[Bug binutils/19054] New: wrong assembly and disassembly for fsubp/fsubrp

[mattiase at acm dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19054

            Bug ID: 19054
           Summary: wrong assembly and disassembly for fsubp/fsubrp
           Product: binutils
           Version: 2.25
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: mattiase at acm dot org
  Target Milestone: ---

The x86 (x87) instructions fsubp and fsubrp seem to be swapped both in assembly
and disassembly. The assembly source:

        fsubp %st, %st(5)
        fsubrp %st, %st(5)

results in the following, after going through as and objdump:

   0:   de e5                   fsubp  %st,%st(5)
   2:   de ed                   fsubrp %st,%st(5)

However, according to the architecture reference (and Intel's XED tool), [de
ed] is fsubp and [de e5] fsubrp, so the "r" bit seems to have been flipped in
both as and objdump. For instance, XED on the same file outputs

XDIS 0: X87_ALU   X87        DEE5                     fsubrp st5, st0
XDIS 2: X87_ALU   X87        DEED                     fsubp st5, st0

The binutils error does not depend on whether AT&T or Intel syntax is used.

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