Re: [Qemu-devel] [PATCH 32/34] target/ppc: Split out VSCR_SAT to a vector field

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

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On Mon, Dec 17, 2018 at 10:39:09PM -0800, Richard Henderson wrote:
> Change the representation of VSCR_SAT such that it is easy
> to set from vector code.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Acked-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  target/ppc/cpu.h        |  4 +++-
>  target/ppc/int_helper.c | 11 ++++++++---
>  2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index a2fe6058b1..26d2e16720 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -1063,10 +1063,12 @@ struct CPUPPCState {
>      /* Special purpose registers */
>      target_ulong spr[1024];
>      ppc_spr_t spr_cb[1024];
> -    /* Vector status and control register */
> +    /* Vector status and control register, minus VSCR_SAT.  */
>      uint32_t vscr;
>      /* VSX registers (including FP and AVR) */
>      ppc_vsr_t vsr[64] QEMU_ALIGNED(16);
> +    /* Non-zero if and only if VSCR_SAT should be set.  */
> +    ppc_vsr_t vscr_sat;
>      /* SPE registers */
>      uint64_t spe_acc;
>      uint32_t spe_fscr;
> diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
> index 38aa3e85a6..9dbcbcd87a 100644
> --- a/target/ppc/int_helper.c
> +++ b/target/ppc/int_helper.c
> @@ -471,18 +471,23 @@ void helper_lvsr(ppc_avr_t *r, target_ulong sh)
>  
>  void helper_mtvscr(CPUPPCState *env, uint32_t vscr)
>  {
> -    env->vscr = vscr;
> +    env->vscr = vscr & ~(1u << VSCR_SAT);
> +    /* Which bit we set is completely arbitrary, but clear the rest.  */
> +    env->vscr_sat.u64[0] = vscr & (1u << VSCR_SAT);
> +    env->vscr_sat.u64[1] = 0;
>      set_flush_to_zero((vscr >> VSCR_NJ) & 1, &env->vec_status);
>  }
>  
>  uint32_t helper_mfvscr(CPUPPCState *env)
>  {
> -    return env->vscr;
> +    uint32_t sat = (env->vscr_sat.u64[0] | env->vscr_sat.u64[1]) != 0;
> +    return env->vscr | (sat << VSCR_SAT);
>  }
>  
>  static inline void set_vscr_sat(CPUPPCState *env)
>  {
> -    env->vscr |= 1 << VSCR_SAT;
> +    /* The choice of non-zero value is arbitrary.  */
> +    env->vscr_sat.u32[0] = 1;
>  }
>  
>  void helper_vaddcuw(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)

-- 
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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