[LLVMdev] Moving instructions from one basic block to another
Frank Winter
fwinter at jlab.org
Fri Jun 26 09:08:01 PDT 2015
Say, you have basic blocks BB_source and BB_dest, where BB_source
contains many instructions and some of them you'd like to move to
BB_dest where the builder's insertion point currently points to. The
instructions to move are stored in a SetVector<Value*> in no particular
order. Thus, moving the instructions (removeFromParent and
Builder->insert) while iterating over the set vector causes problems a
la 'value does not dominate all uses'. However, iterating over BB_source
and checking for presence of the processed instruction in the set vector
and moving it to BB_dest seems to invalidate the iterator. Here's the
code I am trying:
for (BasicBlock::iterator inst = BB_source->begin() ;
inst != BB_source->end() ;
++inst ) {
if (Instruction *Inst = dyn_cast<Instruction>(inst)) {
if (set_vector->instructions.count(Inst)) {
Inst->removeFromParent();
Builder->Insert(Inst);
}
}
}
That doesn't work. I was already wondering if I am on the right path
since the simplified version doesn't compile:
for (BasicBlock::iterator inst = BB_source->begin() ;
inst != BB_source->end() ;
++inst ) {
if (set_vector->instructions.count(inst)) {
inst->removeFromParent();
Builder->Insert(inst);
}
}
How would You do that?
Thanks,
Frank
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