lib/NativeMathPass.cpp

// Copyright 2021 The Clspv Authors. All rights reserved.
//
// 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 "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Transforms/Utils/Cloning.h"

#include "Builtins.h"
#include "BuiltinsEnum.h"
#include "NativeMathPass.h"
#include "ReplaceOpenCLBuiltinPass.h"
#include "clspv/Option.h"

#include <set>

using namespace llvm;

namespace {
bool is_libclc_builtin(llvm::Function *F) {
  return F->getMetadata("clspv_libclc_builtin");
}
} // namespace

PreservedAnalyses clspv::NativeMathPass::run(Module &M,
                                             ModuleAnalysisManager &) {
  PreservedAnalyses PA;

  auto nativeBuiltins = clspv::Option::UseNativeBuiltins();

  for (auto &F : M) {
    auto info = clspv::Builtins::Lookup(F.getName());
    bool have_native_impl =
        Builtins::getExtInstEnum(info) != Builtins::kGlslExtInstBad ||
        ReplaceOpenCLBuiltinPass::ReplaceableBuiltins.count(info.getType()) > 0;
    if (have_native_impl &&
        (nativeBuiltins.count(info.getType()) || clspv::Option::NativeMath())) {
      F.deleteBody();
    } else if (!have_native_impl && nativeBuiltins.count(info.getType())) {
      llvm::report_fatal_error(
          llvm::StringRef("--use-native-builtins: couldn't replace builtin '" +
                          info.getName() + "' with a native implementation!"));
    } else if (is_libclc_builtin(&F)) {
      // Those builtin has been marked with noinline to make sure that we
      // could replace them with native implementation. Now that we know
      // that we will not do it, let's remove the attribute so that they
      // can be inline if appropriate.
      F.removeFnAttr(Attribute::AttrKind::NoInline);
    }
  }

  // Force inlining of builtin inside builtin
  bool changed = true;
  while (changed) {
    std::vector<CallInst *> to_inline;
    for (auto &F : M) {
      if (is_libclc_builtin(&F)) {
        for (auto *user : F.users()) {
          if (auto *call = dyn_cast<CallInst>(user)) {
            if (is_libclc_builtin(call->getParent()->getParent())) {
              to_inline.push_back(call);
            }
          }
        }
      }
    }
    changed = false;
    for (auto call : to_inline) {
      InlineFunctionInfo IFI;
      changed |= InlineFunction(*call, IFI, false, nullptr, false).isSuccess();
    }
  }

  return PA;
}