[PATCH] D153197: [AVR] Expand shifts during AVRISelLowering

[Ben Shi via Phabricator via llvm-commits]

benshi001 added inline comments.


================
Comment at: llvm/lib/Target/AVR/AVRISelLowering.cpp:2207
+  MF->push_back(LoopBB);
+  MachineBasicBlock *ExitBB = EntryBB->splitAt(MI, false);
+
----------------
Patryk27 wrote:
> Alright, this is wrong, after all - I've just tested it on a more elaborate code in rustc and `EntryBB->removeSuccessor(ExitBB);` triggers an LLVM panic (presumably because EntryBB == ExitBB).
> 
> I kinda don't understand why doing something like this:
> 
> ```
> MachineBasicBlock *ExitBB = EntryBB->splitAt(MI, false);
> 
> if (EntryBB == ExitBB) {
>   assert(EntryBB->canFallThrough() && "Expected a fallthrough block!");
>   ExitBB = EntryBB->getFallThrough();
> }
> ```
> 
> ... is not sufficient, though 👀
Is it possible to fix the 32-bit shift issue in moderate way? for example, keep the pass in `AVRShiftExpand.cpp`. 


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153197/new/

https://reviews.llvm.org/D153197