Apply fix for clang incorrectly optimizing part of dns/bind916

Merge commit e5a8af7a90c6 from llvm git (by Gulfem Savrun Yeniceri):

  [Passes] Fix relative lookup table converter pass

  This patch fixes the relative table converter pass for the lookup table
  accesses that are resulted in an instruction sequence, where gep is not
  immediately followed by a load, such as gep being hoisted outside the loop
  or another instruction is inserted in between them. The fix inserts the
  call to load.relative.instrinsic in the original place of load instead of gep.
  Issue is reported by FreeBSD via https://bugs.freebsd.org/259921.

  Differential Revision: https://reviews.llvm.org/D115571

PR:		259921
Reported by:	O. Hartmann <freebsd@walstatt-de.de>
MFC after:	3 days

contrib/llvm-project/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp

@@ -144,6 +144,10 @@ static void convertToRelLookupTable(GlobalVariable &LookupTable) {
   Value *Offset =
       Builder.CreateShl(Index, ConstantInt::get(IntTy, 2), "reltable.shift");
 
+  // Insert the call to load.relative instrinsic before LOAD.
+  // GEP might not be immediately followed by a LOAD, like it can be hoisted
+  // outside the loop or another instruction might be inserted them in between.
+  Builder.SetInsertPoint(Load);
   Function *LoadRelIntrinsic = llvm::Intrinsic::getDeclaration(
       &M, Intrinsic::load_relative, {Index->getType()});
   Value *Base = Builder.CreateBitCast(RelLookupTable, Builder.getInt8PtrTy());