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// Copyright 2023 The Dawn & Tint Authors
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#include "src/tint/lang/spirv/writer/raise/shader_io.h"
#include <memory>
#include <utility>
#include "src/tint/lang/core/ir/builder.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/transform/shader_io.h"
#include "src/tint/lang/core/ir/validator.h"
#include "src/tint/lang/core/type/array.h"
using namespace tint::core::fluent_types; // NOLINT
using namespace tint::core::number_suffixes; // NOLINT
namespace tint::spirv::writer::raise {
namespace {
/// State that persists across the whole module and can be shared between entry points.
struct PerModuleState {
/// The frag_depth clamp arguments.
core::ir::Value* frag_depth_clamp_args = nullptr;
};
/// PIMPL state for the parts of the shader IO transform specific to SPIR-V.
/// For SPIR-V, we declare a global variable for each input and output. The wrapper entry point then
/// loads from and stores to these variables. We also modify the type of the SampleMask builtin to
/// be an array, as required by Vulkan.
struct StateImpl : core::ir::transform::ShaderIOBackendState {
/// The input variables.
Vector<core::ir::Var*, 4> input_vars;
/// The output variables.
Vector<core::ir::Var*, 4> output_vars;
/// The configuration options.
const ShaderIOConfig& config;
/// The per-module state object.
PerModuleState& module_state;
/// Constructor
StateImpl(core::ir::Module& mod,
core::ir::Function* f,
const ShaderIOConfig& cfg,
PerModuleState& mod_state)
: ShaderIOBackendState(mod, f), config(cfg), module_state(mod_state) {}
/// Destructor
~StateImpl() override {}
/// Declare a global variable for each IO entry listed in @p entries.
/// @param vars the list of variables
/// @param entries the entries to emit
/// @param addrspace the address to use for the global variables
/// @param access the access mode to use for the global variables
/// @param name_suffix the suffix to add to struct and variable names
void MakeVars(Vector<core::ir::Var*, 4>& vars,
Vector<core::type::Manager::StructMemberDesc, 4>& entries,
core::AddressSpace addrspace,
core::Access access,
const char* name_suffix) {
for (auto io : entries) {
StringStream name;
name << ir.NameOf(func).Name();
if (io.attributes.builtin) {
// SampleMask must be an array for Vulkan.
if (io.attributes.builtin.value() == core::BuiltinValue::kSampleMask) {
io.type = ty.array<u32, 1>();
}
name << "_" << io.attributes.builtin.value();
// Vulkan requires that fragment integer builtin inputs be Flat decorated.
if (func->Stage() == core::ir::Function::PipelineStage::kFragment &&
addrspace == core::AddressSpace::kIn &&
io.type->is_integer_scalar_or_vector()) {
io.attributes.interpolation = {core::InterpolationType::kFlat};
}
}
if (io.attributes.location) {
name << "_loc" << io.attributes.location.value();
if (io.attributes.index.has_value()) {
name << "_idx" << io.attributes.index.value();
}
}
name << name_suffix;
// Create an IO variable and add it to the root block.
auto* ptr = ty.ptr(addrspace, io.type, access);
auto* var = b.Var(name.str(), ptr);
var->SetAttributes(core::ir::IOAttributes{
io.attributes.location,
io.attributes.index,
io.attributes.builtin,
io.attributes.interpolation,
io.attributes.invariant,
});
ir.root_block->Append(var);
vars.Push(var);
}
}
/// @copydoc ShaderIO::BackendState::FinalizeInputs
Vector<core::ir::FunctionParam*, 4> FinalizeInputs() override {
MakeVars(input_vars, inputs, core::AddressSpace::kIn, core::Access::kRead, "_Input");
return tint::Empty;
}
/// @copydoc ShaderIO::BackendState::FinalizeOutputs
core::ir::Value* FinalizeOutputs() override {
MakeVars(output_vars, outputs, core::AddressSpace::kOut, core::Access::kWrite, "_Output");
return nullptr;
}
/// @copydoc ShaderIO::BackendState::GetInput
core::ir::Value* GetInput(core::ir::Builder& builder, uint32_t idx) override {
// Load the input from the global variable declared earlier.
auto* ptr = ty.ptr(core::AddressSpace::kIn, inputs[idx].type, core::Access::kRead);
auto* from = input_vars[idx]->Result(0);
if (inputs[idx].attributes.builtin) {
if (inputs[idx].attributes.builtin.value() == core::BuiltinValue::kSampleMask) {
// SampleMask becomes an array for SPIR-V, so load from the first element.
from = builder.Access(ptr, input_vars[idx], 0_u)->Result(0);
}
}
return builder.Load(from)->Result(0);
}
/// @copydoc ShaderIO::BackendState::SetOutput
void SetOutput(core::ir::Builder& builder, uint32_t idx, core::ir::Value* value) override {
// Store the output to the global variable declared earlier.
auto* ptr = ty.ptr(core::AddressSpace::kOut, outputs[idx].type, core::Access::kWrite);
auto* to = output_vars[idx]->Result(0);
if (outputs[idx].attributes.builtin) {
if (outputs[idx].attributes.builtin.value() == core::BuiltinValue::kSampleMask) {
// SampleMask becomes an array for SPIR-V, so store to the first element.
to = builder.Access(ptr, to, 0_u)->Result(0);
}
// Clamp frag_depth values if necessary.
if (outputs[idx].attributes.builtin.value() == core::BuiltinValue::kFragDepth) {
value = ClampFragDepth(builder, value);
}
}
builder.Store(to, value);
}
/// Clamp a frag_depth builtin value if necessary.
/// @param builder the builder to use for new instructions
/// @param frag_depth the incoming frag_depth value
/// @returns the clamped value
core::ir::Value* ClampFragDepth(core::ir::Builder& builder, core::ir::Value* frag_depth) {
if (!config.clamp_frag_depth) {
return frag_depth;
}
// Create the clamp args struct and variable.
if (!module_state.frag_depth_clamp_args) {
// Check that there are no push constants in the module already.
for (auto* inst : *ir.root_block) {
if (auto* var = inst->As<core::ir::Var>()) {
auto* ptr = var->Result(0)->Type()->As<core::type::Pointer>();
if (ptr->AddressSpace() == core::AddressSpace::kPushConstant) {
TINT_ICE() << "cannot clamp frag_depth with pre-existing push constants";
}
}
}
// Declare the struct.
auto* str = ty.Struct(ir.symbols.Register("FragDepthClampArgs"),
{
{ir.symbols.Register("min"), ty.f32()},
{ir.symbols.Register("max"), ty.f32()},
});
str->SetStructFlag(core::type::kBlock);
// Declare the variable.
auto* var = b.Var("tint_frag_depth_clamp_args", ty.ptr(push_constant, str));
ir.root_block->Append(var);
module_state.frag_depth_clamp_args = var->Result(0);
}
// Clamp the value.
auto* args = builder.Load(module_state.frag_depth_clamp_args);
auto* frag_depth_min = builder.Access(ty.f32(), args, 0_u);
auto* frag_depth_max = builder.Access(ty.f32(), args, 1_u);
return builder
.Call(ty.f32(), core::BuiltinFn::kClamp, frag_depth, frag_depth_min, frag_depth_max)
->Result(0);
}
/// @copydoc ShaderIO::BackendState::NeedsVertexPointSize
bool NeedsVertexPointSize() const override { return config.emit_vertex_point_size; }
};
} // namespace
Result<SuccessType> ShaderIO(core::ir::Module& ir, const ShaderIOConfig& config) {
auto result = ValidateAndDumpIfNeeded(ir, "ShaderIO transform");
if (result != Success) {
return result;
}
PerModuleState module_state;
core::ir::transform::RunShaderIOBase(ir, [&](core::ir::Module& mod, core::ir::Function* func) {
return std::make_unique<StateImpl>(mod, func, config, module_state);
});
return Success;
}
} // namespace tint::spirv::writer::raise