[RemoveDIs] Enable conversion from dbg.declare to DPValue (llvm#74090)

Note that all the patches that implement support for declare-style
DPValues have tests that are "rotten green" test without this
patch (i.e., they pass at the moment without testing what we
want them to test). See the Pull Request for more detail on this.

llvm/lib/IR/BasicBlock.cpp

@@ -73,7 +73,10 @@ void BasicBlock::convertToNewDbgValues() {
   SmallVector<DPValue *, 4> DPVals;
   for (Instruction &I : make_early_inc_range(InstList)) {
     assert(!I.DbgMarker && "DbgMarker already set on old-format instrs?");
-    if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(&I)) {
+    if (DbgVariableIntrinsic *DVI = dyn_cast<DbgVariableIntrinsic>(&I)) {
+      if (isa<DbgAssignIntrinsic>(DVI))
+        continue;
+
       // Convert this dbg.value to a DPValue.
       DPValue *Value = new DPValue(DVI);
       DPVals.push_back(Value);