[Bug target/81863] New: [7 regression] -mword-relocations is unreliable

[arnd at linaro dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81863

            Bug ID: 81863
           Summary: [7 regression] -mword-relocations is unreliable
           Product: gcc
           Version: 7.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arnd at linaro dot org
  Target Milestone: ---

Created attachment 41989
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41989&action=edit
preprocessed linux/mm/shmem.c file, compressed

I ran into a few files in the linux kernel that while building with
-mword-relocations still produce 16-bit relocations, leading to a link error
with -fpie, e.g.

arm-linux-gnueabi-ld: mm/page_alloc.o: relocation R_ARM_THM_MOVW_ABS_NC against
`vm_zone_stat' can not be used when making a shared object; recompile with
-fPIC

With the attached source file:

$ arm-linux-gnueabi-gcc-7.1.1 -Wall mm/shmem.i -O2 -march=armv7-a -c
-Wno-unused -Wno-pointer-sign -fno-strict-aliasing -mword-relocations
$ objdump -dr mm/shmem.o | grep R_ARM_MOVW
                        326c: R_ARM_MOVW_ABS_NC vm_committed_as
                        34b8: R_ARM_MOVW_ABS_NC vm_committed_as
                        357c: R_ARM_MOVW_ABS_NC vm_committed_as