keil的代码优化产生的问题（Keil code optimization issues）.docVIP

keil的代码优化产生的问题（Keil code optimization issues） Code optimization problem produced by Keil (Collection) From the angle of the sea Read the application of MCU and embedded systems in 2005 tenth issue of exchange of experience section of the article Keil C5l on the same port continuous reading method (original), the author thinks that the in-depth analysis of the issue is not accurate. The two methods mentioned are not direct and simple. I think this is not Keil C51 cannot handle to a port for continuous reading, but the use of Keil C51 is not familiar with design problems and not detailed enough, so I write this paper. In this paper, the original question, put forward three different solutions to the original. Each method is better than the original mentioned in a more direct and simple, the design is more standardized. (no criticism of the original author, please forgive me) 1 problems of review and analysis I met on the same port: repeated reading in practical work, the Keil C5l compiler did not achieve the desired results. The author of the compiled C assembler analysis found that second times on the same port read statements are not compiled. Unfortunately, the author did not analysis without reason is compiled, but quickly by using some methods not standardized testing out two solutions. This problem, read the Keil C51 manual is very easy to find: the KellC51 compiler has set up a set of different optimization, optimization, compiler will produce different results. In general, the default compiler optimization set is set to 8 level optimization, the actual maximum can be set to 9 level optimization: 1. Dead code elimination. The Data overlaymg. The Peephole optimization. The Register variables. The Common subexpression elimination. The Loop rotation. The Extended Index Access 0ptimizing. The Reuse Common. Entry Code. Common Block Subroutines. The above problems, it is because the KeiI C5l compiler generated. Because in the original program will directly address pe