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From: mhx@iae.nl (Marcel Hendrix)
Subject: Re: well formed flag ?
Newsgroups: comp.lang.forth
Message-ID: <19761907938435@frunobulax.edu>
Date: Sun, 28 Oct 2012 16:59:16 +0200
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Bernd Paysan <bernd.paysan@gmx.de> writes Re: well formed flag ?

> Stephen Pelc wrote:
>> The important comparison is the number of hours spent on the
>> code generators for C and Forth.

> IMHO VFX is limited on x86 by the numbers of registers.  As are C 
> compilers.  When I wrote my Wurstkessel cryptography core, Marcel did 
> compare the C compiler result with iForth on x64, where more registers 
> are available, and the speed was about the same.

I redid these just now on an i7 2.66 GHz machine:

64bits - 0.985 seconds; Speed: 518,743,667 bytes/sec. 
32bits - 2.981 seconds; Speed: 171,696,847 bytes/sec. ( rngs_wurst in CODE )
32bits - 4.741 seconds; Speed: 107,971,320 bytes/sec. ( high-level )

> On x86, Andy Glew (one of the designers of the Pentium Pro) suggested 
> adding an instruction for "well formed flags" in the Forth sense - which 
> could be used for bit-wise operations.  It got turned down by senior 
> management, because C compilers couldn't make any benefit from it; 
> though assembly code would.

Rngs_wurst is in CODE because the carry bit is needed.

	: rngs_wurst ( ud1 index -- ud2 )  
	    64s ( 8 * ) 'rngs + 64@ 
	    2>R
	    DUP 0< >R D2* R> DUP D- 2R>
	    ROT XOR >R XOR R> ; PRIVATE

> Later, in the SSE instruction set, the idea was revived, and indeed 
> implemented: SSE compares store their result flags as either all bits 
> set or all bits cleared in the destination register.

-marcel