search for: eh_sjlj_setup

...n. This code is very nearly working, and I've had it working for -O0 optimisation (with a slightly different version to that below), so I know it's close. However, the PowerPC code uses a trick to ensure that optimisations retain the jump targets required, using a Pseudo instruction "EH_SjLj_Setup" that expands simply to an IR comment, but makes the compiler think it needs to preserve the jump target address - which it does, to ensure that the jump target remains valid after any optimisations. Some of the comments at this URL relating to the PowerPC version help with understanding this:...

...le debug output from llc that I'm seeing: Sinking along critical edge. Sink instr %vreg8<def,tied1> = ADD64rr %vreg14<tied0>, %vreg31, %EFLAGS<imp-def,dead>; GR64:%vreg8,%vreg14,%vreg31 into block BB#11: Predecessors according to CFG: BB#8 BB#10 BB#32 ... EH_SjLj_Setup <BB#36>, <regmask> Successors according to CFG: BB#34 BB#36 Sinking along critical edge. Sink instr %vreg8<def,tied1> = ADD64rr %vreg14<tied0>, %vreg31, %EFLAGS<imp-def,dead>; GR64:%vreg8,%vreg14,%vreg31 into block BB#35: Predecessors according to CFG:...