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Re: [Qemu-devel] [PATCH 4/5] softfloat: Implement fused multiply-add
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH 4/5] softfloat: Implement fused multiply-add |
Date: |
Fri, 30 Sep 2011 08:28:03 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:6.0.2) Gecko/20110906 Thunderbird/6.0.2 |
On 09/28/2011 10:27 AM, Peter Maydell wrote:
>
> /*----------------------------------------------------------------------------
> +| Select which NaN to propagate for a three-input operation.
> +| For the moment we assume that no CPU needs the 'larger significand'
> +| information.
> +| Return values : 0 : a; 1 : b; 2 : c; 3 : default-NaN
> +*----------------------------------------------------------------------------*/
> +#if defined(TARGET_ARM)
> +static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag
> bIsSNaN,
> + flag cIsQNaN, flag cIsSNaN, flag infzero
> STATUS_PARAM)
...
> +#elif defined(TARGET_PPC)
> +static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag
> bIsSNaN,
> + flag cIsQNaN, flag cIsSNaN, flag infzero
> STATUS_PARAM)
> +{
The function declaration should be outside the #if, so that the interface is
forcibly consistent across the platforms.
> + cSig64 = (uint64_t)cSig << 39;
This might be more readable as << (62 - 23), since you've just mentioned the
explicit bit at bit 62 above.
> + if (pSign == cSign) {
> + /* Addition */
...
> + shift64RightJamming(zSig64, 32, &zSig64);
> + return roundAndPackFloat32(zSign, zExp, zSig64 STATUS_VAR);
> + } else {
> + /* Subtraction */
...
> + shift64RightJamming(zSig64, 32, &zSig64);
> + return roundAndPackFloat32(zSign, zExp, zSig64 STATUS_VAR);
> + }
> +}
Push those two calls down after the IF?
Similar comments wrt float64_muladd. But I don't see any actual logic errors
wrt the handling of any of the edge cases.
r~
- [Qemu-devel] [PATCH 0/5] target-arm: Implement UDIV/SDIV and fused multiply-accumulate, Peter Maydell, 2011/09/28
- [Qemu-devel] [PATCH 5/5] target-arm: Implement VFPv4 fused multiply-accumulate insns, Peter Maydell, 2011/09/28
- [Qemu-devel] [PATCH 3/5] target-arm: Add ARM UDIV/SDIV support, Peter Maydell, 2011/09/28
- [Qemu-devel] [PATCH 1/5] softfloat: Reinstate accidentally disabled target-specific NaN handling, Peter Maydell, 2011/09/28
- [Qemu-devel] [PATCH 2/5] target-arm: v6 media multiply space: UNDEF on unassigned encodings, Peter Maydell, 2011/09/28
- [Qemu-devel] [PATCH 4/5] softfloat: Implement fused multiply-add, Peter Maydell, 2011/09/28
- Re: [Qemu-devel] [PATCH 4/5] softfloat: Implement fused multiply-add,
Richard Henderson <=
- Re: [Qemu-devel] [PATCH 0/5] target-arm: Implement UDIV/SDIV and fused multiply-accumulate, Blue Swirl, 2011/09/28