2018-02-08 15:59:03 +00:00
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// Copyright (c) 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "const_folding_rules.h"
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namespace spvtools {
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namespace opt {
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namespace {
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const uint32_t kExtractCompositeIdInIdx = 0;
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2018-02-09 18:37:26 +00:00
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// Returns a vector that contains the two 32-bit integers that result from
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// splitting |a| in two. The first entry in vector are the low order bit if
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// |a|.
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inline std::vector<uint32_t> ExtractInts(uint64_t a) {
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std::vector<uint32_t> result;
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result.push_back(static_cast<uint32_t>(a));
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result.push_back(static_cast<uint32_t>(a >> 32));
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return result;
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}
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// Returns true if we are allowed to fold or otherwise manipulate the
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// instruction that defines |id| in the given context.
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bool CanFoldFloatingPoint(ir::IRContext* context, uint32_t id) {
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// TODO: Add the rules for kernels. For now it will be pessimistic.
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if (!context->get_feature_mgr()->HasCapability(SpvCapabilityShader)) {
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return false;
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}
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bool is_nocontract = false;
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context->get_decoration_mgr()->WhileEachDecoration(
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id, SpvDecorationNoContraction, [&is_nocontract](const ir::Instruction&) {
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is_nocontract = true;
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return false;
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});
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return !is_nocontract;
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}
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// Folds an OpcompositeExtract where input is a composite constant.
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2018-02-08 15:59:03 +00:00
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ConstantFoldingRule FoldExtractWithConstants() {
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return [](ir::Instruction* inst,
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const std::vector<const analysis::Constant*>& constants)
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-> const analysis::Constant* {
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const analysis::Constant* c = constants[kExtractCompositeIdInIdx];
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if (c == nullptr) {
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return nullptr;
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}
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for (uint32_t i = 1; i < inst->NumInOperands(); ++i) {
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uint32_t element_index = inst->GetSingleWordInOperand(i);
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if (c->AsNullConstant()) {
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// Return Null for the return type.
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ir::IRContext* context = inst->context();
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analysis::ConstantManager* const_mgr = context->get_constant_mgr();
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analysis::TypeManager* type_mgr = context->get_type_mgr();
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2018-02-09 18:37:26 +00:00
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return const_mgr->GetConstant(type_mgr->GetType(inst->type_id()), {});
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2018-02-08 15:59:03 +00:00
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}
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auto cc = c->AsCompositeConstant();
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assert(cc != nullptr);
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auto components = cc->GetComponents();
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c = components[element_index];
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}
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return c;
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};
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}
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ConstantFoldingRule FoldCompositeWithConstants() {
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// Folds an OpCompositeConstruct where all of the inputs are constants to a
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// constant. A new constant is created if necessary.
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return [](ir::Instruction* inst,
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const std::vector<const analysis::Constant*>& constants)
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-> const analysis::Constant* {
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ir::IRContext* context = inst->context();
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analysis::ConstantManager* const_mgr = context->get_constant_mgr();
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analysis::TypeManager* type_mgr = context->get_type_mgr();
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const analysis::Type* new_type = type_mgr->GetType(inst->type_id());
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std::vector<uint32_t> ids;
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for (const analysis::Constant* element_const : constants) {
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if (element_const == nullptr) {
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return nullptr;
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}
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uint32_t element_id = const_mgr->FindDeclaredConstant(element_const);
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if (element_id == 0) {
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return nullptr;
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}
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ids.push_back(element_id);
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}
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return const_mgr->GetConstant(new_type, ids);
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};
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}
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2018-02-09 18:37:26 +00:00
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// The interface for a function that returns the result of applying a scalar
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// floating-point binary operation on |a| and |b|. The type of the return value
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// will be |type|. The input constants must also be of type |type|.
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using FloatScalarFoldingRule = std::function<const analysis::FloatConstant*(
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const analysis::Float* type, const analysis::Constant* a,
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const analysis::Constant* b, analysis::ConstantManager*)>;
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// Returns an std::vector containing the elements of |constant|. The type of
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// |constant| must be |Vector|.
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std::vector<const analysis::Constant*> GetVectorComponents(
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const analysis::Constant* constant, analysis::ConstantManager* const_mgr) {
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std::vector<const analysis::Constant*> components;
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const analysis::VectorConstant* a = constant->AsVectorConstant();
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const analysis::Vector* vector_type = constant->type()->AsVector();
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assert(vector_type != nullptr);
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if (a != nullptr) {
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for (uint32_t i = 0; i < vector_type->element_count(); ++i) {
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components.push_back(a->GetComponents()[i]);
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}
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} else {
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const analysis::Type* element_type = vector_type->element_type();
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const analysis::Constant* element_null_const =
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const_mgr->GetConstant(element_type, {});
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for (uint32_t i = 0; i < vector_type->element_count(); ++i) {
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components.push_back(element_null_const);
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}
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}
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return components;
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}
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// Returns a |ConstantFoldingRule| that folds floating point scalars using
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// |scalar_rule| and vectors of floating point by applying |scalar_rule| to the
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// elements of the vector. The |ConstantFoldingRule| that is returned assumes
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// that |constants| contains 2 entries. If they are not |nullptr|, then their
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// type is either |Float| or a |Vector| whose element type is |Float|.
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ConstantFoldingRule FoldFloatingPointOp(FloatScalarFoldingRule scalar_rule) {
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return [scalar_rule](ir::Instruction* inst,
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const std::vector<const analysis::Constant*>& constants)
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-> const analysis::Constant* {
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ir::IRContext* context = inst->context();
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analysis::ConstantManager* const_mgr = context->get_constant_mgr();
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analysis::TypeManager* type_mgr = context->get_type_mgr();
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const analysis::Type* result_type = type_mgr->GetType(inst->type_id());
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const analysis::Vector* vector_type = result_type->AsVector();
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const analysis::Float* float_type = nullptr;
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if (!CanFoldFloatingPoint(context, inst->result_id())) {
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return nullptr;
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}
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if (constants[0] == nullptr || constants[1] == nullptr) {
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return nullptr;
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}
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if (vector_type != nullptr) {
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std::vector<const analysis::Constant*> a_componenets;
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std::vector<const analysis::Constant*> b_componenets;
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std::vector<const analysis::FloatConstant*> results_componenets;
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float_type = vector_type->element_type()->AsFloat();
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a_componenets = GetVectorComponents(constants[0], const_mgr);
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b_componenets = GetVectorComponents(constants[1], const_mgr);
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// Fold each component of the vector.
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for (uint32_t i = 0; i < a_componenets.size(); ++i) {
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results_componenets.push_back(scalar_rule(float_type, a_componenets[i],
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b_componenets[i], const_mgr));
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if (results_componenets[i] == nullptr) {
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return nullptr;
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}
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}
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// Build the constant object and return it.
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std::vector<uint32_t> ids;
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for (const analysis::FloatConstant* member : results_componenets) {
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ids.push_back(const_mgr->GetDefiningInstruction(member)->result_id());
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}
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return const_mgr->GetConstant(vector_type, ids);
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} else {
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float_type = result_type->AsFloat();
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return scalar_rule(float_type, constants[0], constants[1], const_mgr);
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}
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};
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}
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// Returns the floating point value of |c|. The constant |c| must have type
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// |Float|, and width |32|.
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float GetFloatFromConst(const analysis::Constant* c) {
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assert(c->type()->AsFloat() != nullptr &&
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c->type()->AsFloat()->width() == 32);
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const analysis::FloatConstant* fc = c->AsFloatConstant();
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if (fc) {
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return fc->GetFloatValue();
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} else {
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assert(c->AsNullConstant() && "c must be a float point constant.");
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return 0.0f;
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}
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}
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// Returns the double value of |c|. The constant |c| must have type
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// |Float|, and width |64|.
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double GetDoubleFromConst(const analysis::Constant* c) {
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assert(c->type()->AsFloat() != nullptr &&
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c->type()->AsFloat()->width() == 64);
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const analysis::FloatConstant* fc = c->AsFloatConstant();
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if (fc) {
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return fc->GetDoubleValue();
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} else {
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assert(c->AsNullConstant() && "c must be a float point constant.");
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return 0.0;
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}
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}
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// This macro defines a |FloatScalarFoldingRule| that applies |op|. The
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// operator |op| must work for both float and double, and use syntax "f1 op f2".
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#define FOLD_OP(op) \
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[](const analysis::Float* type, const analysis::Constant* a, \
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const analysis::Constant* b, \
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analysis::ConstantManager* const_mgr) -> const analysis::FloatConstant* { \
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assert(type != nullptr && a != nullptr && b != nullptr); \
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if (type->width() == 32) { \
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float fa = GetFloatFromConst(a); \
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float fb = GetFloatFromConst(b); \
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spvutils::FloatProxy<float> result(fa op fb); \
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std::vector<uint32_t> words = {result.data()}; \
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return const_mgr->GetConstant(type, words)->AsFloatConstant(); \
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} else if (type->width() == 64) { \
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double fa = GetDoubleFromConst(a); \
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double fb = GetDoubleFromConst(b); \
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spvutils::FloatProxy<double> result(fa op fb); \
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std::vector<uint32_t> words(ExtractInts(result.data())); \
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return const_mgr->GetConstant(type, words)->AsFloatConstant(); \
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} \
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return nullptr; \
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}
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// Define the folding rules for subtraction, addition, multiplication, and
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// division for floating point values.
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ConstantFoldingRule FoldFSub() { return FoldFloatingPointOp(FOLD_OP(-)); }
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ConstantFoldingRule FoldFAdd() { return FoldFloatingPointOp(FOLD_OP(+)); }
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ConstantFoldingRule FoldFMul() { return FoldFloatingPointOp(FOLD_OP(*)); }
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ConstantFoldingRule FoldFDiv() { return FoldFloatingPointOp(FOLD_OP(/)); }
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2018-02-08 15:59:03 +00:00
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} // namespace
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spvtools::opt::ConstantFoldingRules::ConstantFoldingRules() {
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// Add all folding rules to the list for the opcodes to which they apply.
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// Note that the order in which rules are added to the list matters. If a rule
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// applies to the instruction, the rest of the rules will not be attempted.
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// Take that into consideration.
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rules_[SpvOpCompositeConstruct].push_back(FoldCompositeWithConstants());
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2018-02-09 18:37:26 +00:00
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2018-02-08 15:59:03 +00:00
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rules_[SpvOpCompositeExtract].push_back(FoldExtractWithConstants());
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2018-02-09 18:37:26 +00:00
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rules_[SpvOpFAdd].push_back(FoldFAdd());
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rules_[SpvOpFDiv].push_back(FoldFDiv());
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rules_[SpvOpFMul].push_back(FoldFMul());
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rules_[SpvOpFSub].push_back(FoldFSub());
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2018-02-08 15:59:03 +00:00
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}
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} // namespace opt
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} // namespace spvtools
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