Updating the CFG after function modifcation

Updating the CFG after function modifcation

[Matt Davis]

Hello,
I have an IPA pass (implemented as a plugin) which executes after all IPA
passes.  My pass transforms functions by adding code and also modifying the
function prototypes.  I have had this work on a per-function basis, via a
GIMPLE_PASS, which calls update_ssa verify_ssa and cleanup_cfg after each
function is processed.  However, I have recently moved my plugin to execute
after all IPA passes, so I can iterate over the cfg of the program.  The first
iteration is an analysis, and the second iteration does the transformations.
Unfortunately, I keep getting errors now, primarily a segfault in
"compute_call_stmt_bb_frequency" in the processing of the main().  The segfault
occurs because the argument 'bb' is NULL and later dereferenced.  (NOTE: I do
not modify the prototype of main).

The e->call_stmt that the null basic block references is from a statement I have
removed via gsi_remove during my transformation pass.  I need to clean up the
cfg somehow, after I remove the statement.  My gimple pass, with this same
functionality worked fine.  Something tells me that my plugin should be in a
different position.  I also tried calling cleanup_tree_cfg() after my
transformation pass, still no luck

Any suggestions would be welcomed.  Thanks for even reading this far.

-Matt

Re: Updating the CFG after function modifcation

[Eric Botcazou]

> I have an IPA pass (implemented as a plugin) which executes after all IPA
> passes.  My pass transforms functions by adding code and also modifying the
> function prototypes.  I have had this work on a per-function basis, via a
> GIMPLE_PASS, which calls update_ssa verify_ssa and cleanup_cfg after each
> function is processed.  However, I have recently moved my plugin to execute
> after all IPA passes, so I can iterate over the cfg of the program.

Callgraph, not CFG, of the program.

> The e->call_stmt that the null basic block references is from a statement I
> have removed via gsi_remove during my transformation pass.  I need to clean
> up the cfg somehow, after I remove the statement.  My gimple pass, with
> this same functionality worked fine.  Something tells me that my plugin
> should be in a different position.  I also tried calling cleanup_tree_cfg()
> after my transformation pass, still no luck

Try invoking rebuild_cgraph_edges.

-- 
Eric Botcazou