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Unformatted text preview: piled onto. In the course of this analysis, it will become apparent that a RISC architecture such as that of the ARM has a vanilla flavour and leaves a number of important decisions open for the compiler writer to take according to taste. Some of these decisions will affect the ease with which a program can be built up from routines generated from different source languages. Since this is an important issue, there is a defined ARM Procedure Call Standard that compiler writers should use to ensure the consistency of entry and exit conditions. Another area that benefits from agreement across compilers is the support for floating-point operations, which use data types that are not defined in the ARM hardware instruction set.
151 152 Architectural Support for High-Level Languages 6.1 Abstraction in software design
We have already met a level of abstraction that is important to software design. The essence of an ARM processor is captured in the ARM instruction set which was described in Chapter 5. We shall see in Chapter 9 that there are many ways to implement the ARM architecture, but the whole point of an architecture is to ensure that the programmer need not be concerned with particular implementation details. If a program works correctly on one implementation it should work correctly on them all (with certain provisos). Assembly-level abstraction A programmer who writes at the assembly programming level works (almost) directly with the raw machine instruction set, expressing the program in terms of instructions, addresses, registers, bytes and words. A good programmer, faced with a non-trivial task, will begin by determining higher levels of abstraction that simplify the program design; for instance a graphics program may do a lot of line drawing, so a subroutine that will draw a line given the end coordinates will be useful. The rest of the program can then work just in terms of these end coordinates. Abstraction is important, then, at the assembly programming level, but all the responsibility for supporting the abstraction and expressing it in te...
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This document was uploaded on 10/30/2011 for the course CSE 378 380 at SUNY Buffalo.
- Spring '09