[DebugInfo][InstrRef] Correctly ignore DBG_VALUE_LIST in InstrRef mode

This patch makes InstrRefBasedLDV "safe" to work with DBG_VALUE_LISTs. It
doesn't actually interpret them, but it recognises that they specify
variable locations and avoids propagating false locations, which is better
than the current state. Observe the attached tes

 * We avoid propagating DBG_VALUE_LISTs into successor blocks, as they're
   not "currently" supported,
 * We don't propagate other variable locations across DBG_VALUE_LISTs,
   because we know that the variable location is terminated by the
   DBG_VALUE_LIST.

Differential Revision: https://reviews.llvm.org/D108143

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
index 5c1bbf724eb9..233824f1ed75 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -1759,6 +1759,17 @@ bool InstrRefBasedLDV::transferDebugValue(const MachineInstr &MI) {
   if (Scope == nullptr)
     return true; // handled it; by doing nothing
 
+  // For now, ignore DBG_VALUE_LISTs when extending ranges. Allow it to
+  // contribute to locations in this block, but don't propagate further.
+  // Interpret it like a DBG_VALUE $noreg.
+  if (MI.isDebugValueList()) {
+    if (VTracker)
+      VTracker->defVar(MI, Properties, None);
+    if (TTracker)
+      TTracker->redefVar(MI, Properties, None);
+    return true;
+  }
+
   const MachineOperand &MO = MI.getOperand(0);
 
   // MLocTracker needs to know that this register is read, even if it's only