Revert of Mike's radial gradient CL with better float -> int. (patchset #7 id:120001 of https://codereview.chromium.org/1109643002/)

Reason for revert:
compile failures.

Original issue's description:
> Mike's radial gradient CL with better float -> int.
>
> patch from issue 1072303005 at patchset 40001 (http://crrev.com/1072303005#ps40001)
>
> This looks quite launchable.  radial_gradient3, min of 100 samples:
>   N5:  985µs -> 946µs
>   MBP: 395µs -> 279µs
>
> On my MBP, most of the meat looks like it's now in reading the cache and writing to dst one color at a time.  Is that something we could do in float math rather than with a lookup table?
>
> BUG=skia:
>
> CQ_EXTRA_TRYBOTS=client.skia.android:Test-Android-GCC-Nexus5-CPU-NEON-Arm7-Debug-Trybot,Test-Android-GCC-Nexus9-CPU-Denver-Arm64-Debug-Trybot
>
> Committed: https://skia.googlesource.com/skia/+/abf6c5cf95e921fae59efb487480e5b5081cf0ec

TBR=reed@google.com,robertphillips@google.com,mtklein@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1109883003

1 files changed, 7 insertions, 80 deletions

diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index bf3c821f6b..b25a8750a2 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -8,7 +8,6 @@
 
 #include "SkRadialGradient.h"
 #include "SkRadialGradient_Table.h"
-#include "SkNx.h"
 
 #define kSQRT_TABLE_BITS    11
 #define kSQRT_TABLE_SIZE    (1 << kSQRT_TABLE_BITS)
@@ -271,16 +270,13 @@ void SkRadialGradient::flatten(SkWriteBuffer& buffer) const {
 namespace {
 
 inline bool radial_completely_pinned(int fx, int dx, int fy, int dy) {
-    // fast, overly-conservative test: checks unit square instead of unit circle
-    bool xClamped = (fx >= SK_FixedHalf && dx >= 0) || (fx <= -SK_FixedHalf && dx <= 0);
-    bool yClamped = (fy >= SK_FixedHalf && dy >= 0) || (fy <= -SK_FixedHalf && dy <= 0);
-    return xClamped || yClamped;
-}
+    // fast, overly-conservative test: checks unit square instead
+    // of unit circle
+    bool xClamped = (fx >= SK_FixedHalf && dx >= 0) ||
+                    (fx <= -SK_FixedHalf && dx <= 0);
+    bool yClamped = (fy >= SK_FixedHalf && dy >= 0) ||
+                    (fy <= -SK_FixedHalf && dy <= 0);
 
-inline bool radial_completely_pinned(SkScalar fx, SkScalar dx, SkScalar fy, SkScalar dy) {
-    // fast, overly-conservative test: checks unit square instead of unit circle
-    bool xClamped = (fx >= 1 && dx >= 0) || (fx <= -1 && dx <= 0);
-    bool yClamped = (fy >= 1 && dy >= 0) || (fy <= -1 && dy <= 0);
     return xClamped || yClamped;
 }
 
@@ -377,70 +373,6 @@ void shadeSpan_radial_clamp(SkScalar sfx, SkScalar sdx,
     }
 }
 
-// TODO: can we get away with 0th approximatino of inverse-sqrt (i.e. faster than rsqrt)?
-//       seems like ~10bits is more than enough for our use, since we want a byte-index
-static inline Sk4f fast_sqrt(const Sk4f& R) {
-    return R * R.rsqrt();
-}
-
-static inline Sk4f sum_squares(const Sk4f& a, const Sk4f& b) {
-    return a * a + b * b;
-}
-
-void shadeSpan_radial_clamp2(SkScalar sfx, SkScalar sdx, SkScalar sfy, SkScalar sdy,
-                             SkPMColor* SK_RESTRICT dstC, const SkPMColor* SK_RESTRICT cache,
-                             int count, int toggle) {
-    if (radial_completely_pinned(sfx, sdx, sfy, sdy)) {
-        unsigned fi = SkGradientShaderBase::kCache32Count - 1;
-        sk_memset32_dither(dstC,
-                           cache[toggle + fi],
-                           cache[next_dither_toggle(toggle) + fi],
-                           count);
-    } else {
-        const Sk4f max(255);
-        const float scale = 255;
-        sfx *= scale;
-        sfy *= scale;
-        sdx *= scale;
-        sdy *= scale;
-        const Sk4f fx4(sfx, sfx + sdx, sfx + 2*sdx, sfx + 3*sdx);
-        const Sk4f fy4(sfy, sfy + sdy, sfy + 2*sdy, sfy + 3*sdy);
-        const Sk4f dx4(sdx * 4);
-        const Sk4f dy4(sdy * 4);
-
-        Sk4f tmpxy = fx4 * dx4 + fy4 * dy4;
-        Sk4f tmpdxdy = sum_squares(dx4, dy4);
-        Sk4f R = sum_squares(fx4, fy4);
-        Sk4f dR = tmpxy + tmpxy + tmpdxdy;
-        const Sk4f ddR = tmpdxdy + tmpdxdy;
-
-        for (int i = 0; i < (count >> 2); ++i) {
-            Sk4f dist = Sk4f::Min(fast_sqrt(R), max);
-            R += dR;
-            dR += ddR;
-
-            int fi[4];
-            dist.castTrunc().store(fi);
-
-            for (int i = 0; i < 4; i++) {
-                *dstC++ = cache[toggle + fi[i]];
-                toggle = next_dither_toggle(toggle);
-            }
-        }
-        count &= 3;
-        if (count) {
-            Sk4f dist = Sk4f::Min(fast_sqrt(R), max);
-
-            int fi[4];
-            dist.castTrunc().store(fi);
-            for (int i = 0; i < count; i++) {
-                *dstC++ = cache[toggle + fi[i]];
-                toggle = next_dither_toggle(toggle);
-            }
-        }
-    }
-}
-
 // Unrolling this loop doesn't seem to help (when float); we're stalling to
 // get the results of the sqrt (?), and don't have enough extra registers to
 // have many in flight.
@@ -475,11 +407,6 @@ void shadeSpan_radial_repeat(SkScalar fx, SkScalar dx, SkScalar fy, SkScalar dy,
 
 void SkRadialGradient::RadialGradientContext::shadeSpan(int x, int y,
                                                         SkPMColor* SK_RESTRICT dstC, int count) {
-#ifdef SK_SUPPORT_LEGACY_RADIAL_GRADIENT_SQRT
-    const bool use_new_proc = false;
-#else
-    const bool use_new_proc = true;
-#endif
     SkASSERT(count > 0);
 
     const SkRadialGradient& radialGradient = static_cast<const SkRadialGradient&>(fShader);
@@ -508,7 +435,7 @@ void SkRadialGradient::RadialGradientContext::shadeSpan(int x, int y,
 
         RadialShadeProc shadeProc = shadeSpan_radial_repeat;
         if (SkShader::kClamp_TileMode == radialGradient.fTileMode) {
-            shadeProc = use_new_proc ? shadeSpan_radial_clamp2 : shadeSpan_radial_clamp;
+            shadeProc = shadeSpan_radial_clamp;
         } else if (SkShader::kMirror_TileMode == radialGradient.fTileMode) {
             shadeProc = shadeSpan_radial_mirror;
         } else {