initial checkin of SkSL compiler

src/sksl/ir/SkSLSwizzle.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+ 
+#ifndef SKSL_SWIZZLE
+#define SKSL_SWIZZLE
+
+#include "SkSLExpression.h"
+#include "SkSLUtil.h"
+
+namespace SkSL {
+
+/**
+ * Given a type and a swizzle component count, returns the type that will result from swizzling. For 
+ * instance, swizzling a vec3 with two components will result in a vec2. It is possible to swizzle
+ * with more components than the source vector, as in 'vec2(1).xxxx'.
+ */
+static std::shared_ptr<Type> get_type(Expression& value, 
+                                      size_t count) {
+    std::shared_ptr<Type> base = value.fType->componentType();
+    if (count == 1) {
+        return base;
+    }
+    if (base == kFloat_Type) {
+        switch (count) {
+            case 2: return kVec2_Type;
+            case 3: return kVec3_Type;
+            case 4: return kVec4_Type;
+        }
+    } else if (base == kDouble_Type) {
+        switch (count) {
+            case 2: return kDVec2_Type;
+            case 3: return kDVec3_Type;
+            case 4: return kDVec4_Type;
+        }
+    } else if (base == kInt_Type) {
+        switch (count) {
+            case 2: return kIVec2_Type;
+            case 3: return kIVec3_Type;
+            case 4: return kIVec4_Type;
+        }
+    } else if (base == kUInt_Type) {
+        switch (count) {
+            case 2: return kUVec2_Type;
+            case 3: return kUVec3_Type;
+            case 4: return kUVec4_Type;
+        }
+    } else if (base == kBool_Type) {
+        switch (count) {
+            case 2: return kBVec2_Type;
+            case 3: return kBVec3_Type;
+            case 4: return kBVec4_Type;
+        }
+    }
+    ABORT("cannot swizzle %s\n", value.description().c_str());
+}
+
+/**
+ * Represents a vector swizzle operation such as 'vec2(1, 2, 3).zyx'.
+ */
+struct Swizzle : public Expression {
+    Swizzle(std::unique_ptr<Expression> base, std::vector<int> components)
+    : INHERITED(base->fPosition, kSwizzle_Kind, get_type(*base, components.size()))
+    , fBase(std::move(base))
+    , fComponents(std::move(components)) {
+        ASSERT(fComponents.size() >= 1 && fComponents.size() <= 4);
+    }
+
+    std::string description() const override {
+        std::string result = fBase->description() + ".";
+        for (int x : fComponents) {
+            result += "xyzw"[x];
+        }
+        return result;
+    }
+
+    const std::unique_ptr<Expression> fBase;
+    const std::vector<int> fComponents;
+
+    typedef Expression INHERITED;
+};
+
+} // namespace
+
+#endif