[fpc-devel] FPC Performance: MOVAPD vs MOVSD

[Sergei Gorelkin]

19.10.2011 17:45, Graeme Geldenhuys пишет:
>
> Not that I understand much of the assembler generated, but what I did
> notice is that Delphi XE2 64-bit uses the MOVAPD function (introduced in
> SSE2 [1]), but even if I specify -O3 -CfSSE3 with 64-bit FPC, FPC only
> uses the MOVSD (introduced in 386 [2]).
>
> So is there place for optimizing FPC a bit more? Reducing the number of
> instructions and using faster / newer assembler calls?
>
There are actually two different instructions called MOVSD, one for string manipulations, another 
one is SSE2. Another such ambiguous instruction is CMPSD. This causes some confusion, and the wiki 
page [2] contains a note on that.
The MOVSD instruction used by FPC is the from the SSE2 family, as well as MOVAPD, and has nothing to 
do with 386.

Regards,
Sergei