Set up some hooks for premul/swizzzle opts.

src/core/SkOpts.cpp

Index: src/core/SkOpts.cpp
diff --git a/src/core/SkOpts.cpp b/src/core/SkOpts.cpp
index 781977ea68406e01b5db022eb53aa464f2e86f2f..ee88b231690b0e8d7f0cd895a9609f9bf680235b 100644
--- a/src/core/SkOpts.cpp
+++ b/src/core/SkOpts.cpp
@@ -49,6 +49,58 @@
     #include <cpu-features.h>
 #endif
 
+namespace sk_default {
+
+// These variable names in these functions just pretend the input is BGRA.
+// They work fine with both RGBA and BGRA.
+
+static void premul_xxxa(uint32_t dst[], const uint32_t src[], int count) {
+    for (int i = 0; i < count; i++) {
+        uint8_t a = src[i] >> 24,
+                r = src[i] >> 16,
+                g = src[i] >>  8,
+                b = src[i] >>  0;
+        r = (r*a+127)/255;

[msarett, 2016/01/07 21:35:06]

Currently, we use this:

static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
    SkASSERT(a <= 32767);
    SkASSERT(b <= 32767);
    unsigned prod = a*b + 128;
    return (prod + (prod >> 8)) >> 8;
}

Are these identical or will Gold annoy us if I hook up to these?

+        g = (g*a+127)/255;
+        b = (b*a+127)/255;
+        dst[i] = (uint32_t)a << 24
+               | (uint32_t)r << 16
+               | (uint32_t)g <<  8
+               | (uint32_t)b <<  0;
+    }
+}
+
+static void swaprb_xxxa(uint32_t dst[], const uint32_t src[], int count) {
+    for (int i = 0; i < count; i++) {
+        uint8_t a = src[i] >> 24,
+                r = src[i] >> 16,
+                g = src[i] >>  8,
+                b = src[i] >>  0;
+        dst[i] = (uint32_t)a << 24
+               | (uint32_t)b << 16
+               | (uint32_t)g <<  8
+               | (uint32_t)r <<  0;
+    }
+}
+
+static void premul_swaprb_xxxa(uint32_t dst[], const uint32_t src[], int count) {
+    for (int i = 0; i < count; i++) {
+        uint8_t a = src[i] >> 24,
+                r = src[i] >> 16,
+                g = src[i] >>  8,
+                b = src[i] >>  0;
+        r = (r*a+127)/255;
+        g = (g*a+127)/255;
+        b = (b*a+127)/255;
+        dst[i] = (uint32_t)a << 24
+               | (uint32_t)b << 16
+               | (uint32_t)g <<  8
+               | (uint32_t)r <<  0;
+    }
+}
+
+}  // namespace sk_default
+
 namespace SkOpts {
     // Define default function pointer values here...
     // If our global compile options are set high enough, these defaults might even be
@@ -80,6 +132,10 @@ namespace SkOpts {
     decltype(matrix_scale_translate) matrix_scale_translate = sk_default::matrix_scale_translate;
     decltype(matrix_affine)          matrix_affine          = sk_default::matrix_affine;
 
+    decltype(       premul_xxxa)        premul_xxxa = sk_default::       premul_xxxa;
+    decltype(       swaprb_xxxa)        swaprb_xxxa = sk_default::       swaprb_xxxa;
+    decltype(premul_swaprb_xxxa) premul_swaprb_xxxa = sk_default::premul_swaprb_xxxa;
+
     // Each Init_foo() is defined in src/opts/SkOpts_foo.cpp.
     void Init_ssse3();
     void Init_sse41();