[llvm] [CodeExtractor] Improve debug info for input values. (PR #136016)

[Tim Gymnich via llvm-commits]

================
@@ -1273,14 +1280,49 @@ static void fixupDebugInfoPostExtraction(Function &OldFunc, Function &NewFunc,
       /*LineNo=*/0, SPType, /*ScopeLine=*/0, DINode::FlagZero, SPFlags);
   NewFunc.setSubprogram(NewSP);
 
+  auto UpdateOrInsertDebugRecord = [&](auto *DR, Value *OldLoc, Value *NewLoc,
+                                       DIExpression *Expr, bool Declare) {
+    if (DR->getParent()->getParent() == &NewFunc)
+      DR->replaceVariableLocationOp(OldLoc, NewLoc);
+    else {
+      if (Declare)
+        DIB.insertDeclare(NewLoc, DR->getVariable(), Expr, DR->getDebugLoc(),
+                          &NewFunc.getEntryBlock());
+      else
+        DIB.insertDbgValueIntrinsic(
+            NewLoc, DR->getVariable(), Expr, DR->getDebugLoc(),
+            NewFunc.getEntryBlock().getTerminator()->getIterator());
+    }
+  };
+  for (auto [Input, NewVal] : zip_equal(Inputs, NewValues)) {
+    SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
+    SmallVector<DbgVariableRecord *, 1> DPUsers;
+    findDbgUsers(DbgUsers, Input, &DPUsers);
+    DIExpression *Expr = DIB.createExpression();
+
+    // Iterate the debud users of the Input values. If they are in the extracted
+    // function then update their location with the new value. If they are in
+    // the parent function then create a similar debug record.
+    for (auto *DVI : DbgUsers) {
+      UpdateOrInsertDebugRecord(DVI, Input, NewVal, Expr,
+                                isa<DbgDeclareInst>(DVI));
+    }
----------------
tgymnich wrote:

```suggestion
    for (auto *DVI : DbgUsers)
      UpdateOrInsertDebugRecord(DVI, Input, NewVal, Expr,
                                isa<DbgDeclareInst>(DVI));
```

https://github.com/llvm/llvm-project/pull/136016