[LLVMdev] implicit CC register Defs cause "physreg was not killed in defining block!" assert

[Christian Sayer]

Hello,

For my backend, I define and use a CC register similiarly to the EFLAGS register in X86 (I call it CCFLAGS).
But if I make all arithmetic/logic instructions affect it ('let Defs = [CCFLAGS] in...' in InstrInfo.td) I run into

  // The only case we should have a dead physreg here without a killing or
  // instruction where we know it's dead is if it is live-in to the function
  // and never used.
  assert(!CopyMI && "physreg was not killed in defining block!");

in LiveIntervals::handlePhysicalRegisterDef().

The dump() of the MBB from the debugger looks like the following:

entry.ifcont267_crit_edge: 0x12bc368, LLVM BB @0x12bb900, ID#2:
    Predecessors according to CFG: 0x12bc290 (#0) 0x12bca70 (#1)
        %reg1033<def> = addC %reg1025<kill>, 0, %CCFLAGS<imp-def,dead>
        %reg1032<def> = addC %reg1024<kill>, 0, %CCFLAGS<imp-def,dead>
        %reg1095<def> = addC %reg1028, 0, %CCFLAGS<imp-def>
        %reg1096<def> = addC %reg1029<kill>, 0, %CCFLAGS<imp-def>
        %reg1097<def> = addC %reg1033<kill>, 0, %CCFLAGS<imp-def>
        %reg1098<def> = addC %reg1028<kill>, 0, %CCFLAGS<imp-def>
        %reg1099<def> = addC %reg1031<kill>, 0, %CCFLAGS<imp-def>
        %reg1100<def> = addC %reg1030, 0, %CCFLAGS<imp-def>
        %reg1101<def> = addC %reg1032<kill>, 0, %CCFLAGS<imp-def>
        %reg1102<def> = addC %reg1030<kill>, 0, %CCFLAGS<imp-def>
        br mbb<ifcont267,0x12bc518>
    Successors according to CFG: 0x12bc518 (#4)



Do you have any idea what could be wrong, or how to further debug the problem?

Thanks a lot,
Christian


 --







sorry about that, but there is nothing I can do about it:

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