[PATCH] D41044: Implementation of -fextend-lifetimes and -fextend-this-ptr to aid with debugging of optimized code

Vedant Kumar via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Wed Dec 20 15:09:00 PST 2017

vsk added a comment.

I have some results from the development build of our kernel ('-O2 -g -flto'). According to dwarfdump -statistics, when compiled with -fextend-lifetimes, the percentage of covered scope bytes increases from 62% to 69%. The number of inlined scopes decreases by 4%, and (I think relatedly) the size of the binary increases by 14%. There is a small increase in the number of unique source variables (under 1%). I'd be happy to report back on any other suggested quantitative measures.

My qualitative feedback based on spot-checking a few frames is  that -fextend-lifetimes noticeably improves the overall debugging experience. More argument values and local variables tend to be available. I'm not sure how best to put a number to this.


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