[PATCH] D124697: Distinguish between different forms of "address-taken" MachineBasicBlocks

[Eli Friedman via Phabricator via llvm-commits]

efriedma marked an inline comment as done.
efriedma added inline comments.


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Comment at: llvm/include/llvm/CodeGen/MachineBasicBlock.h:152
+  /// to an IR-level "blockaddress" constant.
+  bool IRBlockAddressTaken = false;
 
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arsenm wrote:
> efriedma wrote:
> > arsenm wrote:
> > > If you're going to depend on the underlying IR block, you don't really need another field inside MachineBasicBlock. You can just query directly from the IR
> > In general, there are multiple MachineBasicBlocks which correspond to a single IR BasicBlock; when we split a block for whatever reason, getBasicBlock() is the same for both halves.  We need to know which one is the jump destination.
> Does it actually make sense to preserve the IR block if the block is split? Is the IR block used for anything else? Maybe for block splitting the second half of the block shouldn't have the IR link
It might be possible to mess with the value stored as getBasicBlock(); as far as I can tell, the result is mostly used for debug prints and as an argument to CreateMachineBasicBlock().  It is used for a few other (possibly dubious) things: to get MD_loop/MD_make_implicit metadata, to get debug locations, to get the LandingPadInst for a landing pad.  Nothing we couldn't handle some other way, I think.

If we want to go in that direction, though, I might as well just replace `bool IRBlockAddressTaken` with `BasicBlock *IRBlockAddress`", and avoid the dependency on getBasicBlock() altogether.


Repository:
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  https://reviews.llvm.org/D124697/new/

https://reviews.llvm.org/D124697