[AArch64] Fix a pattern match failure caused by creating improper CONCAT_VECTOR.

ReconstructShuffle() may wrongly creat a CONCAT_VECTOR trying to
concat 2 of v2i32 into v4i16. This commit is to fix this issue and
try to generate UZP1 instead of lots of MOV and INS.
Patch is initalized by Kevin Qin, and refactored by Tim Northover.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211144 91177308-0d34-0410-b5e6-96231b3b80d8
Random Number Generator (llvm)

Summary:
Provides an abstraction for a random number generator (RNG) that produces a stream of pseudo-random numbers.
The current implementation uses C++11 facilities and is therefore not cryptographically secure.

The RNG is salted with the text of the current command line invocation.
In addition, a user may specify a seed (reproducible builds).

In clang, the seed can be set via
  -frandom-seed=X
In the back end, the seed can be set via
  -rng-seed=X

This is the llvm part of the patch.
clang part: D3391

Reviewers: ahomescu, rinon, nicholas, jfb

Reviewed By: jfb

Subscribers: jfb, perl

Differential Revision: http://reviews.llvm.org/D3390

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211145 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Random Number Generator (llvm)"

This reverts commit cccba093090d127e0b6d17473b14c264c14c5259.

It causes build breakage.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211146 91177308-0d34-0410-b5e6-96231b3b80d8