[CodeGen][DebugInfo] Add missing DebugLoc for SplitCriticalEdge (#72192)

In SplitCriticalEdge, DebugLoc of the branch instruction in new created
MBB was set to empty. It should be set and we can find proper DebugLoc
for it in most cases. This patch set it to non empty merged DebugLoc of
current MBB branches.

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 4410fb7..b2114c2 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -1137,7 +1137,6 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
 
   MachineFunction *MF = getParent();
   MachineBasicBlock *PrevFallthrough = getNextNode();
-  DebugLoc DL;  // FIXME: this is nowhere
 
   MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
   NMBB->setCallFrameSize(Succ->getCallFrameSize());
@@ -1218,6 +1217,15 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
     SlotIndexUpdateDelegate SlotUpdater(*MF, Indexes);
     SmallVector<MachineOperand, 4> Cond;
     const TargetInstrInfo *TII = getParent()->getSubtarget().getInstrInfo();
+
+    // In original 'this' BB, there must be a branch instruction targeting at
+    // Succ. We can not find it out since currently getBranchDestBlock was not
+    // implemented for all targets. However, if the merged DL has column or line
+    // number, the scope and non-zero column and line number is same with that
+    // branch instruction so we can safely use it.
+    DebugLoc DL, MergedDL = findBranchDebugLoc();
+    if (MergedDL && (MergedDL.getLine() || MergedDL.getCol()))
+      DL = MergedDL;
     TII->insertBranch(*NMBB, Succ, nullptr, Cond, DL);
   }