[BasicAA] Add test for incorrect handling of small index sizes (NFC)

Author: nikic

llvm/test/Analysis/BasicAA/smaller-index-size-overflow.ll

@@ -0,0 +1,13 @@
+; RUN: opt -S -passes=aa-eval -print-all-alias-modref-info -disable-output < %s 2>&1 | FileCheck %s
+
+target datalayout = "p1:32:32"
+
+; FIXME: This is a miscompile.
+; CHECK: NoAlias:	i32 addrspace(1)* %gep1, i32 addrspace(1)* %gep2
+define void @test(ptr addrspace(1) %p) {
+  %gep1 = getelementptr i8, ptr addrspace(1) %p, i32 u0x7fffffff
+  %gep2 = getelementptr i8, ptr addrspace(1) %p, i32 u0x80000001
+  store i32 0, ptr addrspace(1) %gep1
+  load i32, ptr addrspace(1) %gep2
+  ret void
+}