[PATCH] D12345: [Reassociate]: Add intermediate subtract instructions created while negating to be redone later for more reassociate opportunities

[Owen Anderson via llvm-commits]

> On Nov 13, 2015, at 9:59 AM, Owen Anderson via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
>> 
>> I'm not opposed, I'd like to see compile time numbers first since it transforms reassociate into an iterative algorithm.
> 
> I’ll see what I can get you on that.

I measured the compile time impact on “opt -O3” on a single-bitcode-file for all of opt itself. 

— Reassociate accounts for about 0.5% of total time.
— I had a hard time getting stable numbers, but assuming the worst case Reassociate regresses about 2%.

I would consider this firmly below the noise floor.  

—Owen
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