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Date: Mon, 24 Jul 2023 10:20:56 +1000 (AEST)
From: Damian McGuckin <damianm@....com.au>
To: musl@...ts.openwall.com
Subject: scalbn.c and friends
Probably more an FYI only:
I took some of the logic from an unrelated task to make a change to the
code which involved biasing the exponent a little earlier than it is done
currently for the case of a highly negative 2nd argument.
Using Godbolt, and -O3, the lines of assembler dropped somewhat for the
newer code
CPU/Compiler OLD => NEW
ARM gcc 13 47 -> 36
Power64 gcc 13 50 -> 42
X86 gcc 13 42 -> 35
Performance with my test machine, GCC 11 on X86, remains the same. So no
speed gain. Not that it is doing much computation.
I assume that it is not worth touching this routine.
But the drop in LOC was interesting. Probably just means that optimizing
compilers are getting better which is not news to anybody
- Damian
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