[Bug binutils/29822] New: objdump no longer prints right mnemonic for prefix 3E

[jengelh at inai dot de]

https://sourceware.org/bugzilla/show_bug.cgi?id=29822

            Bug ID: 29822
           Summary: objdump no longer prints right mnemonic for prefix 3E
           Product: binutils
           Version: 2.39
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: jengelh at inai dot de
  Target Milestone: ---

objdump changed the mnemonic output for prefix 3E.
By my reading of the Intel manual,

"""In 64-bit mode, only FS and GS segment-overrides are applicable in this
situation. Other segment override prefixes (CS, DS, ES and SS) are ignored."""

DS-override is still a thing on IA-32.


== Observed ==

$ cat x.s
cs jmp *%eax;
ds jmp *%eax;
$ as --32 -v x.s -o x.o
GNU assembler version 2.39.0 (x86_64-suse-linux) using BFD version (GNU
Binutils; openSUSE Tumbleweed) 2.39.0.20220810-1
$ objdump -d x.o
x.o:     file format elf32-i386
Disassembly of section .text:
00000000 <.text>:
   0:   2e ff e0                cs jmp *%eax
   3:   3e ff e0                notrack jmp *%eax


== Expected to see ==

$ as --32 -v x.s -o x.o
GNU assembler version 2.26.1 (x86_64-suse-linux) using BFD version (GNU
Binutils; openSUSE Leap 42.3) 2.26.1
$ objdump -d x.o
x.o:     file format elf32-i386
Disassembly of section .text:
00000000 <.text>:
   0:   2e ff e0                cs jmp *%eax
   3:   3e ff e0                ds jmp *%eax

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