[LLVMbugs] [Bug 10723] New: [x86 disassembler] vcvtps2pd disassembled incorrectly

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Aug 23 13:53:50 PDT 2011


           Summary: [x86 disassembler] vcvtps2pd disassembled incorrectly
           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. 3-259:

VEX.128.0F.WIG 5A /r
VCVTPS2PD xmm1, xmm2/m64

VEX.256.0F.WIG 5A /r
VCVTPS2PD ymm1, xmm2/m128

'VCVTPS2PD' can be specified with either the 2- or 3-byte VEX prefix (clang on
correctly assembles the following):

vcvtps2pd %xmm0, %ymm0

The object file shows:
C5 FC 5A C0 

But using llvm-mc built from trunk r138250 produces the wrong output
for this byte sequence:
$ echo '0xc5 0xfc 0x5a 0xc0'| ./llvm-mc -disassemble -triple="x86_64"
        cvtps2pd        %xmm0, %xmm0

The mnmemonic is missing the leading 'v' and the second operand is not the
expected 256-bit ymm register.

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