[llvm] 69f3ea0 - [MachineBB] Make sure there are successors in terminatorIsComputedGoto. (#151342)

[via llvm-commits]

Author: Florian Hahn
Date: 2025-07-31T17:52:45+01:00
New Revision: 69f3ea08522eca4b8617145fdafb8fc6595ddf97

URL: https://github.com/llvm/llvm-project/commit/69f3ea08522eca4b8617145fdafb8fc6595ddf97
DIFF: https://github.com/llvm/llvm-project/commit/69f3ea08522eca4b8617145fdafb8fc6595ddf97.diff

LOG: [MachineBB] Make sure there are successors in terminatorIsComputedGoto. (#151342)

Currently terminatorIsComputedGoto will return for blocks with a
indirect branch terminator and no successor. If there are no successor,
the terminator is likely not a computed goto, return false in that case.

Note that this is currently NFC, as the only use checks it only if there
are successors, but it will be needed in
https://github.com/llvm/llvm-project/pull/150911.

PR: https://github.com/llvm/llvm-project/pull/151342

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/MachineBasicBlock.h
    llvm/lib/CodeGen/TailDuplicator.cpp

Removed: 
    


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diff  --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index 938d71dd030e8..9e3d9196cc184 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -323,10 +323,11 @@ class MachineBasicBlock
   const MachineFunction *getParent() const { return xParent; }
   MachineFunction *getParent() { return xParent; }
 
-  /// Returns true if the original IR terminator is an `indirectbr`. This
-  /// typically corresponds to a `goto` in C, rather than jump tables.
-  bool terminatorIsComputedGoto() const {
-    return back().isIndirectBranch() &&
+  /// Returns true if the original IR terminator is an `indirectbr` with
+  /// successor blocks. This typically corresponds to a `goto` in C, rather than
+  /// jump tables.
+  bool terminatorIsComputedGotoWithSuccessors() const {
+    return back().isIndirectBranch() && !succ_empty() &&
            llvm::all_of(successors(), [](const MachineBasicBlock *Succ) {
              return Succ->isIRBlockAddressTaken();
            });

diff  --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
index a88c57fdc165a..d319a979285f7 100644
--- a/llvm/lib/CodeGen/TailDuplicator.cpp
+++ b/llvm/lib/CodeGen/TailDuplicator.cpp
@@ -604,7 +604,7 @@ bool TailDuplicator::shouldTailDuplicate(bool IsSimple,
   bool HasComputedGoto = false;
   if (!TailBB.empty()) {
     HasIndirectbr = TailBB.back().isIndirectBranch();
-    HasComputedGoto = TailBB.terminatorIsComputedGoto();
+    HasComputedGoto = TailBB.terminatorIsComputedGotoWithSuccessors();
   }
 
   if (HasIndirectbr && PreRegAlloc)