[RemoveDIs] Fix removeRedundantDdbgInstrs utils for dbg.declares (llvm#74102)

The intrinsic variants of these functions don't do anything to
dbg.declares so the non-instruction variants should ignore them too.

Tested in llvm/test/DebugInfo/duplicate_dbgvalue.ll, which has
`--try-experimental-debuginfo-iterators` added in llvm#73504.

The tests will become "live" once llvm#74090 lands (see for more info).

Author: OCHyams

llvm/lib/Transforms/Utils/BasicBlockUtils.cpp

@@ -387,6 +387,18 @@ static bool DPValuesRemoveRedundantDbgInstrsUsingBackwardScan(BasicBlock *BB) {
   SmallDenseSet<DebugVariable> VariableSet;
   for (auto &I : reverse(*BB)) {
     for (DPValue &DPV : reverse(I.getDbgValueRange())) {
+      // Skip declare-type records, as the debug intrinsic method only works
+      // on dbg.value intrinsics.
+      if (DPV.getType() == DPValue::LocationType::Declare) {
+        // The debug intrinsic method treats dbg.declares are "non-debug"
+        // instructions (i.e., a break in a consecutive range of debug
+        // intrinsics). Emulate that to create identical outputs. See
+        // "Possible improvements" above.
+        // FIXME: Delete the line below.
+        VariableSet.clear();
+        continue;
+      }
+
       DebugVariable Key(DPV.getVariable(), DPV.getExpression(),
                         DPV.getDebugLoc()->getInlinedAt());
       auto R = VariableSet.insert(Key);
@@ -478,6 +490,8 @@ static bool DPValuesRemoveRedundantDbgInstrsUsingForwardScan(BasicBlock *BB) {
       VariableMap;
   for (auto &I : *BB) {
     for (DPValue &DPV : I.getDbgValueRange()) {
+      if (DPV.getType() == DPValue::LocationType::Declare)
+        continue;
       DebugVariable Key(DPV.getVariable(), std::nullopt,
                         DPV.getDebugLoc()->getInlinedAt());
       auto VMI = VariableMap.find(Key);