SPIRV-Tools/source/opt/eliminate_dead_functions_util.cpp
alan-baker b4c4da3e76
Improve non-semantic instruction handling in the optimizer (#3693)
* No longer blindly add global non-semantic info instructions to global
  types and values
  * functions now have a list of non-semantic instructions that succeed
    them in the global scope
  * global non-semantic instructions go in global types and values if
    they appear before any function, otherwise they are attached to the
    immediate function predecessor in the module
* changed ADCE to use the function removal utility
* Modified EliminateFunction to have special handling for non-semantic
  instructions in the global scope
  * non-semantic instructions are moved to an earlier function (or full
    global set) if the function they are attached to is eliminated
  * Added IRContext::KillNonSemanticInfo to remove the tree of
    non-semantic instructions that use an instruction
  * this is used in function elimination
* There is still significant work in the optimizer to handle
  non-semantic instructions fully in the optimizer
2020-08-13 14:54:14 -04:00

59 lines
2.1 KiB
C++

// Copyright (c) 2019 Google LLC
//
// 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 "eliminate_dead_functions_util.h"
namespace spvtools {
namespace opt {
namespace eliminatedeadfunctionsutil {
Module::iterator EliminateFunction(IRContext* context,
Module::iterator* func_iter) {
bool first_func = *func_iter == context->module()->begin();
bool seen_func_end = false;
(*func_iter)
->ForEachInst(
[context, first_func, func_iter, &seen_func_end](Instruction* inst) {
if (inst->opcode() == SpvOpFunctionEnd) {
seen_func_end = true;
}
// Move non-semantic instructions to the previous function or
// global values if this is the first function.
if (seen_func_end && inst->opcode() == SpvOpExtInst) {
assert(inst->IsNonSemanticInstruction());
std::unique_ptr<Instruction> clone(inst->Clone(context));
context->ForgetUses(inst);
context->AnalyzeDefUse(clone.get());
if (first_func) {
context->AddGlobalValue(std::move(clone));
} else {
auto prev_func_iter = *func_iter;
--prev_func_iter;
prev_func_iter->AddNonSemanticInstruction(std::move(clone));
}
inst->ToNop();
} else {
context->KillNonSemanticInfo(inst);
context->KillInst(inst);
}
},
true, true);
return func_iter->Erase();
}
} // namespace eliminatedeadfunctionsutil
} // namespace opt
} // namespace spvtools