1 files changed, 163 insertions, 0 deletions
diff --git a/src/3rdparty/angle/src/compiler/translator/RewriteDoWhile.cpp b/src/3rdparty/angle/src/compiler/translator/RewriteDoWhile.cpp
new file mode 100644
index 0000000000..8347447546
--- /dev/null
+++ b/src/3rdparty/angle/src/compiler/translator/RewriteDoWhile.cpp
@@ -0,0 +1,163 @@
+//
+// Copyright (c) 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.
+//
+
+// RewriteDoWhile.cpp: rewrites do-while loops using another equivalent
+// construct.
+
+#include "compiler/translator/RewriteDoWhile.h"
+
+#include "compiler/translator/IntermNode.h"
+
+namespace
+{
+
+// An AST traverser that rewrites loops of the form
+//   do {
+//     CODE;
+//   } while (CONDITION)
+//
+// to loops of the form
+//   bool temp = false;
+//   while (true) {
+//     if (temp) {
+//       if (!CONDITION) {
+//         break;
+//       }
+//     }
+//     temp = true;
+//     CODE;
+//   }
+//
+// The reason we don't use a simpler form, with for example just (temp && !CONDITION) in the
+// while condition, is that short-circuit is often badly supported by driver shader compiler.
+// The double if has the same effect, but forces shader compilers to behave.
+//
+// TODO(cwallez) when UnfoldShortCircuitIntoIf handles loops correctly, revisit this as we might
+// be able to use while (temp || CONDITION) with temp initially set to true then run
+// UnfoldShortCircuitIntoIf
+class DoWhileRewriter : public TIntermTraverser
+{
+  public:
+    DoWhileRewriter() : TIntermTraverser(true, false, false) {}
+
+    bool visitAggregate(Visit, TIntermAggregate *node) override
+    {
+        // A well-formed AST can only have do-while in EOpSequence which represent lists of
+        // statements. By doing a prefix traversal we are able to replace the do-while in the
+        // sequence directly as the content of the do-while will be traversed later.
+        if (node->getOp() != EOpSequence)
+        {
+            return true;
+        }
+
+        TIntermSequence *statements = node->getSequence();
+
+        // The statements vector will have new statements inserted when we encounter a do-while,
+        // which prevents us from using a range-based for loop. Using the usual i++ works, as
+        // the (two) new statements inserted replace the statement at the current position.
+        for (size_t i = 0; i < statements->size(); i++)
+        {
+            TIntermNode *statement = (*statements)[i];
+            TIntermLoop *loop      = statement->getAsLoopNode();
+
+            if (loop == nullptr || loop->getType() != ELoopDoWhile)
+            {
+                continue;
+            }
+
+            TType boolType = TType(EbtBool);
+
+            // bool temp = false;
+            TIntermAggregate *tempDeclaration = nullptr;
+            {
+                TConstantUnion *falseConstant = new TConstantUnion();
+                falseConstant->setBConst(false);
+                TIntermTyped *falseValue = new TIntermConstantUnion(falseConstant, boolType);
+
+                tempDeclaration = createTempInitDeclaration(falseValue);
+            }
+
+            // temp = true;
+            TIntermBinary *assignTrue = nullptr;
+            {
+                TConstantUnion *trueConstant = new TConstantUnion();
+                trueConstant->setBConst(true);
+                TIntermTyped *trueValue = new TIntermConstantUnion(trueConstant, boolType);
+
+                assignTrue = createTempAssignment(trueValue);
+            }
+
+            // if (temp) {
+            //   if (!CONDITION) {
+            //     break;
+            //   }
+            // }
+            TIntermSelection *breakIf = nullptr;
+            {
+                TIntermBranch *breakStatement = new TIntermBranch(EOpBreak, nullptr);
+
+                TIntermAggregate *breakBlock = new TIntermAggregate(EOpSequence);
+                breakBlock->getSequence()->push_back(breakStatement);
+
+                TIntermUnary *negatedCondition = new TIntermUnary(EOpLogicalNot);
+                negatedCondition->setOperand(loop->getCondition());
+
+                TIntermSelection *innerIf =
+                    new TIntermSelection(negatedCondition, breakBlock, nullptr);
+
+                TIntermAggregate *innerIfBlock = new TIntermAggregate(EOpSequence);
+                innerIfBlock->getSequence()->push_back(innerIf);
+
+                breakIf = new TIntermSelection(createTempSymbol(boolType), innerIfBlock, nullptr);
+            }
+
+            // Assemble the replacement loops, reusing the do-while loop's body and inserting our
+            // statements at the front.
+            TIntermLoop *newLoop = nullptr;
+            {
+                TConstantUnion *trueConstant = new TConstantUnion();
+                trueConstant->setBConst(true);
+                TIntermTyped *trueValue = new TIntermConstantUnion(trueConstant, boolType);
+
+                TIntermAggregate *body = nullptr;
+                if (loop->getBody() != nullptr)
+                {
+                    body = loop->getBody()->getAsAggregate();
+                }
+                else
+                {
+                    body = new TIntermAggregate(EOpSequence);
+                }
+                auto sequence = body->getSequence();
+                sequence->insert(sequence->begin(), assignTrue);
+                sequence->insert(sequence->begin(), breakIf);
+
+                newLoop = new TIntermLoop(ELoopWhile, nullptr, trueValue, nullptr, body);
+            }
+
+            TIntermSequence replacement;
+            replacement.push_back(tempDeclaration);
+            replacement.push_back(newLoop);
+
+            node->replaceChildNodeWithMultiple(loop, replacement);
+
+            nextTemporaryIndex();
+        }
+        return true;
+    }
+};
+
+}  // anonymous namespace
+
+void RewriteDoWhile(TIntermNode *root, unsigned int *temporaryIndex)
+{
+    ASSERT(temporaryIndex != 0);
+
+    DoWhileRewriter rewriter;
+    rewriter.useTemporaryIndex(temporaryIndex);
+
+    root->traverse(&rewriter);
+}