1 files changed, 38 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 406b52607f0..5a3a89bed2b 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1228,6 +1228,23 @@ static bool PhiHasDebugValue(DILocalVariable *DIVar,
   return false;
 }
 
+/// Check if the store size of \p ValTy is large enough to cover the variable
+/// (or fragment of the variable) described by \p DII.
+///
+/// This is primarily intended as a helper for the different
+/// ConvertDebugDeclareToDebugValue functions. The dbg.declare/dbg.addr that is
+/// converted describes an alloca'd variable, so we need to use the
+/// store size of the value when doing the comparison. E.g. an i1 value will be
+/// identified as covering an n-bit fragment, if the store size of i1 is at
+/// least n bits.
+static bool valueCoversEntireFragment(Type *ValTy, DbgInfoIntrinsic *DII) {
+  const DataLayout &DL = DII->getModule()->getDataLayout();
+  uint64_t ValueSize = DL.getTypeStoreSizeInBits(ValTy);
+  if (auto FragmentSize = DII->getFragmentSizeInBits())
+    return ValueSize >= *FragmentSize;
+  return false;
+}
+
 /// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
 /// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic.
 void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
@@ -1238,6 +1255,21 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
   auto *DIExpr = DII->getExpression();
   Value *DV = SI->getOperand(0);
 
+  if (!valueCoversEntireFragment(SI->getValueOperand()->getType(), DII)) {
+    // FIXME: If storing to a part of the variable described by the dbg.declare,
+    // then we want to insert a dbg.value for the corresponding fragment.
+    LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
+                      << *DII << '\n');
+    // For now, when there is a store to parts of the variable (but we do not
+    // know which part) we insert an dbg.value instrinsic to indicate that we
+    // know nothing about the variable's content.
+    DV = UndefValue::get(DV->getType());
+    if (!LdStHasDebugValue(DIVar, DIExpr, SI))
+      Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, DII->getDebugLoc(),
+                                      SI);
+    return;
+  }
+
   // If an argument is zero extended then use argument directly. The ZExt
   // may be zapped by an optimization pass in future.
   Argument *ExtendedArg = nullptr;
@@ -1281,6 +1313,9 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
   if (LdStHasDebugValue(DIVar, DIExpr, LI))
     return;
 
+  assert(valueCoversEntireFragment(LI->getType(), DII) &&
+         "Load is not loading the full variable fragment.");
+
   // We are now tracking the loaded value instead of the address. In the
   // future if multi-location support is added to the IR, it might be
   // preferable to keep tracking both the loaded value and the original
@@ -1301,6 +1336,9 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
   if (PhiHasDebugValue(DIVar, DIExpr, APN))
     return;
 
+  assert(valueCoversEntireFragment(APN->getType(), DII) &&
+         "PHI node is not describing the full variable.");
+
   BasicBlock *BB = APN->getParent();
   auto InsertionPt = BB->getFirstInsertionPt();