[PATCH] D42813: [Debug] Annotate compiler generated range-for loop variables.

[Matt Davis via Phabricator via cfe-commits]

mattd added inline comments.


================
Comment at: lib/Sema/SemaStmt.cpp:2346
+    // Assume the variables are nested in the inner scope (loop body).
+    const auto DepthStr = std::to_string(S->getDepth() >> 1);
     VarDecl *BeginVar = BuildForRangeVarDecl(*this, ColonLoc, AutoType,
----------------
dblaikie wrote:
> Why shifted right/divided by two? (I'd probably write this as "/ 2" rather thane ">> 1" if this is what's)
> 
> I guess this is because a range-for introduces two (actually 3, I think) scopes?
> 
> But what about if there are other random scopes that could be present? Does that adversely affect anything here?
Thanks for the comment.  Honestly, I discovered the pattern after crafting up a tightly nested loop example, and realized that my Depths were 2,4,6... for each range loop respectively.   I think it's two scopes and the range variables (__begin, __end, __range) are nestled inside each inner scope.  Thus each range loop seems to be created of 2 scopes.

If there are other scopes between two range-loops, such as the 'if' in the example below, then the outer-most "for" is range1/begin1/end1, followed by the middle loop: range3/begin3/end3, and the innermost: range4/begin4/end4.

```
for (...) // range1
  if (...) 
    for(...) // range 3
      for (...) //range4
```
   


https://reviews.llvm.org/D42813