Add an option to unfold short circuiting in AST.

include/GLSLANG/ShaderLang.h

@@ -189,6 +189,13 @@ typedef enum {
   // fragment shader. It is intended as a workaround for drivers which
   // incorrectly fail to link programs if gl_Position is not written.
   SH_INIT_GL_POSITION = 0x8000,
+
+  // This flag replaces
+  //   "a && b" with "a ? b : false",
+  //   "a || b" with "a ? true : b".
+  // This is to work around a MacOSX driver bug that |b| is executed
+  // independent of |a|'s value.
+  SH_UNFOLD_SHORT_CIRCUIT = 0x10000,
 } ShCompileOptions;
 
 // Defines alternate strategies for implementing array index clamping.

src/build_angle.gypi

@@ -82,6 +82,8 @@
         'compiler/TranslatorHLSL.cpp',
         'compiler/TranslatorHLSL.h',
         'compiler/Types.h',
+        'compiler/UnfoldShortCircuitAST.cpp',
+        'compiler/UnfoldShortCircuitAST.h',
         'compiler/UnfoldShortCircuit.cpp',
         'compiler/UnfoldShortCircuit.h',
         'compiler/Uniform.cpp',

src/compiler/Compiler.cpp

@@ -14,6 +14,7 @@
 #include "compiler/ParseHelper.h"
 #include "compiler/RenameFunction.h"
 #include "compiler/ShHandle.h"
+#include "compiler/UnfoldShortCircuitAST.h"
 #include "compiler/ValidateLimitations.h"
 #include "compiler/VariablePacker.h"
 #include "compiler/depgraph/DependencyGraph.h"
@@ -194,6 +195,12 @@ bool TCompiler::compile(const char* const shaderStrings[],
             root->traverse(&initGLPosition);
         }
 
+	if (success && (compileOptions & SH_UNFOLD_SHORT_CIRCUIT)) {
+            UnfoldShortCircuitAST unfoldShortCircuit;
+            root->traverse(&unfoldShortCircuit);
+            unfoldShortCircuit.updateTree();
+	}
+
         if (success && (compileOptions & SH_VARIABLES)) {
             collectVariables(root);
             if (compileOptions & SH_ENFORCE_PACKING_RESTRICTIONS) {

src/compiler/IntermTraverse.cpp

@@ -51,7 +51,7 @@ void TIntermBinary::traverse(TIntermTraverser *it)
     //
     if (visit)
     {
-        it->incrementDepth();
+        it->incrementDepth(this);
 
         if (it->rightToLeft) 
         {
@@ -98,7 +98,7 @@ void TIntermUnary::traverse(TIntermTraverser *it)
         visit = it->visitUnary(PreVisit, this);
 
     if (visit) {
-        it->incrementDepth();
+        it->incrementDepth(this);
         operand->traverse(it);
         it->decrementDepth();
     }
@@ -119,7 +119,7 @@ void TIntermAggregate::traverse(TIntermTraverser *it)
     
     if (visit)
     {
-        it->incrementDepth();
+        it->incrementDepth(this);
 
         if (it->rightToLeft)
         {
@@ -166,7 +166,7 @@ void TIntermSelection::traverse(TIntermTraverser *it)
         visit = it->visitSelection(PreVisit, this);
     
     if (visit) {
-        it->incrementDepth();
+        it->incrementDepth(this);
         if (it->rightToLeft) {
             if (falseBlock)
                 falseBlock->traverse(it);
@@ -199,7 +199,7 @@ void TIntermLoop::traverse(TIntermTraverser *it)
     
     if (visit)
     {
-        it->incrementDepth();
+        it->incrementDepth(this);
 
         if (it->rightToLeft)
         {
@@ -248,7 +248,7 @@ void TIntermBranch::traverse(TIntermTraverser *it)
         visit = it->visitBranch(PreVisit, this);
     
     if (visit && expression) {
-        it->incrementDepth();
+        it->incrementDepth(this);
         expression->traverse(it);
         it->decrementDepth();
     }

src/compiler/Intermediate.cpp

@@ -19,11 +19,13 @@
 
 bool CompareStructure(const TType& leftNodeType, ConstantUnion* rightUnionArray, ConstantUnion* leftUnionArray);
 
-static TPrecision GetHigherPrecision( TPrecision left, TPrecision right ){
+static TPrecision GetHigherPrecision(TPrecision left, TPrecision right)
+{
     return left > right ? left : right;
 }
 
-const char* getOperatorString(TOperator op) {
+const char* getOperatorString(TOperator op)
+{
     switch (op) {
       case EOpInitialize: return "=";
       case EOpAssign: return "=";
@@ -742,6 +744,63 @@ void TIntermediate::remove(TIntermNode* root)
 //
 ////////////////////////////////////////////////////////////////
 
+#define REPLACE_IF_IS(node, type, original, replacement) \
+    if (node == original) { \
+        node = static_cast<type *>(replacement); \
+        return true; \
+    }
+
+bool TIntermLoop::replaceChildNode(
+    TIntermNode *original, TIntermNode *replacement)
+{
+    REPLACE_IF_IS(init, TIntermNode, original, replacement);
+    REPLACE_IF_IS(cond, TIntermTyped, original, replacement);
+    REPLACE_IF_IS(expr, TIntermTyped, original, replacement);
+    REPLACE_IF_IS(body, TIntermNode, original, replacement);
+    return false;
+}
+
+bool TIntermBranch::replaceChildNode(
+    TIntermNode *original, TIntermNode *replacement)
+{
+    REPLACE_IF_IS(expression, TIntermTyped, original, replacement);
+    return false;
+}
+
+bool TIntermBinary::replaceChildNode(
+    TIntermNode *original, TIntermNode *replacement)
+{
+    REPLACE_IF_IS(left, TIntermTyped, original, replacement);
+    REPLACE_IF_IS(right, TIntermTyped, original, replacement);
+    return false;
+}
+
+bool TIntermUnary::replaceChildNode(
+    TIntermNode *original, TIntermNode *replacement)
+{
+    REPLACE_IF_IS(operand, TIntermTyped, original, replacement);
+    return false;
+}
+
+bool TIntermAggregate::replaceChildNode(
+    TIntermNode *original, TIntermNode *replacement)
+{
+    for (size_t ii = 0; ii < sequence.size(); ++ii)
+    {
+        REPLACE_IF_IS(sequence[ii], TIntermNode, original, replacement);
+    }
+    return false;
+}
+
+bool TIntermSelection::replaceChildNode(
+    TIntermNode *original, TIntermNode *replacement)
+{
+    REPLACE_IF_IS(condition, TIntermTyped, original, replacement);
+    REPLACE_IF_IS(trueBlock, TIntermNode, original, replacement);
+    REPLACE_IF_IS(falseBlock, TIntermNode, original, replacement);
+    return false;
+}
+
 //
 // Say whether or not an operation node changes the value of a variable.
 //
@@ -796,6 +855,7 @@ bool TIntermOperator::isConstructor() const
             return false;
     }
 }
+
 //
 // Make sure the type of a unary operator is appropriate for its
 // combination of operation and operand type.

src/compiler/OutputGLSLBase.cpp

@@ -435,7 +435,7 @@ bool TOutputGLSLBase::visitSelection(Visit visit, TIntermSelection* node)
         node->getCondition()->traverse(this);
         out << ")\n";
 
-        incrementDepth();
+        incrementDepth(node);
         visitCodeBlock(node->getTrueBlock());
 
         if (node->getFalseBlock())
@@ -460,7 +460,7 @@ bool TOutputGLSLBase::visitAggregate(Visit visit, TIntermAggregate* node)
             // Scope the sequences except when at the global scope.
             if (depth > 0) out << "{\n";
 
-            incrementDepth();
+            incrementDepth(node);
             const TIntermSequence& sequence = node->getSequence();
             for (TIntermSequence::const_iterator iter = sequence.begin();
                  iter != sequence.end(); ++iter)
@@ -498,7 +498,7 @@ bool TOutputGLSLBase::visitAggregate(Visit visit, TIntermAggregate* node)
             writeVariableType(node->getType());
             out << " " << hashFunctionName(node->getName());
 
-            incrementDepth();
+            incrementDepth(node);
             // Function definition node contains one or two children nodes
             // representing function parameters and function body. The latter
             // is not present in case of empty function bodies.
@@ -638,7 +638,7 @@ bool TOutputGLSLBase::visitLoop(Visit visit, TIntermLoop* node)
 {
     TInfoSinkBase& out = objSink();
 
-    incrementDepth();
+    incrementDepth(node);
     // Loop header.
     TLoopType loopType = node->getType();
     if (loopType == ELoopFor)  // for loop

src/compiler/UnfoldShortCircuitAST.cpp

+//
+// Copyright (c) 2002-2013 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+
+#include "compiler/UnfoldShortCircuitAST.h"
+
+namespace
+{
+
+// "x || y" is equivalent to "x ? true : y".
+TIntermSelection *UnfoldOR(TIntermTyped *x, TIntermTyped *y)
+{
+    const TType boolType(EbtBool, EbpUndefined);
+    ConstantUnion *u = new ConstantUnion;
+    u->setBConst(true);
+    TIntermConstantUnion *trueNode = new TIntermConstantUnion(
+        u, TType(EbtBool, EbpUndefined, EvqConst, 1));
+    return new TIntermSelection(x, trueNode, y, boolType);
+}
+
+// "x && y" is equivalent to "x ? y : false".
+TIntermSelection *UnfoldAND(TIntermTyped *x, TIntermTyped *y)
+{
+    const TType boolType(EbtBool, EbpUndefined);
+    ConstantUnion *u = new ConstantUnion;
+    u->setBConst(false);
+    TIntermConstantUnion *falseNode = new TIntermConstantUnion(
+        u, TType(EbtBool, EbpUndefined, EvqConst, 1));
+    return new TIntermSelection(x, y, falseNode, boolType);
+}
+
+}  // namespace anonymous
+
+bool UnfoldShortCircuitAST::visitBinary(Visit visit, TIntermBinary *node)
+{
+    TIntermSelection *replacement = NULL;
+
+    switch (node->getOp())
+    {
+      case EOpLogicalOr:
+        replacement = UnfoldOR(node->getLeft(), node->getRight());
+        break;
+      case EOpLogicalAnd:
+        replacement = UnfoldAND(node->getLeft(), node->getRight());
+        break;
+      default:
+        break;
+    }
+    if (replacement)
+    {
+        replacements.push_back(
+            NodeUpdateEntry(getParentNode(), node, replacement));
+    }
+    return true;
+}
+
+void UnfoldShortCircuitAST::updateTree()
+{
+    for (size_t ii = 0; ii < replacements.size(); ++ii)
+    {
+        const NodeUpdateEntry& entry = replacements[ii];
+        ASSERT(entry.parent);
+        bool replaced = entry.parent->replaceChildNode(
+            entry.original, entry.replacement);
+        ASSERT(replaced);
+
+        // In AST traversing, a parent is visited before its children.
+        // After we replace a node, if an immediate child is to
+        // be replaced, we need to make sure we don't update the replaced
+	// node; instead, we update the replacement node.
+        for (size_t jj = ii + 1; jj < replacements.size(); ++jj)
+        {
+            NodeUpdateEntry& entry2 = replacements[jj];
+            if (entry2.parent == entry.original)
+                entry2.parent = entry.replacement;
+        }
+    }
+}
+

src/compiler/UnfoldShortCircuitAST.h

+//
+// Copyright (c) 2002-2013 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// UnfoldShortCircuitAST is an AST traverser to replace short-circuiting
+// operations with ternary operations.
+//
+
+#ifndef COMPILER_UNFOLD_SHORT_CIRCUIT_AST_H_
+#define COMPILER_UNFOLD_SHORT_CIRCUIT_AST_H_
+
+#include "common/angleutils.h"
+#include "compiler/intermediate.h"
+
+// This traverser identifies all the short circuit binary  nodes that need to
+// be replaced, and creates the corresponding replacement nodes. However,
+// the actual replacements happen after the traverse through updateTree().
+
+class UnfoldShortCircuitAST : public TIntermTraverser
+{
+  public:
+    UnfoldShortCircuitAST() { }
+
+    virtual bool visitBinary(Visit visit, TIntermBinary *);
+
+    void updateTree();
+
+  private:
+    struct NodeUpdateEntry
+    {
+        NodeUpdateEntry(TIntermNode *_parent,
+                        TIntermNode *_original,
+                        TIntermNode *_replacement)
+            : parent(_parent),
+              original(_original),
+              replacement(_replacement) {}
+
+        TIntermNode *parent;
+        TIntermNode *original;
+        TIntermNode *replacement;
+    };
+
+    // During traversing, save all the replacements that need to happen;
+    // then replace them by calling updateNodes().
+    std::vector<NodeUpdateEntry> replacements;
+
+    DISALLOW_COPY_AND_ASSIGN(UnfoldShortCircuitAST);
+};
+
+#endif  // COMPILER_UNFOLD_SHORT_CIRCUIT_AST_H_

src/compiler/intermediate.h

@@ -227,6 +227,11 @@ public:
     virtual TIntermSymbol* getAsSymbolNode() { return 0; }
     virtual TIntermLoop* getAsLoopNode() { return 0; }
 
+    // Replace a child node. Return true if |original| is a child
+    // node and it is replaced; otherwise, return false.
+    virtual bool replaceChildNode(
+        TIntermNode *original, TIntermNode *replacement) = 0;
+
 protected:
     TSourceLoc line;
 };
@@ -295,6 +300,8 @@ public:
 
     virtual TIntermLoop* getAsLoopNode() { return this; }
     virtual void traverse(TIntermTraverser*);
+    virtual bool replaceChildNode(
+        TIntermNode *original, TIntermNode *replacement);
 
     TLoopType getType() const { return type; }
     TIntermNode* getInit() { return init; }
@@ -325,6 +332,8 @@ public:
             expression(e) { }
 
     virtual void traverse(TIntermTraverser*);
+    virtual bool replaceChildNode(
+        TIntermNode *original, TIntermNode *replacement);
 
     TOperator getFlowOp() { return flowOp; }
     TIntermTyped* getExpression() { return expression; }
@@ -355,6 +364,7 @@ public:
 
     virtual void traverse(TIntermTraverser*);
     virtual TIntermSymbol* getAsSymbolNode() { return this; }
+    virtual bool replaceChildNode(TIntermNode *, TIntermNode *) { return false; }
 
 protected:
     int id;
@@ -374,6 +384,7 @@ public:
 
     virtual TIntermConstantUnion* getAsConstantUnion()  { return this; }
     virtual void traverse(TIntermTraverser*);
+    virtual bool replaceChildNode(TIntermNode *, TIntermNode *) { return false; }
 
     TIntermTyped* fold(TOperator, TIntermTyped*, TInfoSink&);
 
@@ -407,6 +418,8 @@ public:
 
     virtual TIntermBinary* getAsBinaryNode() { return this; }
     virtual void traverse(TIntermTraverser*);
+    virtual bool replaceChildNode(
+        TIntermNode *original, TIntermNode *replacement);
 
     void setLeft(TIntermTyped* n) { left = n; }
     void setRight(TIntermTyped* n) { right = n; }
@@ -435,6 +448,8 @@ public:
 
     virtual void traverse(TIntermTraverser*);
     virtual TIntermUnary* getAsUnaryNode() { return this; }
+    virtual bool replaceChildNode(
+        TIntermNode *original, TIntermNode *replacement);
 
     void setOperand(TIntermTyped* o) { operand = o; }
     TIntermTyped* getOperand() { return operand; }    
@@ -465,6 +480,8 @@ public:
 
     virtual TIntermAggregate* getAsAggregate() { return this; }
     virtual void traverse(TIntermTraverser*);
+    virtual bool replaceChildNode(
+        TIntermNode *original, TIntermNode *replacement);
 
     TIntermSequence& getSequence() { return sequence; }
 
@@ -508,6 +525,8 @@ public:
             TIntermTyped(type), condition(cond), trueBlock(trueB), falseBlock(falseB) {}
 
     virtual void traverse(TIntermTraverser*);
+    virtual bool replaceChildNode(
+        TIntermNode *original, TIntermNode *replacement);
 
     bool usesTernaryOperator() const { return getBasicType() != EbtVoid; }
     TIntermNode* getCondition() const { return condition; }
@@ -547,7 +566,7 @@ public:
             rightToLeft(rightToLeft),
             depth(0),
             maxDepth(0) {}
-    virtual ~TIntermTraverser() {};
+    virtual ~TIntermTraverser() {}
 
     virtual void visitSymbol(TIntermSymbol*) {}
     virtual void visitConstantUnion(TIntermConstantUnion*) {}
@@ -559,8 +578,24 @@ public:
     virtual bool visitBranch(Visit visit, TIntermBranch*) {return true;}
 
     int getMaxDepth() const {return maxDepth;}
-    void incrementDepth() {depth++; maxDepth = std::max(maxDepth, depth); }
-    void decrementDepth() {depth--;}
+
+    void incrementDepth(TIntermNode *current)
+    {
+        depth++;
+        maxDepth = std::max(maxDepth, depth);
+        path.push_back(current);
+    }
+
+    void decrementDepth()
+    {
+        depth--;
+        path.pop_back();
+    }
+
+    TIntermNode *getParentNode()
+    {
+        return path.size() == 0 ? NULL : path.back();
+    }
 
     // Return the original name if hash function pointer is NULL;
     // otherwise return the hashed name.
@@ -574,6 +609,9 @@ public:
 protected:
     int depth;
     int maxDepth;
+
+    // All the nodes from root to the current node's parent during traversing.
+    TVector<TIntermNode *> path;
 };
 
 #endif // __INTERMEDIATE_H