From: Dan Gohman <gohman@apple.com>
Date: Wed, 28 Jan 2009 21:13:08 +0000 (+0000)
Subject: Add some comments on ISD::NodeType.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=f70dab704929cfeaae4fa6bd69b9037cd75a0d48;p=oota-llvm.git

Add some comments on ISD::NodeType.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63234 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index c22b90ceedf..9f496d42afe 100644
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -63,6 +63,13 @@ namespace ISD {
   /// ISD::NodeType enum - This enum defines all of the operators valid in a
   /// SelectionDAG.
   ///
+  /// These are sometimes called the target-independent operators; targets
+  /// may also define target-dependent operators. For example, on x86, these
+  /// are the enum values in the X86ISD namespace. Targets should aim to use
+  /// target-independent operators to model their instruction sets as much
+  /// as possible, and only use target-dependent operators when they have
+  /// special requirements.
+  ///
   enum NodeType {
     // DELETED_NODE - This is an illegal flag value that is used to catch
     // errors.  This opcode is not a legal opcode for any node.