[PATCH] D26437: Use -fno-unit-at-a-time and -funit-at-a-time

Mehdi AMINI via llvm-commits llvm-commits at lists.llvm.org
Sun Nov 13 10:51:39 PST 2016

mehdi_amini requested changes to this revision.
mehdi_amini added a reviewer: mehdi_amini.
mehdi_amini added a comment.
This revision now requires changes to proceed.

I planned for a long time to *remove* the "unit_at_a_time" option in the PassManager builder, I haven't read anything compelling in this thread that justifies disabling IPO right now.
If there is a bug with a particular IPO when optimizing a library, then the bug should be addressed correctly, not by disabling the IPO.

In https://reviews.llvm.org/D26437#593867, @tejohnson wrote:

> I tried to look at the history of when/why DisableUnitAtATime was added to llvm, but wasn't able to find the commit log either via git (it was moved from a different file) or via google searches.

IIRC, it was a compatibility mode from the early days to be able to match what GCC was doing.



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