Simplify: truncate ({zero|sign}_extend (X))
llvm-svn: 19353
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 3fdc7fe..25ec8ff 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -428,6 +428,15 @@
if (Operand.getValueType() == VT) return Operand; // noop truncate
if (OpOpcode == ISD::TRUNCATE)
return getNode(ISD::TRUNCATE, VT, Operand.Val->getOperand(0));
+ else if (OpOpcode == ISD::ZERO_EXTEND || OpOpcode == ISD::SIGN_EXTEND) {
+ // If the source is smaller than the dest, we still need an extend.
+ if (Operand.Val->getOperand(0).getValueType() < VT)
+ return getNode(OpOpcode, VT, Operand.Val->getOperand(0));
+ else if (Operand.Val->getOperand(0).getValueType() > VT)
+ return getNode(ISD::TRUNCATE, VT, Operand.Val->getOperand(0));
+ else
+ return Operand.Val->getOperand(0);
+ }
break;
}