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/*
* Copyright 2021 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.
*/
#include "instrumenter.h"
#include "ir/module-utils.h"
#include "ir/names.h"
#include "support/name.h"
#include "wasm-type.h"
namespace wasm {
Instrumenter::Instrumenter(const std::string& profileExport,
uint64_t moduleHash)
: profileExport(profileExport), moduleHash(moduleHash) {}
void Instrumenter::run(PassRunner* runner, Module* wasm) {
this->runner = runner;
this->wasm = wasm;
addGlobals();
instrumentFuncs();
addProfileExport();
}
void Instrumenter::addGlobals() {
// Create fresh global names (over-reserves, but that's ok)
counterGlobal = Names::getValidGlobalName(*wasm, "monotonic_counter");
functionGlobals.reserve(wasm->functions.size());
ModuleUtils::iterDefinedFunctions(*wasm, [&](Function* func) {
functionGlobals.push_back(Names::getValidGlobalName(
*wasm, std::string(func->name.c_str()) + "_timestamp"));
});
// Create and add new globals
auto addGlobal = [&](Name name) {
auto global = Builder::makeGlobal(
name,
Type::i32,
Builder(*wasm).makeConst(Literal::makeZero(Type::i32)),
Builder::Mutable);
global->hasExplicitName = true;
wasm->addGlobal(std::move(global));
};
addGlobal(counterGlobal);
for (auto& name : functionGlobals) {
addGlobal(name);
}
}
void Instrumenter::instrumentFuncs() {
// Inject the following code at the beginning of each function to advance the
// monotonic counter and set the function's timestamp if it hasn't already
// been set.
//
// (if (i32.eqz (global.get $timestamp))
// (block
// (global.set $monotonic_counter
// (i32.add
// (global.get $monotonic_counter)
// (i32.const 1)
// )
// )
// (global.set $timestamp
// (global.get $monotonic_counter)
// )
// )
// )
Builder builder(*wasm);
auto globalIt = functionGlobals.begin();
ModuleUtils::iterDefinedFunctions(*wasm, [&](Function* func) {
func->body = builder.makeSequence(
builder.makeIf(
builder.makeUnary(EqZInt32,
builder.makeGlobalGet(*globalIt, Type::i32)),
builder.makeSequence(
builder.makeGlobalSet(
counterGlobal,
builder.makeBinary(AddInt32,
builder.makeGlobalGet(counterGlobal, Type::i32),
builder.makeConst(Literal::makeOne(Type::i32)))),
builder.makeGlobalSet(
*globalIt, builder.makeGlobalGet(counterGlobal, Type::i32)))),
func->body,
func->body->type);
++globalIt;
});
}
// wasm-split profile format:
//
// The wasm-split profile is a binary format designed to be simple to produce
// and consume. It is comprised of:
//
// 1. An 8-byte module hash
//
// 2. A 4-byte timestamp for each defined function
//
// The module hash is meant to guard against bugs where the module that was
// instrumented and the module that is being split are different. The timestamps
// are non-zero for functions that were called during the instrumented run and 0
// otherwise. Functions with smaller non-zero timestamps were called earlier in
// the instrumented run than funtions with larger timestamps.
void Instrumenter::addProfileExport() {
// Create and export a function to dump the profile into a given memory
// buffer. The function takes the available address and buffer size as
// arguments and returns the total size of the profile. It only actually
// writes the profile if the given space is sufficient to hold it.
auto name = Names::getValidFunctionName(*wasm, profileExport);
auto writeProfile = Builder::makeFunction(
name, Signature({Type::i32, Type::i32}, Type::i32), {});
writeProfile->hasExplicitName = true;
writeProfile->setLocalName(0, "addr");
writeProfile->setLocalName(1, "size");
// Calculate the size of the profile:
// 8 bytes module hash +
// 4 bytes for the timestamp for each function
const size_t profileSize = 8 + 4 * functionGlobals.size();
// Create the function body
Builder builder(*wasm);
auto getAddr = [&]() { return builder.makeLocalGet(0, Type::i32); };
auto getSize = [&]() { return builder.makeLocalGet(1, Type::i32); };
auto hashConst = [&]() { return builder.makeConst(int64_t(moduleHash)); };
auto profileSizeConst = [&]() {
return builder.makeConst(int32_t(profileSize));
};
// Write the hash followed by all the time stamps
Expression* writeData =
builder.makeStore(8, 0, 1, getAddr(), hashConst(), Type::i64);
uint32_t offset = 8;
for (const auto& global : functionGlobals) {
writeData = builder.blockify(
writeData,
builder.makeStore(4,
offset,
1,
getAddr(),
builder.makeGlobalGet(global, Type::i32),
Type::i32));
offset += 4;
}
writeProfile->body = builder.makeSequence(
builder.makeIf(builder.makeBinary(GeUInt32, getSize(), profileSizeConst()),
writeData),
profileSizeConst());
// Create an export for the function
wasm->addFunction(std::move(writeProfile));
wasm->addExport(
Builder::makeExport(profileExport, name, ExternalKind::Function));
// Also make sure there is a memory with enough pages to write into
size_t pages = (profileSize + Memory::kPageSize - 1) / Memory::kPageSize;
if (!wasm->memory.exists) {
wasm->memory.exists = true;
wasm->memory.initial = pages;
wasm->memory.max = pages;
} else if (wasm->memory.initial < pages) {
wasm->memory.initial = pages;
if (wasm->memory.max < pages) {
wasm->memory.max = pages;
}
}
// TODO: export the memory if it is not already exported.
}
} // namespace wasm
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