Miley Cyrus — Crying in Vegas During First Post-Liam Performance

Miley Cyrus broke down crying in Vegas yesterday … while she performed a song rumored to be about her break up with Liam Hemsworth.

Miley twerked it up on stage at the iHeartRadio Music Festival — but the tears started flowing hard once she began singing “Wrecking Ball.”

As we previously reported — the couple has called it quits … and Liam has gotten tight with telenovela actress Eiza Gonzales — who BTW is crazy hot.

Despite the cry-fest … Miley cleaned up for her second performance of the night.

And wore this.