3ff2cc81a5
Reading extern values meant these couldn't be compile-time constants.
math.h has INFINITY, which is macro that is supposed to expand to float +inf.
On MSVC it seems it's natively a double, so we cast just to make sure.
There's nan(const char*) in math.h for NaN too, but I don't trust that
to be compile-time evaluated. So instead, we keep reinterpreting a bit pattern.
I did try to write
static constexpr float float_nan() { ... }
and completely failed. constexpr seems a bit too restrictive in C++11 to make
it work, but Clang kept telling me, you'll be able to do this with C++14.
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2233853002
Review-Url: https://codereview.chromium.org/2233853002
156 lines
5.3 KiB
C++
156 lines
5.3 KiB
C++
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/*
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* Copyright 2006 The Android Open Source Project
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkFloatingPoint_DEFINED
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#define SkFloatingPoint_DEFINED
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#include "SkTypes.h"
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#include <math.h>
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#include <float.h>
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#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE1
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#include <xmmintrin.h>
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#elif defined(SK_ARM_HAS_NEON)
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#include <arm_neon.h>
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#endif
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// For _POSIX_VERSION
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#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
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#include <unistd.h>
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#endif
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#include "SkFloatBits.h"
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// C++98 cmath std::pow seems to be the earliest portable way to get float pow.
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// However, on Linux including cmath undefines isfinite.
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// http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14608
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static inline float sk_float_pow(float base, float exp) {
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return powf(base, exp);
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}
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#define sk_float_sqrt(x) sqrtf(x)
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#define sk_float_sin(x) sinf(x)
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#define sk_float_cos(x) cosf(x)
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#define sk_float_tan(x) tanf(x)
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#define sk_float_floor(x) floorf(x)
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#define sk_float_ceil(x) ceilf(x)
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#define sk_float_trunc(x) truncf(x)
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#ifdef SK_BUILD_FOR_MAC
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# define sk_float_acos(x) static_cast<float>(acos(x))
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# define sk_float_asin(x) static_cast<float>(asin(x))
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#else
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# define sk_float_acos(x) acosf(x)
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# define sk_float_asin(x) asinf(x)
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#endif
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#define sk_float_atan2(y,x) atan2f(y,x)
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#define sk_float_abs(x) fabsf(x)
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#define sk_float_copysign(x, y) copysignf(x, y)
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#define sk_float_mod(x,y) fmodf(x,y)
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#define sk_float_exp(x) expf(x)
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#define sk_float_log(x) logf(x)
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#define sk_float_round(x) sk_float_floor((x) + 0.5f)
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// can't find log2f on android, but maybe that just a tool bug?
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#ifdef SK_BUILD_FOR_ANDROID
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static inline float sk_float_log2(float x) {
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const double inv_ln_2 = 1.44269504088896;
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return (float)(log(x) * inv_ln_2);
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}
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#else
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#define sk_float_log2(x) log2f(x)
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#endif
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#ifdef SK_BUILD_FOR_WIN
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#define sk_float_isfinite(x) _finite(x)
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#define sk_float_isnan(x) _isnan(x)
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static inline int sk_float_isinf(float x) {
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int32_t bits = SkFloat2Bits(x);
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return (bits << 1) == (0xFF << 24);
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}
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#else
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#define sk_float_isfinite(x) isfinite(x)
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#define sk_float_isnan(x) isnan(x)
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#define sk_float_isinf(x) isinf(x)
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#endif
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#define sk_double_isnan(a) sk_float_isnan(a)
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#ifdef SK_USE_FLOATBITS
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#define sk_float_floor2int(x) SkFloatToIntFloor(x)
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#define sk_float_round2int(x) SkFloatToIntRound(x)
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#define sk_float_ceil2int(x) SkFloatToIntCeil(x)
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#else
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#define sk_float_floor2int(x) (int)sk_float_floor(x)
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#define sk_float_round2int(x) (int)sk_float_floor((x) + 0.5f)
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#define sk_float_ceil2int(x) (int)sk_float_ceil(x)
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#endif
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#define sk_double_floor(x) floor(x)
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#define sk_double_round(x) floor((x) + 0.5)
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#define sk_double_ceil(x) ceil(x)
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#define sk_double_floor2int(x) (int)floor(x)
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#define sk_double_round2int(x) (int)floor((x) + 0.5f)
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#define sk_double_ceil2int(x) (int)ceil(x)
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static const uint32_t kIEEENotANumber = 0x7fffffff;
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#define SK_FloatNaN (*SkTCast<const float*>(&kIEEENotANumber))
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#define SK_FloatInfinity (+(float)INFINITY)
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#define SK_FloatNegativeInfinity (-(float)INFINITY)
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static inline float sk_float_rsqrt_portable(float x) {
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// Get initial estimate.
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int i = *SkTCast<int*>(&x);
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i = 0x5F1FFFF9 - (i>>1);
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float estimate = *SkTCast<float*>(&i);
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// One step of Newton's method to refine.
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const float estimate_sq = estimate*estimate;
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estimate *= 0.703952253f*(2.38924456f-x*estimate_sq);
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return estimate;
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}
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// Fast, approximate inverse square root.
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// Compare to name-brand "1.0f / sk_float_sqrt(x)". Should be around 10x faster on SSE, 2x on NEON.
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static inline float sk_float_rsqrt(float x) {
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// We want all this inlined, so we'll inline SIMD and just take the hit when we don't know we've got
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// it at compile time. This is going to be too fast to productively hide behind a function pointer.
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//
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// We do one step of Newton's method to refine the estimates in the NEON and portable paths. No
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// refinement is faster, but very innacurate. Two steps is more accurate, but slower than 1/sqrt.
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//
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// Optimized constants in the portable path courtesy of http://rrrola.wz.cz/inv_sqrt.html
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#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE1
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return _mm_cvtss_f32(_mm_rsqrt_ss(_mm_set_ss(x)));
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#elif defined(SK_ARM_HAS_NEON)
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// Get initial estimate.
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const float32x2_t xx = vdup_n_f32(x); // Clever readers will note we're doing everything 2x.
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float32x2_t estimate = vrsqrte_f32(xx);
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// One step of Newton's method to refine.
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const float32x2_t estimate_sq = vmul_f32(estimate, estimate);
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estimate = vmul_f32(estimate, vrsqrts_f32(xx, estimate_sq));
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return vget_lane_f32(estimate, 0); // 1 will work fine too; the answer's in both places.
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#else
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return sk_float_rsqrt_portable(x);
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#endif
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}
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// This is the number of significant digits we can print in a string such that when we read that
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// string back we get the floating point number we expect. The minimum value C requires is 6, but
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// most compilers support 9
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#ifdef FLT_DECIMAL_DIG
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#define SK_FLT_DECIMAL_DIG FLT_DECIMAL_DIG
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#else
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#define SK_FLT_DECIMAL_DIG 9
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#endif
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#endif
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