[FastISel][AArch64] Followup commit for 218031 to handle negative offsets too.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218032 91177308-0d34-0410-b5e6-96231b3b80d8
[FastISel][AArch64] Simplify XALU multiplies.

Simplify {s|u}mul.with.overflow to {s|u}add.with.overflow when possible.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218033 91177308-0d34-0410-b5e6-96231b3b80d8
Fix previous commit: [FastISel][AArch64] Simplify XALU multiplies.

When folding the intrinsic flag into the branch or select we also have to
consider the fact if the intrinsic got simplified, because it changes the
flag we have to check for.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218034 91177308-0d34-0410-b5e6-96231b3b80d8