[Bug binutils/25445] New: movsx with 0x66 prefix incorrectly disassembled

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25445

            Bug ID: 25445
           Summary: movsx with 0x66 prefix incorrectly disassembled
           Product: binutils
           Version: 2.35 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: hjl.tools at gmail dot com
  Target Milestone: ---
            Target: i386, x86-64

[hjl@gnu-cfl-1 testsuite]$ cat movsx.s
        .text
        .byte 0x66, 0x63, 0x08
[hjl@gnu-cfl-1 testsuite]$ gcc -c movsx.s
[hjl@gnu-cfl-1 testsuite]$ objdump -dw movsx.o

movsx.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <.text>:
   0:   66 63 08                movslq (%rax),%cx
[hjl@gnu-cfl-1 testsuite]$ 

AMD64 spec has

This instruction requires the REX prefix 64-bit operand size bit (REX.W) to be
set to 1 to sign-extend
a 32-bit source operand to a 64-bit result. Without the REX operand-size
prefix, the operand size will
be 32 bits, the default for 64-bit mode, and the source is zero-extended into a
64-bit register. With a 16-
bit operand size, only 16 bits are copied, without modifying the upper 48 bits
in the destination.

Intel64 spec has

63 /r* MOVSXD r16, r/m16 RM Move word to word with sign-extension.
63 /r* MOVSXD r32, r/m32 RM Move doubleword to doubleword with sign-
extension.
REX.W + 63 /r MOVSXD r64, r/m32 RM Move doubleword to quadword with
sign-extension.

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