[LLVMbugs] [Bug 10677] New: Encoding issue with avx SIB dest

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Aug 16 15:24:05 PDT 2011


           Summary: Encoding issue with avx SIB dest
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: pete.cooper at gmail.com
                CC: llvmbugs at cs.uiuc.edu

Created an attachment (id=7078)
 --> (http://llvm.org/bugs/attachment.cgi?id=7078)
Patch to x86 code emitter and test case

Have found an issue with this assembly writing to a memory location

vmovaps    %xmm3, (%r14,%r11)

The Intel spec says it should have the REX.X bit set to 1 to use r11, but the
code emitter is not setting VEX.X to 0 (which sets REX.X to 1 as its inverted)

I've found the issue is that the switch statement in EmitVEXOpcodePrefix is
checking for MRMSrcReg but not MRMDestReg when checking whether to set the
VEX.X bit.  I'm attaching a patch for this and a patch to the avx encoding test
case which has the correct decoding according to binutils objdump.

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