[GlobalOpt] Add test for PR51879 (NFC)

llvm/test/Transforms/GlobalOpt/pr51879.ll

@@ -0,0 +1,28 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
+; RUN: opt -S -globalopt < %s | FileCheck %s
+
+; TODO: This currently computes an incorrect initializer value.
+
+%type = type { { i8** } }
+
+@g = internal global %type zeroinitializer
+@g2 = external global i8*
+
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @ctor, i8* null }]
+
+;.
+; CHECK: @[[G:[a-zA-Z0-9_$"\\.-]+]] = internal global [[TYPE:%.*]] zeroinitializer
+; CHECK: @[[LLVM_GLOBAL_CTORS:[a-zA-Z0-9_$"\\.-]+]] = appending global [0 x { i32, void ()*, i8* }] zeroinitializer
+;.
+define internal void @ctor() {
+  store i64 0, i64* bitcast (%type* @g to i64*), align 8
+  store i8** @g2, i8*** getelementptr inbounds (%type, %type* @g, i64 0, i32 0, i32 0), align 8
+  ret void
+}
+
+define %type* @test() {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:    ret %type* @g
+;
+  ret %type* @g
+}