SSSE3 opts for RGB -> RGB(FF) or BGR(FF)

src/opts/SkSwizzler_opts.h

Index: src/opts/SkSwizzler_opts.h
diff --git a/src/opts/SkSwizzler_opts.h b/src/opts/SkSwizzler_opts.h
index ad121cfafecc42d33fddaa2227ed9fd0693e659b..14960f3b8f0b36ab09fd0dd49f3da55509347e30 100644
--- a/src/opts/SkSwizzler_opts.h
+++ b/src/opts/SkSwizzler_opts.h
@@ -358,12 +358,47 @@ static void RGBA_to_BGRA(uint32_t* dst, const void* vsrc, int count) {
     RGBA_to_BGRA_portable(dst, src, count);
 }
 
+template <bool kSwapRB>
+static void insert_alpha_should_swaprb(uint32_t dst[], const void* vsrc, int count) {
+    const uint8_t* src = (const uint8_t*) vsrc;
+
+    const __m128i alphaMask = _mm_set1_epi32(0xFF000000);
+    __m128i expand;
+    const uint8_t X = 0xFF; // Used a placeholder.  The value of X is irrelevant.
+    if (kSwapRB) {
+        expand = _mm_setr_epi8(2,1,0,X, 5,4,3,X, 8,7,6,X, 11,10,9,X);
+    } else {
+        expand = _mm_setr_epi8(0,1,2,X, 3,4,5,X, 6,7,8,X, 9,10,11,X);
+    }
+
+    while (count >= 6) {
+        // Load a vector.  While this actually contains 5 pixels plus an
+        // extra component, we will discard all but the first four pixels on
+        // this iteration.
+        __m128i rgb = _mm_loadu_si128((const __m128i*) src);
+
+        // Expand the first four pixels to RGBX and then mask to RGB(FF).
+        __m128i rgba = _mm_or_si128(_mm_shuffle_epi8(rgb, expand), alphaMask);
+
+        // Store 4 pixels.
+        _mm_storeu_si128((__m128i*) dst, rgba);
+
+        src += 4*3;
+        dst += 4;
+        count -= 4;
+    }
+
+    // Call portable code to finish up the tail of [0,4) pixels.
+    auto proc = kSwapRB ? RGB_to_BGR1_portable : RGB_to_RGB1_portable;
+    proc(dst, src, count);
+}
+
 static void RGB_to_RGB1(uint32_t dst[], const void* src, int count) {
-    RGB_to_RGB1_portable(dst, src, count);
+    insert_alpha_should_swaprb<false>(dst, src, count);
 }
 
 static void RGB_to_BGR1(uint32_t dst[], const void* src, int count) {
-    RGB_to_BGR1_portable(dst, src, count);
+    insert_alpha_should_swaprb<true>(dst, src, count);
 }
 
 #else