[llvm-dev] [GlobalISel][AArch64] Toward flipping the switch for O0: Please give it a try!

[Kristof Beyls via llvm-dev]

On 10 May 2017, at 17:36, Quentin Colombet <qcolombet at apple.com<mailto:qcolombet at apple.com>> wrote:

  1.

     *   MultiSource/Benchmarks/mediabench/mpeg2/mpeg2dec/mpeg2decode (46%): Function Reference_IDCT: Probably due to creating all constants in the entry BB + spilling floating point data through an X register:
        *   FastISel:
fadd d0, d1, d0
str d0, [sp,#528]
        *   GlobalISel:
fadd d0, d1, d0
fmov x9, d0
stur x9, [x29,#-48]

Good finding, I forgot to do stores in my previous fix. I’ll do them shortly.

Should be fixed by r302679

Thanks Quentin,

That reduces the slow-down when enabling globalisel at -O0 from 13% (on r302453)  to 9.5% (on r302679) in my experiments.
The code size increase also reduces from just over 3% to 2.8%.

Kristof

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