[PATCH] D32252: [GVN] Add phi-translate for scalarpre as a temporary solution

[Wei Mi via llvm-commits]

> This also needs compile time and performance measurements.

I used spec2006 to do compile time testing. The compile time had a
small increase.

400.perlbench       0.54%
401.bzip2              1.62%
403.gcc                 0.79%
429.mcf                 1.15%
433.milc                 0.24%
445.gobmk             0.71%
456.hmmer            0.26%
458.sjeng              -0.53%
462.libquantum     0.22%
464.h264ref          -0.18%
470.lbm                 0.86%
482.sphinx3           -1.01%
998.specrand        -2.35%
999.specrand        -3.45%
444.namd              0.46%
447.dealII              1.65%
450.soplex             0.92%
453.povray             0.88%
471.omnetpp          1.77%
473.astar                1.23%
483.xalancbmk       1.33%

However, the compile time increase is not caused by phiTranslate call,
but caused by some data structure setting like numberingExpression map
(I removed the phiTranslate call and the compile time increase is
almost the same). I think that is because GVN is already a big compile
time consumer (top3 according to
http://lists.llvm.org/pipermail/llvm-dev/2016-November/107110.html),
and even small increase in the existing cost will be reflected in the
total compile time.

Considering this is a temporary solution, is this compile time
increase acceptable?

About performance testing, I have several internal benchmarks got (>
3%) improvement. No real performance regression found yet.

Wei.