<li><a href="#general">General Information</a>
<ul>
<li><a href="#stl">The C++ Standard Template Library</a>
+<!--
+ <li>The <tt>-time-passes</tt> option
+ <li>How to use the LLVM Makefile system
+ <li>How to write a regression test
+-->
+ </ul>
+ <li><a href="#apis">Important and useful LLVM APIs</a>
+ <ul>
<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt> and
<tt>dyn_cast<></tt> templates</a>
+ <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro &
+ <tt>-debug</tt> option</a>
+ <li><a href="#Statistic">The <tt>Statistic</tt> template &
+ <tt>-stats</tt> option</a>
+<!--
+ <li>The <tt>InstVisitor</tt> template
+ <li>The general graph API
+-->
</ul>
<li><a href="#common">Helpful Hints for Common Operations</a>
<ul>
<li>
<li>
</ul>
- <li>Useful LLVM APIs
- <ul>
- <li>The general graph API
- <li>The <tt>InstVisitor</tt> template
- <li>The DEBUG() macro
- <li>The <tt>Statistic</tt> template
--->
- </ul>
-<!--
- <li>Useful related topics
- <ul>
- <li>The <tt>-time-passes</tt> option
- <li>How to use the LLVM Makefile system
- <li>How to write a regression test
- <li>
- </ul>
-->
</ul>
<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Here are some useful links:<p>
<ol>
-<li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
+<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++
Library reference</a> - an excellent reference for the STL and other parts of
-the standard C++ library.<br>
+the standard C++ library.
+
+<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
+O'Reilly book in the making. It has a decent <a
+href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
+Reference</a> that rivals Dinkumware's, and is actually free until the book is
+published.
<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
Questions</a>
to write maintainable code more than where to put your curly braces.<p>
+<!-- *********************************************************************** -->
+</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
+<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
+<a name="apis">Important and useful LLVM APIs
+</b></font></td></tr></table><ul>
+<!-- *********************************************************************** -->
+
+Here we highlight some LLVM APIs that are generally useful and good to know
+about when writing transformations.<p>
+
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td> </td><td width="100%">
lots of examples in the LLVM source base.<p>
+<!-- ======================================================================= -->
+</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
+<tr><td> </td><td width="100%">
+<font color="#EEEEFF" face="Georgia,Palatino"><b>
+<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
+</b></font></td></tr></table><ul>
+
+Often when working on your pass you will put a bunch of debugging printouts and
+other code into your pass. After you get it working, you want to remove
+it... but you may need it again in the future (to work out new bugs that you run
+across).<p>
+
+Naturally, because of this, you don't want to delete the debug printouts, but
+you don't want them to always be noisy. A standard compromise is to comment
+them out, allowing you to enable them if you need them in the future.<p>
+
+The "<tt><a
+href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>"
+file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
+this problem. Basically, you can put arbitrary code into the argument of the
+<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' is run with the
+'<tt>-debug</tt>' command line argument:
+
+<pre>
+ ...
+ DEBUG(std::cerr << "I am here!\n");
+ ...
+</pre><p>
+
+Then you can run your pass like this:<p>
+
+<pre>
+ $ opt < a.bc > /dev/null -mypass
+ <no output>
+ $ opt < a.bc > /dev/null -mypass -debug
+ I am here!
+ $
+</pre><p>
+
+Using the <tt>DEBUG()</tt> macro instead of a home brewed solution allows you to
+now have to create "yet another" command line option for the debug output for
+your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
+so they do not cause a performance impact at all (for the same reason, they
+should also not contain side-effects!).<p>
+
+One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
+enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
+"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
+program hasn't been started yet, you can always just run it with
+<tt>-debug</tt>.<p>
+
+
+<!-- ======================================================================= -->
+</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
+<tr><td> </td><td width="100%">
+<font color="#EEEEFF" face="Georgia,Palatino"><b>
+<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
+option</a>
+</b></font></td></tr></table><ul>
+
+The "<tt><a
+href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>"
+file provides a template named <tt>Statistic</tt> that is used as a unified way
+to keeping track of what the LLVM compiler is doing and how effective various
+optimizations are. It is useful to see what optimizations are contributing to
+making a particular program run faster.<p>
+
+Often you may run your pass on some big program, and you're interested to see
+how many times it makes a certain transformation. Although you can do this with
+hand inspection, or some ad-hoc method, this is a real pain and not very useful
+for big programs. Using the <tt>Statistic</tt> template makes it very easy to
+keep track of this information, and the calculated information is presented in a
+uniform manner with the rest of the passes being executed.<p>
+
+There are many examples of <tt>Statistic</tt> users, but this basics of using it
+are as follows:<p>
+
+<ol>
+<li>Define your statistic like this:<p>
+
+<pre>
+static Statistic<> NumXForms("mypassname", "The # of times I did stuff");
+</pre><p>
+
+The <tt>Statistic</tt> template can emulate just about any data-type, but if you
+do not specify a template argument, it defaults to acting like an unsigned int
+counter (this is usually what you want).<p>
+
+<li>Whenever you make a transformation, bump the counter:<p>
+
+<pre>
+ ++NumXForms; // I did stuff
+</pre><p>
+
+</ol><p>
+
+That's all you have to do. To get '<tt>opt</tt>' to print out the statistics
+gathered, use the '<tt>-stats</tt>' option:<p>
+
+<pre>
+ $ opt -stats -mypassname < program.bc > /dev/null
+ ... statistic output ...
+</pre><p>
+
+When running <tt>gccas</tt> on a C file from the SPEC benchmark suite, it gives
+a report that looks like this:<p>
+
+<pre>
+ 7646 bytecodewriter - Number of normal instructions
+ 725 bytecodewriter - Number of oversized instructions
+ 129996 bytecodewriter - Number of bytecode bytes written
+ 2817 raise - Number of insts DCEd or constprop'd
+ 3213 raise - Number of cast-of-self removed
+ 5046 raise - Number of expression trees converted
+ 75 raise - Number of other getelementptr's formed
+ 138 raise - Number of load/store peepholes
+ 42 deadtypeelim - Number of unused typenames removed from symtab
+ 392 funcresolve - Number of varargs functions resolved
+ 27 globaldce - Number of global variables removed
+ 2 adce - Number of basic blocks removed
+ 134 cee - Number of branches revectored
+ 49 cee - Number of setcc instruction eliminated
+ 532 gcse - Number of loads removed
+ 2919 gcse - Number of instructions removed
+ 86 indvars - Number of cannonical indvars added
+ 87 indvars - Number of aux indvars removed
+ 25 instcombine - Number of dead inst eliminate
+ 434 instcombine - Number of insts combined
+ 248 licm - Number of load insts hoisted
+ 1298 licm - Number of insts hoisted to a loop pre-header
+ 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
+ 75 mem2reg - Number of alloca's promoted
+ 1444 cfgsimplify - Number of blocks simplified
+</pre><p>
+
+Obviously, with so many optimizations, having a unified framework for this stuff
+is very nice. Making your pass fit well into the framework makes it more
+maintainable and useful.<p>
+
<!-- *********************************************************************** -->
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="common">Helpful Hints for Common Operations
-</b></font></td></tr></table><ul>
-<!-- *********************************************************************** -->
+</b></font></td></tr></table><ul> <!--
+*********************************************************************** -->
This section describes how to perform some very simple transformations of LLVM
code. This is meant to give examples of common idioms used, showing the
</p>
<li>Insertion into an implicit instruction list
-<p>
-<tt>Instruction</tt> instances that are already in
+<p><tt>Instruction</tt> instances that are already in
<tt>BasicBlock</tt>s are implicitly associated with an existing
instruction list: the instruction list of the enclosing basic block.
Thus, we could have accomplished the same thing as the above code
</pre>
which is much cleaner, especially if you're creating a lot of
instructions and adding them to <tt>BasicBlock</tt>s.
-</p>
+ </p>
</p>
</ul>
<pre>
<a href="#Instruction">Instruction</a> *I = .. ;
- <a href="#BasicBlock">BasicBlock</a> *BB = I->getParent();
- BB->getInstList().erase(I);
+ <a href="#BasicBlock">BasicBlock</a> *BB = I->getParent();
+ BB->getInstList().erase(I);
</pre><p>
-
<!--_______________________________________________________________________-->
</ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
<tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
-<!-- Value::replaceAllUsesWith
- User::replaceUsesOfWith
- Point out: include/llvm/Transforms/Utils/
- especially BasicBlockUtils.h with:
- ReplaceInstWithValue, ReplaceInstWithInst
+<p><i>Replacing individual instructions</i></p>
+<p>
+Including "<a
+href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h
+</a>" permits use of two very useful replace functions:
+<tt>ReplaceInstWithValue</tt> and <tt>ReplaceInstWithInst</tt>.
+<ul>
+
+<li><tt>ReplaceInstWithValue</tt>
+
+<p>This function replaces all uses (within a basic block) of a given
+instruction with a value, and then removes the original instruction.
+The following example illustrates the replacement of the result of a
+particular <tt>AllocaInst</tt> that allocates memory for a single
+integer with an null pointer to an integer.</p>
+
+<pre>
+AllocaInst* instToReplace = ...;
+BasicBlock::iterator ii(instToReplace);
+ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,
+ Constant::getNullValue(PointerType::get(Type::IntTy)));
+</pre>
+
+<li><tt>ReplaceInstWithInst</tt>
+
+<p>This function replaces a particular instruction with another
+instruction. The following example illustrates the replacement of one
+<tt>AllocaInst</tt> with another.<p>
+
+<pre>
+AllocaInst* instToReplace = ...;
+BasicBlock::iterator ii(instToReplace);
+ReplaceInstWithInst(instToReplace->getParent()->getInstList(), ii,
+ new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt");
+</pre>
+
+</ul>
+<p><i>Replacing multiple uses of <tt>User</tt>s and
+ <tt>Value</tt>s</i></p>
+
+You can use <tt>Value::replaceAllUsesWith</tt> and
+<tt>User::replaceUsesOfWith</tt> to change more than one use at a
+time. See the doxygen documentation for the <a
+href="/doxygen/classValue.html">Value Class</a> and <a
+href="/doxygen/classUser.html">User Class</a>, respectively, for more
+information.
+
+<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
+include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
+ReplaceInstWithValue, ReplaceInstWithInst
-->
<!-- *********************************************************************** -->
Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
<tt>Instruction</tt> is embedded into.<p>
-<li><tt>bool
hasSideEffects()</tt><p>
+<li><tt>bool
mayWriteToMemory()</tt><p>
-Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
+Returns true if the instruction writes to memory, i.e. it is a <tt>call</tt>,
<tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
<li><tt>unsigned getOpcode()</tt><p>
\end{itemize}
<li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
\begin{itemize}
- <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
+ <li><tt>Value * getPointerOperand()</tt>: Returns the Pointer Operand which is typically the 0th operand.
\end{itemize}
<li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
\begin{itemize}
and returns the return type of the function, or the <a
href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
-
-<li><tt>bool hasSymbolTable() const</tt><p>
-
-Return true if the <tt>Function</tt> has a symbol table allocated to it and if
-there is at least one entry in it.<p>
-
<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
-<tt>Function</tt> or a null pointer if one has not been allocated (because there
-are no named values in the function).<p>
-
-<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
-
-Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
-<tt>Function</tt> or allocate a new <a
-href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
-should only be used when adding elements to the <a
-href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
-not left laying around.<p>
+<tt>Function</tt>.<p>
<!-- Symbol table stuff -->
<hr size=0>
-<li><tt>bool hasSymbolTable() const</tt><p>
-
-Return true if the <tt>Module</tt> has a symbol table allocated to it and if
-there is at least one entry in it.<p>
-
<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
-Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
-<tt>Module</tt> or a null pointer if one has not been allocated (because there
-are no named values in the function).<p>
-
-<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
-
-Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
-<tt>Module</tt> or allocate a new <a
-href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
-should only be used when adding elements to the <a
-href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
-not left laying around.<p>
+Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for
+this <tt>Module</tt>.<p>
<!-- Convenience methods -->
<li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
+<hr>
+Important Subclasses of Constant<p>
-
-\subsection{Important Subclasses of Constant}
-\begin{itemize}
+<ul>
<li>ConstantSInt : This subclass of Constant represents a signed integer constant.
- \begin{itemize}
- <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
- \end{itemize}
+<ul>
+ <li><tt>int64_t getValue() const</tt>: Returns the underlying value of this constant.
+</ul>
<li>ConstantUInt : This class represents an unsigned integer.
- \begin{itemize}
- <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
- \end{itemize}
+<ul>
+ <li><tt>uint64_t getValue() const</tt>: Returns the underlying value of this constant.
+</ul>
<li>ConstantFP : This class represents a floating point constant.
- \begin{itemize}
- <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
- \end{itemize}
+<ul>
+ <li><tt>double getValue() const</tt>: Returns the underlying value of this constant.
+</ul>
<li>ConstantBool : This represents a boolean constant.
- \begin{itemize}
- <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
- \end{itemize}
+<ul>
+ <li><tt>bool getValue() const</tt>: Returns the underlying value of this constant.
+</ul>
<li>ConstantArray : This represents a constant array.
- \begin{itemize}
+<ul>
<li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
- \end{itemize}
+</ul>
<li>ConstantStruct : This represents a constant struct.
- \begin{itemize}
+<ul>
<li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
- \end{itemize}
+</ul>
<li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
- \begin{itemize}
+<ul>
<li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
- \end{itemize}
-\end{itemize}
+</ul>
+</ul>
<!-- ======================================================================= -->
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
-<li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
-<li><tt> bool isSigned () const</tt>: Returns whether an integral numeric type is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is not true for Float and Double.
-<li><tt>bool isUnsigned () const</tt>: Returns whether a numeric type is unsigned. This is not quite the complement of isSigned... nonnumeric types return false as they do with isSigned. This returns true for UByteTy, UShortTy, UIntTy, and ULongTy.
-<li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
-<li><tt>bool isIntegral () const</tt>: Returns true if this is an integral type, which is either Bool type or one of the Integer types.
+<li><tt>PrimitiveID getPrimitiveID() const</tt>: Returns the base type of the type.
+<li><tt> bool isSigned() const</tt>: Returns whether an integral numeric type is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is not true for Float and Double.
+<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is unsigned. This is not quite the complement of isSigned... nonnumeric types return false as they do with isSigned. This returns true for UByteTy, UShortTy, UIntTy, and ULongTy.
+<li><tt> bool isInteger() const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
+<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral type, which is either Bool type or one of the Integer types.
-<li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
-<li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
+<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two floating point types.
+<li><tt>bool isRecursive() const</tt>: Returns rue if the type graph contains a cycle.
<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if this type can be converted to 'Ty' without any reinterpretation of bits. For example, uint to int.
-<li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
-<li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
+<li><tt>bool isPrimitiveType() const</tt>: Returns true if it is a primitive type.
+<li><tt>bool isDerivedType() const</tt>: Returns true if it is a derived type.
<li><tt>const Type * getContainedType (unsigned i) const</tt>:
This method is used to implement the type iterator. For derived types, this returns the types 'contained' in the derived type, returning 0 when 'i' becomes invalid. This allows the user to iterate over the types in a struct, for example, really easily.
-<li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
+<li><tt>unsigned getNumContainedTypes() const</tt>: Return the number of types in the derived type.
+<p>
+<hr>
+Derived Types<p>
-\subsection{Derived Types}
-\begin{itemize}
+<ul>
<li>SequentialType : This is subclassed by ArrayType and PointerType
- \begin{itemize}
- <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
- \end{itemize}
+<ul>
+ <li><tt>const Type * getElementType() const</tt>: Returns the type of each of the elements in the sequential type.
+</ul>
<li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
- \begin{itemize}
- <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
- \end{itemize}
+<ul>
+ <li><tt>unsigned getNumElements() const</tt>: Returns the number of elements in the array.
+</ul>
<li>PointerType : Subclass of SequentialType for pointer types.
<li>StructType : subclass of DerivedTypes for struct types
<li>FunctionType : subclass of DerivedTypes for function types.
- \begin{itemize}
+
+<ul>
- <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
- <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
- <li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
+ <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg function
+ <li><tt> const Type * getReturnType() const</tt>: Returns the return type of the function.
+ <li><tt> const ParamTypes &getParamTypes() const</tt>: Returns a vector of parameter types.
<li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
- <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
- \end{itemize}
-\end{itemize}
+ <li><tt> const unsigned getNumParams() const</tt>: Returns the number of formal parameters.
+</ul>
+</ul>
<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
<!-- hhmts start -->
-Last modified: Tue Sep 17 17:41:54 CDT 2002
+Last modified: Mon Feb 24 14:45:19 CST 2003
<!-- hhmts end -->
</font></body></html>
projects / oota-llvm.git / blobdiff