[LLVMbugs] [Bug 11643] New: [x86 disassembler] jecxz not disassembled

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Thu Dec 22 14:19:38 PST 2011


http://llvm.org/bugs/show_bug.cgi?id=11643

             Bug #: 11643
           Summary: [x86 disassembler] jecxz not disassembled
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: kkhoo at perfwizard.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


>From the "Intel® 64 and IA-32 Architectures Software Developer’s Manual
Volume 2 (2A & 2B): Instruction Set Reference, A-Z", p. 3-544:
Jcc—Jump if Condition Is Met
E3 cb JCXZ rel8 A N.E. Valid Jump short if CX register is
0.
E3 cb JECXZ rel8 A Valid Valid Jump short if ECX register is
0.
E3 cb JRCXZ rel8 A Valid N.E. Jump short if RCX register is
0.

Using llvm-mc from the 3.0 pre-built binaries for MacOS X:

$ echo '0xe3 0x0a' |./llvm-mc -disassemble -triple="x86_64"
<stdin>:1:1: warning: invalid instruction encoding
0xe3 0x0a
^
<stdin>:1:6: warning: invalid instruction encoding
0xe3 0x0a
     ^

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