[LLVMdev] Getting Metadata from the IR through to the Assembly writer

[Andrew Stanford-Jason]

I have a requirement where I need to get metadata on particular IR 
Instructions to survive instruction selection and find their way on to 
the MachineInstrs. In particular, I am interested in labeling 
Instructions for which I know there is a one to one mapping of 
Instruction to MachineInstr, however, if this is was not the case an 
approximation would be alright.

The problem I am trying to solve is one of calculating worst case 
execution time at source level. By labeling I/O operations on the source 
a later analysis program can analyze the generated binary to determine 
WCET for given paths between these labels.

What would be the best approach to solving this problem, thanks for any 
input.

Andrew