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 89c53e8..d3d44a8 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -855,6 +855,15 @@
"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;
}