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Leaf Subroutine
A leaf subroutine is a subroutine which cannot in turn call another subroutine. Some compilers can apply special program optimizations to leaf subroutines to make them more efficient, such as the use of link registers to avoid having to push the return address on the stack, or not allocating a register window on CPU architectures descended from Berkeley RISC. The term "leaf" refers to their position as leaf nodes in the call graph of the program. Usually, most non-leaf subroutines call more than one other subroutine. When this is the case, the majority of subroutine calls in the call graph are calls to leaf subroutines, because a binary tree In computer science, a binary tree is a tree data structure in which each node has at most two children, referred to as the ''left child'' and the ''right child''. That is, it is a ''k''-ary tree with . A recursive definition using set theor ... has more leaf nodes than non-leaf nodes (assuming that all non-leaf nodes have two childre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subroutine
In computer programming, a function (also procedure, method, subroutine, routine, or subprogram) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times. Callable units provide a powerful programming tool. The primary purpose is to allow for the decomposition of a large and/or complicated problem into chunks that have relatively low cognitive load and to assign the chunks meaningful names (unless they are anonymous). Judicious application can reduce the cost of developing and maintaining software, while increasing its quality and reliability. Callable units are present at multiple levels of abstraction in the programming environment. For example, a programmer may write a function in source code that is compiled to machine code that implements similar semantics. There is a callable unit in the source code and an associated one in the machine code, but they are different kinds of callable units with different impl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Link Register
A link register (LR for short) is a register which holds the address to return to when a subroutine call completes. This is more efficient than the more traditional scheme of storing return addresses on a call stack, sometimes called a machine stack. The link register does not require the writes and reads of the memory containing the stack which can save a considerable percentage of execution time with repeated calls of small subroutines. The IBM POWER architecture, and its PowerPC and Power ISA successors, have a special-purpose link register, into which subroutine call instructions put the return address. In some other instruction sets, such as the ARM architectures, SPARC, and OpenRISC, subroutine call instructions put the return address into a specific general-purpose register, so that register is designated by the instruction set architecture as the link register. The ARMv7 architecture uses general-purpose register R14 as the link register, OpenRISC uses register r9, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Register Window
In computer engineering, register windows are a feature which dedicates registers to a subroutine by dynamically aliasing a subset of internal registers to fixed, programmer-visible registers. Register windows are implemented to improve the performance of a processor by reducing the number of stack operations required for function calls and returns. One of the most influential features of the Berkeley RISC design, they were later implemented in instruction set architectures such as AMD Am29000, Intel i960, Sun Microsystems SPARC, and Intel Itanium. General operation Several sets of registers are provided for the different parts of the program. Registers are deliberately hidden from the programmer to force several subroutines to share processor resources. Rendering the registers invisible can be implemented efficiently; the CPU recognizes the movement from one part of the program to another during a procedure call. It is accomplished by one of a small number of instructions (''p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Berkeley RISC
Berkeley RISC is one of two seminal research projects into reduced instruction set computer (RISC) based microprocessor design taking place under the Defense Advanced Research Projects Agency VLSI Project. RISC was led by David Patterson (who coined the term RISC) at the University of California, Berkeley between 1980 and 1984. The other project took place a short distance away at Stanford University under their MIPS effort starting in 1981 and running until 1984. Berkeley's project was so successful that it became the name for all similar designs to follow; even the MIPS would become known as a "RISC processor". The Berkeley RISC design was later commercialized by Sun Microsystems as the SPARC architecture, and inspired the ARM architecture. The RISC concept Both RISC and MIPS were developed from the realization that the vast majority of programs used only a small minority of a processor's available instruction set. In a famous 1978 paper, Andrew S. Tanenbaum demonstrated th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leaf Node
In computer science, a tree is a widely used abstract data type that represents a hierarchical tree structure with a set of connected nodes. Each node in the tree can be connected to many children (depending on the type of tree), but must be connected to exactly one parent, except for the ''root'' node, which has no parent (i.e., the root node as the top-most node in the tree hierarchy). These constraints mean there are no cycles or "loops" (no node can be its own ancestor), and also that each child can be treated like the root node of its own subtree, making recursion a useful technique for tree traversal. In contrast to linear data structures, many trees cannot be represented by relationships between neighboring nodes (parent and children nodes of a node under consideration, if they exist) in a single straight line (called edge or link between two adjacent nodes). Binary trees are a commonly used type, which constrain the number of children for each parent to at most two. When ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Call Graph
A call graph (also known as a call multigraph) is a control-flow graph, which represents calling relationships between subroutines in a computer program. Each node represents a procedure and each edge ''(f, g)'' indicates that procedure ''f'' calls procedure ''g''. Thus, a cycle in the graph indicates recursive procedure calls. Basic concepts Call graphs can be dynamic or static. A dynamic call graph is a record of an execution of the program, for example as output by a profiler. Thus, a dynamic call graph can be exact, but only describes one run of the program. A static call graph is a call graph intended to represent every possible run of the program. The exact static call graph is an undecidable problem, so static call graph algorithms are generally overapproximations. That is, every call relationship that occurs is represented in the graph, and possibly also some call relationships that would never occur in actual runs of the program. Call graphs can be defined to repre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary Tree
In computer science, a binary tree is a tree data structure in which each node has at most two children, referred to as the ''left child'' and the ''right child''. That is, it is a ''k''-ary tree with . A recursive definition using set theory is that a binary tree is a triple , where ''L'' and ''R'' are binary trees or the empty set and ''S'' is a singleton (a single–element set) containing the root. From a graph theory perspective, binary trees as defined here are arborescences. A binary tree may thus be also called a bifurcating arborescence, a term which appears in some early programming books before the modern computer science terminology prevailed. It is also possible to interpret a binary tree as an undirected, rather than directed graph, in which case a binary tree is an ordered, rooted tree. Some authors use rooted binary tree instead of ''binary tree'' to emphasize the fact that the tree is rooted, but as defined above, a binary tree is always rooted. In ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
