Re: optimizing case-statement execution

nr@volkl.Princeton.EDU (Norman Ramsey)
Wed, 25 Nov 1992 23:44:02 GMT

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Newsgroups: comp.compilers
From: nr@volkl.Princeton.EDU (Norman Ramsey)
Organization: Princeton University, Dept. of Computer Science
Date: Wed, 25 Nov 1992 23:44:02 GMT
References: 92-11-126
Keywords: C, code, optimize

Our local `lcc' compiler uses a combination of jump tables and
test-and-branch to implement switch statements. It uses jump tables for
dense portions of the switch statement, binary search elsewhere. The
example you show has three cases: 0, 10, and 31. It may be that gcc will
use a jump table if the cases are closer together. You might be able to
fool it by adding more cases, i.e., case 1: case 2: goto default_lab; and
so on.
--

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