llvm dev - Jun 2012 - [LLVMdev] Replace constant with variable

Hello,

I wondered if there was a standard way in LLVM to replace a constant 
with a variable. The standard replaceAllUsesWith does not work because 
other constants may use the constant-to-be-replaced. I would like to 
recursively replace these by the corresponding expression.

Any ideas? Thanks,
Jonas

Hi Jonas,
> I wondered if there was a standard way in LLVM to replace a constant
> with a variable. The standard replaceAllUsesWith does not work because
> other constants may use the constant-to-be-replaced. I would like to
> recursively replace these by the corresponding expression.
why?

Ciao, Duncan.

Hi,
> why?
It's a good question. The short answer is that I'm working on a program 
analysis tool which, among other things, checks the memory accesses that 
the program performs. To do so, we have a model of the program's memory.

This memory model is quite limited and does not support global 
variables. Hence I convert those into variables that are allocated on 
the stack. Now the address of that global variable (a link-time 
constant) becomes a variable, namely the return value of an alloca 
instruction.

To replace uses of the constant by this variable address, I currently 
have a very ugly solution that involves a large switch on the OpCode of 
a ConstantExpr :-(

Any better solutions are welcome. Cheers,
Jonas