Disappointing math performance compared to GDC
David Nadlinger via digitalmars-d-ldc
digitalmars-d-ldc at puremagic.com
Wed Oct 8 10:37:28 PDT 2014
On Wednesday, 8 October 2014 at 16:23:19 UTC, Gabor Mezo wrote:
> I'm not an ASM expert, but as far as I can see it indeed use
> some SIMD registers and instructions.
On x86_64, scalar single and double precision math uses the SSE
registers and instructions by default too. The relevant mnemonics
(mostly) end with "ss", which stands for "scalar single". On the
other hand, vectorize code would use e.g. the instructions ending
in "ps", for "packed single" (multiple values in one SSE
register).
Your snippet has not actually been vectorized. Assuming that the
code you posted was from a hot loop, a much bigger problem are
the many function calls, though.
David
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