<li><a href="#ds_map">Map-Like Containers (std::map, DenseMap, etc)</a>
<ul>
<li><a href="#dss_sortedvectormap">A sorted 'vector'</a></li>
- <li><a href="#dss_cstringmap">"llvm/ADT/CStringMap.h"</a></li>
+ <li><a href="#dss_stringmap">"llvm/ADT/StringMap.h"</a></li>
<li><a href="#dss_indexedmap">"llvm/ADT/IndexedMap.h"</a></li>
<li><a href="#dss_densemap">"llvm/ADT/DenseMap.h"</a></li>
<li><a href="#dss_map"><map></a></li>
<li><a href="#AbstractTypeUser">The AbstractTypeUser Class</a></li>
</ul></li>
- <li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
+ <li><a href="#SymbolTable">The <tt>ValueSymbolTable</tt> and <tt>TypeSymbolTable</tt> classes </a></li>
</ul></li>
<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
</pre>
</div>
- <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
+ <p> When running <tt>opt</tt> on a C file from the SPEC benchmark
suite, it gives a report that looks like this:</p>
<div class="doc_code">
toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
Mac OS/X, download and install the Mac OS/X <a
href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
-<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or whereever you install
+<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or wherever you install
it) to your path. Once in your system and path are set up, rerun the LLVM
configure script and rebuild LLVM to enable this functionality.</p>
<p><tt>SelectionDAG</tt> has been extended to make it easier to locate
<i>interesting</i> nodes in large complex graphs. From gdb, if you
<tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
-next <tt>call DAG.viewGraph()</tt> would hilight the node in the
+next <tt>call DAG.viewGraph()</tt> would highlight the node in the
specified color (choices of colors can be found at <a
href="http://www.graphviz.org/doc/info/colors.html">colors</a>.) More
complex node attributes can be provided with <tt>call
<div class="doc_text">
-<p>LLVM has a plethora of datastructures in the <tt>llvm/ADT/</tt> directory,
- and we commonly use STL datastructures. This section describes the tradeoffs
+<p>LLVM has a plethora of data structures in the <tt>llvm/ADT/</tt> directory,
+ and we commonly use STL data structures. This section describes the trade-offs
you should consider when you pick one.</p>
<p>
access the container. Based on that, you should use:</p>
<ul>
-<li>a <a href="#ds_map">map-like</a> container if you need efficient lookup
+<li>a <a href="#ds_map">map-like</a> container if you need efficient look-up
of an value based on another value. Map-like containers also support
efficient queries for containment (whether a key is in the map). Map-like
containers generally do not support efficient reverse mapping (values to
<li>a <a href="#ds_sequential">sequential</a> container provides
the most efficient way to add elements and keeps track of the order they are
added to the collection. They permit duplicates and support efficient
- iteration, but do not support efficient lookup based on a key.
+ iteration, but do not support efficient look-up based on a key.
</li>
</ul>
<p>
-Once the proper catagory of container is determined, you can fine tune the
+Once the proper category of container is determined, you can fine tune the
memory use, constant factors, and cache behaviors of access by intelligently
-picking a member of the catagory. Note that constant factors and cache behavior
+picking a member of the category. Note that constant factors and cache behavior
can be a big deal. If you have a vector that usually only contains a few
elements (but could contain many), for example, it's much better to use
<a href="#dss_smallvector">SmallVector</a> than <a href="#dss_vector">vector</a>
consider a <a href="#dss_smallvector">SmallVector</a>). The cost of a heap
allocated array is the cost of the new/delete (aka malloc/free). Also note that
if you are allocating an array of a type with a constructor, the constructor and
-destructors will be run for every element in the array (resizable vectors only
+destructors will be run for every element in the array (re-sizable vectors only
construct those elements actually used).</p>
</div>
itself (which would waste space for elements that aren't in the container).
vector is also useful when interfacing with code that expects vectors :).
</p>
+
+<p>One worthwhile note about std::vector: avoid code like this:</p>
+
+<div class="doc_code">
+<pre>
+for ( ... ) {
+ std::vector<foo> V;
+ use V;
+}
+</pre>
+</div>
+
+<p>Instead, write this as:</p>
+
+<div class="doc_code">
+<pre>
+std::vector<foo> V;
+for ( ... ) {
+ use V;
+ V.clear();
+}
+</pre>
+</div>
+
+<p>Doing so will save (at least) one heap allocation and free per iteration of
+the loop.</p>
+
</div>
<!-- _______________________________________________________________________ -->
<div class="doc_text">
-<p>If you have a set-like datastructure that is usually small and whose elements
+<p>If you have a set-like data structure that is usually small and whose elements
are reasonably small, a <tt>SmallSet<Type, N></tt> is a good choice. This set
has space for N elements in place (thus, if the set is dynamically smaller than
N, no malloc traffic is required) and accesses them with a simple linear search.
<div class="doc_text">
<p>SmallPtrSet has all the advantages of SmallSet (and a SmallSet of pointers is
-transparently implemented with a SmallPtrSet), but also suports iterators. If
+transparently implemented with a SmallPtrSet), but also supports iterators. If
more than 'N' insertions are performed, a single quadratically
probed hash table is allocated and grows as needed, providing extremely
efficient access (constant time insertion/deleting/queries with low constant
</div>
<div class="doc_text">
-<p>LLVM's SetVector<Type> is actually a combination of a set along with
-a <a href="#ds_sequential">Sequential Container</a>. The important property
+<p>LLVM's SetVector<Type> is an adapter class that combines your choice of
+a set-like container along with a <a href="#ds_sequential">Sequential
+Container</a>. The important property
that this provides is efficient insertion with uniquing (duplicate elements are
ignored) with iteration support. It implements this by inserting elements into
both a set-like container and the sequential container, using the set-like
iteration is guaranteed to match the order of insertion into the SetVector.
This property is really important for things like sets of pointers. Because
pointer values are non-deterministic (e.g. vary across runs of the program on
-different machines), iterating over the pointers in a std::set or other set will
+different machines), iterating over the pointers in the set will
not be in a well-defined order.</p>
<p>
set and has the sum of constant factors from the set-like container and the
sequential container that it uses. Use it *only* if you need to iterate over
the elements in a deterministic order. SetVector is also expensive to delete
-elements out of (linear time).
+elements out of (linear time), unless you use it's "pop_back" method, which is
+faster.
</p>
+<p>SetVector is an adapter class that defaults to using std::vector and std::set
+for the underlying containers, so it is quite expensive. However,
+<tt>"llvm/ADT/SetVector.h"</tt> also provides a SmallSetVector class, which
+defaults to using a SmallVector and SmallSet of a specified size. If you use
+this, and if your sets are dynamically smaller than N, you will save a lot of
+heap traffic.</p>
+
</div>
<!-- _______________________________________________________________________ -->
<!-- _______________________________________________________________________ -->
<div class="doc_subsubsection">
- <a name="dss_cstringmap">"llvm/ADT/CStringMap.h"</a>
+ <a name="dss_stringmap">"llvm/ADT/StringMap.h"</a>
</div>
<div class="doc_text">
<p>
Strings are commonly used as keys in maps, and they are difficult to support
efficiently: they are variable length, inefficient to hash and compare when
-long, expensive to copy, etc. CStringMap is a specialized container designed to
-cope with these issues. It supports mapping an arbitrary range of bytes that
-does not have an embedded nul character in it ("C strings") to an arbitrary
-other object.</p>
+long, expensive to copy, etc. StringMap is a specialized container designed to
+cope with these issues. It supports mapping an arbitrary range of bytes to an
+arbitrary other object.</p>
-<p>The CStringMap implementation uses a quadratically-probed hash table, where
+<p>The StringMap implementation uses a quadratically-probed hash table, where
the buckets store a pointer to the heap allocated entries (and some other
stuff). The entries in the map must be heap allocated because the strings are
variable length. The string data (key) and the element object (value) are
object. This container guarantees the "<tt>(char*)(&Value+1)</tt>" points
to the key string for a value.</p>
-<p>The CStringMap is very fast for several reasons: quadratic probing is very
+<p>The StringMap is very fast for several reasons: quadratic probing is very
cache efficient for lookups, the hash value of strings in buckets is not
-recomputed when lookup up an element, CStringMap rarely has to touch the
+recomputed when lookup up an element, StringMap rarely has to touch the
memory for unrelated objects when looking up a value (even when hash collisions
happen), hash table growth does not recompute the hash values for strings
already in the table, and each pair in the map is store in a single allocation
(the string data is stored in the same allocation as the Value of a pair).</p>
-<p>CStringMap also provides query methods that take byte ranges, so it only ever
+<p>StringMap also provides query methods that take byte ranges, so it only ever
copies a string if a value is inserted into the table.</p>
</div>
There are several aspects of DenseMap that you should be aware of, however. The
iterators in a densemap are invalidated whenever an insertion occurs, unlike
map. Also, because DenseMap allocates space for a large number of key/value
-pairs (it starts with 64 by default) if you have large keys or values, it can
-waste a lot of space. Finally, you must implement a partial specialization of
+pairs (it starts with 64 by default), it will waste a lot of space if your keys
+or values are large. Finally, you must implement a partial specialization of
DenseMapKeyInfo for the key that you want, if it isn't already supported. This
is required to tell DenseMap about two special marker values (which can never be
-inserted into the map).</p>
+inserted into the map) that it needs internally.</p>
</div>
<pre>
#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
-// <i>F is a ptr to a Function instance</i>
+// <i>F is a pointer to a Function instance</i>
for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
llvm::cerr << *i << "\n";
</pre>
</div>
<p>Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
-worklist with its initial contents. For example, if you wanted to
-initialize a worklist to contain all instructions in a <tt>Function</tt>
+work list with its initial contents. For example, if you wanted to
+initialize a work list to contain all instructions in a <tt>Function</tt>
F, all you would need to do is something like:</p>
<div class="doc_code">
certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
much more straight-forward manner, but this example will allow us to explore how
-you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
+you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudo-code, this
is what we want to do:</p>
<div class="doc_code">
</div>
<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
-one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
+one integer in the current stack frame, at run time. Each <tt>Instruction</tt>
subclass is likely to have varying default parameters which change the semantics
of the instruction, so refer to the <a
href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
associated with the results of instructions! By supplying a value for the
<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
associate a logical name with the result of the instruction's execution at
-runtime. For example, say that I'm writing a transformation that dynamically
+run time. For example, say that I'm writing a transformation that dynamically
allocates space for an integer on the stack, and that integer is going to be
used as some kind of index by some other code. To accomplish this, I place an
<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
</div>
<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
-execution value, which is a pointer to an integer on the runtime stack.</p>
+execution value, which is a pointer to an integer on the run time stack.</p>
<p><i>Inserting instructions</i></p>
<p>
Some data structures need more to perform more complex updates when types get
-resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
-move and potentially merge type planes in its representation when a pointer
-changes.</p>
-
-<p>
-To support this, a class can derive from the AbstractTypeUser class. This class
+resolved. To support this, a class can derive from the AbstractTypeUser class.
+This class
allows it to get callbacks when certain types are resolved. To register to get
callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
methods can be called on a type. Note that these methods only work for <i>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
+ <a name="SymbolTable">The <tt>ValueSymbolTable</tt> and
+ <tt>TypeSymbolTable</tt> classes</a>
</div>
<div class="doc_text">
-<p>This class provides a symbol table that the <a
+<p>The <tt><a href="http://llvm.org/doxygen/classllvm_1_1ValueSymbolTable.html">
+ValueSymbolTable</a></tt> class provides a symbol table that the <a
href="#Function"><tt>Function</tt></a> and <a href="#Module">
-<tt>Module</tt></a> classes use for naming definitions. The symbol table can
-provide a name for any <a href="#Value"><tt>Value</tt></a>.
-<tt>SymbolTable</tt> is an abstract data type. It hides the data it contains
-and provides access to it through a controlled interface.</p>
+<tt>Module</tt></a> classes use for naming value definitions. The symbol table
+can provide a name for any <a href="#Value"><tt>Value</tt></a>.
+The <tt><a href="http://llvm.org/doxygen/classllvm_1_1TypeSymbolTable.html">
+TypeSymbolTable</a></tt> class is used by the <tt>Module</tt> class to store
+names for types.</p>
<p>Note that the <tt>SymbolTable</tt> class should not be directly accessed
by most clients. It should only be used when iteration over the symbol table
an empty name) do not exist in the symbol table.
</p>
-<p>To use the <tt>SymbolTable</tt> well, you need to understand the
-structure of the information it holds. The class contains two
-<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
-<tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
-Thus, Values are stored in two-dimensions and accessed by <tt>Type</tt> and
-name.</p>
+<p>These symbol tables support iteration over the values/types in the symbol
+table with <tt>begin/end/iterator</tt> and supports querying to see if a
+specific name is in the symbol table (with <tt>lookup</tt>). The
+<tt>ValueSymbolTable</tt> class exposes no public mutator methods, instead,
+simply call <tt>setName</tt> on a value, which will autoinsert it into the
+appropriate symbol table. For types, use the Module::addTypeName method to
+insert entries into the symbol table.</p>
-<p>The interface of this class provides three basic types of operations:
-<ol>
- <li><em>Accessors</em>. Accessors provide read-only access to information
- such as finding a value for a name with the
- <a href="#SymbolTable_lookup">lookup</a> method.</li>
- <li><em>Mutators</em>. Mutators allow the user to add information to the
- <tt>SymbolTable</tt> with methods like
- <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
- <li><em>Iterators</em>. Iterators allow the user to traverse the content
- of the symbol table in well defined ways, such as the method
- <a href="#SymbolTable_plane_begin"><tt>plane_begin</tt></a>.</li>
-</ol>
-
-<h3>Accessors</h3>
-<dl>
- <dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
- </dt>
- <dd>The <tt>lookup</tt> method searches the type plane given by the
- <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
- If a suitable <tt>Value</tt> is not found, null is returned.</dd>
-
- <dt><tt>bool isEmpty() const</tt>:</dt>
- <dd>This function returns true if both the value and types maps are
- empty</dd>
-</dl>
-
-<h3>Mutators</h3>
-<dl>
- <dt><tt>void insert(Value *Val)</tt>:</dt>
- <dd>This method adds the provided value to the symbol table. The Value must
- have both a name and a type which are extracted and used to place the value
- in the correct type plane under the value's name.</dd>
-
- <dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
- <dd> Inserts a constant or type into the symbol table with the specified
- name. There can be a many to one mapping between names and constants
- or types.</dd>
-
- <dt><tt>void remove(Value* Val)</tt>:</dt>
- <dd> This method removes a named value from the symbol table. The
- type and name of the Value are extracted from \p N and used to
- lookup the Value in the correct type plane. If the Value is
- not in the symbol table, this method silently ignores the
- request.</dd>
-
- <dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
- <dd> Remove a constant or type with the specified name from the
- symbol table.</dd>
-
- <dt><tt>Value *remove(const value_iterator& It)</tt>:</dt>
- <dd> Removes a specific value from the symbol table.
- Returns the removed value.</dd>
-
- <dt><tt>bool strip()</tt>:</dt>
- <dd> This method will strip the symbol table of its names leaving
- the type and values. </dd>
-
- <dt><tt>void clear()</tt>:</dt>
- <dd>Empty the symbol table completely.</dd>
-</dl>
-
-<h3>Iteration</h3>
-<p>The following functions describe three types of iterators you can obtain
-the beginning or end of the sequence for both const and non-const. It is
-important to keep track of the different kinds of iterators. There are
-three idioms worth pointing out:</p>
-
-<table>
- <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
- <tr>
- <td align="left">Planes Of name/Value maps</td><td>PI</td>
- <td align="left"><pre><tt>
-for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
- PE = ST.plane_end(); PI != PE; ++PI ) {
- PI->first // <i>This is the Type* of the plane</i>
- PI->second // <i>This is the SymbolTable::ValueMap of name/Value pairs</i>
-}
- </tt></pre></td>
- </tr>
- <tr>
- <td align="left">name/Value pairs in a plane</td><td>VI</td>
- <td align="left"><pre><tt>
-for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
- VE = ST.value_end(SomeType); VI != VE; ++VI ) {
- VI->first // <i>This is the name of the Value</i>
- VI->second // <i>This is the Value* value associated with the name</i>
-}
- </tt></pre></td>
- </tr>
-</table>
-
-<p>Using the recommended iterator names and idioms will help you avoid
-making mistakes. Of particular note, make sure that whenever you use
-value_begin(SomeType) that you always compare the resulting iterator
-with value_end(SomeType) not value_end(SomeOtherType) or else you
-will loop infinitely.</p>
-
-<dl>
-
- <dt><tt>plane_iterator plane_begin()</tt>:</dt>
- <dd>Get an iterator that starts at the beginning of the type planes.
- The iterator will iterate over the Type/ValueMap pairs in the
- type planes. </dd>
-
- <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
- <dd>Get a const_iterator that starts at the beginning of the type
- planes. The iterator will iterate over the Type/ValueMap pairs
- in the type planes. </dd>
-
- <dt><tt>plane_iterator plane_end()</tt>:</dt>
- <dd>Get an iterator at the end of the type planes. This serves as
- the marker for end of iteration over the type planes.</dd>
-
- <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
- <dd>Get a const_iterator at the end of the type planes. This serves as
- the marker for end of iteration over the type planes.</dd>
-
- <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
- <dd>Get an iterator that starts at the beginning of a type plane.
- The iterator will iterate over the name/value pairs in the type plane.
- Note: The type plane must already exist before using this.</dd>
-
- <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
- <dd>Get a const_iterator that starts at the beginning of a type plane.
- The iterator will iterate over the name/value pairs in the type plane.
- Note: The type plane must already exist before using this.</dd>
-
- <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
- <dd>Get an iterator to the end of a type plane. This serves as the marker
- for end of iteration of the type plane.
- Note: The type plane must already exist before using this.</dd>
-
- <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
- <dd>Get a const_iterator to the end of a type plane. This serves as the
- marker for end of iteration of the type plane.
- Note: the type plane must already exist before using this.</dd>
-
- <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
- <dd>This method returns a plane_const_iterator for iteration over
- the type planes starting at a specific plane, given by \p Ty.</dd>
-
- <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
- <dd>This method returns a plane_iterator for iteration over the
- type planes starting at a specific plane, given by \p Ty.</dd>
-
-</dl>
</div>
</dd>
<dt><tt>PointerType</tt></dt>
<dd>Subclass of SequentialType for pointer types.</dd>
- <dt><tt>PackedType</tt></dt>
- <dd>Subclass of SequentialType for packed (vector) types. A
- packed type is similar to an ArrayType but is distinguished because it is
- a first class type wherease ArrayType is not. Packed types are used for
+ <dt><tt>VectorType</tt></dt>
+ <dd>Subclass of SequentialType for vector types. A
+ vector type is similar to an ArrayType but is distinguished because it is
+ a first class type wherease ArrayType is not. Vector types are used for
vector operations and are usually small vectors of of an integer or floating
point type.</dd>
<dt><tt>StructType</tt></dt>