Reduced skslc memory consumption

The big change here is smarter generic type handling which allows us to
keep far fewer entries in the core symboltable. This also comments out
a number of OpenGL builtin functions which Skia does not use and is
unlikely to in the future.
BUG=655673
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2442063002

Committed: https://skia.googlesource.com/skia/+/cffaa70896fa5bc6c7bf98abbaafb1a755b49762
Review-Url: https://codereview.chromium.org/2442063002

3 files changed, 50 insertions, 3 deletions

diff --git a/src/sksl/ir/SkSLFunctionCall.h b/src/sksl/ir/SkSLFunctionCall.h
index 85dba40f2a..5c67a2873c 100644
--- a/src/sksl/ir/SkSLFunctionCall.h
+++ b/src/sksl/ir/SkSLFunctionCall.h
@@ -17,9 +17,9 @@ namespace SkSL {
  * A function invocation.
  */
 struct FunctionCall : public Expression {
-    FunctionCall(Position position, const FunctionDeclaration& function,
+    FunctionCall(Position position, const Type& type, const FunctionDeclaration& function,
                  std::vector<std::unique_ptr<Expression>> arguments)
-    : INHERITED(position, kFunctionCall_Kind, function.fReturnType)
+    : INHERITED(position, kFunctionCall_Kind, type)
     , fFunction(std::move(function))
     , fArguments(std::move(arguments)) {}
 
diff --git a/src/sksl/ir/SkSLFunctionDeclaration.h b/src/sksl/ir/SkSLFunctionDeclaration.h
index ffde0c66c1..52a579a89b 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])) {
+                            genericIndex = j;
+                            break;
+                        }
+                    }
+                    if (genericIndex == -1) {
+                        return false;
+                    }
+                }
+                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;
diff --git a/src/sksl/ir/SkSLType.h b/src/sksl/ir/SkSLType.h
index ad2185b4ee..afd00d8b2a 100644
--- a/src/sksl/ir/SkSLType.h
+++ b/src/sksl/ir/SkSLType.h
@@ -57,7 +57,9 @@ public:
     : INHERITED(Position(), kType_Kind, std::move(name))
     , fTypeKind(kOther_Kind) {}
 
-    // Create a generic type which maps to the listed types.
+    // Create a generic type which maps to the listed types. As currently implemented, there are 
+    // always exactly four coercion targets, mapping to the scalar, vec2, vec3, and vec4 versions of 
+    // a type.
     Type(std::string name, std::vector<const Type*> types)
     : INHERITED(Position(), kType_Kind, std::move(name))
     , fTypeKind(kGeneric_Kind)