Fold zext_inreg(zextload), likewise for sext's

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21204 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 7cf89144c3b51bdb166a3dd8072bb12c731b06cb..6b94adf1d8edebbd4a39e4ec1fcb06ea7403bc09 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1101,6 +1101,12 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,SDOperand N1,
         return N1;
     }
 
+    // If we are (zero|sign) extending a [zs]extload, return just the load.
+    if ((N1.getOpcode() == ISD::ZEXTLOAD && Opcode == ISD::ZERO_EXTEND_INREG) ||
+        (N1.getOpcode() == ISD::SEXTLOAD && Opcode == ISD::SIGN_EXTEND_INREG))
+      if (cast<MVTSDNode>(N1)->getExtraValueType() <= EVT)
+        return N1;
+
     // If we are extending the result of a setcc, and we already know the
     // contents of the top bits, eliminate the extension.
     if (N1.getOpcode() == ISD::SETCC)