VulkanDriver/src/software/interpreter/vertex.zig

const std = @import("std");
const vk = @import("vulkan");
const base = @import("base");
const shader_ir = @import("shader_ir");

const Shader = @import("Shader.zig");
const SoftPipeline = @import("../SoftPipeline.zig");
const Renderer = @import("../device/Renderer.zig");
const blitter = @import("../device/blitter.zig");

const VkError = base.VkError;
const ir = shader_ir.ir;
const interface_blob_padding = @sizeOf(base.zm.F32x4);

pub fn run(
    allocator: std.mem.Allocator,
    pipeline: *SoftPipeline,
    shader: *Shader,
    batch_id: usize,
    batch_size: usize,
    vertex_count: usize,
    first_vertex: usize,
    first_instance: usize,
    indices: ?[]const u32,
    primitive_restart: ?[]const bool,
    instance_index: usize,
    draw_call: *Renderer.DrawCall,
) VkError!void {
    const slot = &shader.runtimes[batch_id];
    const io = draw_call.renderer.device.interface.io();
    slot.mutex.lock(io) catch return VkError.DeviceLost;
    defer slot.mutex.unlock(io);

    var invocation_index = batch_id;
    while (invocation_index < vertex_count) : (invocation_index += batch_size) {
        const output = &draw_call.vertices[(instance_index * vertex_count) + invocation_index];
        if (primitive_restart) |restart| {
            if (restart[invocation_index]) {
                output.primitive_restart = true;
                continue;
            }
        }

        const vertex_index: u32 = if (indices) |draw_indices| draw_indices[invocation_index] else @intCast(first_vertex + invocation_index);
        try populateInputs(
            &slot.runtime,
            &shader.program,
            pipeline,
            draw_call,
            vertex_index,
            @intCast(first_instance + instance_index),
        );
        const outcome = slot.runtime.run(&shader.program, .{}) catch return VkError.Unknown;
        if (outcome == .discarded)
            continue;
        try collectOutputs(allocator, &slot.runtime, &shader.program, output);
    }
}

fn populateInputs(runtime: anytype, program: *const @import("Program.zig"), pipeline: *SoftPipeline, draw_call: *Renderer.DrawCall, vertex_index: u32, instance_index: u32) VkError!void {
    for (program.interfaces, 0..) |optional_binding, index| {
        const binding = optional_binding orelse continue;
        if (binding.direction != .input)
            continue;
        const variable = ir.id.InterfaceVariableId.fromIndex(index);
        var values: [4]u32 = @splat(0);
        switch (binding.semantic) {
            .builtin => |builtin| values[0] = switch (builtin) {
                .vertex_index => vertex_index,
                .instance_index => instance_index,
                else => return VkError.InvalidPipelineDrv,
            },
            .location => |location| {
                const attribute = findAttribute(
                    pipeline.interface.mode.graphics.input_assembly.attribute_description orelse &.{},
                    location.location,
                ) orelse {
                    runtime.writeInput(program, variable, values[0..binding.span.components]) catch return VkError.Unknown;
                    continue;
                };
                const binding_description = findBinding(
                    pipeline.interface.mode.graphics.input_assembly.binding_description orelse return VkError.ValidationFailed,
                    attribute.binding,
                ) orelse return VkError.ValidationFailed;
                const vertex_buffer = draw_call.renderer.state.data.graphics.vertex_buffers[attribute.binding];
                const buffer = vertex_buffer.buffer;
                const memory = buffer.interface.memory orelse return VkError.InvalidDeviceMemoryDrv;
                const input_index = switch (binding_description.input_rate) {
                    .vertex => @as(usize, vertex_index),
                    .instance => @as(usize, instance_index),
                    else => return VkError.ValidationFailed,
                };
                const offset = buffer.interface.offset + vertex_buffer.offset + binding_description.stride * input_index + attribute.offset;
                const input_size = base.format.texelSize(attribute.format);
                var robust_bytes: [64]u8 = @splat(0);
                if (input_size > robust_bytes.len)
                    return VkError.Unknown;
                if (offset < memory.size) {
                    const available = @min(input_size, @as(usize, @intCast(memory.size - offset)));
                    const mapped = memory.map(offset, available) catch &.{};
                    @memcpy(robust_bytes[0..mapped.len], mapped);
                }
                values = if (base.format.isUnnormalizedInteger(attribute.format))
                    blitter.readInt4(robust_bytes[0..input_size], attribute.format)
                else
                    @bitCast(blitter.readFloat4(robust_bytes[0..input_size], attribute.format));
                const first_component: usize = location.component;
                const end_component = first_component + binding.span.components;
                runtime.writeInput(program, variable, values[first_component..end_component]) catch return VkError.Unknown;
                continue;
            },
        }
        runtime.writeInput(program, variable, values[0..binding.span.components]) catch return VkError.Unknown;
    }
}

fn collectOutputs(allocator: std.mem.Allocator, runtime: anytype, program: *const @import("Program.zig"), output: *Renderer.Vertex) VkError!void {
    for (program.interfaces, 0..) |optional_binding, index| {
        const binding = optional_binding orelse continue;
        if (binding.direction != .output)
            continue;
        const variable = ir.id.InterfaceVariableId.fromIndex(index);
        var values: [4]u32 = @splat(0);
        runtime.readOutput(program, variable, values[0..binding.span.components]) catch return VkError.Unknown;
        switch (binding.semantic) {
            .builtin => |builtin| switch (builtin) {
                .position => @memcpy(std.mem.asBytes(&output.position), std.mem.asBytes(&values)),
                else => return VkError.InvalidPipelineDrv,
            },
            .location => |location| {
                if (location.location >= output.outputs.len or location.component >= output.outputs[0].len)
                    return VkError.ValidationFailed;
                const size = @as(usize, binding.span.components) * @sizeOf(u32);
                const blob = allocator.alloc(u8, size + interface_blob_padding) catch return VkError.OutOfDeviceMemory;
                @memset(blob, 0);
                @memcpy(blob[0..size], std.mem.asBytes(&values)[0..size]);
                output.outputs[location.location][location.component] = .{
                    .interpolation_type = switch (binding.span.kind) {
                        .signed_integer, .unsigned_integer, .boolean => .flat,
                        .floating => .smooth,
                    },
                    .centroid = false,
                    .blob = blob,
                    .size = size,
                };
            },
        }
    }
}

fn findAttribute(attributes: []const vk.VertexInputAttributeDescription, location: u32) ?vk.VertexInputAttributeDescription {
    for (attributes) |attribute|
        if (attribute.location == location) return attribute;
    return null;
}

fn findBinding(bindings: []const vk.VertexInputBindingDescription, binding: u32) ?vk.VertexInputBindingDescription {
    for (bindings) |description|
        if (description.binding == binding) return description;
    return null;
}