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// Copyright (c) 2018 Google Inc.
//
// 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 "source/reduce/remove_unused_instruction_reduction_opportunity_finder.h"
#include "source/opcode.h"
#include "source/opt/instruction.h"
#include "source/reduce/remove_instruction_reduction_opportunity.h"
namespace spvtools {
namespace reduce {
RemoveUnusedInstructionReductionOpportunityFinder::
RemoveUnusedInstructionReductionOpportunityFinder(
bool remove_constants_and_undefs)
: remove_constants_and_undefs_(remove_constants_and_undefs) {}
std::vector<std::unique_ptr<ReductionOpportunity>>
RemoveUnusedInstructionReductionOpportunityFinder::GetAvailableOpportunities(
opt::IRContext* context, uint32_t target_function) const {
std::vector<std::unique_ptr<ReductionOpportunity>> result;
if (!target_function) {
// We are not restricting reduction to a specific function, so we consider
// unused instructions defined outside functions.
for (auto& inst : context->module()->debugs1()) {
if (context->get_def_use_mgr()->NumUses(&inst) > 0) {
continue;
}
result.push_back(
MakeUnique<RemoveInstructionReductionOpportunity>(&inst));
}
for (auto& inst : context->module()->debugs2()) {
if (context->get_def_use_mgr()->NumUses(&inst) > 0) {
continue;
}
result.push_back(
MakeUnique<RemoveInstructionReductionOpportunity>(&inst));
}
for (auto& inst : context->module()->debugs3()) {
if (context->get_def_use_mgr()->NumUses(&inst) > 0) {
continue;
}
result.push_back(
MakeUnique<RemoveInstructionReductionOpportunity>(&inst));
}
for (auto& inst : context->module()->ext_inst_debuginfo()) {
if (context->get_def_use_mgr()->NumUses(&inst) > 0) {
continue;
}
result.push_back(
MakeUnique<RemoveInstructionReductionOpportunity>(&inst));
}
for (auto& inst : context->module()->types_values()) {
if (!remove_constants_and_undefs_ &&
spvOpcodeIsConstantOrUndef(inst.opcode())) {
continue;
}
if (!OnlyReferencedByIntimateDecorationOrEntryPointInterface(context,
inst)) {
continue;
}
result.push_back(
MakeUnique<RemoveInstructionReductionOpportunity>(&inst));
}
for (auto& inst : context->module()->annotations()) {
if (context->get_def_use_mgr()->NumUsers(&inst) > 0) {
continue;
}
if (!IsIndependentlyRemovableDecoration(inst)) {
continue;
}
result.push_back(
MakeUnique<RemoveInstructionReductionOpportunity>(&inst));
}
}
for (auto* function : GetTargetFunctions(context, target_function)) {
for (auto& block : *function) {
for (auto& inst : block) {
if (context->get_def_use_mgr()->NumUses(&inst) > 0) {
continue;
}
if (!remove_constants_and_undefs_ &&
spvOpcodeIsConstantOrUndef(inst.opcode())) {
continue;
}
if (spvOpcodeIsBlockTerminator(inst.opcode()) ||
inst.opcode() == SpvOpSelectionMerge ||
inst.opcode() == SpvOpLoopMerge) {
// In this reduction pass we do not want to affect static
// control flow.
continue;
}
// Given that we're in a block, we should only get here if
// the instruction is not directly related to control flow;
// i.e., it's some straightforward instruction with an
// unused result, like an arithmetic operation or function
// call.
result.push_back(
MakeUnique<RemoveInstructionReductionOpportunity>(&inst));
}
}
}
return result;
}
std::string RemoveUnusedInstructionReductionOpportunityFinder::GetName() const {
return "RemoveUnusedInstructionReductionOpportunityFinder";
}
bool RemoveUnusedInstructionReductionOpportunityFinder::
OnlyReferencedByIntimateDecorationOrEntryPointInterface(
opt::IRContext* context, const opt::Instruction& inst) const {
return context->get_def_use_mgr()->WhileEachUse(
&inst, [this](opt::Instruction* user, uint32_t use_index) -> bool {
return (user->IsDecoration() &&
!IsIndependentlyRemovableDecoration(*user)) ||
(user->opcode() == SpvOpEntryPoint && use_index > 2);
});
}
bool RemoveUnusedInstructionReductionOpportunityFinder::
IsIndependentlyRemovableDecoration(const opt::Instruction& inst) const {
uint32_t decoration;
switch (inst.opcode()) {
case SpvOpDecorate:
case SpvOpDecorateId:
case SpvOpDecorateString:
decoration = inst.GetSingleWordInOperand(1u);
break;
case SpvOpMemberDecorate:
case SpvOpMemberDecorateString:
decoration = inst.GetSingleWordInOperand(2u);
break;
default:
// The instruction is not a decoration. It is legitimate for this to be
// reached: it allows the method to be invoked on arbitrary instructions.
return false;
}
// We conservatively only remove specific decorations that we believe will
// not change the shader interface, will not make the shader invalid, will
// actually be found in practice, etc.
switch (decoration) {
case SpvDecorationRelaxedPrecision:
case SpvDecorationNoSignedWrap:
case SpvDecorationNoContraction:
case SpvDecorationNoUnsignedWrap:
case SpvDecorationUserSemantic:
return true;
default:
return false;
}
}
} // namespace reduce
} // namespace spvtools
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