Llodra, the event's biggest surprise, secured a place in an ATP singles final for the second time this season by improving his career record against the 6-foot-10, big-hitting Croat Karlovic to 2-0.
Soderling trumped France's Gilles Simon 6-2 6-1.
"When I saw the draw, I thought I'd be lucky to win two matches," Llodra told the BBC. "Now I'm into the final."
He won despite just one service break and 16 aces by Karlovic.
The tournament's top three seeds all lost Thursday.
Soderling needed only 50 minutes after winning all five of his break-point chances and dropping just seven points on his own serve.
Sunday's Soderling-Llodra winner will claim a first-place check of $250,000.