Peephole optimization, yes, and the can vary the object code based on the target processor, but I have seen some truly ghastly code generated by older PL/I compilers for unaligned bit strings. How good is the code for unaligned bit strings in Enterprise PL/I.
Assembler has an advantage over compilers when the application needs to do things that do not map well into the source language, but even there the compiler might surprise you. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 עַם יִשְׂרָאֵל חַי נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר ________________________________________ From: IBM Mainframe Discussion List <[email protected]> on behalf of Eric Rossman <[email protected]> Sent: Friday, August 22, 2025 11:09 AM To: [email protected] <[email protected]> Subject: Re: RMODE 64 - Why? External Message: Use Caution I agree with this. The compiler folks work hard to generate the most efficient code based on the target HW. I can (usually) do slightly better than the compiler for small loops (where I know exactly what idiosyncrasies to take advantage of) but for anything more than a couple dozen HLL lines of code, the compiler beats me every time, even without optimizations. With optimizations, I don't stand a chance. My take is that unless I need to very carefully set up for HW instructions that are not supported by the HLL (instructions such as those used for CPACF), it's never worth my time to do the work fully in assembler. Eric Rossman --------------------------------- ICSF Security Architect z/OS Security --------------------------------- -----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Colin Paice Sent: Friday, August 22, 2025 9:26 AM To: [email protected] Subject: [EXTERNAL] Re: RMODE 64 - Why? I remember about 40 years ago, the CICS development team were very pleased with their work optimising the CICS dispatcher code - the key code was written in assembler, and polished till they could get no more benefits from tuning it. Then came the next generation hardware, and all their polishing was of no benefit. They found it was best to structure their code and let the PLS compiler optimise it - which was generally better than they could. Colin ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
