On Wed, 7 Dec 2022, Aaron Puchert wrote:
Am 05.12.22 um 09:21 schrieb Martin Jambor:
The fact is that -v3 baseline means better floating point performance out of the box.
Are the VEX-prefixed single-data instructions really faster, i.e. addsd vs vaddsd or mulsd vs vmulsd? I thought compilers emit the latter preferably if available only to avoid the need for vzeroupper and not because they're faster, but I admit I haven't benchmarked this.
No, they are not faster - unless the upper portions of the destination
register is not cleared (as you say, vzeroupper is needed to avoid
this situation). But they are bigger.
Richard.
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Richard Biener