[llvm] [SelectionDAG] Fold constant min/max vector reductions (PR #209190)

[Simon Pilgrim via llvm-commits]

================
@@ -7479,6 +7483,8 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
   return V;
 }
 
+static APInt getIntegerIdentity(unsigned Opcode, unsigned BitWidth);
----------------
RKSimon wrote:

just move the implementation here - avoid the forward declaration

https://github.com/llvm/llvm-project/pull/209190