Don't try to split weird critical edges that really aren't:
BB#1: derived from LLVM BB %bb.nph28
Live Ins: %AL
Predecessors according to CFG: BB#0
TEST8rr %reg16384<kill>, %reg16384, %EFLAGS<imp-def>; GR8:%reg16384
JNE_4 <BB#2>, %EFLAGS<imp-use,kill>
JMP_4 <BB#2>
Successors according to CFG: BB#2 BB#2
These double CFG edges only ever occur in bugpoint-generated code, so there is
no need to attempt something clever.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117992 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index d4f901d..31d12eb 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -450,14 +450,24 @@
MachineFunction *MF = getParent();
DebugLoc dl; // FIXME: this is nowhere
- // We may need to update this's terminator, but we can't do that if AnalyzeBranch
- // fails. If this uses a jump table, we won't touch it.
+ // We may need to update this's terminator, but we can't do that if
+ // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
MachineBasicBlock *TBB = 0, *FBB = 0;
SmallVector<MachineOperand, 4> Cond;
if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
return NULL;
+ // Avoid bugpoint weirdness: A block may end with a conditional branch but
+ // jumps to the same MBB is either case. We have duplicate CFG edges in that
+ // case that we can't handle. Since this never happens in properly optimized
+ // code, just skip those edges.
+ if (TBB && TBB == FBB) {
+ DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
+ << getNumber() << '\n');
+ return NULL;
+ }
+
MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
DEBUG(dbgs() << "Splitting critical edge:"