1 //
2 // Copyright (c) 2002-2015 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 // SeparateExpressionsReturningArrays splits array-returning expressions that are not array names
7 // from more complex expressions, assigning them to a temporary variable a#.
8 // Examples where a, b and c are all arrays:
9 // (a = b) == (a = c) is split into a = b; type[n] a1 = a; a = c; type[n] a2 = a; a1 == a2;
10 // type d = type[n](...)[i]; is split into type[n] a1 = type[n](...); type d = a1[i];
11
12 #include "compiler/translator/SeparateExpressionsReturningArrays.h"
13
14 #include "compiler/translator/IntermNodePatternMatcher.h"
15 #include "compiler/translator/IntermTraverse.h"
16
17 namespace sh
18 {
19
20 namespace
21 {
22
23 // Traverser that separates one array expression into a statement at a time.
24 class SeparateExpressionsTraverser : public TIntermTraverser
25 {
26 public:
27 SeparateExpressionsTraverser(TSymbolTable *symbolTable);
28
29 bool visitBinary(Visit visit, TIntermBinary *node) override;
30 bool visitAggregate(Visit visit, TIntermAggregate *node) override;
31
32 void nextIteration();
foundArrayExpression() const33 bool foundArrayExpression() const { return mFoundArrayExpression; }
34
35 protected:
36 // Marked to true once an operation that needs to be hoisted out of the expression has been
37 // found. After that, no more AST updates are performed on that traversal.
38 bool mFoundArrayExpression;
39
40 IntermNodePatternMatcher mPatternToSeparateMatcher;
41 };
42
SeparateExpressionsTraverser(TSymbolTable * symbolTable)43 SeparateExpressionsTraverser::SeparateExpressionsTraverser(TSymbolTable *symbolTable)
44 : TIntermTraverser(true, false, false, symbolTable),
45 mFoundArrayExpression(false),
46 mPatternToSeparateMatcher(IntermNodePatternMatcher::kExpressionReturningArray)
47 {
48 }
49
50 // Performs a shallow copy of an assignment node.
51 // These shallow copies are useful when a node gets inserted into an aggregate node
52 // and also needs to be replaced in its original location by a different node.
CopyAssignmentNode(TIntermBinary * node)53 TIntermBinary *CopyAssignmentNode(TIntermBinary *node)
54 {
55 return new TIntermBinary(node->getOp(), node->getLeft(), node->getRight());
56 }
57
visitBinary(Visit visit,TIntermBinary * node)58 bool SeparateExpressionsTraverser::visitBinary(Visit visit, TIntermBinary *node)
59 {
60 if (mFoundArrayExpression)
61 return false;
62
63 // Return if the expression is not an array or if we're not inside a complex expression.
64 if (!mPatternToSeparateMatcher.match(node, getParentNode()))
65 return true;
66
67 ASSERT(node->getOp() == EOpAssign);
68
69 mFoundArrayExpression = true;
70
71 TIntermSequence insertions;
72 insertions.push_back(CopyAssignmentNode(node));
73 // TODO(oetuaho): In some cases it would be more optimal to not add the temporary node, but just
74 // use the original target of the assignment. Care must be taken so that this doesn't happen
75 // when the same array symbol is a target of assignment more than once in one expression.
76 insertions.push_back(createTempInitDeclaration(node->getLeft()));
77 insertStatementsInParentBlock(insertions);
78
79 queueReplacement(createTempSymbol(node->getType()), OriginalNode::IS_DROPPED);
80
81 return false;
82 }
83
visitAggregate(Visit visit,TIntermAggregate * node)84 bool SeparateExpressionsTraverser::visitAggregate(Visit visit, TIntermAggregate *node)
85 {
86 if (mFoundArrayExpression)
87 return false; // No need to traverse further
88
89 if (!mPatternToSeparateMatcher.match(node, getParentNode()))
90 return true;
91
92 ASSERT(node->isConstructor() || node->getOp() == EOpCallFunctionInAST);
93
94 mFoundArrayExpression = true;
95
96 TIntermSequence insertions;
97 insertions.push_back(createTempInitDeclaration(node->shallowCopy()));
98 insertStatementsInParentBlock(insertions);
99
100 queueReplacement(createTempSymbol(node->getType()), OriginalNode::IS_DROPPED);
101
102 return false;
103 }
104
nextIteration()105 void SeparateExpressionsTraverser::nextIteration()
106 {
107 mFoundArrayExpression = false;
108 nextTemporaryId();
109 }
110
111 } // namespace
112
SeparateExpressionsReturningArrays(TIntermNode * root,TSymbolTable * symbolTable)113 void SeparateExpressionsReturningArrays(TIntermNode *root, TSymbolTable *symbolTable)
114 {
115 SeparateExpressionsTraverser traverser(symbolTable);
116 // Separate one expression at a time, and reset the traverser between iterations.
117 do
118 {
119 traverser.nextIteration();
120 root->traverse(&traverser);
121 if (traverser.foundArrayExpression())
122 traverser.updateTree();
123 } while (traverser.foundArrayExpression());
124 }
125
126 } // namespace sh
127