[llvm] r291609 - CodeGen: Allow small copyable blocks to "break" the CFG.

[Matt Arsenault via llvm-commits]

> On Jan 10, 2017, at 15:04, Kyle Butt via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> Author: iteratee
> Date: Tue Jan 10 17:04:30 2017
> New Revision: 291609
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=291609&view=rev
> Log:
> CodeGen: Allow small copyable blocks to "break" the CFG.
> 
> When choosing the best successor for a block, ordinarily we would have preferred
> a block that preserves the CFG unless there is a strong probability the other
> direction. For small blocks that can be duplicated we now skip that requirement
> as well.
> 
> Differential revision: https://reviews.llvm.org/D27742

Hi,

This has caused a code quality regression for me. Attached is a reduced testcase. This patch caused a net gain of 2 branches and a compare instruction. Any idea on how to fix it?

-Matt

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