Re: [Qemu-devel] [PATCH 7/9] target/ppc: Fix vrlwmi and vrlwnm

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

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On Tue, May 07, 2019 at 10:48:09AM +1000, Anton Blanchard wrote:
> We should only look at 5 bits of each byte, not 6.
> 
> Fixes: 3e00884f4e9f ("target-ppc: add vrldnmi and vrlwmi instructions")
> Signed-off-by: Anton Blanchard <anton@ozlabs.org>

Hrm.  So, what lives in those extra bits in the 'w' instructions?  Is
ignoring it correct?  Should we throw an exception?  Does it mean
something else?

> ---
>  target/ppc/int_helper.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
> index fd715b4076..111586c981 100644
> --- a/target/ppc/int_helper.c
> +++ b/target/ppc/int_helper.c
> @@ -1652,7 +1652,7 @@ void helper_vrsqrtefp(CPUPPCState *env, ppc_avr_t *r, ppc_avr_t *b)
>      }
>  }
>  
> -#define VRLMI(name, size, element, insert)                            \
> +#define VRLMI(name, size, element, insert, modifier_bits)             \
>  void helper_##name(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)          \
>  {                                                                     \
>      int i;                                                            \
> @@ -1662,9 +1662,9 @@ void helper_##name(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)          \
>          uint##size##_t src3 = r->element[i];                          \
>          uint##size##_t begin, end, shift, mask, rot_val;              \
>                                                                        \
> -        shift = extract##size(src2, 0, 6);                            \
> -        end   = extract##size(src2, 8, 6);                            \
> -        begin = extract##size(src2, 16, 6);                           \
> +        shift = extract##size(src2, 0, modifier_bits);                \
> +        end   = extract##size(src2, 8, modifier_bits);                \
> +        begin = extract##size(src2, 16, modifier_bits);               \
>          rot_val = rol##size(src1, shift);                             \
>          mask = mask_u##size(begin, end);                              \
>          if (insert) {                                                 \
> @@ -1675,10 +1675,10 @@ void helper_##name(ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b)          \
>      }                                                                 \
>  }
>  
> -VRLMI(vrldmi, 64, u64, 1);
> -VRLMI(vrlwmi, 32, u32, 1);
> -VRLMI(vrldnm, 64, u64, 0);
> -VRLMI(vrlwnm, 32, u32, 0);
> +VRLMI(vrldmi, 64, u64, 1, 6);
> +VRLMI(vrlwmi, 32, u32, 1, 5);
> +VRLMI(vrldnm, 64, u64, 0, 6);
> +VRLMI(vrlwnm, 32, u32, 0, 5);
>  
>  void helper_vsel(CPUPPCState *env, ppc_avr_t *r, ppc_avr_t *a, ppc_avr_t *b,
>                   ppc_avr_t *c)

-- 
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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