[PATCH] D130290: [MachineVerifier] add checks for INLINEASM_BR

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers added inline comments.


================
Comment at: llvm/lib/CodeGen/MachineVerifier.cpp:882
+
+      const BasicBlock *IndirectTarget = MO.getBlockAddress()->getBasicBlock();
+
----------------
arsenm wrote:
> Why is this based on the IR block?
Because AFAIK, there is no corresponding `BlockAddress` `Constant` in the MIR level, so the `MachineInst` uses a `BlockAddress` `Constant` which is just a tuple of (`Function`, `BasicBlock`). What would be helpful here would be if `BlockAddress` `Constants` were lowered to something new (doesn't exist, yet) that is a tuple of (`MachineFunction`, `MachineBasicBlock`).

The existing design seems brittle, because IIUC, there's a one-to-many relationship between `BasicBlock` and `MachineBasicBlock`. A `MachineBasicBlock` can refer to a single `BasicBlock`.

Perhaps that's why in my TODO below that we _don't_ have a mapping of `BasicBlock` to `MachineBasicBlock`; because they are not one-to-one (unless I'm wrong).


================
Comment at: llvm/lib/CodeGen/MachineVerifier.cpp:899-904
+      if (llvm::none_of(MBB->successors(),
+                        [IndirectTargetMBB](const MachineBasicBlock *Succ) {
+                          return Succ == IndirectTargetMBB;
+                        }))
+        report("INLINEASM_BR indirect target missing from successor list", &MO,
+               i);
----------------
arsenm wrote:
> arsenm wrote:
> > I'd expect CFG checks to go with the others in visitMachineBasicBlockBefore
> This is !MBB->isSuccessor
Perhaps, but consider that INLINEASM_BR are relatively rare constructs to see in the wild; I think it might be more efficient to do such scans only when they are encountered.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D130290/new/

https://reviews.llvm.org/D130290