1 files changed, 270 insertions, 0 deletions
diff --git a/gfx/angle/checkout/src/compiler/translator/tree_ops/d3d/RemoveSwitchFallThrough.cpp b/gfx/angle/checkout/src/compiler/translator/tree_ops/d3d/RemoveSwitchFallThrough.cpp
new file mode 100644
index 0000000000..6360f1083c
--- /dev/null
+++ b/gfx/angle/checkout/src/compiler/translator/tree_ops/d3d/RemoveSwitchFallThrough.cpp
@@ -0,0 +1,270 @@
+//
+// Copyright 2002 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.
+//
+// RemoveSwitchFallThrough.cpp: Remove fall-through from switch statements.
+// Note that it is unsafe to do further AST transformations on the AST generated
+// by this function. It leaves duplicate nodes in the AST making replacements
+// unreliable.
+
+#include "compiler/translator/tree_ops/d3d/RemoveSwitchFallThrough.h"
+
+#include "compiler/translator/Diagnostics.h"
+#include "compiler/translator/tree_util/IntermTraverse.h"
+
+namespace sh
+{
+
+namespace
+{
+
+class RemoveSwitchFallThroughTraverser : public TIntermTraverser
+{
+  public:
+    static TIntermBlock *removeFallThrough(TIntermBlock *statementList,
+                                           PerformanceDiagnostics *perfDiagnostics);
+
+  private:
+    RemoveSwitchFallThroughTraverser(TIntermBlock *statementList,
+                                     PerformanceDiagnostics *perfDiagnostics);
+
+    void visitSymbol(TIntermSymbol *node) override;
+    void visitConstantUnion(TIntermConstantUnion *node) override;
+    bool visitDeclaration(Visit, TIntermDeclaration *node) override;
+    bool visitBinary(Visit, TIntermBinary *node) override;
+    bool visitUnary(Visit, TIntermUnary *node) override;
+    bool visitTernary(Visit visit, TIntermTernary *node) override;
+    bool visitSwizzle(Visit, TIntermSwizzle *node) override;
+    bool visitIfElse(Visit visit, TIntermIfElse *node) override;
+    bool visitSwitch(Visit, TIntermSwitch *node) override;
+    bool visitCase(Visit, TIntermCase *node) override;
+    bool visitAggregate(Visit, TIntermAggregate *node) override;
+    bool visitBlock(Visit, TIntermBlock *node) override;
+    bool visitLoop(Visit, TIntermLoop *node) override;
+    bool visitBranch(Visit, TIntermBranch *node) override;
+
+    void outputSequence(TIntermSequence *sequence, size_t startIndex);
+    void handlePreviousCase();
+
+    TIntermBlock *mStatementList;
+    TIntermBlock *mStatementListOut;
+    bool mLastStatementWasBreak;
+    TIntermBlock *mPreviousCase;
+    std::vector<TIntermBlock *> mCasesSharingBreak;
+    PerformanceDiagnostics *mPerfDiagnostics;
+};
+
+TIntermBlock *RemoveSwitchFallThroughTraverser::removeFallThrough(
+    TIntermBlock *statementList,
+    PerformanceDiagnostics *perfDiagnostics)
+{
+    RemoveSwitchFallThroughTraverser rm(statementList, perfDiagnostics);
+    ASSERT(statementList);
+    statementList->traverse(&rm);
+    ASSERT(rm.mPreviousCase || statementList->getSequence()->empty());
+    if (!rm.mLastStatementWasBreak && rm.mPreviousCase)
+    {
+        // Make sure that there's a branch at the end of the final case inside the switch statement.
+        // This also ensures that any cases that fall through to the final case will get the break.
+        TIntermBranch *finalBreak = new TIntermBranch(EOpBreak, nullptr);
+        rm.mPreviousCase->getSequence()->push_back(finalBreak);
+        rm.mLastStatementWasBreak = true;
+    }
+    rm.handlePreviousCase();
+    return rm.mStatementListOut;
+}
+
+RemoveSwitchFallThroughTraverser::RemoveSwitchFallThroughTraverser(
+    TIntermBlock *statementList,
+    PerformanceDiagnostics *perfDiagnostics)
+    : TIntermTraverser(true, false, false),
+      mStatementList(statementList),
+      mLastStatementWasBreak(false),
+      mPreviousCase(nullptr),
+      mPerfDiagnostics(perfDiagnostics)
+{
+    mStatementListOut = new TIntermBlock();
+}
+
+void RemoveSwitchFallThroughTraverser::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 RemoveSwitchFallThroughTraverser::visitConstantUnion(TIntermConstantUnion *node)
+{
+    // Conditions of case labels are not traversed, so this is a constant statement like "0;".
+    // These are no-ops so there's no need to add them back to the statement list. Should have
+    // already been pruned out of the AST, in fact.
+    UNREACHABLE();
+}
+
+bool RemoveSwitchFallThroughTraverser::visitDeclaration(Visit, TIntermDeclaration *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitBinary(Visit, TIntermBinary *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitUnary(Visit, TIntermUnary *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitTernary(Visit, TIntermTernary *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitSwizzle(Visit, TIntermSwizzle *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitIfElse(Visit, TIntermIfElse *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitSwitch(Visit, TIntermSwitch *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    // Don't go into nested switch statements
+    return false;
+}
+
+void RemoveSwitchFallThroughTraverser::outputSequence(TIntermSequence *sequence, size_t startIndex)
+{
+    for (size_t i = startIndex; i < sequence->size(); ++i)
+    {
+        mStatementListOut->getSequence()->push_back(sequence->at(i));
+    }
+}
+
+void RemoveSwitchFallThroughTraverser::handlePreviousCase()
+{
+    if (mPreviousCase)
+        mCasesSharingBreak.push_back(mPreviousCase);
+    if (mLastStatementWasBreak)
+    {
+        for (size_t i = 0; i < mCasesSharingBreak.size(); ++i)
+        {
+            ASSERT(!mCasesSharingBreak.at(i)->getSequence()->empty());
+            if (mCasesSharingBreak.at(i)->getSequence()->size() == 1)
+            {
+                // 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.
+                if (mCasesSharingBreak.size() > i + 1u)
+                {
+                    mPerfDiagnostics->warning(mCasesSharingBreak.at(i)->getLine(),
+                                              "Performance: non-empty fall-through cases in "
+                                              "switch statements generate extra code.",
+                                              "switch");
+                }
+                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 RemoveSwitchFallThroughTraverser::visitCase(Visit, TIntermCase *node)
+{
+    handlePreviousCase();
+    mPreviousCase = new TIntermBlock();
+    mPreviousCase->getSequence()->push_back(node);
+    mPreviousCase->setLine(node->getLine());
+    // Don't traverse the condition of the case statement
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitAggregate(Visit, TIntermAggregate *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool DoesBlockAlwaysBreak(TIntermBlock *node)
+{
+    if (node->getSequence()->empty())
+    {
+        return false;
+    }
+
+    TIntermBlock *lastStatementAsBlock = node->getSequence()->back()->getAsBlock();
+    if (lastStatementAsBlock)
+    {
+        return DoesBlockAlwaysBreak(lastStatementAsBlock);
+    }
+
+    TIntermBranch *lastStatementAsBranch = node->getSequence()->back()->getAsBranchNode();
+    return lastStatementAsBranch != nullptr;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitBlock(Visit, TIntermBlock *node)
+{
+    if (node != mStatementList)
+    {
+        mPreviousCase->getSequence()->push_back(node);
+        mLastStatementWasBreak = DoesBlockAlwaysBreak(node);
+        return false;
+    }
+    return true;
+}
+
+bool RemoveSwitchFallThroughTraverser::visitLoop(Visit, TIntermLoop *node)
+{
+    mPreviousCase->getSequence()->push_back(node);
+    mLastStatementWasBreak = false;
+    return false;
+}
+
+bool RemoveSwitchFallThroughTraverser::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;
+}
+
+}  // anonymous namespace
+
+TIntermBlock *RemoveSwitchFallThrough(TIntermBlock *statementList,
+                                      PerformanceDiagnostics *perfDiagnostics)
+{
+    return RemoveSwitchFallThroughTraverser::removeFallThrough(statementList, perfDiagnostics);
+}
+
+}  // namespace sh