1 files changed, 187 insertions, 0 deletions
diff --git a/gfx/angle/src/compiler/translator/UnfoldShortCircuitToIf.cpp b/gfx/angle/src/compiler/translator/UnfoldShortCircuitToIf.cpp
new file mode 100755
index 000000000..22fa54287
--- /dev/null
+++ b/gfx/angle/src/compiler/translator/UnfoldShortCircuitToIf.cpp
@@ -0,0 +1,187 @@
+//
+// 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.
+//
+// UnfoldShortCircuitToIf is an AST traverser to convert short-circuiting operators to if-else statements.
+// The results are assigned to s# temporaries, which are used by the main translator instead of
+// the original expression.
+//
+
+#include "compiler/translator/UnfoldShortCircuitToIf.h"
+
+#include "compiler/translator/IntermNode.h"
+#include "compiler/translator/IntermNodePatternMatcher.h"
+
+namespace sh
+{
+
+namespace
+{
+
+// Traverser that unfolds one short-circuiting operation at a time.
+class UnfoldShortCircuitTraverser : public TIntermTraverser
+{
+  public:
+    UnfoldShortCircuitTraverser();
+
+    bool visitBinary(Visit visit, TIntermBinary *node) override;
+    bool visitTernary(Visit visit, TIntermTernary *node) override;
+
+    void nextIteration();
+    bool foundShortCircuit() const { return mFoundShortCircuit; }
+
+  protected:
+    // Marked to true once an operation that needs to be unfolded has been found.
+    // After that, no more unfolding is performed on that traversal.
+    bool mFoundShortCircuit;
+
+    IntermNodePatternMatcher mPatternToUnfoldMatcher;
+};
+
+UnfoldShortCircuitTraverser::UnfoldShortCircuitTraverser()
+    : TIntermTraverser(true, false, true),
+      mFoundShortCircuit(false),
+      mPatternToUnfoldMatcher(IntermNodePatternMatcher::kUnfoldedShortCircuitExpression)
+{
+}
+
+bool UnfoldShortCircuitTraverser::visitBinary(Visit visit, TIntermBinary *node)
+{
+    if (mFoundShortCircuit)
+        return false;
+
+    if (visit != PreVisit)
+        return true;
+
+    if (!mPatternToUnfoldMatcher.match(node, getParentNode()))
+        return true;
+
+    // If our right node doesn't have side effects, we know we don't need to unfold this
+    // expression: there will be no short-circuiting side effects to avoid
+    // (note: unfolding doesn't depend on the left node -- it will always be evaluated)
+    ASSERT(node->getRight()->hasSideEffects());
+
+    mFoundShortCircuit = true;
+
+    switch (node->getOp())
+    {
+      case EOpLogicalOr:
+      {
+          // "x || y" is equivalent to "x ? true : y", which unfolds to "bool s; if(x) s = true;
+          // else s = y;",
+          // and then further simplifies down to "bool s = x; if(!s) s = y;".
+
+          TIntermSequence insertions;
+          TType boolType(EbtBool, EbpUndefined, EvqTemporary);
+
+          ASSERT(node->getLeft()->getType() == boolType);
+          insertions.push_back(createTempInitDeclaration(node->getLeft()));
+
+          TIntermBlock *assignRightBlock = new TIntermBlock();
+          ASSERT(node->getRight()->getType() == boolType);
+          assignRightBlock->getSequence()->push_back(createTempAssignment(node->getRight()));
+
+          TIntermUnary *notTempSymbol = new TIntermUnary(EOpLogicalNot, createTempSymbol(boolType));
+          TIntermIfElse *ifNode       = new TIntermIfElse(notTempSymbol, assignRightBlock, nullptr);
+          insertions.push_back(ifNode);
+
+          insertStatementsInParentBlock(insertions);
+
+          queueReplacement(node, createTempSymbol(boolType), OriginalNode::IS_DROPPED);
+          return false;
+      }
+      case EOpLogicalAnd:
+      {
+          // "x && y" is equivalent to "x ? y : false", which unfolds to "bool s; if(x) s = y;
+          // else s = false;",
+          // and then further simplifies down to "bool s = x; if(s) s = y;".
+          TIntermSequence insertions;
+          TType boolType(EbtBool, EbpUndefined, EvqTemporary);
+
+          ASSERT(node->getLeft()->getType() == boolType);
+          insertions.push_back(createTempInitDeclaration(node->getLeft()));
+
+          TIntermBlock *assignRightBlock = new TIntermBlock();
+          ASSERT(node->getRight()->getType() == boolType);
+          assignRightBlock->getSequence()->push_back(createTempAssignment(node->getRight()));
+
+          TIntermIfElse *ifNode =
+              new TIntermIfElse(createTempSymbol(boolType), assignRightBlock, nullptr);
+          insertions.push_back(ifNode);
+
+          insertStatementsInParentBlock(insertions);
+
+          queueReplacement(node, createTempSymbol(boolType), OriginalNode::IS_DROPPED);
+          return false;
+      }
+      default:
+          UNREACHABLE();
+          return true;
+    }
+}
+
+bool UnfoldShortCircuitTraverser::visitTernary(Visit visit, TIntermTernary *node)
+{
+    if (mFoundShortCircuit)
+        return false;
+
+    if (visit != PreVisit)
+        return true;
+
+    if (!mPatternToUnfoldMatcher.match(node))
+        return true;
+
+    mFoundShortCircuit = true;
+
+    // Unfold "b ? x : y" into "type s; if(b) s = x; else s = y;"
+    TIntermSequence insertions;
+
+    TIntermDeclaration *tempDeclaration = createTempDeclaration(node->getType());
+    insertions.push_back(tempDeclaration);
+
+    TIntermBlock *trueBlock       = new TIntermBlock();
+    TIntermBinary *trueAssignment = createTempAssignment(node->getTrueExpression());
+    trueBlock->getSequence()->push_back(trueAssignment);
+
+    TIntermBlock *falseBlock       = new TIntermBlock();
+    TIntermBinary *falseAssignment = createTempAssignment(node->getFalseExpression());
+    falseBlock->getSequence()->push_back(falseAssignment);
+
+    TIntermIfElse *ifNode =
+        new TIntermIfElse(node->getCondition()->getAsTyped(), trueBlock, falseBlock);
+    insertions.push_back(ifNode);
+
+    insertStatementsInParentBlock(insertions);
+
+    TIntermSymbol *ternaryResult = createTempSymbol(node->getType());
+    queueReplacement(node, ternaryResult, OriginalNode::IS_DROPPED);
+
+    return false;
+}
+
+void UnfoldShortCircuitTraverser::nextIteration()
+{
+    mFoundShortCircuit = false;
+    nextTemporaryIndex();
+}
+
+} // namespace
+
+void UnfoldShortCircuitToIf(TIntermNode *root, unsigned int *temporaryIndex)
+{
+    UnfoldShortCircuitTraverser traverser;
+    ASSERT(temporaryIndex != nullptr);
+    traverser.useTemporaryIndex(temporaryIndex);
+    // Unfold one operator at a time, and reset the traverser between iterations.
+    do
+    {
+        traverser.nextIteration();
+        root->traverse(&traverser);
+        if (traverser.foundShortCircuit())
+            traverser.updateTree();
+    }
+    while (traverser.foundShortCircuit());
+}
+
+}  // namespace sh