[LLVMbugs] [Bug 18975] New: Missing Uses/Defs information for x86 short MOV instructions

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18975

            Bug ID: 18975
           Summary: Missing Uses/Defs information for x86 short MOV
                    instructions
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: llvmbugzilla.20.darksys at spamgourmet.org
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 12152
  --> http://llvm.org/bugs/attachment.cgi?id=12152&action=edit
proposed patch

While using LLVM to determine register usage of a dissassembled binary I
noticed
that some MOVs to/from EAX are not listing EAX as an (implicit) used/defined
register.

I think this is the cause:
The shorter instructions for MOVs to/from (E)AX optimized by
SimplifyShortMoveForm (X86MCInstLower.cpp) are missing register Uses and Defs
information in X86InstrInfo.td.

I attached a small patch which achieves expected behaviour in my build, but I'm
not familiar with tablegen.

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