[AArch64] Fix offset calculation

r374772 changed Offset to be an int64_t but left NewOffset as an int.
Scale is unsigned, so in the calculation `Offset - NewOffset * Scale`,
`NewOffset * Scale` was promoted to unsigned and was then zero-extended
to 64 bits, leading to an incorrect computation which manifested as an
out-of-memory when building the Swift standard library for Android
aarch64. Promote NewOffset to int64_t to fix this, and promote
EmittableOffset as well, since its one user passes it to a function
which takes an int64_t anyway.

Test case based on a suggestion by Sander de Smalen!

Differential Revision: https://reviews.llvm.org/D69018

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375043 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/AArch64/framelayout-offset-immediate-change.mir

@@ -0,0 +1,17 @@
+# RUN: llc -mtriple=aarch64-none-linux-gnu -run-pass=prologepilog %s -o - | FileCheck %s
+---
+name: framelayout_offset_immediate_change
+tracksRegLiveness: true
+fixedStack:
+  - { id: 0, offset: 0, size: 1}
+body: |
+  bb.0:
+    $x0 = LDURXi %fixed-stack.0, -264
+    RET_ReallyLR
+...
+# CHECK:      name:            framelayout_offset_immediate_change
+# CHECK:      body:             |
+# CHECK-NEXT:   bb.0:
+# CHECK-NEXT:     $x8 = SUBXri $sp, 8, 0
+# CHECK-NEXT:     $x0 = LDURXi killed $x8, -256
+# CHECK-NEXT:     RET_ReallyLR