SPIRV-Tools/source/opt/pass.cpp
Steven Perron e43c91046b Create the dead function elimination pass
Creates a pass called eliminate dead functions that looks for functions
that could never be called, and deletes them from the module.

To support this change a new function was added to the Pass class to
traverse the call trees from diffent starting points.

Includes a test to ensure that annotations are removed when deleting a
dead function.  They were not, so fixed that up as well.

Did some cleanup of the assembly for the test in pass_test.cpp.  Trying
to make them smaller and easier to read.
2017-09-26 11:18:06 -04:00

103 lines
3.3 KiB
C++

// Copyright (c) 2017 The Khronos Group Inc.
// Copyright (c) 2017 Valve Corporation
// Copyright (c) 2017 LunarG 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 "pass.h"
#include "iterator.h"
namespace spvtools {
namespace opt {
namespace {
const uint32_t kEntryPointFunctionIdInIdx = 1;
} // namespace
void Pass::AddCalls(ir::Function* func, std::queue<uint32_t>* todo) {
for (auto bi = func->begin(); bi != func->end(); ++bi)
for (auto ii = bi->begin(); ii != bi->end(); ++ii)
if (ii->opcode() == SpvOpFunctionCall)
todo->push(ii->GetSingleWordInOperand(0));
}
bool Pass::ProcessEntryPointCallTree(ProcessFunction& pfn, ir::Module* module) {
// Map from function's result id to function
std::unordered_map<uint32_t, ir::Function*> id2function;
for (auto& fn : *module) id2function[fn.result_id()] = &fn;
// Collect all of the entry points as the roots.
std::queue<uint32_t> roots;
for (auto& e : module->entry_points())
roots.push(e.GetSingleWordInOperand(kEntryPointFunctionIdInIdx));
return ProcessCallTreeFromRoots(pfn, id2function, &roots);
}
bool Pass::ProcessReachableCallTree(ProcessFunction& pfn, ir::Module* module) {
// Map from function's result id to function
std::unordered_map<uint32_t, ir::Function*> id2function;
for (auto& fn : *module) id2function[fn.result_id()] = &fn;
std::queue<uint32_t> roots;
// Add all entry points since they can be reached from outside the module.
for (auto& e : module->entry_points())
roots.push(e.GetSingleWordInOperand(kEntryPointFunctionIdInIdx));
// Add all exported functions since they can be reached from outside the
// module.
for (auto& a : module->annotations()) {
// TODO: Handle group decorations as well. Currently not generate by any
// front-end, but could be coming.
if (a.opcode() == SpvOp::SpvOpDecorate) {
if (a.GetSingleWordOperand(1) ==
SpvDecoration::SpvDecorationLinkageAttributes) {
uint32_t lastOperand = a.NumOperands() - 1;
if (a.GetSingleWordOperand(lastOperand) ==
SpvLinkageType::SpvLinkageTypeExport) {
uint32_t id = a.GetSingleWordOperand(0);
if (id2function.count(id) != 0) roots.push(id);
}
}
}
}
return ProcessCallTreeFromRoots(pfn, id2function, &roots);
}
bool Pass::ProcessCallTreeFromRoots(
ProcessFunction& pfn,
const std::unordered_map<uint32_t, ir::Function*>& id2function,
std::queue<uint32_t>* roots) {
// Process call tree
bool modified = false;
std::unordered_set<uint32_t> done;
while (!roots->empty()) {
const uint32_t fi = roots->front();
roots->pop();
if (done.insert(fi).second) {
ir::Function* fn = id2function.at(fi);
modified = pfn(fn) || modified;
AddCalls(fn, roots);
}
}
return modified;
}
} // namespace opt
} // namespace spvtools