Get Module from an IR instruction. Is it necessary to check nullptr in the chain of `getParent()` function call?

IR & Optimizations
#1

Hi,
The use case is to get the Module pointer from a given IR instruction, which is basically Instruction.getParent()->getParent()->getParent().

The question is, is it necessary to check nullptr in the chain of getParent() function call? Could an middle-end pass assume an IR instruction always has a BB, and this BB always has a Function, and this Function always has a Module?

Searching getParent()->getParent()->getParent() gives a bunch of use cases, like llvm-project/InlineAdvisor.cpp at 2f637fe730a7b65f4584ae636c50197ebaf5a4a7 · llvm/llvm-project · GitHub, so it seems to me checking nullptr is not necessary. If this is true, which pass guarantees that an IR instruction always resides in a Module?

#2

IR is usually accessed in ‘top-down’ fashion with clearly defined module and function contexts. Unless it is corrupted, the parent link should point to the contexts which are valid.

#3

got it, thanks!

#4

You usually only need to check these for nullptr if your API is explicitly designed to work on instructions that have not been inserted into a function, or functions that have not been inserted into a module. For example, you’ll find checks like this in InstructionSimplify (which explicitly supports non-inserted instructions), but not most other places: llvm-project/InstructionSimplify.cpp at 0af19ef9ff5364f76f682259f9c7f5579aa95696 · llvm/llvm-project · GitHub

#5

You usually only need to check these for nullptr if your API is explicitly designed to work on instructions that have not been inserted into a function, or functions that have not been inserted into a module.

Acknowledged,thanks for the example!