Correct sRGB <-> linear everywhere.

tests/SkBlend_optsTest.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <string>
 #include <tuple>
 #include <vector>
 #include "Resources.h"
 #include "SkCpu.h"
 #include "SkImage.h"
 #include "SkImage_Base.h"
 #include "SkOpts.h"
 #include "SkPM4fPriv.h"
 #include "SkNx.h"
 #include "Test.h"
 
 typedef void (*Blender)(uint32_t* dst, const uint32_t* const srcStart, int ndst, const int nsrc);
 
+static inline void srcover_srgb_srgb_1(uint32_t* dst, uint32_t src) {
+    // TODO: switch back to pure brute force if we can get Sk4f_toS32(Sk4f_fromS32(...)) to
+    // roundtrip perfectly.
+    if (src >= 0xFF000000) {
+        *dst = src;
+        return;
+    }
+    auto d = Sk4f_fromS32(*dst),
+         s = Sk4f_fromS32( src);
+    *dst = Sk4f_toS32(s + d * (1.0f - s[3]));
+}
+
 static void brute_force_srcover_srgb_srgb(
     uint32_t* dst, const uint32_t* const src, int ndst, const int nsrc) {
     while (ndst > 0) {
         int n = SkTMin(ndst, nsrc);
 
         for (int i = 0; i < n; i++) {
-            srcover_blend_srgb8888_srgb_1(dst++, srgb_to_linear(to_4f(src[i])));
+            srcover_srgb_srgb_1(dst++, src[i]);
         }
         ndst -= n;
     }
 }
 
 static SkString mismatch_message(std::string resourceName, int x, int y,
                                   uint32_t src, uint32_t good, uint32_t bad) {
     return SkStringPrintf(
         "%s - missmatch at %d, %d src: %08x good: %08x bad: %08x",
         resourceName.c_str(), x, y, src, good, bad);
@@ skipping 51 matching lines @@
 DEF_TEST(SkBlend_optsSqrtCheck, reporter) {
     for (int c = 0; c < 256; c++) {
         Sk4f i{(float)c};
         Sk4f ii = i * i;
         Sk4f s = ii.sqrt() + 0.5f;
         Sk4f sf = s.floor();
         REPORTER_ASSERT_MESSAGE(
             reporter, i[0] == sf[0], SkStringPrintf("i: %f, s: %f", i[0], sf[0]));
     }
 }