1 /*
2 * Copyright 2021 Google LLC.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "src/sksl/transform/SkSLTransform.h"
9
10 #include "include/private/SkSLProgramKind.h"
11 #include "src/sksl/SkSLBuiltinMap.h"
12 #include "src/sksl/SkSLCompiler.h"
13 #include "src/sksl/SkSLContext.h"
14 #include "src/sksl/SkSLThreadContext.h"
15 #include "src/sksl/analysis/SkSLProgramVisitor.h"
16 #include "src/sksl/ir/SkSLFunctionDefinition.h"
17 #include "src/sksl/ir/SkSLInterfaceBlock.h"
18 #include "src/sksl/ir/SkSLVarDeclarations.h"
19
20 namespace SkSL {
21
22 namespace Transform {
23
FindAndDeclareBuiltinVariables(const Context & context,ProgramKind programKind,std::vector<const ProgramElement * > & sharedElements)24 void FindAndDeclareBuiltinVariables(const Context& context,
25 ProgramKind programKind, std::vector<const ProgramElement*>& sharedElements) {
26 class BuiltinVariableScanner : public ProgramVisitor {
27 public:
28 BuiltinVariableScanner(const Context& context)
29 : fContext(context) {}
30
31 void addDeclaringElement(const std::string& name) {
32 // If this is the *first* time we've seen this builtin, findAndInclude will return
33 // the corresponding ProgramElement.
34 BuiltinMap& builtins = *fContext.fBuiltins;
35 if (const ProgramElement* decl = builtins.findAndInclude(name)) {
36 SkASSERT(decl->is<GlobalVarDeclaration>() || decl->is<InterfaceBlock>());
37 fNewElements.push_back(decl);
38 }
39 }
40
41 bool visitProgramElement(const ProgramElement& pe) override {
42 if (pe.is<FunctionDefinition>()) {
43 const FunctionDefinition& funcDef = pe.as<FunctionDefinition>();
44 // We synthesize writes to sk_FragColor if main() returns a color, even if it's
45 // otherwise unreferenced. Check main's return type to see if it's half4.
46 if (funcDef.declaration().isMain() &&
47 funcDef.declaration().returnType().matches(*fContext.fTypes.fHalf4)) {
48 fPreserveFragColor = true;
49 }
50 }
51 return INHERITED::visitProgramElement(pe);
52 }
53
54 bool visitExpression(const Expression& e) override {
55 if (e.is<VariableReference>() && e.as<VariableReference>().variable()->isBuiltin()) {
56 this->addDeclaringElement(
57 std::string(e.as<VariableReference>().variable()->name()));
58 }
59 return INHERITED::visitExpression(e);
60 }
61
62 const Context& fContext;
63 std::vector<const ProgramElement*> fNewElements;
64 bool fPreserveFragColor = false;
65
66 using INHERITED = ProgramVisitor;
67 using INHERITED::visitProgramElement;
68 };
69
70 BuiltinVariableScanner scanner(context);
71 for (auto& e : ThreadContext::ProgramElements()) {
72 scanner.visitProgramElement(*e);
73 }
74
75 if (scanner.fPreserveFragColor) {
76 // main() returns a half4, so make sure we don't dead-strip sk_FragColor.
77 scanner.addDeclaringElement(Compiler::FRAGCOLOR_NAME);
78 }
79
80 switch (programKind) {
81 case ProgramKind::kFragment:
82 // Vulkan requires certain builtin variables be present, even if they're unused. At one
83 // time, validation errors would result if sk_Clockwise was missing. Now, it's just
84 // (Adreno) driver bugs that drop or corrupt draws if they're missing.
85 scanner.addDeclaringElement("sk_Clockwise");
86 break;
87 default:
88 break;
89 }
90
91 sharedElements.insert(sharedElements.begin(), scanner.fNewElements.begin(),
92 scanner.fNewElements.end());
93 }
94
95 } // namespace Transform
96
97 } // namespace SkSL
98