[PATCH] D28746: Mention ThinLTO with PGO in ReleaseNotes 4.0

Teresa Johnson via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Sun Jan 15 14:04:35 PST 2017

tejohnson added a comment.

In https://reviews.llvm.org/D28746#646793, @Prazek wrote:

> Maybe I should change ThinLTO for '-flto=thin' and also mention this improvement in LLVM release notes?
> BTW '-flto=thin' is not documented in UsersManual

It's documented here:


and here:


but not (yet) here:


I can add that.


Comment at: docs/ReleaseNotes.rst:69
+  called from cold callsite.
mehdi_amini wrote:
> We need to mention ThinLTO in the Release Notes, so thanks for initiating this. 
> We likely should go with a paragraph summarizing the improvements, I don't know though if there is anything else than 1) PGO and 2) Significant build-time and binary-size improvements with debug-info.
Yes this is a good start. One of the big improvements from PGO is the integration with indirect call promotion. I would suggest something like:

Improvements to ThinLTO (-flto=thin):
- Integration with profile data. When available, profile data enables more accurate function importing decisions, as well as cross-module indirect call promotion.
- Significant build-time and binary-size improvements when compiling with debug info (-g).


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