1 //
2 // Copyright (c) 2017 The ANGLE Project Authors. All rights reserved.
3 // Use of this source code is governed by a BSD-style license that can be
4 // found in the LICENSE file.
5 //
6 // RemoveArrayLengthMethod.cpp:
7 // Fold array length expressions, including cases where the "this" node has side effects.
8 // Example:
9 // int i = (a = b).length();
10 // int j = (func()).length();
11 // becomes:
12 // (a = b);
13 // int i = <constant array length>;
14 // func();
15 // int j = <constant array length>;
16 //
17 // Must be run after SplitSequenceOperator, SimplifyLoopConditions and SeparateDeclarations steps
18 // have been done to expressions containing calls of the array length method.
19 //
20 // Does nothing to length method calls done on runtime-sized arrays.
21
22 #include "compiler/translator/RemoveArrayLengthMethod.h"
23
24 #include "compiler/translator/IntermNode.h"
25 #include "compiler/translator/IntermTraverse.h"
26
27 namespace sh
28 {
29
30 namespace
31 {
32
33 class RemoveArrayLengthTraverser : public TIntermTraverser
34 {
35 public:
RemoveArrayLengthTraverser()36 RemoveArrayLengthTraverser() : TIntermTraverser(true, false, false), mFoundArrayLength(false) {}
37
38 bool visitUnary(Visit visit, TIntermUnary *node) override;
39
nextIteration()40 void nextIteration() { mFoundArrayLength = false; }
41
foundArrayLength() const42 bool foundArrayLength() const { return mFoundArrayLength; }
43
44 private:
45 bool mFoundArrayLength;
46 };
47
visitUnary(Visit visit,TIntermUnary * node)48 bool RemoveArrayLengthTraverser::visitUnary(Visit visit, TIntermUnary *node)
49 {
50 // The only case where we leave array length() in place is for runtime-sized arrays.
51 if (node->getOp() == EOpArrayLength && !node->getOperand()->getType().isUnsizedArray())
52 {
53 mFoundArrayLength = true;
54 if (!node->getOperand()->hasSideEffects())
55 {
56 queueReplacement(node->fold(nullptr), OriginalNode::IS_DROPPED);
57 return false;
58 }
59 insertStatementInParentBlock(node->getOperand()->deepCopy());
60 TConstantUnion *constArray = new TConstantUnion[1];
61 constArray->setIConst(node->getOperand()->getOutermostArraySize());
62 queueReplacement(new TIntermConstantUnion(constArray, node->getType()),
63 OriginalNode::IS_DROPPED);
64 return false;
65 }
66 return true;
67 }
68
69 } // anonymous namespace
70
RemoveArrayLengthMethod(TIntermBlock * root)71 void RemoveArrayLengthMethod(TIntermBlock *root)
72 {
73 RemoveArrayLengthTraverser traverser;
74 do
75 {
76 traverser.nextIteration();
77 root->traverse(&traverser);
78 if (traverser.foundArrayLength())
79 traverser.updateTree();
80 } while (traverser.foundArrayLength());
81 }
82
83 } // namespace sh
84