1346069 - Incremental linking on Windows can take up to 4x as long as full linking

Status: NEW

(Firefox Build System :: General, enhancement)

Description

[(Away)]

I'm currently working on nsTSubstring.h in an --enable-debug --disable-optimize configuration. A full link (i.e. delete the .ilk) takes me just under 2 minutes. If I make some changes to that widely-used header, then in addition to recompiling half the world, the link phase alone takes me 8(!) minutes.

I assume that all those rebuilt obj files are giving link.exe a lot of work to do in figuring out what incremental changes to make. Anecdotally I've heard other people complain about long links (even on debug, where incremental is enabled) and I suspect they're running into the same issue.

I wonder if we could detect whether we're over some threshold of change, and just do a full link.