mirror of
https://github.com/KhronosGroup/SPIRV-Tools
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209 lines
9.1 KiB
C++
209 lines
9.1 KiB
C++
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// Copyright (c) 2020 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 "source/reduce/remove_struct_member_reduction_opportunity.h"
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#include "source/opt/ir_context.h"
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namespace spvtools {
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namespace reduce {
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bool RemoveStructMemberReductionOpportunity::PreconditionHolds() {
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return struct_type_->NumInOperands() == original_number_of_members_;
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}
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void RemoveStructMemberReductionOpportunity::Apply() {
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std::set<opt::Instruction*> decorations_to_kill;
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// We need to remove decorations that target the removed struct member, and
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// adapt decorations that target later struct members by decrementing the
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// member identifier. We also need to adapt composite construction
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// instructions so that no id is provided for the member being removed.
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//
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// To do this, we consider every use of the struct type.
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struct_type_->context()->get_def_use_mgr()->ForEachUse(
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struct_type_, [this, &decorations_to_kill](opt::Instruction* user,
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uint32_t /*operand_index*/) {
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switch (user->opcode()) {
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case SpvOpCompositeConstruct:
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case SpvOpConstantComposite:
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// This use is constructing a composite of the struct type, so we
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// must remove the id that was provided for the member we are
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// removing.
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user->RemoveInOperand(member_index_);
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break;
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case SpvOpMemberDecorate:
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// This use is decorating a member of the struct.
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if (user->GetSingleWordInOperand(1) == member_index_) {
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// The member we are removing is being decorated, so we record
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// that we need to get rid of the decoration.
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decorations_to_kill.insert(user);
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} else if (user->GetSingleWordInOperand(1) > member_index_) {
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// A member beyond the one we are removing is being decorated, so
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// we adjust the index that identifies the member.
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user->SetInOperand(1, {user->GetSingleWordInOperand(1) - 1});
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}
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break;
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default:
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break;
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}
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});
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// Get rid of all the decorations that were found to target the member being
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// removed.
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for (auto decoration_to_kill : decorations_to_kill) {
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decoration_to_kill->context()->KillInst(decoration_to_kill);
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}
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// We now look through all instructions that access composites via sequences
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// of indices. Every time we find an index into the struct whose member is
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// being removed, and if the member being accessed comes after the member
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// being removed, we need to adjust the index accordingly.
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//
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// We go through every relevant instruction in every block of every function,
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// and invoke a helper to adjust it.
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auto context = struct_type_->context();
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for (auto& function : *context->module()) {
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for (auto& block : function) {
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for (auto& inst : block) {
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switch (inst.opcode()) {
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case SpvOpAccessChain:
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case SpvOpInBoundsAccessChain: {
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// These access chain instructions take sequences of ids for
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// indexing, starting from input operand 1.
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auto composite_type_id =
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context->get_def_use_mgr()
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->GetDef(context->get_def_use_mgr()
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->GetDef(inst.GetSingleWordInOperand(0))
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->type_id())
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->GetSingleWordInOperand(1);
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AdjustAccessedIndices(composite_type_id, 1, false, context, &inst);
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} break;
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case SpvOpPtrAccessChain:
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case SpvOpInBoundsPtrAccessChain: {
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// These access chain instructions take sequences of ids for
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// indexing, starting from input operand 2.
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auto composite_type_id =
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context->get_def_use_mgr()
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->GetDef(context->get_def_use_mgr()
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->GetDef(inst.GetSingleWordInOperand(1))
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->type_id())
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->GetSingleWordInOperand(1);
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AdjustAccessedIndices(composite_type_id, 2, false, context, &inst);
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} break;
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case SpvOpCompositeExtract: {
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// OpCompositeExtract uses literals for indexing, starting at input
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// operand 1.
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auto composite_type_id =
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context->get_def_use_mgr()
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->GetDef(inst.GetSingleWordInOperand(0))
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->type_id();
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AdjustAccessedIndices(composite_type_id, 1, true, context, &inst);
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} break;
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case SpvOpCompositeInsert: {
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// OpCompositeInsert uses literals for indexing, starting at input
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// operand 2.
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auto composite_type_id =
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context->get_def_use_mgr()
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->GetDef(inst.GetSingleWordInOperand(1))
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->type_id();
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AdjustAccessedIndices(composite_type_id, 2, true, context, &inst);
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} break;
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default:
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break;
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}
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}
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}
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}
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// Remove the member from the struct type.
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struct_type_->RemoveInOperand(member_index_);
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}
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void RemoveStructMemberReductionOpportunity::AdjustAccessedIndices(
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uint32_t composite_type_id, uint32_t first_index_input_operand,
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bool literal_indices, opt::IRContext* context,
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opt::Instruction* composite_access_instruction) const {
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// Walk the series of types that are encountered by following the
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// instruction's sequence of indices. For all types except structs, this is
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// routine: the type of the composite dictates what the next type will be
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// regardless of the specific index value.
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uint32_t next_type = composite_type_id;
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for (uint32_t i = first_index_input_operand;
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i < composite_access_instruction->NumInOperands(); i++) {
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auto type_inst = context->get_def_use_mgr()->GetDef(next_type);
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switch (type_inst->opcode()) {
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case SpvOpTypeArray:
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case SpvOpTypeMatrix:
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case SpvOpTypeRuntimeArray:
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case SpvOpTypeVector:
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next_type = type_inst->GetSingleWordInOperand(0);
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break;
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case SpvOpTypeStruct: {
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// Struct types are special becuase (a) we may need to adjust the index
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// being used, if the struct type is the one from which we are removing
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// a member, and (b) the type encountered by following the current index
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// is dependent on the value of the index.
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// Work out the member being accessed. If literal indexing is used this
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// is simple; otherwise we need to look up the id of the constant
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// instruction being used as an index and get the value of the constant.
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uint32_t index_operand =
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composite_access_instruction->GetSingleWordInOperand(i);
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uint32_t member = literal_indices ? index_operand
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: context->get_def_use_mgr()
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->GetDef(index_operand)
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->GetSingleWordInOperand(0);
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// The next type we will consider is obtained by looking up the struct
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// type at |member|.
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next_type = type_inst->GetSingleWordInOperand(member);
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if (type_inst == struct_type_ && member > member_index_) {
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// The struct type is the struct from which we are removing a member,
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// and the member being accessed is beyond the member we are removing.
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// We thus need to decrement the index by 1.
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uint32_t new_in_operand;
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if (literal_indices) {
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// With literal indexing this is straightforward.
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new_in_operand = member - 1;
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} else {
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// With id-based indexing this is more tricky: we need to find or
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// create a constant instruction whose value is one less than
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// |member|, and use the id of this constant as the replacement
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// input operand.
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auto constant_inst =
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context->get_def_use_mgr()->GetDef(index_operand);
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auto int_type = context->get_type_mgr()
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->GetType(constant_inst->type_id())
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->AsInteger();
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auto new_index_constant =
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opt::analysis::IntConstant(int_type, {member - 1});
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new_in_operand = context->get_constant_mgr()
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->GetDefiningInstruction(&new_index_constant)
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->result_id();
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}
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composite_access_instruction->SetInOperand(i, {new_in_operand});
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}
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} break;
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default:
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assert(0 && "Unknown composite type.");
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break;
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}
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}
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}
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} // namespace reduce
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} // namespace spvtools
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