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/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index c316ef6..adc225b 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2207,6 +2207,19 @@
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;
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 5f400e9..dfd1df7 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -398,6 +398,10 @@
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);
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,