[Bug target/65604] New: MIPS -fno-delayed-branch generates incorrect code with -mcheck-zero-division

[azonenberg at drawersteak dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65604

            Bug ID: 65604
           Summary: MIPS -fno-delayed-branch generates incorrect code with
                    -mcheck-zero-division
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: azonenberg at drawersteak dot com

When compiling code that performs integer division on MIPS with
-fno-delayed-branch and -mcheck-zero-division enabled, the generated code still
uses delay slots.

Example disassembly:

400002e8:  14400002  bnez    v0,400002f4 <main+0x124>
400002ec:  0062001a  div     zero,v1,v0
400002f0:  0007000d  break   0x7
400002f4:  00001810  mfhi    v1

Expected result: Code generated with -fno-delayed-branch will run correctly on
a MIPS-like processor that does not have delay slots

Actual result: The divide is never executed on processors without delay slots
since the branch jumps.

I first noticed the issue on mips-elf-gcc 4.9.2 and have not yet tested to see
what other version(s) it is present in.