[X86] Add test cases to show missed opportunities to use a sign extended 8 or 32...

[X86] Add test cases to show missed opportunities to use a sign extended 8 or 32 bit immediate AND when reversing SHL+AND to form an LEA.

When we shift the AND mask over we should shift in sign bits instead of zero bits. The scale in the LEA will shift these bits out so it doesn't matter whether we mask the bits off or not. Using sign bits will potentially allow a sign extended immediate to be used.

Also add some other test cases for cases that are currently optimal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357845 91177308-0d34-0410-b5e6-96231b3b80d8