[Bug target/68400] New: ICE in change_address_1, at emit-rtl.c:2125

[nbd at nbd dot name]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68400

            Bug ID: 68400
           Summary: ICE in change_address_1, at emit-rtl.c:2125
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nbd at nbd dot name
  Target Milestone: ---

Created attachment 36748
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36748&action=edit
Proposed fix

When MIPS16 is enabled, I get the following ICE when compiling libpcap:

./pcap-common.c: In function 'swap_linux_usb_header.isra.0':
./pcap-common.c:1296:1: internal compiler error: in change_address_1, at
emit-rtl.c:2125
 }

I've analyzed this, and found that it generates a single-byte load from the
stack, which is not valid in MIPS16 - only size 4 or 8 is valid for access with
offset from the stack pointer, as explained by the comment in
mips_regno_mode_ok_for_base_p().

I've attached a patch which fixes the issue.