[LiveDebugValues] Close range for previous variable's location when adding newly deduced location

When LiveDebugValues deduces new variable's location from spill, restore or
register copy instruction it should close old variable's location. Otherwise
we can have multiple block output locations for same variable. That could lead
to inserting two DBG_VALUEs for same variable to the beginning of the successor
block which results to ignoring of first DBG_VALUE.

Reviewers: aprantl, jmorse, wolfgangp, dstenb

Reviewed By: aprantl

Subscribers: probinson, asowda, ivanbaev, petarj, djtodoro

Tags: #debug-info

Differential Revision: https://reviews.llvm.org/D62196

llvm-svn: 362373

1 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp
index 7f95e12186f..8b8a340c179 100644
--- a/llvm/lib/CodeGen/LiveDebugValues.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues.cpp
@@ -430,9 +430,15 @@ void LiveDebugValues::insertTransferDebugPair(
   MachineFunction *MF = MI.getParent()->getParent();
   MachineInstr *NewDebugInstr;
 
-  auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers,
+  auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &DebugInstr,
                         &VarLocIDs](VarLoc &VL, MachineInstr *NewDebugInstr) {
     unsigned LocId = VarLocIDs.insert(VL);
+
+    // Close this variable's previous location range.
+    DebugVariable V(DebugInstr->getDebugVariable(),
+                    DebugInstr->getDebugLoc()->getInlinedAt());
+    OpenRanges.erase(V);
+
     OpenRanges.insert(LocId, VL.Var);
     // The newly created DBG_VALUE instruction NewDebugInstr must be inserted
     // after MI. Keep track of the pairing.
@@ -714,6 +720,10 @@ bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
   });
   VarLocSet &VLS = OutLocs[CurMBB];
   Changed = VLS |= OpenRanges.getVarLocs();
+  // New OutLocs set may be different due to spill, restore or register
+  // copy instruction processing.
+  if (Changed)
+    VLS = OpenRanges.getVarLocs();
   OpenRanges.clear();
   return Changed;
 }