On Sun, 29 Apr 2012 16:22:48 +0200 (CEST), Nomen Nescio <[email protected]> wrote:
>> much snipped > >Newsgroups: bit.listserv.ibm-main,comp.lang.cobol >Subject: Re: GO TO "cobol" >References: <[email protected]> >Message-ID: <[email protected]> >Date: Thu, 19 Apr 2012 11:42:24 +0200 (CEST) > ><snip> I wrote > >COBOL doesn't inline PERFORM. A coder can choose to code an inline PERFORM, >so there is a good example of one thing the coder can do better in source >than the compiler. If PERFORM READ-RECORD performs a paragraph that CAN NOT be reached via GO TO or a fall through from the previous paragraph AND there is no GO TO or GOBACK / STOP RUN / EXIT PROGRAM in the paragraph AND the OPTIMIZE option is chosen on any IBM 370 / 390 / z series compiler starting with VS COBOL II V1R4, the code may well be inlined (moved out of sequence). I have verified this by reading the procedure division map produced by the compiler. There have been SHARE presentations given by Tom Ross of IBM COBOL development in Santa Teresa stating this and noting that a paragraph may be copied to more than one place. Based on my reading of the generated code back in the 1990s I changed my code to ONLY use PERFORM and NEVER PERFORM ... THRU on new programs. This change in how things worked also allowed me to simplify nested IF ... END-IF statements by moving appropriate nesting levels to a separate paragraph with no loss of efficiency because the compiler moved the statements back in line. Another optimization that came in at the same time was recognizing that an offset related to a subscript had been calculated and using that offset for subsequent subscripted references thus eliminating the value of moving entries to a work area. Any time you get a new version of a compiler in any language, read the manual to see what coding changes would be beneficial and what compiler options can work in your environment. Some techniques that were valuable with the COBOL VS (1974 standard) and saved time using the right OPTIMIZE options became counter productive with VS COBOL II V1R4. Clark Morris > ><snip> I wrote > > PERFORM READ-RECORD. > PERFORM SOMETHING ELSE. > > > > > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
