update this to reflect the new selection daggy world
llvm-svn: 21853
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@ -24,8 +24,8 @@
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</ol>
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</ol>
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<div class="doc_author">
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<div class="doc_author">
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<p>Written by <a href="http://misha.brukman.net">Misha Brukman</a> and
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<p>Written by <a href="http://misha.brukman.net">Misha Brukman</a>,
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Brad Jones</p>
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Brad Jones, and <a href="http://nondot.org/sabre">Chris Lattner</a></p>
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</div>
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</div>
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<!-- *********************************************************************** -->
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<!-- *********************************************************************** -->
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@ -86,9 +86,6 @@ function and then be turned into an instruction if warranted.</p>
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<li><tt>llvm/include/llvm/Intrinsics.h</tt>:
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<li><tt>llvm/include/llvm/Intrinsics.h</tt>:
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add an enum in the <tt>llvm::Intrinsic</tt> namespace</li>
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add an enum in the <tt>llvm::Intrinsic</tt> namespace</li>
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<li><tt>llvm/lib/CodeGen/IntrinsicLowering.cpp</tt>:
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implement the lowering for this intrinsic</li>
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<li><tt>llvm/lib/VMCore/Verifier.cpp</tt>:
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<li><tt>llvm/lib/VMCore/Verifier.cpp</tt>:
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Add code to check the invariants of the intrinsic are respected.</li>
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Add code to check the invariants of the intrinsic are respected.</li>
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@ -100,17 +97,63 @@ function and then be turned into an instruction if warranted.</p>
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not access memory or does not write to memory, add it to the relevant list
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not access memory or does not write to memory, add it to the relevant list
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of functions.</li>
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of functions.</li>
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<li><tt>llvm/lib/Transforms/Utils/Local.cpp</tt>: If it is possible to
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<li><tt>llvm/lib/Transforms/Utils/Local.cpp</tt>: If it is possible to constant
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constant-propagate your intrinsic, add support to it in the
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fold your intrinsic, add support to it in the <tt>canConstantFoldCallTo</tt> and
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<tt>canConstantFoldCallTo</tt> and <tt>ConstantFoldCall</tt> functions.</li>
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<tt>ConstantFoldCall</tt> functions.</li>
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<li>Test your intrinsic</li>
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<li>Test your intrinsic</li>
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<li><tt>llvm/test/Regression/*</tt>: add your test cases to the test suite</li>
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<li><tt>llvm/test/Regression/*</tt>: add your test cases to the test suite</li>
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</ol>
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</ol>
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<p>If this intrinsic requires code generator support (i.e., it cannot be
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<p>Once the intrinsic has been added to the system, you must add code generator
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lowered), you should also add support to the code generator in question.</p>
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support for it. Generally you must do the following steps:</p>
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<dl>
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<dt>Add support to the C backend in <tt>lib/Target/CBackend/</tt></dt>
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<dd>Depending on the intrinsic, there are a few ways to implement this. First,
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if it makes sense to lower the intrinsic to an expanded sequence of C code in
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all cases, just emit the expansion in <tt>visitCallInst</tt>. Second, if the
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intrinsic has some way to express it with GCC (or any other compiler)
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extensions, it can be conditionally supported based on the compiler compiling
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the CBE output (see llvm.prefetch for an example). Third, if the intrinsic
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really has no way to be lowered, just have the code generator emit code that
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prints an error message and calls abort if executed.
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</dd>
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<dt>Add a enum value for the SelectionDAG node in
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<tt>include/llvm/CodeGen/SelectionDAGNodes.h</tt></dt>
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<dd>Also, add code to <tt>lib/CodeGen/SelectionDAG/SelectionDAG.cpp</tt> (and
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<tt>SelectionDAGPrinter.cpp</tt>) to print the node.</dd>
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<dt>Add code to <tt>SelectionDAG/SelectionDAGISel.cpp</tt> to recognize the
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intrinsic.</dt>
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<dd>Presumably the intrinsic should be recognized and turned into the node you
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added above.</dd>
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<dt>Add code to <tt>SelectionDAG/LegalizeDAG.cpp</tt> to <a
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href="CodeGenerator.html#selectiondag_legalize">legalize, promote, and
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expand</a> the node as necessary.</dt>
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<dd>If the intrinsic can be expanded to primitive operations, legalize can break
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the node down into other elementary operations that are be supported.</dd>
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<dt>Add target-specific support to specific code generators.</dt>
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<dd>Extend the code generators you are interested in to recognize and support
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the node, emitting the code you want.</dd>
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</dl>
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<p>
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Unfortunately, the process of extending the code generator to support a new node
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is not extremely well documented. As such, it is often helpful to look at other
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intrinsics (e.g. <tt>llvm.ctpop</tt>) to see how they are recognized and turned
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into a node by <tt>SelectionDAGISel.cpp</tt>, legalized by
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<tt>LegalizeDAG.cpp</tt>, then finally emitted by the various code generators.
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</p>
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</div>
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</div>
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@ -277,7 +320,6 @@ void calcTypeName(const Type *Ty,
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<a href="http://validator.w3.org/check/referer"><img
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<a href="http://validator.w3.org/check/referer"><img
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src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
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src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
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<a href="http://misha.brukman.net">Misha Brukman</a><br>
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<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
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<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
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<br>
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<br>
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Last modified: $Date$
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Last modified: $Date$
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