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From: preston@asta.rice.edu (Preston Briggs)
Newsgroups: comp.arch
Subject: re: isamax and instruction set design
Message-ID: <1991Jun14.163141.17728@rice.edu>
Date: 14 Jun 91 16:31:41 GMT
References: <396@validgh.com> <1991Jun13.234834.22970@neon.Stanford.EDU> <1991Jun14.134338.4673@linus.mitre.org>
Sender: news@rice.edu (News)
Organization: Rice University, Houston
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bs@frieda.mitre.org (Robert D. Silverman) writes:

>:	    ibig  = absdx .le. dmax
>	    ^^^^^^^^^^^^^^^^^^^^^^^^
>
>I would be very interested in seeing the assembler code that gets
>emitted for this line of Fortran. How can this statement get executed
>WITHOUT a branch??

The RS/6000 could do this, basically assigning ibig to one of the
condition code registers.  Actually, many machines could, though they don't
always have enough CC registers to be useful.

If this test can be issued enough in advance, then later tests
of 'ibig' would be free.

Don't know of any conditional assignments, though we might
use a skip instruction to accomplish the purpose.

Preston Briggs