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/*
* Copyright 2020 WebAssembly Community Group participants
*
* 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.
*/
//
// Convert llvm's stack pointer usage from from global.get/global.set into
// cals to external stackSave/stackRestore.
// This is needed to emscripten SIDE_MODULE code where mutable global imports
// are not yet permitted by default.
//
#include "abi/js.h"
#include "ir/import-utils.h"
#include "pass.h"
#include "support/debug.h"
#include "wasm-emscripten.h"
#define DEBUG_TYPE "replace-stack-pointer"
namespace wasm {
static Name STACK_SAVE("stackSave");
static Name STACK_RESTORE("stackRestore");
struct ReplaceStackPointer
: public WalkerPass<PostWalker<ReplaceStackPointer>> {
void visitGlobalGet(GlobalGet* curr) {
if (getModule()->getGlobalOrNull(curr->name) == stackPointer) {
needStackSave = true;
if (!builder) {
builder = make_unique<Builder>(*getModule());
}
replaceCurrent(builder->makeCall(STACK_SAVE, {}, Type::i32));
}
}
void visitGlobalSet(GlobalSet* curr) {
if (getModule()->getGlobalOrNull(curr->name) == stackPointer) {
needStackRestore = true;
if (!builder) {
builder = make_unique<Builder>(*getModule());
}
replaceCurrent(
builder->makeCall(STACK_RESTORE, {curr->value}, Type::none));
}
}
void doWalkModule(Module* module) {
stackPointer = getStackPointerGlobal(*module);
if (!stackPointer) {
BYN_DEBUG(std::cerr << "no stack pointer found\n");
return;
}
BYN_DEBUG(std::cerr << "stack pointer found\n");
super::doWalkModule(module);
if (needStackSave) {
ensureFunctionImport(
module, STACK_SAVE, Signature(Type::none, Type::i32));
}
if (needStackRestore) {
ensureFunctionImport(
module, STACK_RESTORE, Signature(Type::i32, Type::none));
}
// Finally remove the stack pointer global itself. This avoids importing
// a mutable global.
module->removeGlobal(stackPointer->name);
}
void ensureFunctionImport(Module* module, Name name, Signature sig) {
ImportInfo info(*module);
if (info.getImportedFunction(ENV, name)) {
return;
}
auto import = new Function;
import->name = name;
import->module = ENV;
import->base = name;
import->sig = sig;
module->addFunction(import);
}
private:
std::unique_ptr<Builder> builder;
Global* stackPointer = nullptr;
bool needStackSave = false;
bool needStackRestore = false;
};
Pass* createReplaceStackPointerPass() { return new ReplaceStackPointer; }
} // namespace wasm
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