Revert "Direct evaluation of gaussian"

This reverts commit 5e18cdea0a0a3f23d8e8b8140c82a4b54e121402.

Reason for revert: ASAN
Original change's description:
> Direct evaluation of gaussian
> 
> The SVG(CSS) standard allows the 3 pass algorithm for sigma >= 2. But
> sigma < 2, the code must evaluate to the convolution. The old code used
> an interpolation scheme between windowed filters. This code directly
> evaluates the gaussian kernel for sigma < 2.
> 
> This code produces cleaner results, is 25% faster, and does not use a
> temporary memory buffer.
> 
> Change-Id: Ibd0caa73cadd06b637f55ba7bd4fefcfe7ac73db
> Reviewed-on: https://skia-review.googlesource.com/62540
> Commit-Queue: Herb Derby <herb@google.com>
> Reviewed-by: Mike Klein <mtklein@google.com>

TBR=mtklein@google.com,herb@google.com

Change-Id: I936077dfa659d71bc361339d98340c55545a1eb8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/72481
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

4 files changed, 7 insertions, 649 deletions

diff --git a/bench/BlurBench.cpp b/bench/BlurBench.cpp
index 5b94d66ff6..20afd4a2e5 100644
--- a/bench/BlurBench.cpp
+++ b/bench/BlurBench.cpp
@@ -15,11 +15,9 @@
 
 #define MINI   0.01f
 #define SMALL   SkIntToScalar(2)
-#define REAL    0.5f
+#define REAL    1.5f
 #define BIG     SkIntToScalar(10)
 #define REALBIG 100.5f
-// The value that produces a sigma of just over 2.
-#define CUTOVER 2.6f
 
 static const char* gStyleName[] = {
     "normal",
@@ -113,6 +111,5 @@ DEF_BENCH(return new BlurBench(BIG, kNormal_SkBlurStyle, SkBlurMaskFilter::kHigh
 DEF_BENCH(return new BlurBench(REALBIG, kNormal_SkBlurStyle, SkBlurMaskFilter::kHighQuality_BlurFlag);)
 
 DEF_BENCH(return new BlurBench(REAL, kNormal_SkBlurStyle, SkBlurMaskFilter::kHighQuality_BlurFlag);)
-DEF_BENCH(return new BlurBench(CUTOVER, kNormal_SkBlurStyle, SkBlurMaskFilter::kHighQuality_BlurFlag);)
 
 DEF_BENCH(return new BlurBench(0, kNormal_SkBlurStyle);)
diff --git a/src/core/SkGaussFilter.cpp b/src/core/SkGaussFilter.cpp
index c0d612ddec..548ff4398d 100644
--- a/src/core/SkGaussFilter.cpp
+++ b/src/core/SkGaussFilter.cpp
@@ -143,9 +143,10 @@ SkGaussFilter::SkGaussFilter(double sigma, Type type) {
     }
 }
 
-int SkGaussFilter::filterDouble(double values[5]) const {
+int SkGaussFilter::filterDouble(double* values) const {
     for (int i = 0; i < fN; i++) {
         values[i] = fBasis[i];
     }
     return fN;
 }
+
diff --git a/src/core/SkGaussFilter.h b/src/core/SkGaussFilter.h
index be00cf2cc0..9af45c875b 100644
--- a/src/core/SkGaussFilter.h
+++ b/src/core/SkGaussFilter.h
@@ -27,16 +27,10 @@ public:
     int radius() const { return fN - 1; }
     int width() const { return 2 * this->radius() + 1; }
 
-    // TODO: remove filterDouble and use the ranged-for loop interface.
-
     // Take an array of values where the gaussian factors will be placed. Return the number of
     // values filled.
     int filterDouble(double values[5]) const;
 
-    // Allow a filter to be used in a C++ ranged-for loop.
-    const double* begin() const { return &fBasis[0];  }
-    const double* end()   const { return &fBasis[fN]; }
-
 private:
     double fBasis[5];
     int    fN;
diff --git a/src/core/SkMaskBlurFilter.cpp b/src/core/SkMaskBlurFilter.cpp
index 9de68fcedc..fea98d6e77 100644
--- a/src/core/SkMaskBlurFilter.cpp
+++ b/src/core/SkMaskBlurFilter.cpp
@@ -11,7 +11,6 @@
 #include <climits>
 
 #include "SkArenaAlloc.h"
-#include "SkGaussFilter.h"
 #include "SkNx.h"
 #include "SkSafeMath.h"
 
@@ -569,644 +568,8 @@ static SkMask prepare_destination(int radiusX, int radiusY, const SkMask& src) {
     return dst;
 }
 
-#if !defined(SK_USE_LEGACY_INTERP_BLUR)
-static constexpr uint16_t _____ = 0u;
-static constexpr uint16_t kHalf = 0x80u;
-
-static SK_ALWAYS_INLINE Sk8h load(const uint8_t* from, int width) {
-    uint8_t buffer[8];
-    if (width < 8) {
-        sk_bzero(buffer, sizeof(buffer));
-        for (int i = 0; i < width; i++) {
-            buffer[i] = from[i];
-        }
-        from = buffer;
-    }
-    auto v = SkNx_cast<uint16_t>(Sk8b::Load(from));
-    // Convert from 0-255 to 8.8 encoding.
-    return v << 8;
-};
-
-static SK_ALWAYS_INLINE void store(uint8_t* to, const Sk8h& v, int width) {
-    Sk8b b = SkNx_cast<uint8_t>(v >> 8);
-    if (width == 8) {
-        b.store(to);
-    } else {
-        uint8_t buffer[8];
-        b.store(buffer);
-        for (int i = 0; i < width; i++) {
-            to[i] = buffer[i];
-        }
-    }
-};
-
-// In all the blur_x_radius_N and blur_y_radius_N functions the gaussian values are encoded
-// in 0.16 format, none of the values is greater than one. The incoming mask values are in 8.8
-// format. The resulting multiply has a 8.24 format, by the mulhi truncates the lower 16 bits
-// resulting in a 8.8 format.
-//
-// The blur_x_radius_N function below blur along a row of pixels using a kernel with radius N. This
-// system is setup to minimize the number of multiplies needed.
-//
-// Explanation:
-//    Blurring a specific mask value is given by the following equation where D_n is the resulting
-// mask value and S_n is the source value. The example below is for a filter with a radius of 1
-// and a width of 3 (radius == (width-1)/2). The indexes for the source and destination are
-// aligned. The filter is given by G_n where n is the symmetric filter value.
-//
-//   D[n] = S[n-1]*G[1] + S[n]*G[0] + S[n+1]*G[1].
-//
-// We can start the source index at an offset relative to the destination separated by the
-// radius. This results in a non-traditional restating of the above filter.
-//
-//  D[n] = S[n]*G[1] + S[n+1]*G[0] + S[n+2]*G[1]
-//
-// If we look at three specific consecutive destinations the following equations result:
-//
-//   D[5] = S[5]*G[1] + S[6]*G[0] + S[7]*G[1]
-//   D[7] = S[6]*G[1] + S[7]*G[0] + S[8]*G[1]
-//   D[8] = S[7]*G[1] + S[8]*G[0] + S[9]*G[1].
-//
-// In the above equations, notice that S[7] is used in all three. In particular, two values are
-// used: S[7]*G[0] and S[7]*G[1]. So, S[7] is only multiplied twice, but used in D[5], D[6] and
-// D[7].
-//
-// From the point of view of a source value we end up with the following three equations.
-//
-// Given S[7]:
-//   D[5] += S[7]*G[1]
-//   D[6] += S[7]*G[0]
-//   D[7] += S[7]*G[1]
-//
-// In General:
-//   D[n]   += S[n]*G[1]
-//   D[n+1] += S[n]*G[0]
-//   D[n+2] += S[n]*G[1]
-//
-// Now these equations can be ganged using SIMD to form:
-//   D[n..n+7]   += S[n..n+7]*G[1]
-//   D[n+1..n+8] += S[n..n+7]*G[0]
-//   D[n+2..n+9] += S[n..n+7]*G[1]
-// The next set of values becomes.
-//   D[n+8..n+15]  += S[n+8..n+15]*G[1]
-//   D[n+9..n+16]  += S[n+8..n+15]*G[0]
-//   D[n+10..n+17] += S[n+8..n+15]*G[1]
-// You can see that the D[n+8] and D[n+9] values overlap the two sets, using parts of both
-// S[n..7] and S[n+8..n+15].
-//
-// Just one more transformation allows the code to maintain all working values in
-// registers. I introduce the notation {0, S[n..n+7] * G[k]} to mean that the value where 0 is
-// prepended to the array of values to form {0, S[n] * G[k], ..., S[n+7]*G[k]}.
-//
-//   D[n..n+7]  += S[n..n+7] * G[1]
-//   D[n..n+8]  += {0, S[n..n+7] * G[0]}
-//   D[n..n+9]  += {0, 0, S[n..n+7] * G[1]}
-//
-// Now we can encode D[n..n+7] in a single Sk8h register called d0, and D[n+8..n+15] in a
-// register d8. In addition, S[0..n+7] becomes s0.
-//
-// The translation of the {0, S[n..n+7] * G[k]} is translated in the following way below.
-//
-// Sk8h v0 = s0*G[0]
-// Sk8h v1 = s0*G[1]
-// /* D[n..n+7]  += S[n..n+7] * G[1] */
-// d0 += v1;
-// /* D[n..n+8]  += {0, S[n..n+7] * G[0]} */
-// d0 += {_____, v0[0], v0[1], v0[2], v0[3], v0[4], v0[5], v0[6]}
-// d1 += {v0[7], _____, _____, _____, _____, _____, _____, _____}
-// /* D[n..n+9]  += {0, 0, S[n..n+7] * G[1]} */
-// d0 += {_____, _____, v1[0], v1[1], v1[2], v1[3], v1[4], v1[5]}
-// d1 += {v1[6], v1[7], _____, _____, _____, _____, _____, _____}
-// Where we rely on the compiler to generate efficient code for the {____, n, ....} notation.
-
-static SK_ALWAYS_INLINE void blur_x_radius_1(
-        const Sk8h& s0,
-        const Sk8h& g0, const Sk8h& g1, const Sk8h&, const Sk8h&, const Sk8h&,
-        Sk8h* d0, Sk8h* d8) {
-
-    auto v1 = s0.mulHi(g1);
-    auto v0 = s0.mulHi(g0);
-
-    // D[n..n+7]  += S[n..n+7] * G[1]
-    *d0 += v1;
-
-    //D[n..n+8]  += {0, S[n..n+7] * G[0]}
-    *d0 += Sk8h{_____, v0[0], v0[1], v0[2], v0[3], v0[4], v0[5], v0[6]};
-    *d8 += Sk8h{v0[7], _____, _____, _____, _____, _____, _____, _____};
-
-    // D[n..n+9]  += {0, 0, S[n..n+7] * G[1]}
-    *d0 += Sk8h{_____, _____, v1[0], v1[1], v1[2], v1[3], v1[4], v1[5]};
-    *d8 += Sk8h{v1[6], v1[7], _____, _____, _____, _____, _____, _____};
-
-}
-
-static SK_ALWAYS_INLINE void blur_x_radius_2(
-        const Sk8h& s0,
-        const Sk8h& g0, const Sk8h& g1, const Sk8h& g2, const Sk8h&, const Sk8h&,
-        Sk8h* d0, Sk8h* d8) {
-    auto v0 = s0.mulHi(g0);
-    auto v1 = s0.mulHi(g1);
-    auto v2 = s0.mulHi(g2);
-
-    // D[n..n+7]  += S[n..n+7] * G[2]
-    *d0 += v2;
-
-    // D[n..n+8]  += {0, S[n..n+7] * G[1]}
-    *d0 += Sk8h{_____, v1[0], v1[1], v1[2], v1[3], v1[4], v1[5], v1[6]};
-    *d8 += Sk8h{v1[7], _____, _____, _____, _____, _____, _____, _____};
-
-    // D[n..n+9]  += {0, 0, S[n..n+7] * G[0]}
-    *d0 += Sk8h{_____, _____, v0[0], v0[1], v0[2], v0[3], v0[4], v0[5]};
-    *d8 += Sk8h{v0[6], v0[7], _____, _____, _____, _____, _____, _____};
-
-    // D[n..n+10]  += {0, 0, 0, S[n..n+7] * G[1]}
-    *d0 += Sk8h{_____, _____, _____, v1[0], v1[1], v1[2], v1[3], v1[4]};
-    *d8 += Sk8h{v1[5], v1[6], v1[7], _____, _____, _____, _____, _____};
-
-    // D[n..n+11]  += {0, 0, 0, 0, S[n..n+7] * G[2]}
-    *d0 += Sk8h{_____, _____, _____, _____, v2[0], v2[1], v2[2], v2[3]};
-    *d8 += Sk8h{v2[4], v2[5], v2[6], v2[7], _____, _____, _____, _____};
-}
-
-static SK_ALWAYS_INLINE void blur_x_radius_3(
-        const Sk8h& s0,
-        const Sk8h& gauss0, const Sk8h& gauss1, const Sk8h& gauss2, const Sk8h& gauss3, const Sk8h&,
-        Sk8h* d0, Sk8h* d8) {
-    auto v0 = s0.mulHi(gauss0);
-    auto v1 = s0.mulHi(gauss1);
-    auto v2 = s0.mulHi(gauss2);
-    auto v3 = s0.mulHi(gauss3);
-
-    // D[n..n+7]  += S[n..n+7] * G[3]
-    *d0 += v3;
-
-    // D[n..n+8]  += {0, S[n..n+7] * G[2]}
-    *d0 += Sk8h{_____, v2[0], v2[1], v2[2], v2[3], v2[4], v2[5], v2[6]};
-    *d8 += Sk8h{v2[7], _____, _____, _____, _____, _____, _____, _____};
-
-    // D[n..n+9]  += {0, 0, S[n..n+7] * G[1]}
-    *d0 += Sk8h{_____, _____, v1[0], v1[1], v1[2], v1[3], v1[4], v1[5]};
-    *d8 += Sk8h{v1[6], v1[7], _____, _____, _____, _____, _____, _____};
-
-    // D[n..n+10]  += {0, 0, 0, S[n..n+7] * G[0]}
-    *d0 += Sk8h{_____, _____, _____, v0[0], v0[1], v0[2], v0[3], v0[4]};
-    *d8 += Sk8h{v0[5], v0[6], v0[7], _____, _____, _____, _____, _____};
-
-    // D[n..n+11]  += {0, 0, 0, 0, S[n..n+7] * G[1]}
-    *d0 += Sk8h{_____, _____, _____, _____, v1[0], v1[1], v1[2], v1[3]};
-    *d8 += Sk8h{v1[4], v1[5], v1[6], v1[7], _____, _____, _____, _____};
-
-    // D[n..n+12]  += {0, 0, 0, 0, 0, S[n..n+7] * G[2]}
-    *d0 += Sk8h{_____, _____, _____, _____, _____, v2[0], v2[1], v2[2]};
-    *d8 += Sk8h{v2[3], v2[4], v2[5], v2[6], v2[7], _____, _____, _____};
-
-    // D[n..n+13]  += {0, 0, 0, 0, 0, 0, S[n..n+7] * G[3]}
-    *d0 += Sk8h{_____, _____, _____, _____, _____, _____, v3[0], v3[1]};
-    *d8 += Sk8h{v3[2], v3[3], v3[4], v3[5], v3[6], v3[7], _____, _____};
-}
-
-static SK_ALWAYS_INLINE void blur_x_radius_4(
-        const Sk8h& s0,
-        const Sk8h& gauss0,
-        const Sk8h& gauss1,
-        const Sk8h& gauss2,
-        const Sk8h& gauss3,
-        const Sk8h& gauss4,
-        Sk8h* d0, Sk8h* d8) {
-    auto v0 = s0.mulHi(gauss0);
-    auto v1 = s0.mulHi(gauss1);
-    auto v2 = s0.mulHi(gauss2);
-    auto v3 = s0.mulHi(gauss3);
-    auto v4 = s0.mulHi(gauss4);
-
-    // D[n..n+7]  += S[n..n+7] * G[4]
-    *d0 += v4;
-
-    // D[n..n+8]  += {0, S[n..n+7] * G[3]}
-    *d0 += Sk8h{_____, v3[0], v3[1], v3[2], v3[3], v3[4], v3[5], v3[6]};
-    *d8 += Sk8h{v3[7], _____, _____, _____, _____, _____, _____, _____};
-
-    // D[n..n+9]  += {0, 0, S[n..n+7] * G[2]}
-    *d0 += Sk8h{_____, _____, v2[0], v2[1], v2[2], v2[3], v2[4], v2[5]};
-    *d8 += Sk8h{v2[6], v2[7], _____, _____, _____, _____, _____, _____};
-
-    // D[n..n+10]  += {0, 0, 0, S[n..n+7] * G[1]}
-    *d0 += Sk8h{_____, _____, _____, v1[0], v1[1], v1[2], v1[3], v1[4]};
-    *d8 += Sk8h{v1[5], v1[6], v1[7], _____, _____, _____, _____, _____};
-
-    // D[n..n+11]  += {0, 0, 0, 0, S[n..n+7] * G[0]}
-    *d0 += Sk8h{_____, _____, _____, _____, v0[0], v0[1], v0[2], v0[3]};
-    *d8 += Sk8h{v0[4], v0[5], v0[6], v0[7], _____, _____, _____, _____};
-
-    // D[n..n+12]  += {0, 0, 0, 0, 0, S[n..n+7] * G[1]}
-    *d0 += Sk8h{_____, _____, _____, _____, _____, v1[0], v1[1], v1[2]};
-    *d8 += Sk8h{v1[3], v1[4], v1[5], v1[6], v1[7], _____, _____, _____};
-
-    // D[n..n+13]  += {0, 0, 0, 0, 0, 0, S[n..n+7] * G[2]}
-    *d0 += Sk8h{_____, _____, _____, _____, _____, _____, v2[0], v2[1]};
-    *d8 += Sk8h{v2[2], v2[3], v2[4], v2[5], v2[6], v2[7], _____, _____};
-
-    // D[n..n+14]  += {0, 0, 0, 0, 0, 0, 0, S[n..n+7] * G[3]}
-    *d0 += Sk8h{_____, _____, _____, _____, _____, _____, _____, v3[0]};
-    *d8 += Sk8h{v3[1], v3[2], v3[3], v3[4], v3[5], v3[6], v3[7], _____};
-
-    // D[n..n+15]  += {0, 0, 0, 0, 0, 0, 0, 0, S[n..n+7] * G[4]}
-    *d8 += v4;
-}
-
-using BlurX = decltype(blur_x_radius_1);
-
-// BlurX will only be one of the functions blur_x_radius_(1|2|3|4).
-static SK_ALWAYS_INLINE void blur_row(
-        BlurX blur,
-        const Sk8h& g0, const Sk8h& g1, const Sk8h& g2, const Sk8h& g3, const Sk8h& g4,
-        const uint8_t* src, int srcW,
-              uint8_t* dst, int dstW) {
-    // Clear the buffer to handle summing wider than source.
-    Sk8h d0{kHalf}, d8{kHalf};
-
-    // Go by multiples of 8 in src.
-    int x = 0;
-    for (; x <= srcW - 8; x += 8) {
-        blur(load(src, 8), g0, g1, g2, g3, g4, &d0, &d8);
-
-        store(dst, d0, 8);
-
-        d0 = d8;
-        d8 = Sk8h{kHalf};
-
-        src += 8;
-        dst += 8;
-    }
-
-    // There are src values left, but the remainder of src values is not a multiple of 8.
-    int srcTail = srcW - x;
-    if (srcTail > 0) {
-
-        blur(load(src, srcTail), g0, g1, g2, g3, g4, &d0, &d8);
-
-        int dstTail = std::min(8, dstW - x);
-        store(dst, d0, dstTail);
-
-        d0 = d8;
-        dst += dstTail;
-        x += dstTail;
-    }
-
-    // There are dst mask values to complete.
-    int dstTail = dstW - x;
-    if (dstTail > 0) {
-        store(dst, d0, dstTail);
-    }
-}
-
-// BlurX will only be one of the functions blur_x_radius_(1|2|3|4).
-static SK_ALWAYS_INLINE void blur_x_rect(
-        BlurX blur,
-        uint16_t* gauss,
-        const uint8_t* src, size_t srcStride, int srcW,
-              uint8_t* dst, size_t dstStride, int dstW, int dstH) {
-
-    Sk8h g0{gauss[0]},
-         g1{gauss[1]},
-         g2{gauss[2]},
-         g3{gauss[3]},
-         g4{gauss[4]};
-
-    // Blur *ALL* the rows.
-    for (int y = 0; y < dstH; y++) {
-        blur_row(blur, g0, g1, g2, g3, g4, src, srcW, dst, dstW);
-        src += srcStride;
-        dst += dstStride;
-    }
-}
-
-SK_ATTRIBUTE(noinline) static void direct_blur_x(
-    int radius, uint16_t* gauss,
-    const uint8_t* src, size_t srcStride, int srcW,
-          uint8_t* dst, size_t dstStride, int dstW, int dstH) {
-
-    switch (radius) {
-        case 1:
-            blur_x_rect(blur_x_radius_1, gauss, src, srcStride, srcW, dst, dstStride, dstW, dstH);
-            break;
-
-        case 2:
-            blur_x_rect(blur_x_radius_2, gauss, src, srcStride, srcW, dst, dstStride, dstW, dstH);
-            break;
-
-        case 3:
-            blur_x_rect(blur_x_radius_3, gauss, src, srcStride, srcW, dst, dstStride, dstW, dstH);
-            break;
-
-        case 4:
-            blur_x_rect(blur_x_radius_4, gauss, src, srcStride, srcW, dst, dstStride, dstW, dstH);
-            break;
-
-        default:
-            SkASSERTF(false, "The radius %d is not handled\n", radius);
-    }
-}
-
-// The operations of the blur_y_radius_N functions work on a theme similar to the blur_x_radius_N
-// functions, but end up being simpler because there is no complicated shift of registers. We
-// start with the non-traditional form of the gaussian filter. In the following r is the value
-// when added generates the next value in the column.
-//
-//   D[n+0r] = S[n+0r]*G[1]
-//           + S[n+1r]*G[0]
-//           + S[n+2r]*G[1]
-//
-// Expanding out in a way similar to blur_x_radius_N for specific values of n.
-//
-//   D[n+0r] = S[n-2r]*G[1] + S[n-1r]*G[0] + S[n+0r]*G[1]
-//   D[n+1r] = S[n-1r]*G[1] + S[n+0r]*G[0] + S[n+1r]*G[1]
-//   D[n+2r] = S[n+0r]*G[1] + S[n+1r]*G[0] + S[n+2r]*G[1]
-//
-// We can see that S[n+0r] is in all three D[] equations, but is only multiplied twice. Now we
-// can look at the calculation form the point of view of a source value.
-//
-//   Given S[n+0r]:
-//   D[n+0r] += S[n+0r]*G[1];
-//   /* D[n+0r] is done and can be stored now. */
-//   D[n+1r] += S[n+0r]*G[0];
-//   D[n+2r]  = S[n+0r]*G[1];
-//
-// Remember, by induction, that D[n+0r] == S[n-2r]*G[1] + S[n-1r]*G[0] before adding in
-// S[n+0r]*G[1]. So, after the addition D[n+0r] has finished calculation and can be stored. Also,
-// notice that D[n+2r] is receiving its first value from S[n+0r]*G[1] and is not added in. Notice
-// how values flow in the following two iterations in source.
-//
-//   D[n+0r] += S[n+0r]*G[1]
-//   D[n+1r] += S[n+0r]*G[0]
-//   D[n+2r]  = S[n+0r]*G[1]
-//   /* ------- */
-//   D[n+1r] += S[n+1r]*G[1]
-//   D[n+2r] += S[n+1r]*G[0]
-//   D[n+3r]  = S[n+1r]*G[1]
-//
-// Instead of using memory we can introduce temporaries d01 and d12. The update step changes
-// to the following.
-//
-//   answer = d01 + S[n+0r]*G[1]
-//   d01    = d12 + S[n+0r]*G[0]
-//   d12    =       S[n+0r]*G[1]
-//   return answer
-//
-// Finally, this can be ganged into SIMD style.
-//   answer[0..7] = d01[0..7] + S[n+0r..n+0r+7]*G[1]
-//   d01[0..7]    = d12[0..7] + S[n+0r..n+0r+7]*G[0]
-//   d12[0..7]    =             S[n+0r..n+0r+7]*G[1]
-//   return answer[0..7]
-static SK_ALWAYS_INLINE Sk8h blur_y_radius_1(
-        const Sk8h& s0,
-        const Sk8h& g0, const Sk8h& g1, const Sk8h&, const Sk8h&, const Sk8h&,
-        Sk8h* d01, Sk8h* d12, Sk8h*, Sk8h*, Sk8h*, Sk8h*, Sk8h*, Sk8h*) {
-    auto v0 = s0.mulHi(g0);
-    auto v1 = s0.mulHi(g1);
-
-    Sk8h answer = *d01 + v1;
-           *d01 = *d12 + v0;
-           *d12 =        v1 + kHalf;
-
-    return answer;
-}
-
-static SK_ALWAYS_INLINE Sk8h blur_y_radius_2(
-        const Sk8h& s0,
-        const Sk8h& g0, const Sk8h& g1, const Sk8h& g2, const Sk8h&, const Sk8h&,
-        Sk8h* d01, Sk8h* d12, Sk8h* d23, Sk8h* d34, Sk8h*, Sk8h*, Sk8h*, Sk8h*) {
-    auto v0 = s0.mulHi(g0);
-    auto v1 = s0.mulHi(g1);
-    auto v2 = s0.mulHi(g2);
-
-    Sk8h answer = *d01 + v2;
-           *d01 = *d12 + v1;
-           *d12 = *d23 + v0;
-           *d23 = *d34 + v1;
-           *d34 =        v2 + kHalf;
-
-    return answer;
-}
-
-static SK_ALWAYS_INLINE Sk8h blur_y_radius_3(
-        const Sk8h& s0,
-        const Sk8h& g0, const Sk8h& g1, const Sk8h& g2, const Sk8h& g3, const Sk8h&,
-        Sk8h* d01, Sk8h* d12, Sk8h* d23, Sk8h* d34, Sk8h* d45, Sk8h* d56, Sk8h*, Sk8h*) {
-    auto v0 = s0.mulHi(g0);
-    auto v1 = s0.mulHi(g1);
-    auto v2 = s0.mulHi(g2);
-    auto v3 = s0.mulHi(g3);
-
-    Sk8h answer = *d01 + v3;
-           *d01 = *d12 + v2;
-           *d12 = *d23 + v1;
-           *d23 = *d34 + v0;
-           *d34 = *d45 + v1;
-           *d45 = *d56 + v2;
-           *d56 =        v3 + kHalf;
-
-    return answer;
-}
-
-static SK_ALWAYS_INLINE Sk8h blur_y_radius_4(
-    const Sk8h& s0,
-    const Sk8h& g0, const Sk8h& g1, const Sk8h& g2, const Sk8h& g3, const Sk8h& g4,
-    Sk8h* d01, Sk8h* d12, Sk8h* d23, Sk8h* d34, Sk8h* d45, Sk8h* d56, Sk8h* d67, Sk8h* d78) {
-    auto v0 = s0.mulHi(g0);
-    auto v1 = s0.mulHi(g1);
-    auto v2 = s0.mulHi(g2);
-    auto v3 = s0.mulHi(g3);
-    auto v4 = s0.mulHi(g4);
-
-    Sk8h answer = *d01 + v4;
-           *d01 = *d12 + v3;
-           *d12 = *d23 + v2;
-           *d23 = *d34 + v1;
-           *d34 = *d45 + v0;
-           *d45 = *d56 + v1;
-           *d56 = *d67 + v2;
-           *d67 = *d78 + v3;
-           *d78 =        v4 + kHalf;
-
-    return answer;
-}
-
-using BlurY = decltype(blur_y_radius_1);
-
-// BlurY will be one of blur_y_radius_(1|2|3|4).
-static SK_ALWAYS_INLINE void blur_column(
-        BlurY blur, int radius, int width,
-        const Sk8h& g0, const Sk8h& g1, const Sk8h& g2, const Sk8h& g3, const Sk8h& g4,
-        const uint8_t* src, size_t srcStride, int srcH,
-        uint8_t* dst, size_t dstStride) {
-    Sk8h d01{kHalf}, d12{kHalf}, d23{kHalf}, d34{kHalf},
-         d45{kHalf}, d56{kHalf}, d67{kHalf}, d78{kHalf};
-
-    auto flush = [&](uint8_t* to, const Sk8h& v0, const Sk8h& v1) {
-        store(to, v0, width);
-        to += dstStride;
-        store(to, v1, width);
-        return to + dstStride;
-    };
-
-    for (int y = 0; y < srcH; y += 1) {
-        auto s = load(src, width);
-        auto b = blur(s,
-                      g0, g1, g2, g3, g4,
-                      &d01, &d12, &d23, &d34, &d45, &d56, &d67, &d78);
-        store(dst, b, width);
-        src += srcStride;
-        dst += dstStride;
-    }
-
-    if (radius >= 1) {
-        dst = flush(dst, d01, d12);
-    }
-    if (radius >= 2) {
-        dst = flush(dst, d23, d34);
-    }
-    if (radius >= 3) {
-        dst = flush(dst, d45, d56);
-    }
-    if (radius >= 4) {
-              flush(dst, d67, d78);
-    }
-}
-
-// BlurY will be one of blur_y_radius_(1|2|3|4).
-static SK_ALWAYS_INLINE void blur_y_rect(
-        BlurY blur, int radius, uint16_t *gauss,
-        const uint8_t *src, size_t srcStride, int srcW, int srcH,
-        uint8_t *dst, size_t dstStride) {
-
-    Sk8h g0{gauss[0]},
-         g1{gauss[1]},
-         g2{gauss[2]},
-         g3{gauss[3]},
-         g4{gauss[4]};
-
-    int x = 0;
-    for (; x <= srcW - 8; x += 8) {
-        blur_column(blur, radius, 8,
-                    g0, g1, g2, g3, g4,
-                    src, srcStride, srcH,
-                    dst, dstStride);
-        src += 8;
-        dst += 8;
-    }
-
-    int xTail = srcW - x;
-    if (xTail > 0) {
-        blur_column(blur, radius, xTail,
-                    g0, g1, g2, g3, g4,
-                    src, srcStride, srcH,
-                    dst, dstStride);
-    }
-}
-
-SK_ATTRIBUTE(noinline) static void direct_blur_y(
-        int radius, uint16_t* gauss,
-        const uint8_t* src, size_t srcStride, int srcW, int srcH,
-              uint8_t* dst, size_t dstStride) {
-
-    switch (radius) {
-        case 1:
-            blur_y_rect(blur_y_radius_1, 1, gauss,
-                        src, srcStride, srcW, srcH,
-                        dst, dstStride);
-            break;
-
-        case 2:
-            blur_y_rect(blur_y_radius_2, 2, gauss,
-                        src, srcStride, srcW, srcH,
-                        dst, dstStride);
-            break;
-
-        case 3:
-            blur_y_rect(blur_y_radius_3, 3, gauss,
-                        src, srcStride, srcW, srcH,
-                        dst, dstStride);
-            break;
-
-        case 4:
-            blur_y_rect(blur_y_radius_4, 4, gauss,
-                        src, srcStride, srcW, srcH,
-                        dst, dstStride);
-            break;
-
-        default:
-            SkASSERTF(false, "The radius %d is not handled\n", radius);
-    }
-}
-
-static SkIPoint small_blur(double sigmaX, double sigmaY, const SkMask& src, SkMask* dst) {
-    SkASSERT(0 <= sigmaX && sigmaX < 2);
-    SkASSERT(0 <= sigmaY && sigmaY < 2);
-
-    SkGaussFilter filterX{sigmaX, SkGaussFilter::Type::Bessel},
-                  filterY{sigmaY, SkGaussFilter::Type::Bessel};
-
-    int radiusX = filterX.radius(),
-        radiusY = filterY.radius();
-
-    SkASSERT(radiusX <= 4 && radiusY <= 4);
-
-    auto prepareGauss = [](const SkGaussFilter& filter, uint16_t* factors) {
-        int i = 0;
-        for (double d : filter) {
-            factors[i++] = static_cast<uint16_t>(round(d * (1 << 16)));
-        }
-    };
-
-    uint16_t gaussFactorsX[5],
-             gaussFactorsY[5];
-
-    prepareGauss(filterX, gaussFactorsX);
-    prepareGauss(filterY, gaussFactorsY);
-
-    *dst = prepare_destination(radiusX, radiusY, src);
-    if (src.fImage == nullptr) {
-        return {SkTo<int32_t>(radiusX), SkTo<int32_t>(radiusY)};
-    }
-    if (dst->fImage == nullptr) {
-        dst->fBounds.setEmpty();
-        return {0, 0};
-    }
-
-    int srcW = src.fBounds.width(),
-        srcH = src.fBounds.height();
-
-    int dstW = dst->fBounds.width(),
-        dstH = dst->fBounds.height();
-
-    size_t srcStride = src.fRowBytes,
-           dstStride = dst->fRowBytes;
-
-    //TODO: handle bluring in only one direction.
-
-    // Blur vertically and copy to destination.
-    direct_blur_y(radiusY, gaussFactorsY,
-                  src.fImage,  srcStride, srcW, srcH,
-                  dst->fImage + radiusX, dstStride);
-
-    // Blur horizontally in place.
-    direct_blur_x(radiusX, gaussFactorsX,
-                  dst->fImage + radiusX,  dstStride, srcW,
-                  dst->fImage,            dstStride, dstW, dstH);
-
-    return {radiusX, radiusY};
-}
-#endif  // SK_USE_LEGACY_INTERP_BLUR
-
 SkIPoint SkMaskBlurFilter::blur(const SkMask& src, SkMask* dst) const {
 
-    #if !defined(SK_USE_LEGACY_INTERP_BLUR)
-        if (fSigmaW < 2.0 && fSigmaH < 2.0) {
-            return small_blur(fSigmaW, fSigmaH, src, dst);
-        }
-    #endif
-
     // 1024 is a place holder guess until more analysis can be done.
     SkSTArenaAlloc<1024> alloc;
 
@@ -1260,6 +623,7 @@ SkIPoint SkMaskBlurFilter::blur(const SkMask& src, SkMask* dst) const {
                         tmpStart, tmpW, tmpStart + tmpW * tmpH);
         }
 
+
         // Blur vertically (scan in memory order because of the transposition),
         // and transpose back to the original orientation.
         auto scanH = planH->makeBlurScan(&alloc, tmpW, buffer);
@@ -1301,7 +665,7 @@ SkIPoint SkMaskBlurFilter::blur(const SkMask& src, SkMask* dst) const {
         for (size_t x = 0; x < srcW; x++) {
             auto srcStart = &src.fImage[x];
             auto dstStart = &dst->fImage[x];
-            scanH->blur(srcStart, src.fRowBytes,  srcEnd,
+            scanH->blur(srcStart, src.fRowBytes, srcEnd,
                         dstStart, dst->fRowBytes, dstEnd);
         }
     } else {
@@ -1314,3 +678,5 @@ SkIPoint SkMaskBlurFilter::blur(const SkMask& src, SkMask* dst) const {
 
     return {SkTo<int32_t>(borderW), SkTo<int32_t>(borderH)};
 }
+
+