Reduced skslc memory consumption

src/sksl/ir/SkSLFunctionDeclaration.h

Index: src/sksl/ir/SkSLFunctionDeclaration.h
diff --git a/src/sksl/ir/SkSLFunctionDeclaration.h b/src/sksl/ir/SkSLFunctionDeclaration.h
index ffde0c66c130aedb069da390899b5011eb1cc1af..52a579a89b9e13dbb2f36e22feaf224d0b04fbe8 100644
--- a/src/sksl/ir/SkSLFunctionDeclaration.h
+++ b/src/sksl/ir/SkSLFunctionDeclaration.h
@@ -8,6 +8,7 @@
 #ifndef SKSL_FUNCTIONDECLARATION
 #define SKSL_FUNCTIONDECLARATION
 
+#include "SkSLExpression.h"
 #include "SkSLModifiers.h"
 #include "SkSLSymbol.h"
 #include "SkSLSymbolTable.h"
@@ -55,6 +56,50 @@ struct FunctionDeclaration : public Symbol {
         return true;
     }
 
+    /**
+     * Determine the effective types of this function's parameters and return value when called with
+     * the given arguments. This is relevant for functions with generic parameter types, where this 
+     * will collapse the generic types down into specific concrete types.
+     *
+     * Returns true if it was able to select a concrete set of types for the generic function, false
+     * if there is no possible way this can match the argument types. Note that even a true return
+     * does not guarantee that the function can be successfully called with those arguments, merely
+     * indicates that an attempt should be made. If false is returned, the state of
+     * outParameterTypes and outReturnType are undefined.
+     */
+    bool determineFinalTypes(const std::vector<std::unique_ptr<Expression>>& arguments,
+                             std::vector<const Type*>* outParameterTypes,
+                             const Type** outReturnType) const {
+        assert(arguments.size() == fParameters.size());
+        int genericIndex = -1;
+        for (size_t i = 0; i < arguments.size(); i++) {
+            if (fParameters[i]->fType.kind() == Type::kGeneric_Kind) {
+                std::vector<const Type*> types = fParameters[i]->fType.coercibleTypes();
+                if (genericIndex == -1) {
+                    for (size_t j = 0; j < types.size(); j++) {
+                        if (arguments[i]->fType.canCoerceTo(*types[j])) {

[dogben, 2016/10/25 13:56:50]

Is it always the case that a generic type's coercible types are the size-1,
size-2, size-3, and size-4 versions of a scalar type? IWBN to document that
here:
https://skia.googlesource.com/skia/+/0730be7c303ac415484b15ef44ff1dce077a93b8...

If not, ISTM that canCoerceTo could return true even when it's not the type we
really want. Instead, we would need to do something similar to
IRGenerator::determineCallCost.

+                            genericIndex = j;
+                            break;
+                        }
+                    }
+                    if (genericIndex == -1) {
+                        return false;
+                    }
+                }

[dogben, 2016/10/25 13:56:50]

Do we need a range check here? i.e.
  ...
} else {
  if (genericIndex >= types.size()) {
    return false;
  }
}

Also below for fReturnType.coercibleTypes()?

+                outParameterTypes->push_back(types[genericIndex]);
+            } else {
+                outParameterTypes->push_back(&fParameters[i]->fType);
+            }
+        }
+        if (fReturnType.kind() == Type::kGeneric_Kind) {
+            assert(genericIndex != -1);
+            *outReturnType = fReturnType.coercibleTypes()[genericIndex];
+        } else {
+            *outReturnType = &fReturnType;
+        }
+        return true;
+    }
+
     mutable bool fDefined;
     bool fBuiltin;
     const std::vector<const Variable*> fParameters;