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Fixed float denorm conversion handling for XMConvertFloatToHalf #114

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Merged
walbourn merged 7 commits into from
Jun 25, 2020
Merged

Fixed float denorm conversion handling for XMConvertFloatToHalf #114

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6219461
Code review
walbourn May 12, 2020
d85ac93
Return 0 for values smaller than e-24
walbourn May 13, 2020
2840d6d
Fixed XMConvertFloatToHalf denorm handling
walbourn May 13, 2020
9e6bc6e
Code review
walbourn May 13, 2020
a2e37bc
range tweak
walbourn May 15, 2020
6ba47ce
Merge branch 'master' into float16denorm
walbourn May 19, 2020
e84cc09
Fixed XMConvertFloatToHalf to match F16C intrinsic
walbourn Jun 8, 2020
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2 changes: 1 addition & 1 deletion Inc/DirectXPackedVector.h
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Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,7 @@ namespace DirectX
//------------------------------------------------------------------------------
// 16 bit floating point number consisting of a sign bit, a 5 bit biased
// exponent, and a 10 bit mantissa
typedef uint16_t HALF;
using HALF = uint16_t;

//------------------------------------------------------------------------------
// 2D Vector; 16 bit floating point components
Expand Down
61 changes: 26 additions & 35 deletions Inc/DirectXPackedVector.inl
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Original file line number Diff line number Diff line change
Expand Up @@ -387,8 +387,8 @@ inline HALF XMConvertFloatToHalf(float Value) noexcept
{
#if defined(_XM_F16C_INTRINSICS_) && !defined(_XM_NO_INTRINSICS_)
__m128 V1 = _mm_set_ss(Value);
__m128i V2 = _mm_cvtps_ph(V1, 0);
return static_cast<HALF>(_mm_cvtsi128_si32(V2));
__m128i V2 = _mm_cvtps_ph(V1, _MM_FROUND_TO_NEAREST_INT);
return static_cast<HALF>(_mm_extract_epi16(V2, 0));
#elif defined(_XM_ARM_NEON_INTRINSICS_) && (defined(_M_ARM64) || defined(_M_HYBRID_X86_ARM64) || __aarch64__) && !defined(_XM_NO_INTRINSICS_)
float32x4_t vFloat = vdupq_n_f32(Value);
float16x4_t vHalf = vcvt_f16_f32(vFloat);
Expand All @@ -399,38 +399,29 @@ inline HALF XMConvertFloatToHalf(float Value) noexcept
auto IValue = reinterpret_cast<uint32_t*>(&Value)[0];
uint32_t Sign = (IValue & 0x80000000U) >> 16U;
IValue = IValue & 0x7FFFFFFFU; // Hack off the sign

if (IValue > 0x477FE000U)
if (IValue >= 0x47800000 /*e+16*/)
{
// The number is too large to be represented as a half. Saturate to infinity.
if (((IValue & 0x7F800000) == 0x7F800000) && ((IValue & 0x7FFFFF) != 0))
{
Result = 0x7FFF; // NAN
}
else
{
Result = 0x7C00U; // INF
}
// The number is too large to be represented as a half. Return infinity or NaN
Result = 0x7C00U | ((IValue > 0x7F800000) ? (0x200 | ((IValue >> 13U) & 0x3FFU)) : 0U);
}
else if (!IValue)
else if (IValue <= 0x33000000U /*e-25*/)
{
Result = 0;
}
else if (IValue < 0x38800000U /*e-14*/)
{
// The number is too small to be represented as a normalized half.
// Convert it to a denormalized value.
uint32_t Shift = 125U - (IValue >> 23U);
IValue = 0x800000U | (IValue & 0x7FFFFFU);
Result = IValue >> (Shift + 1);
uint32_t s = (IValue & ((1U << Shift) - 1)) != 0;
Result += (Result | s) & ((IValue >> Shift) & 1U);
}
else
{
if (IValue < 0x38800000U)
{
// The number is too small to be represented as a normalized half.
// Convert it to a denormalized value.
uint32_t Shift = 113U - (IValue >> 23U);
IValue = (0x800000U | (IValue & 0x7FFFFFU)) >> Shift;
}
else
{
// Rebias the exponent to represent the value as a normalized half.
IValue += 0xC8000000U;
}

// Rebias the exponent to represent the value as a normalized half.
IValue += 0xC8000000U;
Result = ((IValue + 0x0FFFU + ((IValue >> 13U) & 1U)) >> 13U) & 0x7FFFU;
}
return static_cast<HALF>(Result | Sign);
Expand Down Expand Up @@ -477,7 +468,7 @@ inline HALF* XMConvertFloatToHalfStream
__m128 FV = _mm_load_ps(reinterpret_cast<const float*>(pFloat));
pFloat += InputStride * 4;

__m128i HV = _mm_cvtps_ph(FV, 0);
__m128i HV = _mm_cvtps_ph(FV, _MM_FROUND_TO_NEAREST_INT);

_mm_storel_epi64(reinterpret_cast<__m128i*>(pHalf), HV);
pHalf += OutputStride * 4;
Expand All @@ -492,7 +483,7 @@ inline HALF* XMConvertFloatToHalfStream
__m128 FV = _mm_loadu_ps(reinterpret_cast<const float*>(pFloat));
pFloat += InputStride * 4;

__m128i HV = _mm_cvtps_ph(FV, 0);
__m128i HV = _mm_cvtps_ph(FV, _MM_FROUND_TO_NEAREST_INT);

_mm_storel_epi64(reinterpret_cast<__m128i*>(pHalf), HV);
pHalf += OutputStride * 4;
Expand All @@ -510,7 +501,7 @@ inline HALF* XMConvertFloatToHalfStream
__m128 FV = _mm_load_ps(reinterpret_cast<const float*>(pFloat));
pFloat += InputStride * 4;

__m128i HV = _mm_cvtps_ph(FV, 0);
__m128i HV = _mm_cvtps_ph(FV, _MM_FROUND_TO_NEAREST_INT);

*reinterpret_cast<HALF*>(pHalf) = static_cast<HALF>(_mm_extract_epi16(HV, 0));
pHalf += OutputStride;
Expand All @@ -531,7 +522,7 @@ inline HALF* XMConvertFloatToHalfStream
__m128 FV = _mm_loadu_ps(reinterpret_cast<const float*>(pFloat));
pFloat += InputStride * 4;

__m128i HV = _mm_cvtps_ph(FV, 0);
__m128i HV = _mm_cvtps_ph(FV, _MM_FROUND_TO_NEAREST_INT);

*reinterpret_cast<HALF*>(pHalf) = static_cast<HALF>(_mm_extract_epi16(HV, 0));
pHalf += OutputStride;
Expand Down Expand Up @@ -567,7 +558,7 @@ inline HALF* XMConvertFloatToHalfStream
__m128 FT = _mm_blend_ps(FV3, FV4, 0x8);
FV = _mm_blend_ps(FV, FT, 0xC);

__m128i HV = _mm_cvtps_ph(FV, 0);
__m128i HV = _mm_cvtps_ph(FV, _MM_FROUND_TO_NEAREST_INT);

_mm_storel_epi64(reinterpret_cast<__m128i*>(pHalf), HV);
pHalf += OutputStride * 4;
Expand Down Expand Up @@ -595,7 +586,7 @@ inline HALF* XMConvertFloatToHalfStream
__m128 FT = _mm_blend_ps(FV3, FV4, 0x8);
FV = _mm_blend_ps(FV, FT, 0xC);

__m128i HV = _mm_cvtps_ph(FV, 0);
__m128i HV = _mm_cvtps_ph(FV, _MM_FROUND_TO_NEAREST_INT);

*reinterpret_cast<HALF*>(pHalf) = static_cast<HALF>(_mm_extract_epi16(HV, 0));
pHalf += OutputStride;
Expand Down Expand Up @@ -2099,7 +2090,7 @@ inline void XM_CALLCONV XMStoreHalf2
{
assert(pDestination);
#if defined(_XM_F16C_INTRINSICS_) && !defined(_XM_NO_INTRINSICS_)
__m128i V1 = _mm_cvtps_ph(V, 0);
__m128i V1 = _mm_cvtps_ph(V, _MM_FROUND_TO_NEAREST_INT);
_mm_store_ss(reinterpret_cast<float*>(pDestination), _mm_castsi128_ps(V1));
#else
pDestination->x = XMConvertFloatToHalf(XMVectorGetX(V));
Expand Down Expand Up @@ -2655,7 +2646,7 @@ inline void XM_CALLCONV XMStoreHalf4
{
assert(pDestination);
#if defined(_XM_F16C_INTRINSICS_) && !defined(_XM_NO_INTRINSICS_)
__m128i V1 = _mm_cvtps_ph(V, 0);
__m128i V1 = _mm_cvtps_ph(V, _MM_FROUND_TO_NEAREST_INT);
_mm_storel_epi64(reinterpret_cast<__m128i*>(pDestination), V1);
#else
XMFLOAT4A t;
Expand Down