LibJS/Bytecode: Bring back the bytecode optimization pipeline

...minus the EliminateLoads pass, since it was not compatible with the
new bytecode format.

Userland/Libraries/LibJS/Bytecode/PassManager.h

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibCore/ElapsedTimer.h>
+#include <LibJS/Bytecode/BasicBlock.h>
+#include <LibJS/Bytecode/Generator.h>
+
+namespace JS::Bytecode {
+
+struct PassPipelineExecutable {
+    Executable& executable;
+    Optional<HashMap<BasicBlock const*, HashTable<BasicBlock const*>>> cfg {};
+    Optional<HashMap<BasicBlock const*, HashTable<BasicBlock const*>>> inverted_cfg {};
+    Optional<HashTable<BasicBlock const*>> exported_blocks {};
+};
+
+class Pass {
+public:
+    Pass() = default;
+    virtual ~Pass() = default;
+
+    virtual void perform(PassPipelineExecutable&) = 0;
+    void started()
+    {
+        m_timer.start();
+    }
+    void finished()
+    {
+        m_time_difference = m_timer.elapsed_time();
+    }
+
+    u64 elapsed() const { return m_time_difference.to_microseconds(); }
+
+protected:
+    Core::ElapsedTimer m_timer;
+    Duration m_time_difference {};
+};
+
+class PassManager : public Pass {
+public:
+    PassManager() = default;
+    ~PassManager() override = default;
+
+    void add(NonnullOwnPtr<Pass> pass) { m_passes.append(move(pass)); }
+
+    template<typename PassT, typename... Args>
+    void add(Args&&... args) { m_passes.append(make<PassT>(forward<Args>(args)...)); }
+
+    void perform(Executable& executable)
+    {
+        PassPipelineExecutable pipeline_executable { executable };
+        perform(pipeline_executable);
+    }
+
+    virtual void perform(PassPipelineExecutable& executable) override
+    {
+        started();
+        for (auto& pass : m_passes)
+            pass->perform(executable);
+        finished();
+    }
+
+private:
+    Vector<NonnullOwnPtr<Pass>> m_passes;
+};
+
+namespace Passes {
+
+class GenerateCFG : public Pass {
+public:
+    GenerateCFG() = default;
+    ~GenerateCFG() override = default;
+
+private:
+    virtual void perform(PassPipelineExecutable&) override;
+};
+
+class MergeBlocks : public Pass {
+public:
+    MergeBlocks() = default;
+    ~MergeBlocks() override = default;
+
+private:
+    virtual void perform(PassPipelineExecutable&) override;
+};
+
+class PlaceBlocks : public Pass {
+public:
+    PlaceBlocks() = default;
+    ~PlaceBlocks() override = default;
+
+private:
+    virtual void perform(PassPipelineExecutable&) override;
+};
+
+class UnifySameBlocks : public Pass {
+public:
+    UnifySameBlocks() = default;
+    ~UnifySameBlocks() override = default;
+
+private:
+    virtual void perform(PassPipelineExecutable&) override;
+};
+
+class DumpCFG : public Pass {
+public:
+    DumpCFG(FILE* file)
+        : m_file(file)
+    {
+    }
+
+    ~DumpCFG() override = default;
+
+private:
+    virtual void perform(PassPipelineExecutable&) override;
+
+    FILE* m_file { nullptr };
+};
+
+}
+
+}