Re-land MachineInstr: Reason locally about some memory objects before going to AA.

Summary:
Reverts r311008 to reinstate r310825 with a fix.

Refine alias checking for pseudo vs value to be conservative.
This fixes the original failure in builtbot unittest SingleSource/UnitTests/2003-07-09-SignedArgs.

Reviewers: hfinkel, nemanjai, efriedma

Reviewed By: efriedma

Subscribers: bjope, mcrosier, nhaehnle, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D36900

llvm-svn: 312126
diff --git a/llvm/test/CodeGen/AArch64/ldst-opt.ll b/llvm/test/CodeGen/AArch64/ldst-opt.ll
index 975e5ae..9307b6a 100644
--- a/llvm/test/CodeGen/AArch64/ldst-opt.ll
+++ b/llvm/test/CodeGen/AArch64/ldst-opt.ll
@@ -1531,7 +1531,7 @@
 ; CHECK-LABEL: merge_zr64_unalign:
 ; CHECK: // %entry
 ; NOSTRICTALIGN-NEXT: stp xzr, xzr, [x{{[0-9]+}}]
-; STRICTALIGN: strb wzr,
+; STRICTALIGN: strb
 ; STRICTALIGN: strb
 ; STRICTALIGN: strb
 ; STRICTALIGN: strb