When isel is emitting instructions for an x86 target without CMOV, the CFG is

edited during emission.

If the basic block ends in a switch that gets lowered to a jump table, any
phis at the default edge were getting updated wrong. The jump table data
structure keeps a pointer to the header blocks that wasn't getting updated
after the MBB is split.

This bug was exposed on 32-bit Linux when disabling critical edge splitting in
codegen prepare.

The fix is to uipdate stale MBB pointers whenever a block is split during
emission.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115191 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 5f400e9c83..dfd1df75f1 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -398,6 +398,10 @@ public:
   void LowerCallTo(ImmutableCallSite CS, SDValue Callee, bool IsTailCall,
                    MachineBasicBlock *LandingPad = NULL);
 
+  /// UpdateSplitBlock - When an MBB was split during scheduling, update the
+  /// references that ned to refer to the last resulting block.
+  void UpdateSplitBlock(MachineBasicBlock *First, MachineBasicBlock *Last);
+
 private:
   // Terminator instructions.
   void visitRet(const ReturnInst &I);