--- /dev/null
+/* PR tree-optimization/42587 */
+/* { dg-do compile } */
+/* { dg-require-effective-target bswap } */
+/* { dg-options "-O2 -fdump-tree-store-merging" } */
+/* { dg-additional-options "-march=z900" { target s390-*-* } } */
+
+typedef unsigned char u8;
+typedef unsigned int u32;
+union __anonunion_out_195
+{
+ u32 value;
+ u8 bytes[4];
+};
+union __anonunion_in_196
+{
+ u32 value;
+ u8 bytes[4];
+};
+extern void acpi_ut_track_stack_ptr (void);
+u32 acpi_ut_dword_byte_swap (u32 value);
+u32
+acpi_ut_dword_byte_swap (u32 value)
+{
+ union __anonunion_out_195 out;
+ union __anonunion_in_196 in;
+
+ {
+ acpi_ut_track_stack_ptr ();
+ in.value = value;
+ out.bytes[0] = in.bytes[3];
+ out.bytes[1] = in.bytes[2];
+ out.bytes[2] = in.bytes[1];
+ out.bytes[3] = in.bytes[0];
+ return (out.value);
+ }
+}
+
+/* { dg-final { scan-tree-dump "32 bit bswap implementation found at" "store-merging" } } */