diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
--- a/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
@@ -632,7 +632,9 @@
         // from the size of the operand.
         {
           uint8_t ExtractorAddressSize = DebugLineData.getAddressSize();
-          if (ExtractorAddressSize != Len - 1 && ExtractorAddressSize != 0)
+          uint64_t OpcodeAddressSize = Len - 1;
+          if (ExtractorAddressSize != OpcodeAddressSize &&
+              ExtractorAddressSize != 0)
             RecoverableErrorCallback(createStringError(
                 errc::invalid_argument,
                 "mismatching address size at offset 0x%8.8" PRIx64
@@ -640,14 +642,25 @@
                 ExtOffset, ExtractorAddressSize, Len - 1));
 
           // Assume that the line table is correct and temporarily override the
-          // address size.
-          DebugLineData.setAddressSize(Len - 1);
-          State.Row.Address.Address = DebugLineData.getRelocatedAddress(
-              OffsetPtr, &State.Row.Address.SectionIndex);
-
-          // Restore the address size if the extractor already had it.
-          if (ExtractorAddressSize != 0)
-            DebugLineData.setAddressSize(ExtractorAddressSize);
+          // address size. If the size is unsupported, give up trying to read
+          // the address and continue to the next opcode.
+          if (OpcodeAddressSize != 4 && OpcodeAddressSize != 8) {
+            RecoverableErrorCallback(createStringError(
+                errc::invalid_argument,
+                "address size 0x%2.2" PRIx64
+                " of DW_LNE_set_address opcode at offset 0x%8.8" PRIx64
+                " is unsupported",
+                OpcodeAddressSize, ExtOffset));
+            *OffsetPtr += OpcodeAddressSize;
+          } else {
+            DebugLineData.setAddressSize(OpcodeAddressSize);
+            State.Row.Address.Address = DebugLineData.getRelocatedAddress(
+                OffsetPtr, &State.Row.Address.SectionIndex);
+
+            // Restore the address size if the extractor already had it.
+            if (ExtractorAddressSize != 0)
+              DebugLineData.setAddressSize(ExtractorAddressSize);
+          }
 
           if (OS)
             *OS << format(" (0x%16.16" PRIx64 ")", State.Row.Address.Address);
diff --git a/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp b/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp
--- a/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp
+++ b/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp
@@ -621,6 +621,90 @@
   EXPECT_EQ((*ExpectedLineTable)->Rows[1].Address.Address, Addr2);
 }
 
+TEST_F(DebugLineBasicFixture,
+       ErrorForUnsupportedAddressSizeInSetAddressLength) {
+  // Use DWARF v4, and 0 for data extractor address size so that the address
+  // size is derived from the opcode length.
+  if (!setupGenerator(4, 0))
+    return;
+
+  LineTable &LT = Gen->addLineTable();
+  LT.addExtendedOpcode(2, DW_LNE_set_address, {{0x42, LineTable::Byte}});
+  LT.addStandardOpcode(DW_LNS_copy, {});
+  LT.addByte(0xaa);
+  LT.addExtendedOpcode(1, DW_LNE_end_sequence, {});
+
+  generate();
+
+  auto ExpectedLineTable = Line.getOrParseLineTable(LineData, 0, *Context,
+                                                    nullptr, RecordRecoverable);
+  checkError(
+      "address size 0x01 of DW_LNE_set_address opcode at offset 0x00000030 is "
+      "unsupported",
+      std::move(Recoverable));
+  ASSERT_THAT_EXPECTED(ExpectedLineTable, Succeeded());
+  ASSERT_EQ((*ExpectedLineTable)->Rows.size(), 3u);
+  EXPECT_EQ((*ExpectedLineTable)->Sequences.size(), 1u);
+  // Show that the set address opcode is ignored in this case.
+  EXPECT_EQ((*ExpectedLineTable)->Rows[0].Address.Address, 0);
+}
+
+TEST_F(DebugLineBasicFixture, ErrorForAddressSizeGreaterThanByteSize) {
+  // Use DWARF v4, and 0 for data extractor address size so that the address
+  // size is derived from the opcode length.
+  if (!setupGenerator(4, 0))
+    return;
+
+  LineTable &LT = Gen->addLineTable();
+  // Specifically use an operand size that has a trailing byte of a supported
+  // size (8), so that any potential truncation would result in a valid size.
+  std::vector<LineTable::ValueAndLength> Operands(0x108);
+  LT.addExtendedOpcode(Operands.size() + 1, DW_LNE_set_address, Operands);
+  LT.addExtendedOpcode(1, DW_LNE_end_sequence, {});
+
+  generate();
+
+  auto ExpectedLineTable = Line.getOrParseLineTable(LineData, 0, *Context,
+                                                    nullptr, RecordRecoverable);
+  checkError(
+      "address size 0x108 of DW_LNE_set_address opcode at offset 0x00000031 is "
+      "unsupported",
+      std::move(Recoverable));
+  ASSERT_THAT_EXPECTED(ExpectedLineTable, Succeeded());
+}
+
+TEST_F(DebugLineBasicFixture, ErrorForUnsupportedAddressSizeDefinedInHeader) {
+  // Use 0 for data extractor address size so that it does not clash with the
+  // header address size.
+  if (!setupGenerator(5, 0))
+    return;
+
+  LineTable &LT = Gen->addLineTable();
+  uint8_t AddressSize = 9;
+  LT.addExtendedOpcode(AddressSize + 1, DW_LNE_set_address,
+                       {{0x12345678, LineTable::Quad}, {0, LineTable::Byte}});
+  LT.addStandardOpcode(DW_LNS_copy, {});
+  LT.addByte(0xaa);
+  LT.addExtendedOpcode(1, DW_LNE_end_sequence, {});
+  DWARFDebugLine::Prologue Prologue = LT.createBasicPrologue();
+  Prologue.FormParams.AddrSize = AddressSize;
+  LT.setPrologue(Prologue);
+
+  generate();
+
+  auto ExpectedLineTable = Line.getOrParseLineTable(LineData, 0, *Context,
+                                                    nullptr, RecordRecoverable);
+  checkError(
+      "address size 0x09 of DW_LNE_set_address opcode at offset 0x00000035 is "
+      "unsupported",
+      std::move(Recoverable));
+  ASSERT_THAT_EXPECTED(ExpectedLineTable, Succeeded());
+  ASSERT_EQ((*ExpectedLineTable)->Rows.size(), 3u);
+  EXPECT_EQ((*ExpectedLineTable)->Sequences.size(), 1u);
+  // Show that the set address opcode is ignored in this case.
+  EXPECT_EQ((*ExpectedLineTable)->Rows[0].Address.Address, 0);
+}
+
 TEST_F(DebugLineBasicFixture, CallbackUsedForUnterminatedSequence) {
   if (!setupGenerator())
     return;
diff --git a/llvm/unittests/DebugInfo/DWARF/DwarfGenerator.h b/llvm/unittests/DebugInfo/DWARF/DwarfGenerator.h
--- a/llvm/unittests/DebugInfo/DWARF/DwarfGenerator.h
+++ b/llvm/unittests/DebugInfo/DWARF/DwarfGenerator.h
@@ -171,8 +171,8 @@
   enum ValueLength { Byte = 1, Half = 2, Long = 4, Quad = 8, ULEB, SLEB };
 
   struct ValueAndLength {
-    uint64_t Value;
-    ValueLength Length;
+    uint64_t Value = 0;
+    ValueLength Length = Byte;
   };
 
   LineTable(uint16_t Version, dwarf::DwarfFormat Format, uint8_t AddrSize,