[Bug gas/16763] New: RL78 - Ranges of relative branches are not checked correctly

[peper03 at yahoo dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16763

            Bug ID: 16763
           Summary: RL78 - Ranges of relative branches are not checked
                    correctly
           Product: binutils
           Version: 2.24
            Status: NEW
          Severity: critical
          Priority: P2
         Component: gas
          Assignee: unassigned at sourceware dot org
          Reporter: peper03 at yahoo dot com

gas quietly allows out-of-range relative branches.  The RL78 processors allow
8-bit and 16-bit relative branches (so -128/+127 or -32768/+32767 bytes from
PC) but gas seems to be calculating the distance using unsigned values so it
will allow a forward jump of, say, 200 bytes without complaint that actually
ends up as a backwards jump of 56 bytes (i.e. -56).

A build-time error only occurs once the distance is too large to fit in an 8 or
16-bit value (as appropriate).

Backwards jumps are left for the linker to fix-up, so there's no error until
the linker runs (but at least there *is* a build-time error).

    .list

    .global _branchTest8
    .global _branchTest16

_branchTest8:
    br      $label8
    .zero   200
    br      $_branchTest8
label8:
    ret

_branchTest16:
    br      $label16
    .zero   32769
    br      $_branchTest16
label16:
    ret

    .end

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