Re: [PATCH v4 12/17] target/ppc: Remove MSR_SA and MSR_AP from hflags

[David Gibson]

On Mon, Mar 15, 2021 at 12:46:10PM -0600, Richard Henderson wrote:
> Nothing within the translator -- or anywhere else for that
> matter -- checks MSR_SA or MSR_AP on the 602.  This may be
> a mistake.  However, for the moment, we need not record these
> bits in hflags.
> 
> This allows us to simplify HFLAGS_VSX computation by moving
> it to overlap with MSR_VSX.

This leans into the requirement that certain hflags and msr bits line
up, which makes me nervous.  Apart from that

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

> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/ppc/cpu.h         | 4 +---
>  target/ppc/helper_regs.c | 7 +++----
>  2 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index 07a4331eec..23ff16c154 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -599,14 +599,12 @@ enum {
>      HFLAGS_DR = 4,   /* MSR_DR */
>      HFLAGS_IR = 5,   /* MSR_IR */
>      HFLAGS_SPE = 6,  /* from MSR_SPE if cpu has SPE; avoid overlap w/ MSR_VR 
> */
> -    HFLAGS_VSX = 7,  /* from MSR_VSX if cpu has VSX; avoid overlap w/ MSR_AP 
> */
>      HFLAGS_TM = 8,   /* computed from MSR_TM */
>      HFLAGS_BE = 9,   /* MSR_BE -- from elsewhere on embedded ppc */
>      HFLAGS_SE = 10,  /* MSR_SE -- from elsewhere on embedded ppc */
>      HFLAGS_GTSE = 11, /* computed from SPR_LPCR[GTSE] */
>      HFLAGS_FP = 13,  /* MSR_FP */
> -    HFLAGS_SA = 22,  /* MSR_SA */
> -    HFLAGS_AP = 23,  /* MSR_AP */
> +    HFLAGS_VSX = 23, /* MSR_VSX if cpu has VSX */
>      HFLAGS_VR = 25,  /* MSR_VR if cpu has VRE */
>  };
>  
> diff --git a/target/ppc/helper_regs.c b/target/ppc/helper_regs.c
> index 8479789e24..d62921c322 100644
> --- a/target/ppc/helper_regs.c
> +++ b/target/ppc/helper_regs.c
> @@ -95,8 +95,7 @@ void hreg_compute_hflags(CPUPPCState *env)
>  
>      /* Some bits come straight across from MSR. */
>      msr_mask = ((1 << MSR_LE) | (1 << MSR_PR) |
> -                (1 << MSR_DR) | (1 << MSR_IR) |
> -                (1 << MSR_FP) | (1 << MSR_SA) | (1 << MSR_AP));
> +                (1 << MSR_DR) | (1 << MSR_IR) | (1 << MSR_FP));
>  
>      if (ppc_flags & POWERPC_FLAG_HID0_LE) {
>          /*
> @@ -133,8 +132,8 @@ void hreg_compute_hflags(CPUPPCState *env)
>      if (ppc_flags & POWERPC_FLAG_VRE) {
>          msr_mask |= 1 << MSR_VR;
>      }
> -    if ((ppc_flags & POWERPC_FLAG_VSX) && (msr & (1 << MSR_VSX))) {
> -        hflags |= 1 << HFLAGS_VSX;
> +    if (ppc_flags & POWERPC_FLAG_VSX) {
> +        msr_mask |= 1 << MSR_VSX;
>      }
>      if ((ppc_flags & POWERPC_FLAG_TM) && (msr & (1ull << MSR_TM))) {
>          hflags |= 1 << HFLAGS_TM;

-- 
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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