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Mention the IRBuilder in Programmer's Manual with a few small examples.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210354 91177308-0d34-0410-b5e6-96231b3b80d8
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Dan Liew 2014-06-06 17:25:47 +00:00
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docs/ProgrammersManual.rst
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@ -1918,7 +1918,7 @@ which is a pointer to an integer on the run time stack.
*Inserting instructions*
There are essentially two ways to insert an ``Instruction`` into an existing
There are essentially three ways to insert an ``Instruction`` into an existing
sequence of instructions that form a ``BasicBlock``:
* Insertion into an explicit instruction list
@ -1988,6 +1988,41 @@ sequence of instructions that form a ``BasicBlock``:
which is much cleaner, especially if you're creating a lot of instructions and
adding them to ``BasicBlock``\ s.
* Insertion using an instance of ``IRBuilder``
Inserting several ``Instuction``\ s can be quite laborious using the previous
methods. The ``IRBuilder`` is a convenience class that can be used to add
several instructions to the end of a ``BasicBlock`` or before a particular
``Instruction``. It also supports constant folding and renaming named
registers (see ``IRBuilder``'s template arguments).
The example below demonstrates a very simple use of the ``IRBuilder`` where
three instructions are inserted before the instruction ``pi``. The first two
instructions are Call instructions and third instruction multiplies the return
value of the two calls.
.. code-block:: c++
Instruction *pi = ...;
IRBuilder<> Builder(pi);
CallInst* callOne = Builder.CreateCall(...);
CallInst* callTwo = Builder.CreateCall(...);
Value* result = Builder.CreateMul(callOne, callTwo);
The example below is similar to the above example except that the created
``IRBuilder`` inserts instructions at the end of the ``BasicBlock`` ``pb``.
.. code-block:: c++
BasicBlock *pb = ...;
IRBuilder<> Builder(pb);
CallInst* callOne = Builder.CreateCall(...);
CallInst* callTwo = Builder.CreateCall(...);
Value* result = Builder.CreateMul(callOne, callTwo);
See :doc:`tutorial/LangImpl3` for a practical use of the ``IRBuilder``.
.. _schanges_deleting:
Deleting Instructions