[SelectionDAG] Add ComputeNumSignBits support for CONCAT_VECTORS opcode

llvm-svn: 287541

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index ef560ac30bf..c3230726b1e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2874,6 +2874,13 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, unsigned Depth) const {
       return ComputeNumSignBits(Op.getOperand(0), Depth+1);
     break;
   }
+  case ISD::CONCAT_VECTORS:
+    // Determine the minimum number of sign bits across all input vectors.
+    // Early out if the result is already 1.
+    Tmp = ComputeNumSignBits(Op.getOperand(0), Depth + 1);
+    for (unsigned i = 1, e = Op.getNumOperands(); (i < e) && (Tmp > 1); ++i)
+      Tmp = std::min(Tmp, ComputeNumSignBits(Op.getOperand(i), Depth + 1));
+    return Tmp;
   }
 
   // If we are looking at the loaded value of the SDNode.