Re: [Qemu-devel] [PATCH2] ppc64: fix mtmsr behavior on 64-bit targets

[Nathan Whitehorn]

On 06/13/11 05:20, Alexander Graf wrote:
> Am 12.06.2011 um 17:49 schrieb Nathan Whitehorn<address@hidden>:
>
> > The mtmsr instruction is required not to modify the upper 32-bits of the 
> > machine state register, but checks the current value of MSR[SF] to decide 
> > whether to do this. This has the effect of zeroing the upper 32 bits of the MSR 
> > whenever mtmsr is executed in 64-bit mode. Unconditionally preserve the upper 
> > 32-bits in mtmsr for TARGET_PPC64.
> >
> > Signed-off-by: Nathan Whitehorn<address@hidden>
> > ---
> > target-ppc/translate.c |    5 ++---
> > 1 files changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> > index 59aef85..38d2e2e 100644
> > --- a/target-ppc/translate.c
> > +++ b/target-ppc/translate.c
> > @@ -3884,18 +3884,17 @@ static void gen_mtmsr(DisasContext *ctx)
> >           */
> >          gen_update_nip(ctx, ctx->nip);
> > #if defined(TARGET_PPC64)
> > -        if (!ctx->sf_mode) {
> > -            TCGv t0 = tcg_temp_new();
> > -            TCGv t1 = tcg_temp_new();
> > -            tcg_gen_andi_tl(t0, cpu_msr, 0xFFFFFFFF00000000ULL);
> > -            tcg_gen_ext32u_tl(t1, cpu_gpr[rS(ctx->opcode)]);
> > -            tcg_gen_or_tl(t0, t0, t1);
> > -            tcg_temp_free(t1);
> > -            gen_helper_store_msr(t0);
> > -            tcg_temp_free(t0);
> > -        } else
> > +        TCGv t0 = tcg_temp_new();
> > +        TCGv t1 = tcg_temp_new();
> You're declaring variables in mid-scope. Please open a new scope :).

Does the gen_update_nip(ctx, ctx->nip); need to be first here? If not, 
we can just move it to the end and avoid the scoping issue.
> > +        tcg_gen_andi_tl(t0, cpu_msr, 0xFFFFFFFF00000000ULL);
> > +        tcg_gen_ext32u_tl(t1, cpu_gpr[rS(ctx->opcode)]);
> > +        tcg_gen_or_tl(t0, t0, t1);
> While at it, this is a perfect scenario for the deposit tcg op! :)
>
> If you feel like this is too cumbersome work for such a small patch, please let 
> me know and I'll do the changes for you :)

I have no idea what that is, so I'd prefer you do it :)
-Nathan