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Object code optimizer : ウィキペディア英語版 | Object code optimizer
An object code optimizer, sometimes also known as a post pass optimizer or, for small sections of code, peephole optimizer, takes the output from a source language compile step - the object code or binary file - and tries to replace identifiable sections of the code with replacement code that is more algorithmically efficient (usually improved speed). ==Examples==
*The "COBOL Optimizer" developed by Capex Corporation in the mid 1970s for COBOL. This type of optimizer depended, in this case, upon knowledge of 'weaknesses' in the standard IBM COBOL compiler, and actually replaced (or patched) sections of the object code with more efficient code. The replacement code might replace a linear table lookup with a binary search for example or sometimes simply replace a relatively slow instruction with a known faster one that was otherwise functionally equivalent within its context. This technique is now known as strength reduction. For example, on the IBM/360 hardware the CLI instruction was, depending on the particular model, between twice and 5 times as fast as a CLC instruction for single byte comparisons.〔http://www.bitsavers.org/pdf/ibm/360/A22_6825-1_360instrTiming.pdf〕〔http://portal.acm.org/citation.cfm?id=358732&dl=GUIDE&dl=ACM〕
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