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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.
*/
//
// Create `dynCall` helper functions used by emscripten. These allow JavaScript
// to call back into WebAssembly given a function pointer (table index). These
// are used primarily to implement the `invoke` functions which in turn are used
// to implment exceptions handling and setjmp/longjmp. Creates one for each
// signature in the indirect function table.
//
#include "abi/js.h"
#include "asm_v_wasm.h"
#include "ir/import-utils.h"
#include "pass.h"
#include "support/debug.h"
#include "wasm-builder.h"
#define DEBUG_TYPE "generate-dyncalls"
namespace wasm {
struct GenerateDynCalls : public WalkerPass<PostWalker<GenerateDynCalls>> {
GenerateDynCalls(bool onlyI64) : onlyI64(onlyI64) {}
void doWalkModule(Module* wasm) {
PostWalker<GenerateDynCalls>::doWalkModule(wasm);
for (auto& sig : invokeSigs) {
generateDynCallThunk(sig);
}
}
void visitTable(Table* table) {
// Generate dynCalls for functions in the table
if (table->segments.size() > 0) {
std::vector<Name> tableSegmentData;
for (const auto& indirectFunc : table->segments[0].data) {
generateDynCallThunk(getModule()->getFunction(indirectFunc)->sig);
}
}
}
void visitFunction(Function* func) {
// Generate dynCalls for invokes
if (func->imported() && func->module == ENV &&
func->base.startsWith("invoke_")) {
Signature sig = func->sig;
// The first parameter is a pointer to the original function that's called
// by the invoke, so skip it
std::vector<Type> newParams(sig.params.begin() + 1, sig.params.end());
invokeSigs.insert(Signature(Type(newParams), sig.results));
}
}
void generateDynCallThunk(Signature sig);
bool onlyI64;
// The set of all invokes' signatures
std::set<Signature> invokeSigs;
};
static bool hasI64(Signature sig) {
// We only generate dynCall functions for signatures that contain i64. This is
// because any other function can be called directly from JavaScript using the
// wasm table.
for (auto t : sig.results) {
if (t.getID() == Type::i64) {
return true;
}
}
for (auto t : sig.params) {
if (t.getID() == Type::i64) {
return true;
}
}
return false;
}
static void exportFunction(Module& wasm, Name name, bool must_export) {
if (!wasm.getFunctionOrNull(name)) {
assert(!must_export);
return;
}
if (wasm.getExportOrNull(name)) {
return; // Already exported
}
auto exp = new Export;
exp->name = exp->value = name;
exp->kind = ExternalKind::Function;
wasm.addExport(exp);
}
void GenerateDynCalls::generateDynCallThunk(Signature sig) {
if (onlyI64 && !hasI64(sig)) {
return;
}
Module* wasm = getModule();
Builder builder(*wasm);
Name name = std::string("dynCall_") + getSig(sig.results, sig.params);
if (wasm->getFunctionOrNull(name) || wasm->getExportOrNull(name)) {
return; // module already contains this dyncall
}
std::vector<NameType> params;
params.emplace_back("fptr", Type::i32); // function pointer param
int p = 0;
for (const auto& param : sig.params) {
params.emplace_back(std::to_string(p++), param);
}
auto f = builder.makeFunction(name, std::move(params), sig.results, {});
Expression* fptr = builder.makeLocalGet(0, Type::i32);
std::vector<Expression*> args;
Index i = 0;
for (const auto& param : sig.params) {
args.push_back(builder.makeLocalGet(++i, param));
}
// FIXME: Should the existence of a table be ensured here? i.e. create one if
// there is none?
assert(wasm->tables.size() > 0);
f->body = builder.makeCallIndirect(wasm->tables[0]->name, fptr, args, sig);
wasm->addFunction(std::move(f));
exportFunction(*wasm, name, true);
}
Pass* createGenerateDynCallsPass() { return new GenerateDynCalls(false); }
Pass* createGenerateI64DynCallsPass() { return new GenerateDynCalls(true); }
} // namespace wasm
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