[PATCH] D24164: Remove debug info when hoisting instruction from then/else branch.

Paul Robinson via llvm-commits llvm-commits at lists.llvm.org
Fri Sep 2 11:43:11 PDT 2016

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probinson added a comment.

In https://reviews.llvm.org/D24164#533199, @andreadb wrote:

> > About https://reviews.llvm.org/D24180, we just use -mllvm -use-unknown-locations=true for similar purposes.
> Interesting, I will look at it.
>  At the moment I am using https://reviews.llvm.org/D24180 and it seems to be doing a good job with sample pgo. In my experiments, it fixes a few nasty cases where instructions at the top of a basic block are implicitly attributed to the source line for the physically preceding instruction simply because they don't have a debug loc. Anyway, I will explain all the details in the email that I will send to you :-).

Using `-mllvm -use-unknown-locations=true` is a superset of https://reviews.llvm.org/D24180.  The latter tries to be smarter about where the line-0 attributions are really needed, in order to minimize the size penalty in the debug line table.  Also https://reviews.llvm.org/D24180 works for Codeview as well as DWARF.


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