Enable merging all constants without looking at use in GlobalMerge by
default to replace PPCMergeStringPool pass on Linux.

PowerPC subtargets prior to Power9 use the 'legacy' itinerary way to
provide scheduling information. This patch re-writes the tablegen file
to define the scheduling information in the new SchedModel way, which
can bring improvements to some benchmarks.

Reviewed By: shchenz

Differential Revision: https://reviews.llvm.org/D154488

We added a new post-isel CTRLoop pass in D122125. That pass will expand
the hardware loop related intrinsic to CTR loop or normal loop based
on the loop context. So we don't need to conservatively check the CTR
clobber now on the IR level.

Reviewed By: lkail

Differential Revision: https://reviews.llvm.org/D135847

mflr is kind of expensive on Power version smaller than 10, so we should
schedule the store for the mflr's def away from mflr.

In epilogue, the expensive mtlr has no user for its def, so it doesn't
matter that the load and the mtlr are back-to-back.

Reviewed By: RolandF

Differential Revision: https://reviews.llvm.org/D137423

The LIT test cases were migrated with the script provided by
Nikita Popov. Due to the size of the change it is split into
several parts.

Reviewed By: nemanja, amyk, nikic, PowerPC

Differential Revision: https://reviews.llvm.org/D135470

Reviewed By: shchenz

Differential Revision: https://reviews.llvm.org/D117459

Summary:
For PPC BinaryOperator of fp128 will become libcall, we shouldn't
convert loop to CTR loop if the loop contain libCall.

But currently, in the PPCTTIImpl::mightUseCTR() function, we only deal
with BinaryOperator for ppc_fp128, don't deal with the fp128.

Reviewed By: shchenz

Differential Revision: https://reviews.llvm.org/D81353