Writing a compiler in common lisp pdf

In most cases, following published standards is convenient for users—it means that their programs or scripts will work more portably.

Writing a compiler in common lisp pdf

Generally speaking, locally scoped techniques are easier to implement than global ones but result in smaller writing a compiler in common lisp pdf.

Lisp (programming language) - Wikipedia

Some examples of scopes include: Peephole optimizations Usually performed late in the compilation process after machine code has been generated. This form of optimization examines a few adjacent instructions like "looking through a peephole" at the code to see whether they can be replaced by a single instruction or a shorter sequence of instructions.

Local optimizations These only consider information local to a basic block. Global optimizations These are also called "intraprocedural methods" and act on whole functions.

Worst case assumptions have to be made when function calls occur or global variables are accessed because little information about them is available.

These act on the statements which make up a loop, such as a for loop e. Loop optimizations can have a significant impact because many programs spend a large percentage of their time inside loops. Prescient store optimizations Allow store operations to occur earlier than would otherwise be permitted in the context of threads and locks.

The process needs some way of knowing ahead of time what value will be stored by the assignment that it should have followed. The purpose of this relaxation is to allow compiler optimization to perform certain kinds of code rearrangement that preserve the semantics of properly synchronized programs.

writing a compiler in common lisp pdf

The greater quantity of information extracted means that optimizations can be more effective compared to when they only have access to local information i.

This kind of optimization can also allow new techniques to be performed. For instance function inliningwhere a call to a function is replaced by a copy of the function body. Machine code optimization These analyze the executable task image of the program after all of an executable machine code has been linked.

Some of the techniques that can be applied in a more limited scope, such as macro compression which saves space by collapsing common sequences of instructionsare more effective when the entire executable task image is available for analysis.

Programming language —independent vs language-dependent Most high-level languages share common programming constructs and abstractions: Thus similar optimization techniques can be used across languages.

However, certain language features make some kinds of optimizations difficult. Conversely, some language features make certain optimizations easier. For example, in some languages functions are not permitted to have side effects. Therefore, if a program makes several calls to the same function with the same arguments, the compiler can immediately infer that the function's result need be computed only once.

In languages where functions are allowed to have side effects, another strategy is possible. The optimizer can determine which function has no side effects, and restrict such optimizations to side effect free functions.

This optimization is only possible when the optimizer has access to the called function. Machine independent vs machine dependent Many optimizations that operate on abstract programming concepts loops, objects, structures are independent of the machine targeted by the compiler, but many of the most effective optimizations are those that best exploit special features of the target platform.

Instructions which do several things at once, such as decrement register and branch if not zero. The following is an instance of a local machine dependent optimization.

To set a register to 0, the obvious way is to use the constant '0' in an instruction that sets a register value to a constant. A less obvious way is to XOR a register with itself.

It is up to the compiler to know which instruction variant to use. On many RISC machines, both instructions would be equally appropriate, since they would both be the same length and take the same time. On many other microprocessors such as the Intel x86 family, it turns out that the XOR variant is shorter and probably faster, as there will be no need to decode an immediate operand, nor use the internal "immediate operand register".

A potential problem with this is that XOR may introduce a data dependency on the previous value of the register, causing a pipeline stall. However, processors often have XOR of a register with itself as a special case that does not cause stalls.

Factors affecting optimization[ edit ] The machine itself Many of the choices about which optimizations can and should be done depend on the characteristics of the target machine.

It is sometimes possible to parameterize some of these machine dependent factors, so that a single piece of compiler code can be used to optimize different machines just by altering the machine description parameters. GCC is a compiler which exemplifies this approach. To a certain extent, the more registers, the easier it is to optimize for performance.

Local variables can be allocated in the registers and not on the stack. CISC instruction sets often have variable instruction lengths, often have a larger number of possible instructions that can be used, and each instruction could take differing amounts of time.

RISC instruction sets attempt to limit the variability in each of these:Build Your Own Lisp Learn C and build your own programming language in lines of code! If you're looking to learn C, or you've ever wondered how to build your own programming language, this is the book for you.

In computing, an optimizing compiler is a compiler that tries to minimize or maximize some attributes of an executable computer program. The most common requirement is to minimize the time taken to execute a program; a less common one is to minimize the amount of memory occupied.

The growth of portable computers has created a market for minimizing the power consumed by a program. For a list of free machine learning books available for download, go here. For a list of (mostly) free machine learning courses available online, go here. For a list of blogs on data science and machine learning, go here.

For a list of free-to-attend meetups and local events, go here. 1 About the GNU Coding Standards. The GNU Coding Standards were written by Richard Stallman and other GNU Project volunteers.

writing a compiler in common lisp pdf

Their purpose is to make the GNU . A Common Lisp implementation (compiler and interpreter) that supports the ANSI standard and the Lisp descibed in "Common Lisp: The Language (2nd edition)". It is released under the GNU General Public License and supports MSDOS, OS/2, Windows NT/95/98, Amiga , Acorn RISC PC, Linux and other Unices.

Literature GNU Emacs and XEmacs: A Better Way to Learn Emacs and Lisp Title: GNU Emacs and XEmacs: A Better Way to Learn Emacs and Lisp Author(s): Larry Ayers Publisher: Prima Publishing Size: pp ISBN: Price: $

Common Lisp - Wikipedia