From: Chris Lattner <sabre@nondot.org>
Date: Sun, 16 Jan 2005 00:17:20 +0000 (+0000)
Subject: Eliminate unneeded extensions.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=950aa3ca2c60863510bee45ec1b9180f975b8e79;p=oota-llvm.git

Eliminate unneeded extensions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19577 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 89c53e8c1ba..d3d44a82e08 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -855,6 +855,15 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,SDOperand N1,
            "Cannot *_EXTEND_INREG FP types");
     if (EVT == VT) return N1;  // Not actually extending
     assert(EVT < VT && "Not extending!");
+
+    // If we are sign extending an extension, use the original source.
+    if (N1.getOpcode() == ISD::ZERO_EXTEND_INREG ||
+        N1.getOpcode() == ISD::SIGN_EXTEND_INREG) {
+      if (N1.getOpcode() == Opcode &&
+          cast<MVTSDNode>(N1)->getExtraValueType() <= EVT)
+        return N1;
+    }
+
     break;
   }