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authorDan Gohman <gohman@apple.com>2009-01-28 21:13:08 +0000
committerDan Gohman <gohman@apple.com>2009-01-28 21:13:08 +0000
commitf70dab704929cfeaae4fa6bd69b9037cd75a0d48 (patch)
tree2a8dad4d3f7620ec0e2f71f30e36197e1f6396b6
parentf9235748567e065b3b3c3bd48c3d4dfe1d664e8b (diff)
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Add some comments on ISD::NodeType.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63234 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--include/llvm/CodeGen/SelectionDAGNodes.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index c22b90c..9f496d4 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.