Re: [Qemu-devel] [PATCHv2 06/10] target-ppc: Remove unused mmu models from ppc_tlb_invalidate_one

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jan 28, 2016 at 04:45:21PM +0100, Thomas Huth wrote:
> On 27.01.2016 11:13, David Gibson wrote:
> > ppc_tlb_invalidate_one() has a big switch handling many different MMU
> > types.  However, most of those branches can never be reached:
> > 
> > It is called from 3 places: from remove_hpte() and h_protect() in
> > spapr_hcall.c (which always has a 64-bit hash MMU type), and from
> > helper_tlbie() in mmu_helper.c.
> > 
> > Calls to helper_tlbie() are generated from gen_tlbiel, gen_tlbiel and
> > gen_tlbiva.  The first two are only used with the PPC_MEM_TLBIE flag,
> > set only with 32-bit or 64-bit hash MMU models, and gen_tlbiva() is
> > used only on 440 and 460 models with the BookE mmu model.
> > 
> > These means the exhaustive list of MMU types which may call
> > ppc_tlb_invalidate_one() is: POWERPC_MMU_SOFT_6xx, POWERPC_MMU_601,
> > POWERPC_MMU_32B, POWERPC_MMU_SOFT_74xx, POWERPC_MMU_64B, POWERPC_MMU_2_03,
> > POWERPC_MMU_2_06, POWERPC_MMU_2_07 and POWERPC_MMU_BOOKE.
> > 
> > Clean up by removing logic for all other MMU types from
> > ppc_tlb_invalidate_one().
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> ...
> > @@ -2031,9 +2016,8 @@ void ppc_tlb_invalidate_one(CPUPPCState *env, target_ulong addr)
> >          break;
> >  #endif /* defined(TARGET_PPC64) */
> >      default:
> > -        /* XXX: TODO */
> > -        cpu_abort(CPU(cpu), "Unknown MMU model\n");
> > -        break;
> > +        /* Should never reach here with other MMU models */
> > +        assert(0);
> >      }
> 
> May I suggest to simply use "abort()" instead of "assert(0)" ?

I actually prefer assert(0), because it documents that this is really
a "can't happen" rather than just "we can't cope".  It also means it
can be elided with -DNDEBUG.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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