[PATCH] D94137: [coroutine] update promise object's final layout index

[Yuanfang Chen via Phabricator via llvm-commits]

ychen added inline comments.


================
Comment at: llvm/lib/Transforms/Coroutines/CoroFrame.cpp:750
       FrameData.setFieldIndex(
           PromiseAlloca, B.addFieldForAlloca(PromiseAlloca, /*header*/ true));
 
----------------
lxfind wrote:
> PromiseAlloca is added here as a header field, which means it should have a fixed index?
> Could it be there are bugs in performOptimizedStructLayout that moved it around somehow?
I'm inclined to say it should be fixed offset which is not changed after `performOptimizedStructLayout`.

1) The use of `IsHeader` in addFieldForAllocas suggests that.
2) The comment below in OptimizedStructLayout.h

```
/// - Fields may be assigned a fixed offset in the layout.  If there are
///   gaps among the fixed-offset fields, the algorithm may attempt
///   to allocate flexible-offset fields into those gaps.  If that's
///   undesirable, the caller should "block out" those gaps by e.g.
///   just creating a single fixed-offset field that represents the
///   entire "header".
```



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https://reviews.llvm.org/D94137