Fix llvm::huge_valf multiple initializations with Visual C++.

llvm::huge_valf is defined in a header file, so it is initialized
multiple times in every compiled unit upon program startup.

With non-VC compilers huge_valf is set to a HUGE_VALF which the
compiler can probably optimize out.

With VC numeric_limits<float>::infinity() does not return a number
but a runtime structure member which therotically may change 
between calls so the compiler does not optimize out the 
initialization and it happens many times. It can be easily seen by 
placing a breakpoint on the initialization line.

This patch moves llvm::huge_valf initialization to a source file
instead of the header.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218567 91177308-0d34-0410-b5e6-96231b3b80d8
[AArch64] Redundant store instructions should be removed as dead code

If there is a store followed by a store with the same value to the same location, then the store is dead/noop. It can be removed.

This problem is found in spec2006-197.parser.

For example,
  stur    w10, [x11, #-4]
  stur    w10, [x11, #-4]
Then one of the two stur instructions can be removed.

Patch by David Xu!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218569 91177308-0d34-0410-b5e6-96231b3b80d8
WinCOFFObjectWriter.cpp: make write_uint32_le more efficient

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218574 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Fix yet another bug in the new vector shuffle lowering's handling
of widening masks.

We can't widen a zeroing mask unless both elements that would be merged
are either zeroed or undef. This is the only way to widen a mask if it
has a zeroed element.

Also clean up the code here by ordering the checks in a more logical way
and by using the symoblic values for undef and zero. I'm actually torn
on using the symbolic values because the existing code is littered with
the assumption that -1 is undef, and moreover that entries '< 0' are the
special entries. While that works with the values given to these
constants, using the symbolic constants actually makes it a bit more
opaque why this is the case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218575 91177308-0d34-0410-b5e6-96231b3b80d8
[x86] Fix a really silly bug that I introduced fixing another bug in the
new vector shuffle target DAG combines -- it helps to actually test for
the value you want rather than just using an integer in a boolean
context.

Have I mentioned that I loathe implicit conversions recently? :: sigh ::

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218576 91177308-0d34-0410-b5e6-96231b3b80d8
Merge branch 'master', remote-tracking branch 'trunk/master'