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

[Christian Sayer]

Hi,

I was a little confused by all the passes I went through last time.
LiveVariables *is* actually being run before and after PNE (of course,
because it crashed in the second run...)

The problem was that the CCFLAGS register was not marked
non-allocatable. AFAICS this is also the case in the X86 backend, which
I took as model, although it does not make problems there - but maybe
it should not be anyway?

>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
...which turned out to be the correct assumption ; )

Regards,
Christian





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

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