the compile command.
compile_shader: {
std.fs.accessAbsolute(shader_out_path, .{}) catch |err| switch (err) {
error.FileNotFound => break :compile_shader,
else => |e| return e,
};
continue;
}
cmd.items.len = base_cmd_len;
try cmd.appendSlice(shader.options.args);
try cmd.appendSlice(&.{ shader.source_path, self.output_flag, shader_out_path });
_ = try step.evalChildProcess(cmd.items);
}
// Generate a file name for the shaders zig source based on the contents of shaders_file_contents.
// In this case we don't need to omit writing the file - Zig does this check already for us.
var hasher = std.crypto.hash.blake2.Blake2b384.init(.{});
// Note: don't need to seed the hasher - it transitively contains the seed from
// hashShaderToFileName. Change that if the implementation changes.
hasher.update(shaders_file_contents.items);
const shaders_path = try std.fs.path.join(
b.allocator,
&.{ shaders_dir, &digest(&hasher) },
);
try cwd.writeFile(.{
.sub_path = shaders_path,
.data = shaders_file_contents.items,
});
self.generated_file.path = shaders_path;
}
};