src/transform/glsl.cc

// Copyright 2021 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "src/transform/glsl.h"

#include <utility>

#include "src/program_builder.h"
#include "src/transform/calculate_array_length.h"
#include "src/transform/canonicalize_entry_point_io.h"
#include "src/transform/decompose_memory_access.h"
#include "src/transform/external_texture_transform.h"
#include "src/transform/fold_trivial_single_use_lets.h"
#include "src/transform/loop_to_for_loop.h"
#include "src/transform/manager.h"
#include "src/transform/pad_array_elements.h"
#include "src/transform/promote_initializers_to_const_var.h"
#include "src/transform/remove_phonies.h"
#include "src/transform/simplify_pointers.h"
#include "src/transform/single_entry_point.h"
#include "src/transform/unshadow.h"
#include "src/transform/zero_init_workgroup_memory.h"

TINT_INSTANTIATE_TYPEINFO(tint::transform::Glsl);
TINT_INSTANTIATE_TYPEINFO(tint::transform::Glsl::Config);

namespace tint {
namespace transform {

Glsl::Glsl() = default;
Glsl::~Glsl() = default;

Output Glsl::Run(const Program* in, const DataMap& inputs) {
  Manager manager;
  DataMap data;

  auto* cfg = inputs.Get<Config>();

  manager.Add<Unshadow>();

  // Attempt to convert `loop`s into for-loops. This is to try and massage the
  // output into something that will not cause FXC to choke or misbehave.
  manager.Add<FoldTrivialSingleUseLets>();
  manager.Add<LoopToForLoop>();

  if (!cfg || !cfg->disable_workgroup_init) {
    // ZeroInitWorkgroupMemory must come before CanonicalizeEntryPointIO as
    // ZeroInitWorkgroupMemory may inject new builtin parameters.
    manager.Add<ZeroInitWorkgroupMemory>();
  }
  manager.Add<CanonicalizeEntryPointIO>();
  manager.Add<SimplifyPointers>();

  // Running SingleEntryPoint before RemovePhonies prevents variables
  // referenced only by phonies from being optimized out. Strictly
  // speaking, that optimization isn't incorrect, but it prevents some
  // tests (e.g., types/texture/*) from producing useful results.
  if (cfg) {
    manager.Add<SingleEntryPoint>();
    data.Add<SingleEntryPoint::Config>(cfg->entry_point);
  }
  manager.Add<RemovePhonies>();
  manager.Add<CalculateArrayLength>();
  manager.Add<ExternalTextureTransform>();
  manager.Add<PromoteInitializersToConstVar>();
  manager.Add<PadArrayElements>();

  // For now, canonicalize to structs for all IO, as in HLSL.
  // TODO(senorblanco): we could skip this by accessing global entry point
  // variables directly.
  data.Add<CanonicalizeEntryPointIO::Config>(
      CanonicalizeEntryPointIO::ShaderStyle::kHlsl);
  auto out = manager.Run(in, data);
  if (!out.program.IsValid()) {
    return out;
  }

  ProgramBuilder builder;
  CloneContext ctx(&builder, &out.program);
  AddEmptyEntryPoint(ctx);
  ctx.Clone();
  builder.SetTransformApplied(this);
  return Output{Program(std::move(builder))};
}

void Glsl::AddEmptyEntryPoint(CloneContext& ctx) const {
  for (auto* func : ctx.src->AST().Functions()) {
    if (func->IsEntryPoint()) {
      return;
    }
  }
  ctx.dst->Func(ctx.dst->Symbols().New("unused_entry_point"), {},
                ctx.dst->ty.void_(), {},
                {ctx.dst->Stage(ast::PipelineStage::kCompute),
                 ctx.dst->WorkgroupSize(1)});
}

Glsl::Config::Config(const std::string& ep, bool disable_wi)
    : entry_point(ep), disable_workgroup_init(disable_wi) {}
Glsl::Config::Config(const Config&) = default;
Glsl::Config::~Config() = default;

}  // namespace transform
}  // namespace tint