[LLVMdev] Selection of multiple instructions

Artjom Kochtchi artjom.kochtchi at googlemail.com
Thu Jul 9 08:59:13 PDT 2009

Evan Cheng-2 wrote:
> It's not. It requires updating CFG. I'd do this as a separate pass.  
> Another possibility is to use the usesCustomDAGSchedInserter hack.

I've looked into this and it appears that a pass is probably better because
I want to add the check to every indirect call/jump/branch instruction which
-- using the hack -- would lead to rather many pseudo instructions.

In the runtime check I need to access the address of the jump target. That's
why it probably needs to happen after instruction selection. So is it the
right spot to put the pass between selection and scheduling (so the register
or memory locations that during runtime will contain the jump target is
already known)? Do I just create a PassManager, put my pass in and run it or
is there another approach to run passes at more or less arbitrary places?
Examples on that are rather sparse...

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