diff --git a/gdb/compile/compile-loc2c.c b/gdb/compile/compile-loc2c.c
index 037b6433bc8..e9698a758e6 100644
--- a/gdb/compile/compile-loc2c.c
+++ b/gdb/compile/compile-loc2c.c
@@ -361,6 +361,10 @@ compute_stack_depth_worker (int start, int *need_tempvar,
 	  --stack_depth;
 	  break;
 
+	case DW_OP_LLVM_undefined:
+	  ++stack_depth;
+	  break;
+
 	case DW_OP_LLVM_offset_constu:
 	case DW_OP_nop:
 	  break;
diff --git a/gdb/dwarf2/expr.c b/gdb/dwarf2/expr.c
index dfe34f877a7..a65d18d492a 100644
--- a/gdb/dwarf2/expr.c
+++ b/gdb/dwarf2/expr.c
@@ -3738,6 +3738,10 @@ dwarf_expr_context::execute_stack_op (const gdb_byte *op_ptr,
 	  }
 	  break;
 
+	case DW_OP_LLVM_undefined:
+	  result_entry = entry_factory->create_undefined ();
+	  break;
+
 	default:
 	  error (_("Unhandled dwarf expression opcode 0x%x"), op);
 	}
diff --git a/gdb/dwarf2/loc.c b/gdb/dwarf2/loc.c
index fe2174ab14a..1a903ce1233 100644
--- a/gdb/dwarf2/loc.c
+++ b/gdb/dwarf2/loc.c
@@ -1831,6 +1831,7 @@ dwarf2_get_symbol_read_needs (gdb::array_view<const gdb_byte> expr,
 	case DW_OP_push_object_address:
 	case DW_OP_LLVM_offset:
 	case DW_OP_LLVM_bit_offset:
+	case DW_OP_LLVM_undefined:
 	  break;
 
 	case DW_OP_form_tls_address:
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-llvm-undefined.exp b/gdb/testsuite/gdb.dwarf2/dw2-llvm-undefined.exp
new file mode 100644
index 00000000000..be677a1ddce
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-llvm-undefined.exp
@@ -0,0 +1,144 @@
+# Copyright 2017-2020 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test the new DW_OP_LLVM_undefined operation.
+#
+# The test uses a composite location description, where some pieces
+# of that location description are undefined location description.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Choose suitable integer registers for the test.
+
+set dwarf_regnum 0
+
+if { [is_aarch64_target] } {
+    set regname x0
+} elseif { [is_aarch32_target]
+	   || [istarget "s390*-*-*" ]
+	   || [istarget "powerpc*-*-*"]
+	   || [istarget "rs6000*-*-aix*"] } {
+    set regname r0
+} elseif { [is_x86_like_target] } {
+    set regname eax
+} elseif { [is_amd64_regs_target] } {
+    set regname rax
+} else {
+    verbose "Skipping ${gdb_test_file_name}."
+    return
+}
+
+standard_testfile var-access.c ${gdb_test_file_name}-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global dwarf_regnum regname srcdir subdir srcfile
+    set buf_src [gdb_target_symbol buf]
+
+    set main_result [function_range main ${srcdir}/${subdir}/${srcfile}]
+    set main_start [lindex $main_result 0]
+    set main_length [lindex $main_result 1]
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_name var-access.c}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels int_type_label char_type_label array_type_label
+
+	    # define char type
+	    char_type_label: DW_TAG_base_type {
+		{DW_AT_name "char"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 1 DW_FORM_sdata}
+	    }
+
+	    int_type_label: DW_TAG_base_type {
+		{DW_AT_name "int"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    array_type_label: DW_TAG_array_type {
+		{DW_AT_type :$char_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 5 DW_FORM_udata}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{DW_AT_name main}
+		{DW_AT_low_pc $main_start addr}
+		{DW_AT_high_pc $main_length data8}
+	    } {
+
+		# Array spread in different pieces of which some are
+		# undefined (1st and sixth bytes) and some are in a
+		# REGNAME register.
+		DW_TAG_variable {
+		    {DW_AT_name var_array}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			DW_OP_LLVM_undefined
+			DW_OP_piece 0x1
+			DW_OP_regx $dwarf_regnum
+			DW_OP_piece 0x4
+			DW_OP_LLVM_undefined
+			DW_OP_piece 0x1
+		    } SPECIAL_expr}
+		}
+
+		DW_TAG_variable {
+		    {DW_AT_name var_int}
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_location {
+			DW_OP_LLVM_undefined
+		    } SPECIAL_expr}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+     [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set var \$$regname = 0x04030201" "init reg"
+
+# Determine byte order.
+set endian [get_endianness]
+
+switch $endian {
+	little {set val "<optimized out>, 0x1, 0x2, 0x3, 0x4, <optimized out>"}
+	big {set val "<optimized out>, 0x4, 0x3, 0x2, 0x1, <optimized out>"}
+}
+
+gdb_test "print/x var_array" " = \\{${val}\\}" "var_array print"
+gdb_test "print/x var_int" " = <optimized out>" "var_int print"
diff --git a/include/dwarf2.def b/include/dwarf2.def
index 4880a2268f6..b58560296d6 100644
--- a/include/dwarf2.def
+++ b/include/dwarf2.def
@@ -708,6 +708,7 @@ DW_OP (DW_OP_AARCH64_operation, 0xea)
 DW_OP_DUP (DW_OP_LLVM_offset, 0xe3)
 DW_OP_DUP (DW_OP_LLVM_offset_constu, 0xe4)
 DW_OP_DUP (DW_OP_LLVM_bit_offset, 0xe5)
+DW_OP (DW_OP_LLVM_undefined, 0xe7)
 DW_END_OP
 
 DW_FIRST_ATE (DW_ATE_void, 0x0)