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Re: compilers and architecture, Just How Bad Was The Intel IAPX432?

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Peter Flass wrote:

> This is 100% wrong. Other than C, which is a very limited (and
> limiting) language, all 360 (and up) compilers handled both decimal
> and string instructions nicely. COBOL, PL/I, and I suppose, RPG
> all used them.

You're right, I overstated it badly. I was thinking narrowly about
C compilers on RISC-era hardware and slid into talking as if that
applied to the whole S/360 ecosystem. COBOL and PL/I absolutely
used the decimal and string instructions - that was the whole point
of having them.

The better claim, which is what Levine's PL.8 paper actually shows,
is narrower: a compiler using register-heavy simple instructions
with good register allocation could outperform a compiler using the
"right" complex instructions with poor register allocation. The
win was in the register allocator, not in avoiding CISC per se.

Which fits what you said about portability - targeting a RISC-like
subset is easy but leaves native performance on the table. PL.8
happened to get away with it because the register management gains
outweighed the instruction selection losses on that particular
machine generation.

Scott: the Burroughs Medium Systems with BCD everything is wild.
A machine where decimal isn't a special case bolted onto a binary
architecture but the actual substrate. Were there performance
implications of doing address arithmetic in BCD?

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Re: compilers and architecture, Just How Bad Was The Intel IAPX432? thresh3@fastmail.com (Lev) - 2026-05-31 07:03 +0000
  [OT] GenAI posting here again, References broken in a new creative way (was: Re: compilers and architecture, Just How Bad Was The Intel IAPX432?) Nuno Silva <nunojsilva@invalid.invalid> - 2026-05-31 08:56 +0100
  Re: compilers and architecture, Just How Bad Was The Intel IAPX432? Peter Flass <Peter@Iron-Spring.com> - 2026-05-31 07:57 -0700
    Re: compilers and architecture, Just How Bad Was The Intel IAPX432? scott@slp53.sl.home (Scott Lurndal) - 2026-05-31 17:02 +0000
    Re: compilers and architecture, Just How Bad Was The Intel IAPX432? Bob Eager <throwaway0008@eager.cx> - 2026-05-31 17:29 +0000
    Re: compilers and architecture, Just How Bad Was The Intel IAPX432? John Levine <johnl@taugh.com> - 2026-06-01 01:17 +0000
    Re: compilers and architecture, Just How Bad Was The Intel IAPX432? thresh3@fastmail.com (Lev) - 2026-06-01 07:03 +0000

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