[LLVMbugs] [Bug 11403] New: [x86 disassembler] is "fucompi" documented Intel syntax?

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Nov 18 15:53:43 PST 2011


             Bug #: 11403
           Summary: [x86 disassembler] is "fucompi" documented Intel
           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
    Classification: Unclassified

>From the "Intel® 64 and IA-32 Architectures Software Developer’s Manual
Volume 2 (2A & 2B): Instruction Set Reference, A-Z", p. 3-348:
Compare ST(0) with ST(i), check for ordered values, set status flags
accordingly, and pop register stack

Using llvm-mc built from r144979:
$ echo '0xdf 0xe9' |./llvm-mc -disassemble -triple="x86_64"
    fucompi    ST(1)

I'm guessing that "fucompi" is some AT&T syntax shortcut to omit the ST
operand, but this isn't documented anywhere by Intel that I can find. When
specifying Intel syntax, should this disassemble as specified by Intel:

fucomip ST, ST(1)

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