These can be generally described as removing redundant condition checks, using logical operators instead of bitwise operators, removal of redundant parenthesis, and consistent use of pragma push and pragma pop. There is very little observable behavior change in this CL.
Changes that required further review are pending in 2489753
[CL 2489804 by Dan Oconnor in Main branch]
Most code accessing brush/landscape data by calculating indexes (e.g. Data + (Y-Y1)*XSize + (X-X1)) replaced with scanline[X] style for speed
LandscapeInfo->SelectedRegion is now only queried if it contains anything, to avoid hashing the key unneccessarily (the hash function was showing on profiles :( )
Smoothing tool's SmoothFilterKernel*Scale* replaced by the more intuitive Size
Component brush fixed to be properly centered on the cursor at odd sizes and work correctly with the add component tool when cursor is over the landscape (but part of the brush is off the landscape) and size is >1
Copy tool fixed to copy the selected area and not a circle when using ctrl+c
Also a few style cleanups. for (auto it = xyz.CreateIterator...) replaced with ranged for, enums replaced with enum classes, 0.f -> 0.0f, NULL->nullptr, etc.
[CL 2392355 by Gareth Martin in Main branch]