SkRuntimeEffect: Handle different main() signatures on CPU

Bug: skia:10603
Change-Id: Ib4d2b36c09c30a9a112f5a2d2d7060c09009671b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/309782
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

Author: brianosman

gm/runtimecolorfilter.cpp

@@ -20,7 +20,7 @@
 #include <stddef.h>
 #include <utility>
 
-const char* SKSL_TEST_SRC = R"(
+const char* gLumaSrc = R"(
     void main(inout half4 color) {
         color.a = color.r*0.3 + color.g*0.6 + color.b*0.1;
         color.r = 0;
@@ -29,14 +29,24 @@ const char* SKSL_TEST_SRC = R"(
     }
 )";
 
-DEF_SIMPLE_GM(runtimecolorfilter, canvas, 512, 256) {
+const char* gLumaSrcWithCoords = R"(
+    void main(float2 p, inout half4 color) {
+        color.a = color.r*0.3 + color.g*0.6 + color.b*0.1;
+        color.r = 0;
+        color.g = 0;
+        color.b = 0;
+    }
+)";
+
+DEF_SIMPLE_GM(runtimecolorfilter, canvas, 256 * 3, 256) {
     auto img = GetResourceAsImage("images/mandrill_256.png");
     canvas->drawImage(img, 0, 0, nullptr);
 
-    sk_sp<SkRuntimeEffect> effect = std::get<0>(SkRuntimeEffect::Make(SkString(SKSL_TEST_SRC)));
-
-    auto cf1 = effect->makeColorFilter(nullptr);
-    SkPaint p;
-    p.setColorFilter(cf1);
-    canvas->drawImage(img, 256, 0, &p);
+    for (auto src : { gLumaSrc, gLumaSrcWithCoords }) {
+        sk_sp<SkRuntimeEffect> effect = std::get<0>(SkRuntimeEffect::Make(SkString(src)));
+        SkPaint p;
+        p.setColorFilter(effect->makeColorFilter(nullptr));
+        canvas->translate(256, 0);
+        canvas->drawImage(img, 0, 0, &p);
+    }
 }

gm/runtimeshader.cpp

@@ -299,9 +299,11 @@ DEF_GM(return new ColorCubeRT;)
 
 class DefaultColorRT : public RuntimeShaderGM {
 public:
+    // This test also *explicitly* doesn't include coords in main's parameter list, to test that
+    // runtime shaders work without them being declared (when they're not used).
     DefaultColorRT() : RuntimeShaderGM("default_color_rt", {512, 256}, R"(
         in shader input;
-        void main(float2 xy, inout half4 color) {
+        void main(inout half4 color) {
             color = sample(input);
         }
     )") {}

src/core/SkRuntimeEffect.cpp

@@ -336,15 +336,28 @@ SkRuntimeEffect::ByteCodeResult SkRuntimeEffect::toByteCode() const {
 
 using SampleChildFn = std::function<skvm::Color(int, skvm::Coord)>;
 
-static std::vector<skvm::F32> program_fn(skvm::Builder* p,
-                                         const SkSL::ByteCodeFunction& fn,
-                                         const std::vector<skvm::F32>& uniform,
-                                         std::vector<skvm::F32> stack,
-                                         SampleChildFn sampleChild,
-                                         skvm::Coord device, skvm::Coord local) {
+static skvm::Color program_fn(skvm::Builder* p,
+                              const SkSL::ByteCodeFunction& fn,
+                              const std::vector<skvm::F32>& uniform,
+                              skvm::Color inColor,
+                              SampleChildFn sampleChild,
+                              skvm::Coord device, skvm::Coord local) {
+    std::vector<skvm::F32> stack;
+
     auto push = [&](skvm::F32 x) { stack.push_back(x); };
     auto pop  = [&]{ skvm::F32 x = stack.back(); stack.pop_back(); return x; };
 
+    // main(inout half4 color) or main(float2 local, inout half4 color)
+    SkASSERT(fn.getParameterCount() == 4 || fn.getParameterCount() == 6);
+    if (fn.getParameterCount() == 6) {
+        push(local.x);
+        push(local.y);
+    }
+    push(inColor.r);
+    push(inColor.g);
+    push(inColor.b);
+    push(inColor.a);
+
     for (int i = 0; i < fn.getLocalCount(); i++) {
         push(p->splat(0.0f));
     }
@@ -586,7 +599,12 @@ static std::vector<skvm::F32> program_fn(skvm::Builder* p,
     for (int i = 0; i < fn.getLocalCount(); i++) {
         pop();
     }
-    return stack;
+    SkASSERT(stack.size() == (size_t)fn.getParameterCount());
+    skvm::F32 a = pop(),
+              b = pop(),
+              g = pop(),
+              r = pop();
+    return { r, g, b, a };
 }
 
 static sk_sp<SkData> get_xformed_uniforms(const SkRuntimeEffect* effect,
@@ -752,14 +770,8 @@ class SkRuntimeColorFilter : public SkColorFilterBase {
         // Regardless, just to be extra-safe, we pass something valid (0, 0) as both coords, so
         // the builder isn't trying to do math on invalid values.
         skvm::Coord zeroCoord = { p->splat(0.0f), p->splat(0.0f) };
-        std::vector<skvm::F32> stack =
-                program_fn(p, *fn, uniform, {c.r, c.g, c.b, c.a}, sampleChild,
-                           /*device=*/ zeroCoord, /*local=*/ zeroCoord);
-
-        if (stack.size() == 4) {
-            return {stack[0], stack[1], stack[2], stack[3]};
-        }
-        return {};
+        return program_fn(p, *fn, uniform, c, sampleChild,
+                          /*device=*/zeroCoord, /*local=*/zeroCoord);
     }
 
     void flatten(SkWriteBuffer& buffer) const override {
@@ -914,15 +926,7 @@ class SkRTShader : public SkShaderBase {
             }
         };
 
-        std::vector<skvm::F32> stack =
-            program_fn(p, *fn, uniform,
-                       {local.x,local.y, paint.r, paint.g, paint.b, paint.a},
-                       sampleChild, device, local);
-
-        if (stack.size() == 6) {
-            return {stack[2], stack[3], stack[4], stack[5]};
-        }
-        return {};
+        return program_fn(p, *fn, uniform, paint, sampleChild, device, local);
     }
 
     void flatten(SkWriteBuffer& buffer) const override {