[PATCH] D140790: [BranchRelaxation] Prevent analyzing indirectBr during uncondBr fixup

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: llvm/lib/CodeGen/BranchRelaxation.cpp:516
+    if (PrevBBTerm == PrevBB->end() ||
+        (PrevBBTerm != PrevBB->end() && !PrevBBTerm->isIndirectBranch())) {
+      if (TII->analyzeBranch(*PrevBB, TBB, FBB, Cond))
----------------
This condition doesn't seem right.

The point of the existing code is to handle fallthrough from PrevBB to DestBB: we're inserting a block between those two blocks, so any fallthrough must be rewritten to a direct branch.  We can only skip this if we can prove there isn't any fallthrough.

isIndirectBranch() doesn't prove there isn't any fallthrough; whether a branch is indirect isn't related to whether it's conditional.  MachineBasicBlock::canFallThrough() is probably appropriate.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D140790/new/

https://reviews.llvm.org/D140790