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| author | Misha Brukman <brukman+llvm@gmail.com> | 2004-04-06 03:53:49 +0000 |
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| committer | Misha Brukman <brukman+llvm@gmail.com> | 2004-04-06 03:53:49 +0000 |
| commit | a3ce42921c5669b0e8b82e4ac827e2fb3f4a238b (patch) | |
| tree | 9ca85ec0ee20e36e6e517542c47b6462b8c29ef8 /docs/ExtendingLLVM.html | |
| parent | 722070e0bad559b622ef50eb52216d05042a3904 (diff) | |
| download | external_llvm-a3ce42921c5669b0e8b82e4ac827e2fb3f4a238b.zip external_llvm-a3ce42921c5669b0e8b82e4ac827e2fb3f4a238b.tar.gz external_llvm-a3ce42921c5669b0e8b82e4ac827e2fb3f4a238b.tar.bz2 | |
Added notes on extending LLVM with new instructions, intrinsics, types, etc.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12689 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/ExtendingLLVM.html')
| -rw-r--r-- | docs/ExtendingLLVM.html | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/docs/ExtendingLLVM.html b/docs/ExtendingLLVM.html new file mode 100644 index 0000000..8c880e5 --- /dev/null +++ b/docs/ExtendingLLVM.html @@ -0,0 +1,213 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" + "http://www.w3.org/TR/html4/strict.dtd"> +<html> +<head> + <title>Extending LLVM: Adding instructions, intrinsics, types, etc.</title> + <link rel="stylesheet" href="llvm.css" type="text/css"> +</head> + +<body> + +<div class="doc_title"> + Extending LLVM: Adding instructions, intrinsics, types, etc. +</div> + +<ol> + <li><a href="#introduction">Introduction and Warning</a></li> + <li><a href="#instruction">Adding a new instruction</a></li> + <li><a href="#intrinsic">Adding a new intrinsic function</a></li> + <li><a href="#type">Adding a new type</a> + <ol> + <li><a href="#fund_type">Adding a new fundamental type</a></li> + <li><a href="#derived_type">Adding a new derived type</a></li> + </ol></li> +</ol> + +<div class="doc_text"> + <p><b>Written by <a href="http://misha.brukman.net">Misha Brukman</a></b></p> +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="introduction">Introduction and Warning</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>During the course of using LLVM, you may wish to customize it for your +research project or for experimentation. At this point, you may realize that +you need to add something to LLVM, whether it be a new fundamental type, a new +intrinsic function, or a whole new instruction.</p> + +<p>When you come to this realization, stop and think. Do you really need to +extend LLVM? Is it a new fundamental capability that LLVM does not support at +its current incarnation or can it be synthesized from already pre-existing LLVM +elements? If you are not sure, ask on the <a +href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM-dev</a> list. The +reason is that extending LLVM will get involved as you need to update all the +different passes that you intend to use with your extension, and there are +<em>many</em> LLVM analyses and transformations, so it may be quite a bit of +work.</p> + +<p>Before you invest a significant amount of effort into a non-trivial +extension, <span class="doc_warning">ask on the list</span> if what you are +looking to do can be done with already-existing infrastructure, or if maybe +someone else is already working on it. You will save yourself a lot of time and +effort by doing so.</p> + +<p>Finally, these are my notes, and since my extensions are not complete, I may +be missing steps. If you find some omissions, please let me know <a +href="http://misha.brukman.net/contact.html">directly</a> or post on <a +href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM-dev</a>.</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="instruction">Adding a new instruction</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p><span class="doc_warning">WARNING: adding instructions changes the bytecode +format, and will break compatibility with currently-existing LLVM +installations.</span> Only add an instruction if it is absolutely +necessary.</p> + +<ol> +<li><tt>llvm/include/llvm/Instruction.def</tt>: + add a number for your instruction and an enum name</li> + +<li><tt>llvm/include/llvm/i*.h</tt>: + add a definition for the class that will represent your instruction</li> + +<li><tt>llvm/include/llvm/Support/InstVisitor.h</tt>: + add a prototype for a visitor to your new instruction type</li> + +<li><tt>llvm/lib/AsmParser/Lexer.l</tt>: + add a new token to parse your instruction from assembly text file</li> + +<li><tt>llvm/lib/AsmParser/llvmAsmParser.y</tt>: + add the grammar on how your instruction can be read and what it will + construct as a result</li> + +<li><tt>llvm/lib/Bytecode/Reader/InstructionReader.cpp</tt>: + add a case for your instruction and how it will be parsed from bytecode</li> + +<li><tt>llvm/lib/VMCore/Instruction.cpp</tt>: + add a case for how your instruction will be printed out to assembly</li> + +<li><tt>llvm/lib/VMCore/i*.cpp</tt>: + implement the class you defined in <tt>llvm/include/llvm/i*.h</tt></li> + +</ol> + +<p>Also, you need to implement (or modify) any analyses or passes that you want +to understand this new instruction.</p> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="intrinsic">Adding a new intrinsic function</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p>Adding an intrinsic function is easier than adding an instruction, and is +transparent to optimization passes which treat it as an unanalyzable function. +If your added functionality can be expressed as a function call, an intrinsic +function is the method of choice for LLVM extension.</p> + +<ol> + +<li><tt>llvm/include/llvm/Intrinsics.h</tt>: + add an enum in the <tt>llvm::Intrinsic</tt> namespace</li> + +<li><tt>llvm/lib/VMCore/IntrinsicLowering.cpp</tt>: + implement the lowering for this intrinsic</li> + +<li><tt>llvm/lib/VMCore/Verifier.cpp</tt>: + handle the new intrinsic</li> + +<li><tt>llvm/lib/VMCore/Function.cpp</tt>: + handle the new intrinsic</li> + +</ol> + +</div> + +<!-- *********************************************************************** --> +<div class="doc_section"> + <a name="type">Adding a new type</a> +</div> +<!-- *********************************************************************** --> + +<div class="doc_text"> + +<p><span class="doc_warning">WARNING: adding new types changes the bytecode +format, and will break compatibility with currently-existing LLVM +installations.</span> Only add new types if it is absolutely necessary.</p> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="fund_type">Adding a fundamental type</a> +</div> + +<div class="doc_text"> + +<ol> + +<li><tt>llvm/include/llvm/Type.def</tt>: + add enum for the type</li> + +<li><tt>llvm/include/llvm/Type.h</tt>: + add ID number for the new type; add static <tt>Type*</tt> for this type</li> + +<li><tt>llvm/lib/VMCore/Type.cpp</tt>: + add mapping from <tt>TypeID</tt> => <tt>Type*</tt>; + initialize the static <tt>Type*</tt></li> + +<li><tt>llvm/lib/AsmReader/Lexer.l</tt>: + add ability to parse in the type from text assembly</li> + +<li><tt>llvm/lib/AsmReader/llvmAsmParser.y</tt>: + add a token for that type</li> + +</ol> + +</div> + +<!-- ======================================================================= --> +<div class="doc_subsection"> + <a name="derived_type">Adding a derived type</a> +</div> + +<div class="doc_text"> + +<p>TODO</p> + +</div> + +<!-- *********************************************************************** --> + +<hr> +<address> + <a href="http://jigsaw.w3.org/css-validator/check/referer"><img + src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a> + <a href="http://validator.w3.org/check/referer"><img + src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a> + + <a href="http://misha.brukman.net">Misha Brukman</a><br> + <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a> + <br> + Last modified: $Date$ +</address> + +</body> +</html> |