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
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 63ba1c4..450b7ef 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -564,13 +564,19 @@
// Emit machine code to BB. This can change 'BB' to the last block being
// inserted into.
+ MachineBasicBlock *FirstMBB = FuncInfo->MBB, *LastMBB;
{
NamedRegionTimer T("Instruction Creation", GroupName, TimePassesIsEnabled);
- FuncInfo->MBB = Scheduler->EmitSchedule();
+ LastMBB = FuncInfo->MBB = Scheduler->EmitSchedule();
FuncInfo->InsertPt = Scheduler->InsertPos;
}
+ // If the block was split, make sure we update any references that are used to
+ // update PHI nodes later on.
+ if (FirstMBB != LastMBB)
+ SDB->UpdateSplitBlock(FirstMBB, LastMBB);
+
// Free the scheduler state.
{
NamedRegionTimer T("Instruction Scheduling Cleanup", GroupName,