Remove switch fall-through on HLSL

src/compiler.gypi

@@ -149,6 +149,8 @@
             'compiler/translator/DetectDiscontinuity.h',
             'compiler/translator/OutputHLSL.cpp',
             'compiler/translator/OutputHLSL.h',
+            'compiler/translator/RemoveSwitchFallThrough.cpp',
+            'compiler/translator/RemoveSwitchFallThrough.h',
             'compiler/translator/RewriteElseBlocks.cpp',
             'compiler/translator/RewriteElseBlocks.h',
             'compiler/translator/StructureHLSL.cpp',

src/compiler/translator/IntermNode.h

@@ -513,6 +513,7 @@ class TIntermSwitch : public TIntermNode
     TIntermSwitch *getAsSwitchNode() override { return this; }
 
     TIntermAggregate *getStatementList() { return mStatementList; }
+    void setStatementList(TIntermAggregate *statementList) { mStatementList = statementList; }
 
   protected:
     TIntermTyped *mInit;

src/compiler/translator/OutputHLSL.cpp

@@ -17,6 +17,7 @@
 #include "compiler/translator/FlagStd140Structs.h"
 #include "compiler/translator/InfoSink.h"
 #include "compiler/translator/NodeSearch.h"
+#include "compiler/translator/RemoveSwitchFallThrough.h"
 #include "compiler/translator/RewriteElseBlocks.h"
 #include "compiler/translator/SearchSymbol.h"
 #include "compiler/translator/StructureHLSL.h"
@@ -2276,6 +2277,7 @@ bool OutputHLSL::visitSwitch(Visit visit, TIntermSwitch *node)
 {
     if (node->getStatementList())
     {
+        node->setStatementList(RemoveSwitchFallThrough::removeFallThrough(node->getStatementList()));
         outputTriplet(visit, "switch (", ") ", "");
         // The curly braces get written when visiting the statementList aggregate
     }

src/compiler/translator/RemoveSwitchFallThrough.cpp

+//
+// Copyright (c) 2002-2015 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/translator/RemoveSwitchFallThrough.h"
+
+TIntermAggregate *RemoveSwitchFallThrough::removeFallThrough(TIntermAggregate *statementList)
+{
+    RemoveSwitchFallThrough rm(statementList);
+    ASSERT(statementList);
+    statementList->traverse(&rm);
+    bool lastStatementWasBreak = rm.mLastStatementWasBreak;
+    rm.mLastStatementWasBreak = true;
+    rm.handlePreviousCase();
+    if (!lastStatementWasBreak)
+    {
+        TIntermBranch *finalBreak = new TIntermBranch(EOpBreak, nullptr);
+        rm.mStatementListOut->getSequence()->push_back(finalBreak);
+    }
+    return rm.mStatementListOut;
+}
+
+RemoveSwitchFallThrough::RemoveSwitchFallThrough(TIntermAggregate *statementList)
+    : TIntermTraverser(true, false, false),
+      mStatementList(statementList),
+      mLastStatementWasBreak(false),
+      mPreviousCase(nullptr)
+{
+    mStatementListOut = new TIntermAggregate();
+    mStatementListOut->setOp(EOpSequence);
+}
+
+void RemoveSwitchFallThrough::visitSymbol(TIntermSymbol *node)
+{
+    // Note that this assumes that switch statements which don't begin by a case statement
+    // have already been weeded out in validation.
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+}
+
+void RemoveSwitchFallThrough::visitConstantUnion(TIntermConstantUnion *node)
+{
+    // Conditions of case labels are not traversed, so this is some other constant
+    // Could be just a statement like "0;"
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+}
+
+bool RemoveSwitchFallThrough::visitBinary(Visit, TIntermBinary *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThrough::visitUnary(Visit, TIntermUnary *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThrough::visitSelection(Visit, TIntermSelection *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThrough::visitSwitch(Visit, TIntermSwitch *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    // Don't go into nested switch statements
+    return false;
+}
+
+void RemoveSwitchFallThrough::outputSequence(TIntermSequence *sequence, size_t startIndex)
+{
+    for (size_t i = startIndex; i < sequence->size(); ++i)
+    {
+        mStatementListOut->getSequence()->push_back(sequence->at(i));
+    }
+}
+
+void RemoveSwitchFallThrough::handlePreviousCase()
+{
+    if (mPreviousCase)
+        mCasesSharingBreak.push_back(mPreviousCase);
+    if (mLastStatementWasBreak)
+    {
+        bool labelsWithNoStatements = true;
+        for (size_t i = 0; i < mCasesSharingBreak.size(); ++i)
+        {
+            if (mCasesSharingBreak.at(i)->getSequence()->size() > 1)
+            {
+                labelsWithNoStatements = false;
+            }
+            if (labelsWithNoStatements)
+            {
+                // Fall-through is allowed in case the label has no statements.
+                outputSequence(mCasesSharingBreak.at(i)->getSequence(), 0);
+            }
+            else
+            {
+                // Include all the statements that this case can fall through under the same label.
+                for (size_t j = i; j < mCasesSharingBreak.size(); ++j)
+                {
+                    size_t startIndex = j > i ? 1 : 0; // Add the label only from the first sequence.
+                    outputSequence(mCasesSharingBreak.at(j)->getSequence(), startIndex);
+
+                }
+            }
+        }
+        mCasesSharingBreak.clear();
+    }
+    mLastStatementWasBreak = false;
+    mPreviousCase = nullptr;
+}
+
+bool RemoveSwitchFallThrough::visitCase(Visit, TIntermCase *node)
+{
+    handlePreviousCase();
+    mPreviousCase = new TIntermAggregate();
+    mPreviousCase->setOp(EOpSequence);
+    mPreviousCase->getSequence()->push_back(node);
+    // Don't traverse the condition of the case statement
+    return false;
+}
+
+bool RemoveSwitchFallThrough::visitAggregate(Visit, TIntermAggregate *node)
+{
+    if (node != mStatementList)
+    {
+        mPreviousCase->getSequence()->push_back(node);
+        mLastStatementWasBreak = false;
+        return false;
+    }
+    return true;
+}
+
+bool RemoveSwitchFallThrough::visitLoop(Visit, TIntermLoop *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThrough::visitBranch(Visit, TIntermBranch *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    // TODO: Verify that accepting return or continue statements here doesn't cause problems.
+    mLastStatementWasBreak = true;
+    return false;
+}

src/compiler/translator/RemoveSwitchFallThrough.h

+//
+// Copyright (c) 2002-2015 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.
+//
+
+#ifndef COMPILER_TRANSLATOR_REMOVESWITCHFALLTHROUGH_H_
+#define COMPILER_TRANSLATOR_REMOVESWITCHFALLTHROUGH_H_
+
+#include "compiler/translator/IntermNode.h"
+
+class RemoveSwitchFallThrough : public TIntermTraverser
+{
+  public:
+    // When given a statementList from a switch AST node, return an updated
+    // statementList that has fall-through removed.
+    static TIntermAggregate *removeFallThrough(TIntermAggregate *statementList);
+
+  private:
+    RemoveSwitchFallThrough(TIntermAggregate *statementList);
+
+    void visitSymbol(TIntermSymbol *node) override;
+    void visitConstantUnion(TIntermConstantUnion *node) override;
+    bool visitBinary(Visit, TIntermBinary *node) override;
+    bool visitUnary(Visit, TIntermUnary *node) override;
+    bool visitSelection(Visit visit, TIntermSelection *node) override;
+    bool visitSwitch(Visit, TIntermSwitch *node) override;
+    bool visitCase(Visit, TIntermCase *node) override;
+    bool visitAggregate(Visit, TIntermAggregate *node) override;
+    bool visitLoop(Visit, TIntermLoop *node) override;
+    bool visitBranch(Visit, TIntermBranch *node) override;
+
+    void outputSequence(TIntermSequence *sequence, size_t startIndex);
+    void handlePreviousCase();
+
+    TIntermAggregate *mStatementList;
+    TIntermAggregate *mStatementListOut;
+    bool mLastStatementWasBreak;
+    TIntermAggregate *mPreviousCase;
+    std::vector<TIntermAggregate *> mCasesSharingBreak;
+};
+
+#endif // COMPILER_TRANSLATOR_REMOVESWITCHFALLTHROUGH_H_