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

[Evan Cheng]

A physical register cannot be live across the block. So it must have a  
use in the block or it must be marked dead. From your dump, it looks  
like the CCFLAGS defs are not being marked dead. It's unclear where  
things went wrong, but you can step through LiveVariables to debug this.

Evan

On Jan 9, 2009, at 2:50 AM, Christian Sayer wrote:

> 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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