Re: [Qemu-devel] [PATCH] target/ppc: Fix carry flag setting for shift algebraic instructions

[Richard Henderson <richard.henderson@linaro.org>]

On 09/30/2017 07:36 AM, Sandipan Das wrote:
> For POWER ISA v3.0, the XER bit CA32 needs to be set by the shift
> right algebraic instructions whenever the CA bit is to be set. This
> change affects the following instructions:
>   * Shift Right Algebraic Word (sraw[.])
>   * Shift Right Algebraic Word Immediate (srawi[.])
>   * Shift Right Algebraic Doubleword (srad[.])
>   * Shift Right Algebraic Doubleword Immediate (sradi[.])
> 
> Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
> ---
>  target/ppc/helper.h     |  4 ++--
>  target/ppc/int_helper.c | 10 ++++++++--
>  target/ppc/translate.c  | 16 ++++++++++++++--
>  3 files changed, 24 insertions(+), 6 deletions(-)
> 
> diff --git a/target/ppc/helper.h b/target/ppc/helper.h
> index bb6a94a8b3..069d65ad7b 100644
> --- a/target/ppc/helper.h
> +++ b/target/ppc/helper.h
> @@ -40,12 +40,12 @@ DEF_HELPER_4(divwe, tl, env, tl, tl, i32)
>  
>  DEF_HELPER_FLAGS_1(popcntb, TCG_CALL_NO_RWG_SE, tl, tl)
>  DEF_HELPER_FLAGS_2(cmpb, TCG_CALL_NO_RWG_SE, tl, tl, tl)
> -DEF_HELPER_3(sraw, tl, env, tl, tl)
> +DEF_HELPER_4(sraw, tl, env, tl, tl, tl)
>  #if defined(TARGET_PPC64)
>  DEF_HELPER_FLAGS_2(cmpeqb, TCG_CALL_NO_RWG_SE, i32, tl, tl)
>  DEF_HELPER_FLAGS_1(popcntw, TCG_CALL_NO_RWG_SE, tl, tl)
>  DEF_HELPER_FLAGS_2(bpermd, TCG_CALL_NO_RWG_SE, i64, i64, i64)
> -DEF_HELPER_3(srad, tl, env, tl, tl)
> +DEF_HELPER_4(srad, tl, env, tl, tl, tl)
>  DEF_HELPER_0(darn32, tl)
>  DEF_HELPER_0(darn64, tl)
>  #endif
> diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
> index da4e1a62c9..4f270eb49d 100644
> --- a/target/ppc/int_helper.c
> +++ b/target/ppc/int_helper.c
> @@ -210,7 +210,7 @@ target_ulong helper_cmpb(target_ulong rs, target_ulong rb)
>  
>  /* shift right arithmetic helper */
>  target_ulong helper_sraw(CPUPPCState *env, target_ulong value,
> -                         target_ulong shift)
> +                         target_ulong shift, target_ulong is_isa300)
>  {
>      int32_t ret;
>  
> @@ -231,12 +231,15 @@ target_ulong helper_sraw(CPUPPCState *env, target_ulong value,
>          ret = (int32_t)value >> 31;
>          env->ca = (ret != 0);
>      }
> +    if (is_isa300) {
> +        env->ca32 = env->ca;
> +    }

You do not need to pass a new parameter, because ca32 does not exist prior to
ISA 3.00, and thus any code running ISA 2.x does not care about its value.

You only need set ca32 when ca is set.  Move those assignments adjacent.


r~