[LLVMbugs] [Bug 10700] New: [x86 disassembler] arpl should not be possible with 64-bit target

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Thu Aug 18 14:36:10 PDT 2011


           Summary: [x86 disassembler] arpl should not be possible with
                    64-bit target
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: kkhoo at perfwizard.com
                CC: llvmbugs at cs.uiuc.edu

>From the "Intel® 64 and IA-32 Architectures Software Developer’s Manual
Volume 2 (2A & 2B): Instruction Set Reference, A-Z", p. 3-75:
ARPL—Adjust RPL Field of Segment Selector
63 /r
"This instruction executes as described in compatibility mode and legacy mode.
It is not encodable in 64-bit mode."

P. 3-730 shows the encoding in 64-bit mode:
MOVSX/MOVSXD—Move with Sign-Extension
REX.W** + 63 /r

With llvm-mc built from trunk revision 135913:
$ echo '0x63 0xc0'| ./llvm-mc -disassemble -triple="x86_64"
        arpl    %ax, %ax

With the 64-bit target set, this should have disassembled as 'movsx'.

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