llvm dev - Jul 2015 - [LLVMdev] Identifying function call targets at the MachineInstr level

Thanks – extracting the call destination from the instruction operand is working
much better! For my test bitcode, which contains only direct calls, this
correctly matches all calls to their targets.

 

I don’t suppose there’s an “easy” solution for identifying the targets of
indirect calls (i.e., through function pointers)? I’ve been told that LLVM’s
IR-level CallGraph analysis doesn’t account for indirect calls; is this still
the case?

 

Thanks,

Ethan Johnson 

 

From: Hal Finkel [mailto:hfinkel at anl.gov] 
Sent: Thursday, July 16, 2015 1:34 AM
To: Ethan J. Johnson <ejohns48 at cs.rochester.edu>
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Identifying function call targets at the MachineInstr
level

 

This will not work in general, as you note below, this depends on a
correspondence between calls on the IR and MI levels, and nothing guarantees
this (and will not be true in practice because lowering of many different IR
constructs inserts calls to libc, etc.). Instead, you can extract the call
destination from the call instruction itself. If you iterate over the
instruction's operands, you should find that one of them returns true for
isGlobal(). On such an operand, you can call getGlobal() to get the IR-level
GlobalValue* representing the function.

You might also find that isSymbol() is true, in which case you can call
getSymbolName() (which returns a const char * with the symbol name).

 -Hal

 

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