Changes in directory llvm/docs:
ExtendingLLVM.html updated: 1.26 -> 1.27
---
Log message:
Update adding an intrinsic to describe that you can now just plop it into the
target .td file instead of adding SDNodes etc.
---
Diffs of the changes: (+13 -21)
ExtendingLLVM.html | 34 +++++++++++++---------------------
1 files changed, 13 insertions(+), 21 deletions(-)
Index: llvm/docs/ExtendingLLVM.html
diff -u llvm/docs/ExtendingLLVM.html:1.26 llvm/docs/ExtendingLLVM.html:1.27
--- llvm/docs/ExtendingLLVM.html:1.26 Mon Mar 13 23:39:39 2006
+++ llvm/docs/ExtendingLLVM.html Wed Apr 12 12:42:39 2006
@@ -53,9 +53,9 @@
<em>many</em> LLVM analyses and transformations, so it may be quite a bit of
work.</p>
-<p>Adding an <a href="#intrinsic">intrinsic function</a> 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
+<p>Adding an <a href="#intrinsic">intrinsic function</a> is far easier than
+adding an instruction, and is transparent to optimization passes. If your
added
+functionality can be expressed as a
function call, an intrinsic function is the method of choice for LLVM
extension.</p>
@@ -85,8 +85,9 @@
what the restrictions are. Talk to other people about it so that you are
sure it's a good idea.</li>
-<li><tt>llvm/include/llvm/Intrinsics.td</tt>:
- Add an entry for your intrinsic.</li>
+<li><tt>llvm/include/llvm/Intrinsics*.td</tt>:
+ Add an entry for your intrinsic. Describe its memory access
characteristics
+ for optimization (this controls whether it will be DCE'd, CSE'd, etc).</li>
<li><tt>llvm/lib/Analysis/ConstantFolding.cpp</tt>: If it is possible to
constant fold your intrinsic, add support to it in the
@@ -116,22 +117,13 @@
</dd>
<dl>
-<dt>Add support to the SelectionDAG Instruction Selector in
-<tt>lib/CodeGen/SelectionDAG/</tt></dt>
+<dt>Add support to the .td file for the target(s) of your choice in
+ <tt>lib/Target/*/*.td</tt>.</dt>
-<dd>Since most targets in LLVM use the SelectionDAG framework for generating
-code, you will likely need to add support for your intrinsic there as well.
-This is usually accomplished by adding a new node, and then teaching the
-SelectionDAG code how to handle that node. To do this, follow the steps in
-the <a href="#sdnode">Adding a new SelectionDAG node</a> section.</dd>
-
-<dl>
-<dt>Once you have added the new node, add code to
-<tt>SelectionDAG/SelectionDAGISel.cpp</tt> to recognize the intrinsic. In most
-cases, the intrinsic will just be turned into the node you just added. For an
-example of this, see how <tt>visitIntrinsicCall</tt> handles
-<tt>Intrinsic::ctpop_*</tt>.
-</dt>
+<dd>This is usually a matter of adding a pattern to the .td file that matches
+ the intrinsic, though it may obviously require adding the instructions you
+ want to generate as well. There are lots of examples in the PowerPC and
X86
+ backend to follow.</dd>
</div>
@@ -390,7 +382,7 @@
<a href="http://llvm.org";>The LLVM Compiler Infrastructure</a>
<br>
- Last modified: $Date: 2006/03/14 05:39:39 $
+ Last modified: $Date: 2006/04/12 17:42:39 $
</address>
</body>
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