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.

llvm-svn: 115191

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index c316ef6c54a..adc225b94bc 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2207,6 +2207,19 @@ size_t SelectionDAGBuilder::Clusterify(CaseVector& Cases,
   return numCmps;
 }
 
+void SelectionDAGBuilder::UpdateSplitBlock(MachineBasicBlock *First,
+                                           MachineBasicBlock *Last) {
+  // Update JTCases.
+  for (unsigned i = 0, e = JTCases.size(); i != e; ++i)
+    if (JTCases[i].first.HeaderBB == First)
+      JTCases[i].first.HeaderBB = Last;
+
+  // Update BitTestCases.
+  for (unsigned i = 0, e = BitTestCases.size(); i != e; ++i)
+    if (BitTestCases[i].Parent == First)
+      BitTestCases[i].Parent = Last;
+}
+
 void SelectionDAGBuilder::visitSwitch(const SwitchInst &SI) {
   MachineBasicBlock *SwitchMBB = FuncInfo.MBB;