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

[Michael Kruse via llvm-commits]

================
@@ -1270,14 +1278,48 @@ 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));
+    for (auto *DVR : DPUsers)
+      UpdateOrInsertDebugRecord(DVR, Input, NewVal, Expr, DVR->isDbgDeclare());
+  }
+
   auto IsInvalidLocation = [&NewFunc](Value *Location) {
-    // Location is invalid if it isn't a constant or an instruction, or is an
-    // instruction but isn't in the new function.
-    if (!Location ||
-        (!isa<Constant>(Location) && !isa<Instruction>(Location)))
+    // Location is invalid if it isn't a constant, an instruction or an
+    // argument, or is an instruction/argument but isn't in the new function.
+    if (!Location || (!isa<Constant>(Location) && !isa<Argument>(Location) &&
+                      !isa<Instruction>(Location)))
       return true;
-    Instruction *LocationInst = dyn_cast<Instruction>(Location);
-    return LocationInst && LocationInst->getFunction() != &NewFunc;
+
+    if (Argument *Arg = dyn_cast<Argument>(Location))
+      return Arg->getParent() != &NewFunc;
+    else if (Instruction *LocationInst = dyn_cast<Instruction>(Location))
----------------
Meinersbur wrote:

```suggestion
    if (Instruction *LocationInst = dyn_cast<Instruction>(Location))
```
[Don't use else after a return](https://llvm.org/docs/CodingStandards.html#don-t-use-else-after-a-return)

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