[LLVMdev] How to know if an instruction is "usable"

[Krzysztof Parzyszek]

On 4/25/2013 12:06 PM, Giacomo Tagliabue wrote:
> Thanks,
> So, how do I check if a block dominates another one?

In IR use analysis DominatorTree from 
"include/llvm/Analysis/Dominators.h".  For machine instructions, use 
MachineDominatorTree
from "include/llvm/CodeGen/MachineDominators.h".

Both of them implement function "dominates" that takes two blocks 
(BasicBlock* or MachineBasicBlock*) and returns a boolean value 
indicating whether one dominates the other.  A block will always 
dominate itself, so this case needs to be handled separately to 
determine relative position between the def and the use instruction.

-Krzysztof

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