Re: [Qemu-devel] [PATCH 10/10] target-arm/helper.c: For float-int conversion helpers pass ints as ints

[Blue Swirl]

On Fri, Apr 1, 2011 at 5:30 PM, Peter Maydell <address@hidden> wrote:
> Correct the argument and return types for the float<->int conversion helper
> functions so that integer arguments and return values are declared as
> uint32_t/uint64_t, not float32/float64. This allows us to remove the
> hand-rolled functions which were doing bitwise copies between the types
> via unions.
>
> Signed-off-by: Peter Maydell <address@hidden>
> Reviewed-by: Nathan Froyd <address@hidden>
> ---
>  target-arm/helper.c  |  155 
> ++++++++++++++++++--------------------------------
>  target-arm/helpers.h |   60 ++++++++++----------
>  2 files changed, 85 insertions(+), 130 deletions(-)
>
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 78f3d39..6788a4c 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -2486,135 +2486,90 @@ DO_VFP_cmp(s, float32)
>  DO_VFP_cmp(d, float64)
>  #undef DO_VFP_cmp
>
> -/* Helper routines to perform bitwise copies between float and int.  */
> -static inline float32 vfp_itos(uint32_t i)
> -{
> -    union {
> -        uint32_t i;
> -        float32 s;
> -    } v;
> -
> -    v.i = i;
> -    return v.s;
> -}
> -
> -static inline uint32_t vfp_stoi(float32 s)
> -{
> -    union {
> -        uint32_t i;
> -        float32 s;
> -    } v;
> -
> -    v.s = s;
> -    return v.i;
> -}
> -
> -static inline float64 vfp_itod(uint64_t i)
> -{
> -    union {
> -        uint64_t i;
> -        float64 d;
> -    } v;
> -
> -    v.i = i;
> -    return v.d;
> -}
> -
> -static inline uint64_t vfp_dtoi(float64 d)
> -{
> -    union {
> -        uint64_t i;
> -        float64 d;
> -    } v;
> -
> -    v.d = d;
> -    return v.i;
> -}
> -
>  /* Integer to float conversion.  */
> -float32 VFP_HELPER(uito, s)(float32 x, CPUState *env)
> +float32 VFP_HELPER(uito, s)(uint32_t x, CPUState *env)

If you moved these functions to op_helper.c, passing env would not be
needed anymore.

Another possible optimization is that maybe the softfloat functions
could be used directly as helpers if type of fp_status could be
changed to something that can be passed in a register, like uint32_t.
This would be useful for most targets.