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

[Christian Sayer]

Evan,

>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.

Thanks for your response. I did quite some stepping through the llc
passes, and it turned out what now looks fairly obvious:
The instructions containing the CCFLAGS which are not marked dead
in the dump below (line 3+) are reg-to-reg copies inserted by the PHI elimination.
In my backend, a mov instruction is currently implemented as an add with
constant 0 (affecting condition codes).
Now LiveVariables gets executed before PHI elimination, so I am trying
to figure out if there is code in PNE which is supposed to update the
defs. Otherwise I might try to re-run LiveVariables after PNE, or
some similiar approach combining these two passes - unless you tell
me they don't get marked dead because of an implementation flaw in my
backend (or something completely else : )

Thanks again,
Christian


>>        %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>






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

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