[LLVMbugs] [Bug 10840] New: [AVX] encoding issue with roundss instruction?

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=10840

           Summary: [AVX] encoding issue with roundss instruction?
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: matt at pharr.org
                CC: llvmbugs at cs.uiuc.edu


Created an attachment (id=7203)
 --> (http://llvm.org/bugs/attachment.cgi?id=7203)
test case

If I run llvm-objdump -disassemble on the object file generated by running the
attached test case through llc -filetype=obj, I get errors about invalid
instruction encoding.

Specifically, if I run "llc -mattr=+avx bug.ll -o -", there is this instruction
sequence toward the end:

    vmulss    LCPI0_1(%rip), %xmm1, %xmm2
    vroundss    $9, %xmm2, %xmm2, %xmm2
    vcvttss2si    %xmm2, %edx
    andl    $3, %edx

However, if I run "llc -mattr=+avx -filetype=obj bug.ll -o - | llvm-objdump -
-disassemble", then the output for the corresponding part is:

     160:    c5 f2 59 15 bc 00 00 00                          vmulss   
188(%rip), %xmm1, %xmm2
llvm-objdump: warning: invalid instruction encoding
     16c:    d2 09                                            rorb    %cl,
(%rcx)
     16e:    c5 fa 2c d2                                      vcvttss2si   
%xmm2, %edx
     172:    83 e2 03                                         andl    $3, %edx

So either the wrong encoding is being generated when making object files, or
llvm-objdump doesn't know about this instruction.  (I hope it's the former,
since I'm seeing crashes when running the generated code. :-) ).

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