[PATCH] D27853: [CodeGenPrep]Restructure promoting Ext to form ExtLoad

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added a comment.

Hi Jun,

Just so that I get the idea, when you say:

> Based on this change, I will move the transformation performed in aarch64-type-promotion into CGP.

You mean that you are going to add more transformation that will reuse that refactoring, right?

Because as it is, if I understand the code correctly (I haven't finished the review yet), the promotions are gated on forming an extending load, which is probably not what we want on the long run.

Second question, do you have performance number for the current version?

I remember that I settled on only strict improvement in the cost model to stop, i.e., I was not waiting for the cost to become unprofitable, because the cost model was not precise enough and supposedly neutral transformations ended up in regressions.

Cheers,
-Quentin



================
Comment at: lib/CodeGen/CodeGenPrepare.cpp:4250
 ///
-/// \return true when promoting was necessary to expose the ext(load)
-/// opportunity, false otherwise.
+/// \return true when promoting can be happend, false otherwise.
 ///
----------------
I don't quite get the last sentence.


https://reviews.llvm.org/D27853