code optimization in embedded systems

yusibin · 2007-11-15T13:53:08+00:00

1. using switch kerword properlyRemember that put the most frequently used case branch on the firstplace of switch-case branches. It helps to reduce time spent ondetemining which branch to execute. 2. using assembly language for time-critical operationsReplace codes written in C language with assembly language wouldgreatly improve the performance especially when the code is executedfrequently. Note that using assembly language may decrease thereadability of the code3. using register keywordUsing a register variable tell the compiler to put this variable inthe CPU's registers instead of stack. The speed to read variablesstored in registers is faster than read variables store in memory. 4. Avoid using some standard C library functionsStandard C functions are designed for general use. They must considerall the possibility, this increase the code size(e.g, springf isoversized for some embedded systems). You can write your own standard-C-fuction-like functions, with some features ignored.for more info, refer to

Nov 15, 2007 121 Replies

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While using C functions, Take care while passing parameters to functions with more arguments. Passing parameters is an interesting part of optimisation. If the function has more number of arguments, then both the caller and callee have to access and use the stack for some arguments. The compiler can pass all the arguments in registers if the functions are with 4 / less arguments. (Dependent on the architecture). But, if more than 4 / supported set of arguments (w.r.t register w.r.t that particular architecture) then that will decrease the speed(increase the operation time). In that case, you have to opt for passing using structures. Pass a structure pointer instead of passing large number of arguments.

Karthik Balaguru