There's a target hook that's called in DAGCombiner that we stub here, I'll
implement the equivalent override for AArch64 in a subsequent patch since it's
used by different shift combine.
This change by itself has minor code size improvements on arm64 -Os CTMark:
Program size.__text
outputg181ppyy output8av1cxfn diff
consumer-typeset/consumer-typeset 410648.00 410648.00 0.0%
tramp3d-v4/tramp3d-v4 364176.00 364176.00 0.0%
kimwitu++/kc 449216.00 449212.00 -0.0%
7zip/7zip-benchmark 576128.00 576120.00 -0.0%
sqlite3/sqlite3 285108.00 285100.00 -0.0%
SPASS/SPASS 411720.00 411688.00 -0.0%
ClamAV/clamscan 379868.00 379764.00 -0.0%
Bullet/bullet 452064.00 451928.00 -0.0%
mafft/pairlocalalign 246184.00 246108.00 -0.0%
lencod/lencod 428524.00 428152.00 -0.1%
Geomean difference -0.0%
Differential Revision: https://reviews.llvm.org/D150086
e1472db58e