[LLVMbugs] [Bug 10900] New: [x86 disassembler] pause instruction isn't disassembled

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=10900

           Summary: [x86 disassembler] pause instruction isn't
                    disassembled
           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


According to the "Intel® 64 and IA-32 Architectures Software Developer’s Manual
Volume 2 (2A & 2B): Instruction Set Reference, A-Z", p. 4-64:

F3 90 PAUSE

This is a special form of a nop and has been available since the Pentium 4. The
assembler recognizes the 'pause' mnemonic, but the disassembler just shows
'nop':

$ echo '0xf3 0x90'| ./llvm-mc -disassemble -triple="x86_64"
     nop

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