Thomas Wuerthinger

Oracle Corporation · Oracle Labs

Designing a whole-program static analysis requires trade-offs between precision and scalability. While a context-insensitive points-to analysis is often considered a good compromise, it still has non-linear complexity that leads to scalability problems when analyzing large applications. On the other hand, rapid type analysis scales well but lacks p...

Our paper published in the proceedings of the 40th ACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI 2019) [Pr19a] proposes Renaissance, a modern benchmark suite whose aim is to advance compiler and virtual machine (VM) research. The publication is complemented by an accepted artifact [Pr19b]. To demonstrate that a comp...

This paper describes Renaissance, a new benchmark suite that covers modern JVM concurrency and parallelism paradigms.

Arbitrary program extension at run time in language-based VMs, e.g., Java's dynamic class loading, comes at a startup cost: high memory footprint and slow warmup. Cloud computing amplifies the startup overhead. Microservices and serverless cloud functions lead to small, self-contained applications that are started often. Slow startup and high memor...

Established benchmark suites for the Java Virtual Machine (JVM), such as DaCapo, ScalaBench, and SPECjvm2008, lack workloads that take advantage of the parallel programming abstractions and concurrency primitives offered by the JVM and the Java Class Library. However, such workloads are fundamental for understanding the way in which modern applicat...

When a computer program is written, the computer program is written as source code. A compiler is a software program that translates the source code into object code or byte code. During compilation, the compiler may perform various optimizations. For example, optimizations may reduce the number of instructions executed by a computer processor. By...

The recently proposed Renaissance suite is composed of modern, real-world, concurrent, and object-oriented workloads that exercise various concurrency primitives of the JVM. Renaissance was used to compare performance of two state-of-the-art, production-quality JIT compilers (HotSpot C2 and Graal), and to show that the performance differences are m...

Inlining is one of the most important compiler optimizations. It reduces call overheads and widens the scope of other optimizations. But, inlining is somewhat of a black art of an optimizing compiler, and was characterized as a computationally intractable problem. Intricate heuristics, tuned during countless hours of compiler engineering, are often...

Compilers provide many architecture-agnostic, high-level optimizations trading off peak performance for code size. High-level optimizations typically cannot precisely reason about their impact, as they are applied before the final shape of the generated machine code can be determined. However, they still need a way to estimate their transformation’...

Java programs can contain non-counted loops, that is, loops for which the iteration count can neither be determined at compile time nor at run time. State-of-the-art compilers do not aggressively optimize them, since unrolling non-counted loops often involves duplicating also a loop's exit condition, which thus only improves run-time performance if...

In large-scale software applications, programmers often combine different programming languages because this allows them to use the most suitable language for a given problem, to gradually migrate existing projects from one language to another, or to reuse existing source code. However, different programming languages have fundamentally different i...

Context: Software development tools that interact with running programs such as debuggers, profilers, and dynamic analysis frameworks are presumed to demand difficult tradeoffs among implementation complexity (cost), functionality, usability, and performance. Among the many consequences, tools are often delivered late (if ever), have limited functi...

Compilers perform a variety of advanced optimizations to improve the quality of the generated machine code. However, optimizations that depend on the data flow of a program are often limited by control-flow merges. Code duplication can solve this problem by hoisting, i.e. duplicating, instructions from merge blocks to their predecessors. However, f...

Functional collection combinators are a neat and widely accepted data processing abstraction. However, their generic nature results in high abstraction overheads -- Scala collections are known to be notoriously slow for typical tasks. We show that proper optimizations in a JIT compiler can widely eliminate overheads imposed by these abstractions. U...

Register allocation is an integral part of compilation, regardless of whether a compiler aims for fast compilation or optimal code quality. State-of-the-art dynamic compilers often use global register allocation approaches such as linear scan. Recent results suggest that non-global trace-based register allocation approaches can compete with global...

While Java is a statically-typed language, some of its features make it behave like a dynamically-typed language at run time. This includes Java's boxing of primitive values as well as generics, which rely on type erasure. This paper investigates how runtime technology for dynamically-typed languages such as JavaScript and Python can be used for Ja...

Most high-performance dynamic language virtual machines duplicate language semantics in the interpreter, compiler, and runtime system. This violates the principle to not repeat yourself. In contrast, we define languages solely by writing an interpreter. The interpreter performs specializations, e.g., augments the interpreted program with type infor...

Most high-performance dynamic language virtual machines duplicate language semantics in the interpreter, compiler, and runtime system. This violates the principle to not repeat yourself. In contrast, we define languages solely by writing an interpreter. The interpreter performs specializations, e.g., augments the interpreted program with type infor...

A multi-tier virtual machine (VM) deoptimizes and transfers last-tier execution to the first-tier execution when a speculative optimization is invalidated. The first-tier target of deoptimization is either an interpreter or code compiled by a baseline compiler. Because such a first-tier execution uses a fixed stack frame layout, this complicates al...

Although the Java platform has been used as a multi-language platform, most of the low-level languages (such as C, Fortran, and C++) cannot be executed efficiently on the JVM. We propose Sulong, a system that can execute LLVM-based languages on the JVM. By targeting LLVM IR, Sulong is able to execute C, Fortran, and other languages that can be comp...

State-of-the-art dynamic compilers often use global approaches, like Linear Scan or Graph Coloring, for register allocation. These algorithms consider the complete compilation unit for allocation, which increases the complexity of the implementation (e.g., support for lifetime holes in Linear Scan) and potentially also affects compilation time. We...

Programmers combine different programming languages because it allows them using the most suitable language for a given problem, gradually migrating existing projects from one language to another, or reusing existing source code. However, existing cross-language mechanisms suffer from complex interfaces, insufficient flexibility, or poor performanc...

Programmers combine different programming languages because it allows them to use the most suitable language for a given problem, to gradually migrate existing projects from one language to another, or to reuse existing source code. However, existing cross-language mechanisms suffer from complex interfaces, insufficient flexibility, or poor perform...

In low-level languages such as C, spatial and temporal safety errors (e.g. buffer overflows or dangling pointer dereferences) are hard to find and can cause security vulnerabilities. Modern high-level languages such as Java avoid these problems by running programs on a virtual machine that provides automated memory management. In this paper we sho...

When building a compiler for a high-level language, certain intrinsic features of the language must be expressed in terms of the resulting low-level operations. Complex features are often expressed by explicitly weaving together bits of low-level IR, a process that is tedious, error prone, difficult to read, difficult to reason about, and machine d...

Many dynamic languages such as Ruby, Python and Perl offer some kind of functionality for writing parts of applications in a lower-level language such as C. These C extension modules are usually written against the API of an interpreter, which provides access to the higher-level language's internal data structures. Alternative implementations of th...

A method for resource management, including: identifying a resource map corresponding to a thread stack of a first thread; reading, in the resource map and by a computer processor, a bit value referencing an address of a first binary value in the thread stack; determining, based on the bit value and by the computer processor, that the first binary...

A method for a compiler includes receiving, by the compiler and from an interpreter, a representation of a code section having a control path that changes the representation. The representation has profiling data, and the profiling data has a threshold. The method further includes performing, by the compiler and based on the threshold, a partial ev...

Speculative optimizations are used in most Just In Time (JIT) compilers in order to take advantage of dynamic runtime feedback. These speculative optimizations usually require the compiler to produce meta-data that the Virtual Machine (VM) can use as fallback when a speculation fails. This meta-data can be large and incurs a significant memory over...

Self-optimizing AST interpreters dynamically adapt to the provided input for faster execution. This adaptation includes initial tests of the input, changes to AST nodes, and insertion of guards that ensure assumptions still hold. Such specialization and speculation is essential for the performance of dynamic programming languages such as JavaScript...

We present a novel approach for allowing JavaScript applications to access C data structures without performance overhead or additional boiler plate code. Dynamic languages such as JavaScript do not have a fixed memory layout for run-time data nor do they allow low-level memory accesses, which makes interoperability with languages such as C hard. O...

Multi-language runtimes providing simultaneously high performance for several programming languages still remain an illusion. Industrial-strength managed language runtimes are built with a focus on one language (e.g., Java or C#). Other languages may compile to the bytecode formats of those managed language runtimes. However, the performance charac...

Escape Analysis allows a compiler to determine whether an object is accessible outside the allocating method or thread. This information is used to perform optimizations such as Scalar Replacement, Stack Allocation and Lock Elision, allowing modern dynamic compilers to remove some of the abstractions introduced by advanced programming models. The a...

Building high-performance virtual machines is a complex and expensive undertaking; many popular languages still have low-performance implementations. We describe a new approach to virtual machine (VM) construction that amortizes much of the effort in initial construction by allowing new languages to be implemented with modest additional effort. The...

We present a compiler intermediate representation (IR) that allows dynamic speculative optimizations for high-level languages. The IR is graph-based and contains nodes fixed to control flow as well as floating nodes. Side-effecting nodes include a framestate that maps values back to the original program. Guard nodes dynamically check assumptions an...

Java Virtual Machines are optimized for performing well on traditional Java benchmarks, which consist almost exclusively of code generated by the Java source compiler (javac). Code generated by compilers for other languages has not received nearly as much attention, which results in performance problems for those languages. One important specimen o...

Dynamic code evolution is a technique to update a program while it is running. In an object-oriented language such as Java, this can be seen as replacing a set of classes by new versions. We modified an existing high-performance virtual machine to allow arbitrary changes to the definition of loaded classes. Besides adding and deleting fields and me...

We present an intermediate representation (IR) for a Java just in time (JIT) compiler written in Java. It is a graph-based IR that models both control-flow and data-flow dependencies between nodes. We show the framework in which we developed our IR. Much care has been taken to allow the programmer to focus on compiler optimization rather than IR bo...

syntax tree (AST) interpreter is a simple and natural way to implement a programming language. However, it is also considered the slowest approach because of the high overhead of virtual method dispatch. Language implementers therefore define bytecodes to speed up interpretation, at the cost of introducing inflexible and hard to maintain bytecode f...

An abstract syntax tree (AST) interpreter is a simple and natural way to implement a programming language. However, it is also considered the slowest approach because of the high overhead of virtual method dispatch. Language implementers therefore define bytecodes to speed up interpretation, at the cost of introducing inflexible and hard to maintai...

Modern virtual machines for Java use a dynamic compiler to optimize the program at run time. The compilation time therefore impacts the performance of the application in two ways: First, the compilation and the program's execution compete for CPU resources. Second, the sooner the compilation of a method finishes, the sooner the method will execute...

We present Truffle, a novel framework for implementing managed languages in Java™. The language implementer writes an AST interpreter, which is integrated in our framework that allows tree rewriting during AST interpretation. Tree rewrites incorporate type feedback and other profiling information into the tree, thus specializing the tree and augmen...

Dynamic updates to running programs improve development productivity and reduce downtime of long-running applications. This feature is however severely limited in current virtual machines for object-oriented languages. In particular, changes to classes often apply only to methods invoked after a class change, but not to active methods on the call s...

The Graal compiler is an optimizing just-in-time compiler written in Java that works with both the Maxine VM and the HotSpot VM. It allows Java libraries to extend its functionality for example by providing new intermediate representation nodes and new optimization phases. We demonstrate how to write such plug-ins for the Graal compiler.

While dynamic code evolution in object-oriented systems is an important feature supported by dynamic languages, there is currently only limited support for dynamic code evolution in high-performance, state-of-the-art runtime systems for statically typed languages, such as the Java Virtual Machine. In this tool demonstration, we present the Dynamic...

Coroutines are non-preemptive lightweight processes. Their advantage over threads is that they do not have to be synchronized because they pass control to each other explicitly and deterministically. Coroutines are therefore an elegant and efficient implementation construct for numerous algorithmic problems. Many mainstream languages and runtime en...

Dynamic code evolution is a technique to update a program while it is running. In an object-oriented language such as Java, this can be seen as replacing a set of classes by new versions. We modified an existing high-performance virtual machine to allow arbitrary changes to the definition of loaded classes. Besides adding and deleting fields and me...

Intense research on virtual machines has highlighted the need for flexible software architectures that allow quick evaluation of new design and implementation techniques. The interface between the compiler and runtime system is a principal factor in the flexibility of both components and is critical to enabling rapid pursuit of new optimizations an...

Dynamic aspect-oriented programming (AOP) is a powerful approach for integrating new features into running applications without disrupting their execution. In Java, dynamic AOP frameworks often use runtime weaving of previously loaded classes, which is however severely restricted because of limitations in current Java Virtual Machines (JVMs). These...

Continuations, or 'the rest of the computation', are a con- cept that is most often used in the context of functional and dynamic programming languages. Implementations of such languages that work on top of the Java virtual ma- chine (JVM) have traditionally been complicated by the lack of continuations because they must be simulated. We propose an...

Debugging virtual machines (VMs) presents unique challenges, especially meta-circular VMs, which are written in the same language they implement. Making sense of runtime state for such VMs requires insight and interaction at multiple levels of abstraction simultaneously. For example, debugging a Java VM written in Java requires understanding execut...

Whenever an array element is accessed, Java virtual machines execute a compare instruction to ensure that the index value is within the valid bounds. This reduces the execution speed of Java programs. Array bounds check elimination identifies situations in which such checks are redundant and can be removed. We present an array bounds check eliminat...

The analysis of a compiler’s intermediate data structures helps at debugging complex optimizations. We present a graphical tool for analyzing the program dependence graph of Sun Microsystems’ Java HotSpotTM server compiler. The tool saves snapshots of the graph during the compilation. It displays the graphs and provides filtering mechanisms based o...

Whenever an array element is accessed, Java virtual machines execute a compare instruction to ensure that the index value is within the valid bounds. This reduces the execution speed of Java programs. Array bounds check elimination identifies situations in which such checks are redundant and can be removed. We present an array bounds check eliminat...

This paper gives a short introduction to ACL2, a Lisp-like language used to make automatic proofs. ACL2 is used to prove the correctness of a compiler at source level. However it is shown that source level verification is not enough to be sure to have a correct compiler. Even if a compiler is correct at source level and passes the bootstrap test, i...