Qt 4.8
qoptimizationpasses.cpp
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41 
42 #include "qcommonsequencetypes_p.h"
43 #include "qoptimizerblocks_p.h"
44 
45 #include "qoptimizationpasses_p.h"
46 
48 
49 using namespace QPatternist;
50 
55 
57 {
58  static bool isInitialized = false; // STATIC DATA
59 
60  if(isInitialized)
61  return;
62 
63  isInitialized = true;
64 
65  /* Note, below is many of the building blocks re-used in several passes
66  * in order to reduce memory use. Thus, when changing one building block
67  * it potentially affects many passes. */
68 
69  /* ****************************************************** */
70  /* Rewrite "count(<expr>) ge 1" into "exists(<expr>)" */
71  OptimizationPass::ExpressionMarker firstFirstChild;
72  firstFirstChild.append(0);
73  firstFirstChild.append(0);
74 
77  geOpIDs.append(countFN);
79 
80  QVector<Expression::ID> geMatcher;
83 
84  const ExpressionIdentifier::Ptr ge(new ComparisonIdentifier(geMatcher,
86 
88  const OptimizationPass::Ptr geToExists(new OptimizationPass(ge, geOpIDs, firstFirstChild, existsFN));
89  comparisonPasses.append(geToExists);
90  /* ****************************************************** */
91 
92  /* ****************************************************** */
93  /* Rewrite "count(<expr>) gt 0" into "exists(<expr>)" */
94  ExpressionIdentifier::List countAndIntZero;
95  countAndIntZero.append(countFN);
96  const ExpressionIdentifier::Ptr zeroInteger(new IntegerIdentifier(0));
97  countAndIntZero.append(zeroInteger);
98 
99  const ExpressionIdentifier::Ptr gt(new ComparisonIdentifier(geMatcher,
101 
102  const OptimizationPass::Ptr gtToExists(new OptimizationPass(gt, countAndIntZero,
103  firstFirstChild, existsFN));
104  comparisonPasses.append(gtToExists);
105  /* ****************************************************** */
106 
107  /* ****************************************************** */
108  /* Rewrite "count(<expr>) ne 0" into "exists(<expr>)" */
109 
110  const ExpressionIdentifier::Ptr ne(new ComparisonIdentifier(geMatcher,
112  const OptimizationPass::Ptr neToExists(new OptimizationPass(ne, countAndIntZero, firstFirstChild,
113  existsFN,
115  comparisonPasses.append(neToExists);
116  /* ****************************************************** */
117 
118  /* ****************************************************** */
119  /* Rewrite "count(<expr>) eq 0" into "empty(<expr>)" */
121  eqOpIDs.append(countFN);
122  eqOpIDs.append(zeroInteger);
124  const ExpressionIdentifier::Ptr eq(new ComparisonIdentifier(geMatcher,
126  const OptimizationPass::Ptr eqToEmpty(new OptimizationPass(eq, eqOpIDs, firstFirstChild,
127  emptyFN,
129  comparisonPasses.append(eqToEmpty);
130 
131  /* ****************************************************** */
132 
133  /* ****************************************************** */
134  /* Rewrite "for $var in <expr> return $var" into "<expr>" */
137  firstChild.append(0);
138 
141  const OptimizationPass::Ptr simplifyFor(new OptimizationPass(ExpressionIdentifier::Ptr(), forOps,
142  firstChild, ExpressionCreator::Ptr()));
143  forPasses.append(simplifyFor);
144  /* ****************************************************** */
145 
146  /* ****************************************************** */
147  /* Rewrite "if(<expr>) then true() else false()" to "<expr>" */
149  marker.append(0);
150 
156 
157  const OptimizationPass::Ptr pass(new OptimizationPass(ExpressionIdentifier::Ptr(), opIDs, marker));
158  ifThenPasses.append(pass);
159  /* ****************************************************** */
160 
161  /* ****************************************************** */
162  /* Rewrite "not(exists(X))" into "empty(X)" */
163  ExpressionIdentifier::List idExistsFN;
165 
167  idExistsFN,
168  firstFirstChild,
169  emptyFN)));
170 
171  /* Rewrite "not(empty(X))" into "exists(X)" */
172  ExpressionIdentifier::List idEmptyFN;
174 
176  idEmptyFN,
177  firstFirstChild,
178  existsFN)));
179  /* ****************************************************** */
180 }
181 
Describes how a particular optimization pass should be carried out.
Creates a particular Expression instance identified by an Expression::ID.
#define QT_END_NAMESPACE
This macro expands to.
Definition: qglobal.h:90
The QExplicitlySharedDataPointer class represents a pointer to an explicitly shared object...
Definition: qshareddata.h:136
Matches numeric literals that are of type xs:integer and has a specific value.
void append(const T &t)
Inserts value at the end of the list.
Definition: qlist.h:507
OptimizationPass::List comparisonPasses
#define QT_BEGIN_NAMESPACE
This macro expands to.
Definition: qglobal.h:89
The namespace for the internal API of QtXmlPatterns.
void append(const T &t)
Inserts value at the end of the vector.
Definition: qvector.h:573
Identifies Expression instances based on their static type.
Matches boolean literals.
static const SequenceType::Ptr ExactlyOneBoolean
Determines whether an Expression is a value or general comparison or both, with a certain operator...
Identifies Expression instances by their Expression::id().
The QList class is a template class that provides lists.
Definition: qdatastream.h:62