[PATCH] D116821: [DebugInfo][InstrRef] Move instr-ref controlling flag out of TargetOptions

Wed Jan 19 02:52:40 PST 2022

jmorse added a comment.

(Apologies that this didn't arrive in the patch that said "turn instr-ref on by default", there were a few mistakes there),

In D116821#3253911 <https://reviews.llvm.org/D116821#3253911>, @xbolva00 wrote:

> +- 6% compile time regresion observed. This is kinda huge change.
>
> http://llvm-compile-time-tracker.com/compare.php?from=23e8a4d16018076e6eed4aa821c020b7fe348c69&to=6a605b97a2006bd391f129a606483656b7c6fb28&stat=instructions

Yup this enables a significantly different mechanism for tracking variable locations [0] -- if you switch to the  "size-file" difference on the compile time tracker, there's a corresponding (in one sample 13.5%) increase in DWARF + location lists produced. It significantly increases our variable location coverage: on the one hand there will definitely be a performance cost caused by producing more information, on the other hand, maybe it can be faster.

[0] https://www.youtube.com/watch?v=yxuwfNnp064

Repository:
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  https://reviews.llvm.org/D116821/new/

https://reviews.llvm.org/D116821