llvm - How to check the opcode of an instruction? -


in fact have found 2 solutions, , want know if there difference :

  • using isa, isa<loadinst>(i).
  • using getopcode (i.getopcode() method , comparing load

which 1 use ?

isa used check existing dirived instruction class. class i.getopcode() operations information.

according the inheritance diagram llvm::instruction,llvm internally divide instruction several different classes, llvm::binaryoperator, llvm::callinst, llvm::cmpinst, etc. there no exact operation information these classes.

however, instruction::getopcode(), directly operation llvm::instruction object. refer instruction.def idea defination of each instruction. basically, opcode exact operations instruction intends to.

say, llvm ir add. can use isa<llvm::binaryoperator>, know binaryoperator. instruction class is. if want know whether add or sub. i.getopcode() should used here.


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