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From: mitchalsup@aol.com (MitchAlsup1)
Newsgroups: comp.arch
Subject: Re: My 66000 and High word facility
Date: Tue, 13 Aug 2024 01:23:12 +0000
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On Tue, 13 Aug 2024 0:34:55 +0000, BGB wrote:

> On 8/12/2024 5:35 PM, MitchAlsup1 wrote:
>> On Mon, 12 Aug 2024 20:58:45 +0000, BGB wrote:
>>
>>> On 8/12/2024 3:12 PM, MitchAlsup1 wrote:
>>
>>>> See polpak:: r8_erf()
>>>>
>>>>
>>>> r8_erf:                                 ; @r8_erf
<snip>
>>
>> Why don't yuo download polpack, compile it, and state how many
>> instructions it takes and how many words of storage it takes ??
>
> Found what I assume you are talking about.
>
> Needed to add "polpak_test.c" as otherwise BGBCC lacks a main and prunes
> everything;
> Also needed to hack over some compiler holes related to "complex
> _Double" to get it to build;
> Also needed to stub over some library functions that were added in C99
> but missing in my C library.

I only ask for r8_erf()
>
<snip>

> As for "r8_erf()":
>
> <===
>
> r8_erf:
<snip>

I count 283 instructions compared to my 85 including the 104
instructions
it takes your compiler to get to the 1st instruction in My 66000 code !!

In the middle I see much the same problems as RISC-V has:: while you
have
the ability to poof constants, you can't use them without wasting
registers
and in general an inefficient FP instruction set {no FMAC, no sign
control
on operands, no transcendental instructions, and at least you are not as
poor of FP compare-branches as RISC-V}

It is true that LLVM can unroll loops and when the loop is consuming
only
constants Brian's compiler just emits the polynomial directly with nary
a LD or ST, just constants as operands, whereas your compiler poofs
constants into existence rather than forwarding them directly into
execution. Every poof cost you an instruction, mine just cost
instruction
space not pipeline delay.

I think this demonstrates my point perfectly--universal constants inside
a RISC instruction set is a BIG WIN.

It also illustrates the fact that a RIOSC ISA needs a good compiler.