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From: | Marius Vollmer |
Subject: | Re: Does anyone have a better scm_string_hash ? |
Date: | Mon, 17 Nov 2003 17:29:48 +0100 |
User-agent: | Gnus/5.1002 (Gnus v5.10.2) Emacs/21.3 (gnu/linux) |
Marius Vollmer <address@hidden> writes: > Just for kicks, I'm now going to see what kind of code GCC generates > for h*37 as compared to (h<<5) + (h<<2) + h... Interesting. For h = a + (h<<5) + (h<<2) + h we get this sequence (one line is one machine instruction): x = h x = x << 5 a = a + x a = a + h*4 h = a + h and for h = a + h*37 we get x = h + h*8 x = h + x*4 h = x + a*1 which is nearly twice as clever... -- GPG: D5D4E405 - 2F9B BCCC 8527 692A 04E3 331E FAF8 226A D5D4 E405
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