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/*
* Copyright 2017 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.
*/
#ifndef wasm_abi_stack_h
#define wasm_abi_stack_h
#include "asmjs/shared-constants.h"
#include "ir/find_all.h"
#include "ir/global-utils.h"
#include "shared-constants.h"
#include "wasm-builder.h"
#include "wasm-emscripten.h"
#include "wasm.h"
namespace wasm {
namespace ABI {
enum { StackAlign = 16 };
inline Index stackAlign(Index size) {
return (size + StackAlign - 1) & -StackAlign;
}
// Allocate some space on the stack, and assign it to a local.
// The local will have the same constant value in all the function, so you can
// just local.get it anywhere there.
inline void
getStackSpace(Index local, Function* func, Index size, Module& wasm) {
auto* stackPointer = getStackPointerGlobal(wasm);
if (!stackPointer) {
Fatal() << "getStackSpace: failed to find the stack pointer";
}
// align the size
size = stackAlign(size);
auto pointerType =
!wasm.memories.empty() ? wasm.memories[0]->addressType : Type::i32;
// TODO: find existing stack usage, and add on top of that - carefully
Builder builder(wasm);
auto* block = builder.makeBlock();
// TODO: add stack max check
Expression* added;
if (pointerType == Type::i32) {
// The stack goes downward in the LLVM wasm backend.
added =
builder.makeBinary(SubInt32,
builder.makeGlobalGet(stackPointer->name, pointerType),
builder.makeConst(int32_t(size)));
} else {
WASM_UNREACHABLE("unhandled pointerType");
}
block->list.push_back(builder.makeGlobalSet(
stackPointer->name, builder.makeLocalTee(local, added, pointerType)));
auto makeStackRestore = [&]() {
return builder.makeGlobalSet(
stackPointer->name,
builder.makeBinary(AddInt32,
builder.makeLocalGet(local, pointerType),
builder.makeConst(int32_t(size))));
};
// add stack restores to the returns
FindAllPointers<Return> finder(func->body);
for (auto** ptr : finder.list) {
auto* ret = (*ptr)->cast<Return>();
if (ret->value && ret->value->type != Type::unreachable) {
// handle the returned value
auto* block = builder.makeBlock();
auto temp = builder.addVar(func, ret->value->type);
block->list.push_back(builder.makeLocalSet(temp, ret->value));
block->list.push_back(makeStackRestore());
block->list.push_back(
builder.makeReturn(builder.makeLocalGet(temp, ret->value->type)));
block->finalize();
*ptr = block;
} else {
// restore, then return
*ptr = builder.makeSequence(makeStackRestore(), ret);
}
}
// add stack restores to the body
if (func->body->type == Type::none) {
block->list.push_back(func->body);
block->list.push_back(makeStackRestore());
} else if (func->body->type == Type::unreachable) {
block->list.push_back(func->body);
// no need to restore the old stack value, we're gone anyhow
} else {
// save the return value
auto temp = builder.addVar(func, func->getResults());
block->list.push_back(builder.makeLocalSet(temp, func->body));
block->list.push_back(makeStackRestore());
block->list.push_back(builder.makeLocalGet(temp, func->getResults()));
}
block->finalize();
func->body = block;
}
} // namespace ABI
} // namespace wasm
#endif // wasm_abi_stack_h
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