The synthesis results of version 0.32 and 0.33 are different. Why?

[shengqilong]

Why is the synthesis results of version 0.32 are better than those of version 0.33? version 0.32 has fewer logical levels than version 0.33
yosys -q -p "read -sv xxx.sv;
hierarchy -check -top xxx;
flatten;
proc; fsm; opt; memory; opt;
techmap; opt;
write_json xxx.json;
dfflibmap -liberty $syn_lib;
abc -liberty $syn_lib;
opt_clean -purge;
write_verilog -noattr -noexpr xxx_netlist.v; "

[whitequark]

This is a question you could answer yourself with git bisect.