[llvm-dev] How to count instructions in a function?

[Zubin Pahuja via llvm-dev]

Dear Professor Criswell,

I was trying to do the same for higher levels of clang++ optimizations -O2
and above. I need the IR instruction counts of a specific function name but
it seems the optimizations are in-lining the function code (or something
else). Is there anyway to map optimized IR with un-optimized IR through
some metadata class? All I really need is the original function name in a
pass over optimized IR.

In addition, is there any existing way to detect cycles and infinite
recursion in CallGraph? How I can fairly account instruction counts of a
function and its callees in event of cycles/ infinite recursion (when the
branch prediction can be done in static analysis).

Many Thanks,
Zubin


On Thu, Nov 30, 2017 at 2:02 PM, Zubin Pahuja <zpahuja2 at illinois.edu> wrote:

> Thanks so much John! That works :)
>
> Previously I wrote a pass that inherited from CallGraphWrapperPass and
> used its getCallGraph() function within runOnModule() which resulted in
> segmentation faults for me. Not sure why that happened, perhaps callgraph
> wasn't setup by the time runOnModule() was called internally. If you know
> why, kindly enlighten me and perhaps document the behavior for the benefit
> of others.
>
> Your email was the best thing to happen to me all day. I really appreciate
> you taking out the time to help.
>
> Sincerely,
> Zubin
>
> On Thu, Nov 30, 2017 at 11:33 AM, John Criswell <jtcriswel at gmail.com>
> wrote:
>
>> Dear Zubin,
>>
>> If I were you, I would write a ModulePass that uses the CallGraph
>> analysis to get a call graph.  I would then iterate over the nodes in the
>> call graph and propagate information from callees to callers.
>>
>> Regards,
>>
>> John Criswell
>>
>>
>> On 11/29/17 4:02 PM, Zubin Pahuja via llvm-dev wrote:
>>
>> Hello,
>>
>> I am trying to count IR instructions in a function for static analysis
>> using llvm pass. In contrast with existing examples, I am trying to include
>> instruction counts of all the callees of the function.
>>
>> Counting the instructions of a function is easy using passes, but
>> iterating through the module's CallGraph is proving to be confusing. I
>> believe I have to use CallGraphWrapperPass to get both module pass and its
>> CallGraph. How do I iterate through the CallGraph in runOnModule()? A
>> simple print callee names example would be highly appreciated.
>>
>> Thanks,
>> Zubin
>>
>>
>> _______________________________________________
>> LLVM Developers mailing listllvm-dev at lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>>
>> --
>> John Criswell
>> Assistant Professor
>> Department of Computer Science, University of Rochesterhttp://www.cs.rochester.edu/u/criswell
>>
>>
>
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