[X86, X87 stackifier] Do not mark an operand of a debug instruction as kill.

<rdar://problem/16952634>



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215962 91177308-0d34-0410-b5e6-96231b3b80d8
IR: Split up Constant{Array,Vector}::get(), NFC

Introduce `getImpl()` that tries the simplification logic from `get()`
and then gives up.  This allows the logic to be reused elsewhere in a
follow-up commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215963 91177308-0d34-0410-b5e6-96231b3b80d8
IR: Factor out replaceUsesOfWithOnConstantImpl(), NFC

Factor out common code, and take advantage of the new function to
add early returns to the callers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215964 91177308-0d34-0410-b5e6-96231b3b80d8
IR: Fix ConstantArray::replaceUsesOfWithOnConstant()

Previously, `ConstantArray::replaceUsesOfWithOnConstant()` neglected to
check whether it becomes a `ConstantDataArray`.  Call
`ConstantArray::getImpl()` to check for that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215965 91177308-0d34-0410-b5e6-96231b3b80d8
IR: Reduce RAUW traffic in ConstantVector

Avoid creating a new `ConstantVector` on an RAUW of one of its members.
This reduces RAUW traffic on any containing constant.

This is part of PR20515.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215966 91177308-0d34-0410-b5e6-96231b3b80d8