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Re: [Qemu-devel] [PATCH 135/147] softfloat: Fix uint64_to_float64
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH 135/147] softfloat: Fix uint64_to_float64 |
Date: |
Fri, 28 Sep 2012 15:14:33 +0100 |
On 28 September 2012 02:12, Richard Henderson <address@hidden> wrote:
> The interface to normalizeRoundAndPackFloat64 requires that the
> high bit be clear. Perform one shift-right-and-jam if needed.
>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
> fpu/softfloat.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index b29256a..45f105a 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -1273,9 +1273,14 @@ float64 int64_to_float64( int64 a STATUS_PARAM )
>
> float64 uint64_to_float64( uint64 a STATUS_PARAM )
> {
> - if ( a == 0 ) return float64_zero;
> - return normalizeRoundAndPackFloat64( 0, 0x43C, a STATUS_VAR );
> + int exp = 0x43C;
>
> + if ( a == 0 ) return float64_zero;
> + if ( (int64_t)a < 0 ) {
> + a = (a >> 1) | (a & 1);
> + exp += 1;
> + }
You could just use
shift64RightJamming(a, 1, &a);
rather than calculating a like that; gcc is smart enough to emit
the same code as your longhand version.
> + return normalizeRoundAndPackFloat64( 0, exp, a STATUS_VAR );
I worked through it and I believe this patch does the right thing
with raising or not raising the inexact flag...
-- PMM
- [Qemu-devel] [PATCH 126/147] target-s390: Implement COMPARE AND TRAP, (continued)
- [Qemu-devel] [PATCH 126/147] target-s390: Implement COMPARE AND TRAP, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 127/147] target-s390: Implement LOAD ON CONDITION, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 128/147] target-s390: Implement STORE ON CONDITION, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 129/147] target-s390: Implement CONVERT TO LOGICAL, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 130/147] target-s390: Implement CONVERT FROM LOGICAL, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 131/147] target-s390: Implement POPCNT, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 132/147] target-s390: Implement CPSDR, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 133/147] target-s390: Check insn operand specifications, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 134/147] target-s390: Implement LCDFR, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 135/147] softfloat: Fix uint64_to_float64, Richard Henderson, 2012/09/27
- Re: [Qemu-devel] [PATCH 135/147] softfloat: Fix uint64_to_float64,
Peter Maydell <=
- [Qemu-devel] [PATCH 136/147] softfloat: Implement uint64_to_float128, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 137/147] target-s390: Use uint64_to_float128, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 138/147] target-s390: Implement SET ROUNDING MODE, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 139/147] target-s390: Implement LOAD/SET FP AND SIGNAL, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 140/147] target-s390: Fix cpu_clone_regs, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 141/147] target-s390: Optimize XC, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 142/147] target-s390: Optmize emitting discards, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 143/147] target-s390: Tidy comparisons, Richard Henderson, 2012/09/27
- [Qemu-devel] [PATCH 144/147] target-s390: Optimize ADDU/SUBU CC testing, Richard Henderson, 2012/09/27