Add test

Author: nikic

llvm/test/Transforms/InstSimplify/ConstProp/inttoptr-gep-index-width.ll

@@ -0,0 +1,14 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instsimplify < %s | FileCheck %s
+
+target datalayout = "p:16:16:16:8"
+
+; The GEP should only modify the low 8 bits of the pointer.
+define ptr @test() {
+; CHECK-LABEL: define ptr @test() {
+; CHECK-NEXT:    ret ptr null
+;
+  %base = inttoptr i16 -1 to ptr
+  %gep = getelementptr i8, ptr %base, i8 1
+  ret ptr %gep
+}