[Bug c/70646] New: Corrupt truncated function

["jpoimboe at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646

            Bug ID: 70646
           Summary: Corrupt truncated function
           Product: gcc
           Version: 5.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jpoimboe at redhat dot com
  Target Milestone: ---

Created attachment 38255
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38255&action=edit
qla_attr.i.gz

The linux kernel has a new tool named "objtool" which follows all possible code
paths for every .o file, looking for abnormalities.  In one rare case it has
discovered a corrupt truncated function.

From the disassembly of drivers/scsi/qla2xxx/qla_attr.o:

0000000000002f53 <qla2x00_get_host_fabric_name>:
    2f53:       55                      push   %rbp
    2f54:       48 89 e5                mov    %rsp,%rbp

0000000000002f57 <qla2x00_get_fc_host_stats>:
    2f57:       55                      push   %rbp
    2f58:       b9 e8 00 00 00          mov    $0xe8,%ecx
    2f5d:       48 89 e5                mov    %rsp,%rbp
...

Note that qla2x00_get_host_fabric_name() is inexplicably truncated after
setting up the frame pointer.  It falls through to the next function, which is
very bad.

I can recreate it with gcc 5.3.1 or gcc 6.0 on the upstream Linux kernel at tag
v4.6-rc3.

The call chain which appears to trigger the problem is:

qla2x00_get_host_fabric_name()
  wwn_to_u64()
    get_unaligned_be64()
      be64_to_cpup()
        __be64_to_cpup()

It occurs with the combination of the following two recent Linux commits:

- bc27fb68aaad ("include/uapi/linux/byteorder, swab: force inlining of some
byteswap operations")
- ef3fb2422ffe ("scsi: fc: use get/put_unaligned64 for wwn access")


The gzipped .i file is attached.  I'll also attach the kernel .config file.