4-at-a-time SkPMColor -> SkPMFloat API.

bench/PMFloatBench.cpp

 #include "Benchmark.h"
 #include "SkPMFloat.h"
 
 // Used to prevent the compiler from optimizing away the whole loop.
 volatile uint32_t blackhole = 0;
 
 // Not a great random number generator, but it's very fast.
 // The code we're measuring is quite fast, so low overhead is essential.
 static uint32_t lcg_rand(uint32_t* seed) {
     *seed *= 1664525;
     *seed += 1013904223;
     return *seed;
 }
 
+// I'm having better luck getting these to constant-propagate away as template parameters.
+template <bool kClamp, bool kWide>
 struct PMFloatBench : public Benchmark {
-    explicit PMFloatBench(bool clamp) : fClamp(clamp) {}
+    PMFloatBench() {}
 
-    const char* onGetName() SK_OVERRIDE { return fClamp ? "SkPMFloat_clamp" : "SkPMFloat_get"; }
+    const char* onGetName() SK_OVERRIDE {
+        switch (kClamp << 1 | kWide) {
+            case 0: return "SkPMFloat_get_1x";
+            case 1: return "SkPMFloat_get_4x";
+            case 2: return "SkPMFloat_clamp_1x";
+            case 3: return "SkPMFloat_clamp_4x";
+        }
+        SkFAIL("unreachable");
+        return "oh bother";
+    }
     bool isSuitableFor(Backend backend) SK_OVERRIDE { return backend == kNonRendering_Backend; }
 
     void onDraw(const int loops, SkCanvas* canvas) SK_OVERRIDE {
         // Unlike blackhole, junk can and probably will be a register.
         uint32_t junk = 0;
         uint32_t seed = 0;
         for (int i = 0; i < loops; i++) {
+            SkPMColor colors[4];
         #ifdef SK_DEBUG
-            // Our SkASSERTs will remind us that it's technically required that we premultiply.
-            SkPMColor c = SkPreMultiplyColor(lcg_rand(&seed));
+            for (int i = 0; i < 4; i++) {
+                // Our SkASSERTs will remind us that it's technically required that we premultiply.
+                colors[i] = SkPreMultiplyColor(lcg_rand(&seed));
+            }
         #else
             // But it's a lot faster not to, and this code won't really mind the non-PM colors.
-            SkPMColor c = lcg_rand(&seed);
+            (void)lcg_rand(&seed);
+            colors[0] = seed + 0;
+            colors[1] = seed + 1;
+            colors[2] = seed + 2;
+            colors[3] = seed + 3;
         #endif
-            SkPMFloat pmf = SkPMFloat::FromPMColor(c);
-            SkPMColor back = fClamp ? pmf.clamped() : pmf.get();
-            junk ^= back;
+
+            SkPMFloat floats[4];
+            if (kWide) {
+                SkPMFloat::From4PMColors(floats, colors);
+            } else {
+                for (int i = 0; i < 4; i++) {
+                    floats[i] = SkPMFloat::FromPMColor(colors[i]);
+                }
+            }
+
+            SkPMColor back[4];
+            switch (kClamp << 1 | kWide) {
+                case 0: for (int i = 0; i < 4; i++) { back[i] = floats[i].get(); }     break;
+                case 1: SkPMFloat::To4PMColors(back, floats);                          break;
+                case 2: for (int i = 0; i < 4; i++) { back[i] = floats[i].clamped(); } break;
+                case 3: SkPMFloat::ClampTo4PMColors(back, floats);                     break;
+            }
+            for (int i = 0; i < 4; i++) {
+                junk ^= back[i];
+            }
         }
         blackhole ^= junk;
     }
+};
 
-    bool fClamp;
-};
-DEF_BENCH(return new PMFloatBench( true);)
-DEF_BENCH(return new PMFloatBench(false);)
+// Extra () help DEF_BENCH not get confused by the comma inside the <>.
+DEF_BENCH(return (new PMFloatBench< true,  true>);)
+DEF_BENCH(return (new PMFloatBench<false,  true>);)
+DEF_BENCH(return (new PMFloatBench< true, false>);)
+DEF_BENCH(return (new PMFloatBench<false, false>);)