From: Dan Gohman <gohman@apple.com>
Date: Sat, 25 Apr 2009 17:09:45 +0000 (+0000)
Subject: Add a top-level comment about DAGCombiner's role in the compiler.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4128700ab11d0db62e5ba7ed8a8fc301c7aaa8b1;p=oota-llvm.git

Add a top-level comment about DAGCombiner's role in the compiler.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70052 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 72b3e3627ed..b937eaff757 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10,6 +10,10 @@
 // This pass combines dag nodes to form fewer, simpler DAG nodes.  It can be run
 // both before and after the DAG is legalized.
 //
+// This pass is not a substitute for the LLVM IR instcombine pass. This pass is
+// primarily intended to handle simplification opportunities that are implicit
+// in the LLVM IR and exposed by the various codegen lowering phases.
+//
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "dagcombine"