Revert of SkPx: new approach to fixed-point SIMD (patchset #12 id:220001 of https://codereview.chromium.org/1317233005/ )

Reason for revert:
master-skia unhappy:
https://android-build.storage.googleapis.com/builds/git_master-skia-linux-volantis-userdebug/2404853/e6c439e806fb0bd0f872a3d7a5cf0637d4ad11bfaa89e9bc18b651dc65f0a36b/logs/build_error.log?GoogleAccessId=701025073339-mqn0q2nvir9iurm6q5d00tdv7blbgvjr%40developer.gserviceaccount.com&Signature=WOqQO7xHkv83SmC4h5tNUIp%2BREaYULqK11hNTWlhj1XXo0NAOQd7GNSIHl775uRRZpBw2LkHeb2Ups3LsgRPrldqymposFtDa%2BUEW0Jv2NWAr%2F1Cqt6lwWsfknvJLN9NiEGfpCCye3Q%2FEYx9bU1ozMBG6h2DRHJUMRS%2FjstkJg0%3D&Expires=1446838937

Original issue's description:
> SkPx: new approach to fixed-point SIMD
>
> SkPx is like Sk4px, except each platform implementation of SkPx can declare
> a different sweet spot of N pixels, with extra loads and stores to handle the
> ragged edge of 0<n<N pixels.
>
> In this case, _sse's sweet spot remains 4 pixels.   _neon jumps up to 8 so
> we can now use NEON's transposing loads and stores, and _none is just 1.
> This makes operations involving alpha considerably more efficient on NEON,
> as alpha is its own distinct 8x8 bit plane that's easy to toss around.
>
> This incorporates a few other improvements I've been wanting:
>   - no requirement that we're dealing with SkPMColor.  SkColor works too.
>   - no anonymous namespace hack to differentiate implementations.
>
> Codegen and perf look good on Clang/x86-64 and GCC/ARMv7.
> The NEON code looks very similar to the old NEON code, as intended.
> No .skp or GM diffs on my laptop.  Don't expect any.
>
> I intend this to replace Sk4px.  Plan after landing:
>   - port SkXfermode_opts.h
>   - port Color32 in SkBlitRow_D32.cpp (and move to SkBlitRow_opts.h like other
>     SkOpts code)
>   - delete all Sk4px-related code
>   - clean up evolutionary dead ends in SkNx (Sk16b, Sk16h, Sk4i, Sk4d, etc.)
>     leaving Sk2f, Sk4f (and Sk2s, Sk4s).
>   - find a machine with AVX2 to work on, write SkPx_avx2.h handling 8 pixels
>     at a time.
>
> In the end we'll have Sk4f for float pixels, SkPx for fixed-point pixels.
>
> BUG=skia:4117
>
> Committed: https://skia.googlesource.com/skia/+/82c93b45ed6ac0b628adb8375389c202d1f586f9
>
> CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot;client.skia.compile:Build-Mac10.8-Clang-Arm7-Debug-Android-Trybot
>
> Committed: https://skia.googlesource.com/skia/+/a7627dc5cc2bf5d9a95d883d20c40d477ecadadf

TBR=msarett@google.com,mtklein@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:4117

Review URL: https://codereview.chromium.org/1409843005

1 files changed, 173 insertions, 40 deletions

diff --git a/src/opts/SkBlitMask_opts.h b/src/opts/SkBlitMask_opts.h
index f4d7e7973f..2f4fe6ffb8 100644
--- a/src/opts/SkBlitMask_opts.h
+++ b/src/opts/SkBlitMask_opts.h
@@ -9,62 +9,195 @@
 #define SkBlitMask_opts_DEFINED
 
 #include "Sk4px.h"
-#include "SkPx.h"
 
 namespace SK_OPTS_NS {
 
-template <typename Fn>
-static void blit_mask_d32_a8(const Fn& fn, SkPMColor* dst, size_t dstRB,
-                                           const SkAlpha* mask, size_t maskRB,
-                                           int w, int h) {
-    while (h --> 0) {
-        int n = w;
-        while (n >= SkPx::N) {
-            fn(SkPx::Load(dst), SkPx::Alpha::Load(mask)).store(dst);
-            dst += SkPx::N; mask += SkPx::N; n -= SkPx::N;
+#if defined(SK_ARM_HAS_NEON)
+    // The Sk4px versions below will work fine with NEON, but we have had many indications
+    // that it doesn't perform as well as this NEON-specific code.  TODO(mtklein): why?
+    #include "SkColor_opts_neon.h"
+
+    template <bool isColor>
+    static void D32_A8_Opaque_Color_neon(void* SK_RESTRICT dst, size_t dstRB,
+                                         const void* SK_RESTRICT maskPtr, size_t maskRB,
+                                         SkColor color, int width, int height) {
+        SkPMColor pmc = SkPreMultiplyColor(color);
+        SkPMColor* SK_RESTRICT device = (SkPMColor*)dst;
+        const uint8_t* SK_RESTRICT mask = (const uint8_t*)maskPtr;
+        uint8x8x4_t vpmc;
+
+        maskRB -= width;
+        dstRB -= (width << 2);
+
+        if (width >= 8) {
+            vpmc.val[NEON_A] = vdup_n_u8(SkGetPackedA32(pmc));
+            vpmc.val[NEON_R] = vdup_n_u8(SkGetPackedR32(pmc));
+            vpmc.val[NEON_G] = vdup_n_u8(SkGetPackedG32(pmc));
+            vpmc.val[NEON_B] = vdup_n_u8(SkGetPackedB32(pmc));
         }
-        if (n > 0) {
-            fn(SkPx::Load(dst, n), SkPx::Alpha::Load(mask, n)).store(dst, n);
-            dst += n; mask += n;
+        do {
+            int w = width;
+            while (w >= 8) {
+                uint8x8_t vmask = vld1_u8(mask);
+                uint16x8_t vscale, vmask256 = SkAlpha255To256_neon8(vmask);
+                if (isColor) {
+                    vscale = vsubw_u8(vdupq_n_u16(256),
+                            SkAlphaMul_neon8(vpmc.val[NEON_A], vmask256));
+                } else {
+                    vscale = vsubw_u8(vdupq_n_u16(256), vmask);
+                }
+                uint8x8x4_t vdev = vld4_u8((uint8_t*)device);
+
+                vdev.val[NEON_A] =   SkAlphaMul_neon8(vpmc.val[NEON_A], vmask256)
+                    + SkAlphaMul_neon8(vdev.val[NEON_A], vscale);
+                vdev.val[NEON_R] =   SkAlphaMul_neon8(vpmc.val[NEON_R], vmask256)
+                    + SkAlphaMul_neon8(vdev.val[NEON_R], vscale);
+                vdev.val[NEON_G] =   SkAlphaMul_neon8(vpmc.val[NEON_G], vmask256)
+                    + SkAlphaMul_neon8(vdev.val[NEON_G], vscale);
+                vdev.val[NEON_B] =   SkAlphaMul_neon8(vpmc.val[NEON_B], vmask256)
+                    + SkAlphaMul_neon8(vdev.val[NEON_B], vscale);
+
+                vst4_u8((uint8_t*)device, vdev);
+
+                mask += 8;
+                device += 8;
+                w -= 8;
+            }
+
+            while (w--) {
+                unsigned aa = *mask++;
+                if (isColor) {
+                    *device = SkBlendARGB32(pmc, *device, aa);
+                } else {
+                    *device = SkAlphaMulQ(pmc, SkAlpha255To256(aa))
+                        + SkAlphaMulQ(*device, SkAlpha255To256(255 - aa));
+                }
+                device += 1;
+            };
+
+            device = (uint32_t*)((char*)device + dstRB);
+            mask += maskRB;
+
+        } while (--height != 0);
+    }
+
+    static void blit_mask_d32_a8_general(SkPMColor* dst, size_t dstRB,
+                                         const SkAlpha* mask, size_t maskRB,
+                                         SkColor color, int w, int h) {
+        D32_A8_Opaque_Color_neon<true>(dst, dstRB, mask, maskRB, color, w, h);
+    }
+
+    // As above, but made slightly simpler by requiring that color is opaque.
+    static void blit_mask_d32_a8_opaque(SkPMColor* dst, size_t dstRB,
+                                        const SkAlpha* mask, size_t maskRB,
+                                        SkColor color, int w, int h) {
+        D32_A8_Opaque_Color_neon<false>(dst, dstRB, mask, maskRB, color, w, h);
+    }
+
+    // Same as _opaque, but assumes color == SK_ColorBLACK, a very common and even simpler case.
+    static void blit_mask_d32_a8_black(SkPMColor* dst, size_t dstRB,
+                                       const SkAlpha* maskPtr, size_t maskRB,
+                                       int width, int height) {
+        SkPMColor* SK_RESTRICT device = (SkPMColor*)dst;
+        const uint8_t* SK_RESTRICT mask = (const uint8_t*)maskPtr;
+
+        maskRB -= width;
+        dstRB -= (width << 2);
+        do {
+            int w = width;
+            while (w >= 8) {
+                uint8x8_t vmask = vld1_u8(mask);
+                uint16x8_t vscale = vsubw_u8(vdupq_n_u16(256), vmask);
+                uint8x8x4_t vdevice = vld4_u8((uint8_t*)device);
+
+                vdevice = SkAlphaMulQ_neon8(vdevice, vscale);
+                vdevice.val[NEON_A] += vmask;
+
+                vst4_u8((uint8_t*)device, vdevice);
+
+                mask += 8;
+                device += 8;
+                w -= 8;
+            }
+            while (w-- > 0) {
+                unsigned aa = *mask++;
+                *device = (aa << SK_A32_SHIFT)
+                            + SkAlphaMulQ(*device, SkAlpha255To256(255 - aa));
+                device += 1;
+            };
+            device = (uint32_t*)((char*)device + dstRB);
+            mask += maskRB;
+        } while (--height != 0);
+    }
+
+#else
+    static void blit_mask_d32_a8_general(SkPMColor* dst, size_t dstRB,
+                                         const SkAlpha* mask, size_t maskRB,
+                                         SkColor color, int w, int h) {
+        auto s = Sk4px::DupPMColor(SkPreMultiplyColor(color));
+        auto fn = [&](const Sk4px& d, const Sk4px& aa) {
+            //  = (s + d(1-sa))aa + d(1-aa)
+            //  = s*aa + d(1-sa*aa)
+            auto left  = s.approxMulDiv255(aa),
+                 right = d.approxMulDiv255(left.alphas().inv());
+            return left + right;  // This does not overflow (exhaustively checked).
+        };
+        while (h --> 0) {
+            Sk4px::MapDstAlpha(w, dst, mask, fn);
+            dst  +=  dstRB / sizeof(*dst);
+            mask += maskRB / sizeof(*mask);
         }
-        dst  +=  dstRB / sizeof(*dst)  - w;
-        mask += maskRB / sizeof(*mask) - w;
     }
-}
 
-static void blit_mask_d32_a8(SkPMColor* dst, size_t dstRB,
-                             const SkAlpha* mask, size_t maskRB,
-                             SkColor color, int w, int h) {
-    auto s = SkPx::Dup(SkPreMultiplyColor(color));
+    // As above, but made slightly simpler by requiring that color is opaque.
+    static void blit_mask_d32_a8_opaque(SkPMColor* dst, size_t dstRB,
+                                        const SkAlpha* mask, size_t maskRB,
+                                        SkColor color, int w, int h) {
+        SkASSERT(SkColorGetA(color) == 0xFF);
+        auto s = Sk4px::DupPMColor(SkPreMultiplyColor(color));
+        auto fn = [&](const Sk4px& d, const Sk4px& aa) {
+            //  = (s + d(1-sa))aa + d(1-aa)
+            //  = s*aa + d(1-sa*aa)
+            //   ~~~>
+            //  = s*aa + d(1-aa)
+            return s.approxMulDiv255(aa) + d.approxMulDiv255(aa.inv());
+        };
+        while (h --> 0) {
+            Sk4px::MapDstAlpha(w, dst, mask, fn);
+            dst  +=  dstRB / sizeof(*dst);
+            mask += maskRB / sizeof(*mask);
+        }
+    }
 
-    if (color == SK_ColorBLACK) {
-        auto fn = [](const SkPx& d, const SkPx::Alpha& aa) {
+    // Same as _opaque, but assumes color == SK_ColorBLACK, a very common and even simpler case.
+    static void blit_mask_d32_a8_black(SkPMColor* dst, size_t dstRB,
+                                       const SkAlpha* mask, size_t maskRB,
+                                       int w, int h) {
+        auto fn = [](const Sk4px& d, const Sk4px& aa) {
             //   = (s + d(1-sa))aa + d(1-aa)
             //   = s*aa + d(1-sa*aa)
             //   ~~~>
             // a = 1*aa + d(1-1*aa) = aa + d(1-aa)
             // c = 0*aa + d(1-1*aa) =      d(1-aa)
-            return d.approxMulDiv255(aa.inv()).addAlpha(aa);
+            return aa.zeroColors() + d.approxMulDiv255(aa.inv());
         };
-        blit_mask_d32_a8(fn, dst, dstRB, mask, maskRB, w, h);
+        while (h --> 0) {
+            Sk4px::MapDstAlpha(w, dst, mask, fn);
+            dst  +=  dstRB / sizeof(*dst);
+            mask += maskRB / sizeof(*mask);
+        }
+    }
+#endif
+
+static void blit_mask_d32_a8(SkPMColor* dst, size_t dstRB,
+                             const SkAlpha* mask, size_t maskRB,
+                             SkColor color, int w, int h) {
+    if (color == SK_ColorBLACK) {
+        blit_mask_d32_a8_black(dst, dstRB, mask, maskRB, w, h);
     } else if (SkColorGetA(color) == 0xFF) {
-        auto fn = [&](const SkPx& d, const SkPx::Alpha& aa) {
-            //  = (s + d(1-sa))aa + d(1-aa)
-            //  = s*aa + d(1-sa*aa)
-            //   ~~~>
-            //  = s*aa + d(1-aa)
-            return s.approxMulDiv255(aa) + d.approxMulDiv255(aa.inv());
-        };
-        blit_mask_d32_a8(fn, dst, dstRB, mask, maskRB, w, h);
+        blit_mask_d32_a8_opaque(dst, dstRB, mask, maskRB, color, w, h);
     } else {
-        auto fn = [&](const SkPx& d, const SkPx::Alpha& aa) {
-            //  = (s + d(1-sa))aa + d(1-aa)
-            //  = s*aa + d(1-sa*aa)
-            auto left  = s.approxMulDiv255(aa),
-                 right = d.approxMulDiv255(left.alpha().inv());
-            return left + right;  // This does not overflow (exhaustively checked).
-        };
-        blit_mask_d32_a8(fn, dst, dstRB, mask, maskRB, w, h);
+        blit_mask_d32_a8_general(dst, dstRB, mask, maskRB, color, w, h);
     }
 }