Make test lower-level, make const_cast more visible.

I can only think there's something funky going on with the hidden
const_cast inside SkRasterPipeline.cpp, or with the Sk4h -> Sk4f
conversion.  So make the const_cast visible and write the test
directly in halfs instead of floats.

CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Mac-Clang-MacMini6.2-CPU-AVX-x86_64-Release-GN-Trybot

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3003

Change-Id: I3a7e19ae165fce44f177b4968a63ec04e25c4b93
Reviewed-on: https://skia-review.googlesource.com/3003
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>

src/core/SkRasterPipeline.cpp

@@ -12,7 +12,7 @@ SkRasterPipeline::SkRasterPipeline() {}
 
 void SkRasterPipeline::append(SkRasterPipeline::Fn body,
                               SkRasterPipeline::Fn tail,
-                              const void* ctx) {
+                              void* ctx) {
     // Each stage holds its own context and the next function to call.
     // So the pipeline itself has to hold onto the first function that starts the pipeline.
     (fBody.empty() ? fBodyStart : fBody.back().fNext) = body;
@@ -20,11 +20,11 @@ void SkRasterPipeline::append(SkRasterPipeline::Fn body,
 
     // Each last stage starts with its next function set to JustReturn as a safety net.
     // It'll be overwritten by the next call to append().
-    fBody.push_back({ &JustReturn, const_cast<void*>(ctx) });
-    fTail.push_back({ &JustReturn, const_cast<void*>(ctx) });
+    fBody.push_back({ &JustReturn, ctx });
+    fTail.push_back({ &JustReturn, ctx });
 }
 
-void SkRasterPipeline::append(StockStage stage, const void* ctx) {
+void SkRasterPipeline::append(StockStage stage, void* ctx) {
     this->append(SkOpts::stages_4[stage], SkOpts::stages_1_3[stage], ctx);
 }
 

src/core/SkRasterPipeline.h

@@ -131,7 +131,8 @@ public:
 
         kNumStockStages,
     };
-    void append(StockStage, const void* ctx=nullptr);
+    void append(StockStage, void* = nullptr);
+    void append(StockStage stage, const void* ctx) { this->append(stage, const_cast<void*>(ctx)); }
 
 
     // Append all stages to this pipeline.
@@ -140,7 +141,7 @@ public:
 private:
     using Stages = SkSTArray<10, Stage, /*MEM_COPY=*/true>;
 
-    void append(Fn body, Fn tail, const void*);
+    void append(Fn body, Fn tail, void*);
 
     // This no-op default makes fBodyStart and fTailStart unconditionally safe to call,
     // and is always the last stage's fNext as a sort of safety net to make sure even a

tests/SkRasterPipelineTest.cpp

@@ -12,16 +12,9 @@
 DEF_TEST(SkRasterPipeline, r) {
     // Build and run a simple pipeline to exercise SkRasterPipeline,
     // drawing 50% transparent blue over opaque red in half-floats.
-
-    Sk4h red  = SkFloatToHalf_finite_ftz({ 1.0f, 0.0f, 0.0f, 1.0f }),
-         blue = SkFloatToHalf_finite_ftz({ 0.0f, 0.0f, 0.5f, 0.5f }),
-         result = { 1, 2, 3, 4 };
-
-    uint64_t bits;
-    memcpy(&bits, &red, 8);
-    SkDebugf("SkRasterPipeline red: 0x%016llx, want 0x3c00000000003c00\n", bits);
-    memcpy(&bits, &blue, 8);
-    SkDebugf("SkRasterPipeline blue: 0x%016llx, want 0x3800380000000000\n", bits);
+    uint64_t red  = 0x3c00000000003c00ull,
+             blue = 0x3800380000000000ull,
+             result;
 
     SkRasterPipeline p;
     p.append(SkRasterPipeline::load_s_f16, &blue);
@@ -30,16 +23,11 @@ DEF_TEST(SkRasterPipeline, r) {
     p.append(SkRasterPipeline::store_f16, &result);
     p.run(1);
 
-    Sk4f f = SkHalfToFloat_finite_ftz(result);
-
-    memcpy(&bits, &result, 8);
-    SkDebugf("SkRasterPipeline result: 0x%016llx, want 0x3c00380000003800\n", bits);
-
     // We should see half-intensity magenta.
-    REPORTER_ASSERT(r, f[0] == 0.5f);
-    REPORTER_ASSERT(r, f[1] == 0.0f);
-    REPORTER_ASSERT(r, f[2] == 0.5f);
-    REPORTER_ASSERT(r, f[3] == 1.0f);
+    REPORTER_ASSERT(r, ((result >>  0) & 0xffff) == 0x3800);
+    REPORTER_ASSERT(r, ((result >> 16) & 0xffff) == 0x0000);
+    REPORTER_ASSERT(r, ((result >> 32) & 0xffff) == 0x3800);
+    REPORTER_ASSERT(r, ((result >> 48) & 0xffff) == 0x3c00);
 }
 
 DEF_TEST(SkRasterPipeline_empty, r) {