[PATCH] D26256: [InstCombine] Don't set debug location when folding through a phi node

[Adrian Prantl via llvm-commits]

aprantl added a comment.

In https://reviews.llvm.org/D26256#586228, @rob.lougher wrote:

> In https://reviews.llvm.org/D26256#586214, @aprantl wrote:
>
> > Shouldn't it only drop the location if the two locations are distinct (and perhaps add a discriminator)?
>
>
> Sorry, didn't make myself clear in the last comment.  As the two instructions feed into a phi node they are in different basic-blocks, so the two locations must be distinct (they are in different scopes and will have different discriminators).   But in the case where we have an if-then-else all on the same line we could create a new debug location with a different scope/discriminator.


Yes, that sounds reasonable.

I think the single-line situation is not just an edge case and we should handle it correctly. In C++11 it is becoming quite common to have a lot of control flow on a single line (think anything from <algorithm> with lambdas or the ternary operator).


https://reviews.llvm.org/D26256