From 64d39d3281aaabc09ee792312a48251fd3114a3b Mon Sep 17 00:00:00 2001 From: Dan Liew Date: Fri, 6 Jun 2014 17:25:47 +0000 Subject: Mention the IRBuilder in Programmer's Manual with a few small examples. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210354 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/ProgrammersManual.rst | 37 ++++++++++++++++++++++++++++++++++++- 1 file changed, 36 insertions(+), 1 deletion(-) (limited to 'docs') diff --git a/docs/ProgrammersManual.rst b/docs/ProgrammersManual.rst index 9838ba2ecc..2ec02964e1 100644 --- a/docs/ProgrammersManual.rst +++ b/docs/ProgrammersManual.rst @@ -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 -- cgit v1.2.3