src/tint/lang/spirv/writer/raise/var_for_dynamic_index.cc - tint - Git at Google

 // Copyright 2023 The Dawn & Tint Authors
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //
 // 1. Redistributions of source code must retain the above copyright notice, this
 //    list of conditions and the following disclaimer.
 //
 // 2. Redistributions in binary form must reproduce the above copyright notice,
 //    this list of conditions and the following disclaimer in the documentation
 //    and/or other materials provided with the distribution.
 //
 // 3. Neither the name of the copyright holder nor the names of its
 //    contributors may be used to endorse or promote products derived from
 //    this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include "src/tint/lang/spirv/writer/raise/var_for_dynamic_index.h"

 #include <utility>

 #include "src/tint/lang/core/fluent_types.h"
 #include "src/tint/lang/core/ir/builder.h"
 #include "src/tint/lang/core/ir/module.h"
 #include "src/tint/lang/core/ir/validator.h"
 #include "src/tint/lang/core/type/array.h"
 #include "src/tint/lang/core/type/matrix.h"
 #include "src/tint/lang/core/type/pointer.h"
 #include "src/tint/lang/core/type/vector.h"
 #include "src/tint/utils/containers/hashmap.h"

 using namespace tint::core::number_suffixes;  // NOLINT
 using namespace tint::core::fluent_types;     // NOLINT

 namespace tint::spirv::writer::raise {

 namespace {
 // An access that needs replacing.
 struct AccessToReplace {
     // The access instruction.
     core::ir::Access* access = nullptr;
     // The index of the first dynamic index.
     size_t first_dynamic_index = 0;
     // The object type that corresponds to the source of the first dynamic index.
     const core::type::Type* dynamic_index_source_type = nullptr;
     // If the access indexes a vector, then the type of that vector
     const core::type::Vector* vector_access_type = nullptr;
 };

 // A partial access chain that uses constant indices to get to an object that will be
 // dynamically indexed.
 struct PartialAccess {
     // The base object.
     core::ir::Value* base = nullptr;
     // The list of constant indices to get from the base to the source object.
     Vector<core::ir::Value*, 4> indices;

     // A specialization of Hasher for PartialAccess.
     struct Hasher {
         inline std::size_t operator()(const PartialAccess& src) const {
             return Hash(src.base, src.indices);
         }
     };

     // An equality helper for PartialAccess.
     bool operator==(const PartialAccess& other) const {
         return base == other.base && indices == other.indices;
     }
 };

 enum class Action { kStop, kContinue };

 template <typename CALLBACK>
 void WalkAccessChain(core::ir::Access* access, CALLBACK&& callback) {
     auto indices = access->Indices();
     auto* ty = access->Object()->Type();
     for (size_t i = 0; i < indices.Length(); i++) {
         if (callback(i, indices[i], ty) == Action::kStop) {
             break;
         }
         auto* const_idx = indices[i]->As<core::ir::Constant>();
         ty = const_idx ? ty->Element(const_idx->Value()->ValueAs<u32>()) : ty->Elements().type;
     }
 }

 std::optional<AccessToReplace> ShouldReplace(core::ir::Access* access) {
     if (access->Result(0)->Type()->Is<core::type::Pointer>()) {
         // No need to modify accesses into pointer types.
         return {};
     }

     std::optional<AccessToReplace> result;
     WalkAccessChain(access, [&](size_t i, core::ir::Value* index, const core::type::Type* ty) {
         if (auto* vec = ty->As<core::type::Vector>()) {
             // If we haven't found a dynamic index before the vector, then the transform doesn't
             // need to hoist the access into a var as a vector value can be dynamically indexed.
             // If we have found a dynamic index before the vector, then make a note that we're
             // indexing a vector as we can't obtain a pointer to a vector element, so this needs to
             // be handled specially.
             if (result) {
                 result->vector_access_type = vec;
             }
             return Action::kStop;
         }

         // Check if this is the first dynamic index.
         if (!result && !index->Is<core::ir::Constant>()) {
             result = AccessToReplace{access, i, ty};
         }

         return Action::kContinue;
     });

     return result;
 }

 void Run(core::ir::Module& ir) {
     core::ir::Builder builder(ir);

     // Find the access instructions that need replacing.
     Vector<AccessToReplace, 4> worklist;
     for (auto* inst : ir.instructions.Objects()) {
         if (auto* access = inst->As<core::ir::Access>(); access && access->Alive()) {
             if (auto to_replace = ShouldReplace(access)) {
                 worklist.Push(to_replace.value());
             }
         }
     }

     // Replace each access instruction that we recorded.
     Hashmap<core::ir::Value*, core::ir::Value*, 4> object_to_local;
     Hashmap<PartialAccess, core::ir::Value*, 4, PartialAccess::Hasher> source_object_to_value;
     for (const auto& to_replace : worklist) {
         auto* access = to_replace.access;
         auto* source_object = access->Object();

         // If the access starts with at least one constant index, extract the source of the first
         // dynamic access to avoid copying the whole object.
         if (to_replace.first_dynamic_index > 0) {
             PartialAccess partial_access = {
                 access->Object(), access->Indices().Truncate(to_replace.first_dynamic_index)};
             source_object = source_object_to_value.GetOrCreate(partial_access, [&] {
                 auto* intermediate_source = builder.Access(to_replace.dynamic_index_source_type,
                                                            source_object, partial_access.indices);
                 intermediate_source->InsertBefore(access);
                 return intermediate_source->Result(0);
             });
         }

         // Declare a local variable and copy the source object to it.
         auto* local = object_to_local.GetOrCreate(source_object, [&] {
             auto* decl = builder.Var(ir.Types().ptr(
                 core::AddressSpace::kFunction, source_object->Type(), core::Access::kReadWrite));
             decl->SetInitializer(source_object);
             decl->InsertBefore(access);
             return decl->Result(0);
         });

         // Create a new access instruction using the local variable as the source.
         Vector<core::ir::Value*, 4> indices{
             access->Indices().Offset(to_replace.first_dynamic_index)};
         const core::type::Type* access_type = access->Result(0)->Type();
         core::ir::Value* vector_index = nullptr;
         if (to_replace.vector_access_type) {
             // The old access indexed the element of a vector.
             // Its not valid to obtain the address of an element of a vector, so we need to access
             // up to the vector, then use LoadVectorElement to load the element.
             // As a vector element is always a scalar, we know the last index of the access is the
             // index on the vector. Pop that index to obtain the index to pass to
             // LoadVectorElement(), and perform the rest of the access chain.
             access_type = to_replace.vector_access_type;
             vector_index = indices.Pop();
         }

         core::ir::Instruction* new_access = builder.Access(
             ir.Types().ptr(core::AddressSpace::kFunction, access_type, core::Access::kReadWrite),
             local, indices);
         new_access->InsertBefore(access);

         core::ir::Instruction* load = nullptr;
         if (to_replace.vector_access_type) {
             load = builder.LoadVectorElement(new_access->Result(0), vector_index);
         } else {
             load = builder.Load(new_access);
         }

         // Replace all uses of the old access instruction with the loaded result.
         access->Result(0)->ReplaceAllUsesWith(load->Result(0));
         access->ReplaceWith(load);
         access->Destroy();
     }
 }

 }  // namespace

 Result<SuccessType> VarForDynamicIndex(core::ir::Module& ir) {
     auto result = ValidateAndDumpIfNeeded(ir, "VarForDynamicIndex transform");
     if (result != Success) {
         return result;
     }

     Run(ir);

     return Success;
 }

 }  // namespace tint::spirv::writer::raise
	// Copyright 2023 The Dawn & Tint Authors
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// 1. Redistributions of source code must retain the above copyright notice, this
	// list of conditions and the following disclaimer.
	//
	// 2. Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	//
	// 3. Neither the name of the copyright holder nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#include "src/tint/lang/spirv/writer/raise/var_for_dynamic_index.h"

	#include <utility>

	#include "src/tint/lang/core/fluent_types.h"
	#include "src/tint/lang/core/ir/builder.h"
	#include "src/tint/lang/core/ir/module.h"
	#include "src/tint/lang/core/ir/validator.h"
	#include "src/tint/lang/core/type/array.h"
	#include "src/tint/lang/core/type/matrix.h"
	#include "src/tint/lang/core/type/pointer.h"
	#include "src/tint/lang/core/type/vector.h"
	#include "src/tint/utils/containers/hashmap.h"

	using namespace tint::core::number_suffixes; // NOLINT
	using namespace tint::core::fluent_types; // NOLINT

	namespace tint::spirv::writer::raise {

	namespace {
	// An access that needs replacing.
	struct AccessToReplace {
	// The access instruction.
	core::ir::Access* access = nullptr;
	// The index of the first dynamic index.
	size_t first_dynamic_index = 0;
	// The object type that corresponds to the source of the first dynamic index.
	const core::type::Type* dynamic_index_source_type = nullptr;
	// If the access indexes a vector, then the type of that vector
	const core::type::Vector* vector_access_type = nullptr;
	};

	// A partial access chain that uses constant indices to get to an object that will be
	// dynamically indexed.
	struct PartialAccess {
	// The base object.
	core::ir::Value* base = nullptr;
	// The list of constant indices to get from the base to the source object.
	Vector<core::ir::Value*, 4> indices;

	// A specialization of Hasher for PartialAccess.
	struct Hasher {
	inline std::size_t operator()(const PartialAccess& src) const {
	return Hash(src.base, src.indices);
	}
	};

	// An equality helper for PartialAccess.
	bool operator==(const PartialAccess& other) const {
	return base == other.base && indices == other.indices;
	}
	};

	enum class Action { kStop, kContinue };

	template <typename CALLBACK>
	void WalkAccessChain(core::ir::Access* access, CALLBACK&& callback) {
	auto indices = access->Indices();
	auto* ty = access->Object()->Type();
	for (size_t i = 0; i < indices.Length(); i++) {
	if (callback(i, indices[i], ty) == Action::kStop) {
	break;
	}
	auto* const_idx = indices[i]->As<core::ir::Constant>();
	ty = const_idx ? ty->Element(const_idx->Value()->ValueAs<u32>()) : ty->Elements().type;
	}
	}

	std::optional<AccessToReplace> ShouldReplace(core::ir::Access* access) {
	if (access->Result(0)->Type()->Is<core::type::Pointer>()) {
	// No need to modify accesses into pointer types.
	return {};
	}

	std::optional<AccessToReplace> result;
	WalkAccessChain(access, [&](size_t i, core::ir::Value* index, const core::type::Type* ty) {
	if (auto* vec = ty->As<core::type::Vector>()) {
	// If we haven't found a dynamic index before the vector, then the transform doesn't
	// need to hoist the access into a var as a vector value can be dynamically indexed.
	// If we have found a dynamic index before the vector, then make a note that we're
	// indexing a vector as we can't obtain a pointer to a vector element, so this needs to
	// be handled specially.
	if (result) {
	result->vector_access_type = vec;
	}
	return Action::kStop;
	}

	// Check if this is the first dynamic index.
	if (!result && !index->Is<core::ir::Constant>()) {
	result = AccessToReplace{access, i, ty};
	}

	return Action::kContinue;
	});

	return result;
	}

	void Run(core::ir::Module& ir) {
	core::ir::Builder builder(ir);

	// Find the access instructions that need replacing.
	Vector<AccessToReplace, 4> worklist;
	for (auto* inst : ir.instructions.Objects()) {
	if (auto* access = inst->As<core::ir::Access>(); access && access->Alive()) {
	if (auto to_replace = ShouldReplace(access)) {
	worklist.Push(to_replace.value());
	}
	}
	}

	// Replace each access instruction that we recorded.
	Hashmap<core::ir::Value, core::ir::Value, 4> object_to_local;
	Hashmap<PartialAccess, core::ir::Value*, 4, PartialAccess::Hasher> source_object_to_value;
	for (const auto& to_replace : worklist) {
	auto* access = to_replace.access;
	auto* source_object = access->Object();

	// If the access starts with at least one constant index, extract the source of the first
	// dynamic access to avoid copying the whole object.
	if (to_replace.first_dynamic_index > 0) {
	PartialAccess partial_access = {
	access->Object(), access->Indices().Truncate(to_replace.first_dynamic_index)};
	source_object = source_object_to_value.GetOrCreate(partial_access, [&] {
	auto* intermediate_source = builder.Access(to_replace.dynamic_index_source_type,
	source_object, partial_access.indices);
	intermediate_source->InsertBefore(access);
	return intermediate_source->Result(0);
	});
	}

	// Declare a local variable and copy the source object to it.
	auto* local = object_to_local.GetOrCreate(source_object, [&] {
	auto* decl = builder.Var(ir.Types().ptr(
	core::AddressSpace::kFunction, source_object->Type(), core::Access::kReadWrite));
	decl->SetInitializer(source_object);
	decl->InsertBefore(access);
	return decl->Result(0);
	});

	// Create a new access instruction using the local variable as the source.
	Vector<core::ir::Value*, 4> indices{
	access->Indices().Offset(to_replace.first_dynamic_index)};
	const core::type::Type* access_type = access->Result(0)->Type();
	core::ir::Value* vector_index = nullptr;
	if (to_replace.vector_access_type) {
	// The old access indexed the element of a vector.
	// Its not valid to obtain the address of an element of a vector, so we need to access
	// up to the vector, then use LoadVectorElement to load the element.
	// As a vector element is always a scalar, we know the last index of the access is the
	// index on the vector. Pop that index to obtain the index to pass to
	// LoadVectorElement(), and perform the rest of the access chain.
	access_type = to_replace.vector_access_type;
	vector_index = indices.Pop();
	}

	core::ir::Instruction* new_access = builder.Access(
	ir.Types().ptr(core::AddressSpace::kFunction, access_type, core::Access::kReadWrite),
	local, indices);
	new_access->InsertBefore(access);

	core::ir::Instruction* load = nullptr;
	if (to_replace.vector_access_type) {
	load = builder.LoadVectorElement(new_access->Result(0), vector_index);
	} else {
	load = builder.Load(new_access);
	}

	// Replace all uses of the old access instruction with the loaded result.
	access->Result(0)->ReplaceAllUsesWith(load->Result(0));
	access->ReplaceWith(load);
	access->Destroy();
	}
	}

	} // namespace

	Result<SuccessType> VarForDynamicIndex(core::ir::Module& ir) {
	auto result = ValidateAndDumpIfNeeded(ir, "VarForDynamicIndex transform");
	if (result != Success) {
	return result;
	}

	Run(ir);

	return Success;
	}

	} // namespace tint::spirv::writer::raise