while loop code generation

ast@halcyon.com (Andrew Tucker)
14 Dec 1997 22:36:44 -0500

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From: ast@halcyon.com (Andrew Tucker)
Newsgroups: comp.compilers
Date: 14 Dec 1997 22:36:44 -0500
Organization: Northwest Nexus, Inc.
Keywords: code, question

On page 227 of Fraser and Hanson's _A Retargetable C Compiler_,
they claim that the code


goto L+1
L: statement
L+1: if expression != 0 goto L
L+2:


generates n+2 goto's for a loop executing statement n times while
the code


L:
L+1: if expression == 0 goto L+2
statement
goto L
L+2:


generates 2n+1 goto's.


Maybe my analysis (and my test code) are severely flawed, but
I see both layouts as equivalent, with n+1 gotos executed when
statement is executed n times.


Am I missing something or is their claim incorrect?




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