This program should run successfully: https://play.golang.org/p/XIVsN45Oyzz

It does with gccgo and with cmd/compile using -gcflags=-N, but not when compiled normally. It also still fails at CL 286712, PS 3.

The problem is the "defer step(12)" and "defer step(13)" calls are being missed. Instead, execution jumps directly to the "step(14)" defer.

Sorry the reproducer is still so large. I'm having trouble minimizing it any further. It seems particularly sensitive to changes that I wouldn't expect to have any effect.

/cc @danscales @randall77