diff --git a/llvm/docs/CommandGuide/llvm-addr2line.rst b/llvm/docs/CommandGuide/llvm-addr2line.rst
--- a/llvm/docs/CommandGuide/llvm-addr2line.rst
+++ b/llvm/docs/CommandGuide/llvm-addr2line.rst
@@ -17,17 +17,24 @@
 
 Here are some of those differences:
 
--  Defaults not to print function names. Use `-f`_ to enable that.
+-  ``llvm-addr2line`` interprets all addresses as hexadecimal and ignores an
+   optional ``0x`` prefix, whereas ``llvm-symbolizer`` attempts to determine
+   the base from the literal's prefix and defaults to decimal if there is no
+   prefix.
 
--  Defaults not to demangle function names. Use `-C`_ to switch the
-   demangling on.
+-  ``llvm-addr2line`` defaults not to print function names. Use `-f`_ to enable
+   that.
 
--  Defaults not to print inlined frames. Use `-i`_ to show inlined
-   frames for a source code location in an inlined function.
+-  ``llvm-addr2line`` defaults not to demangle function names. Use `-C`_ to
+   switch the demangling on.
 
--  Uses `--output-style=GNU`_ by default.
+-  ``llvm-addr2line`` defaults not to print inlined frames. Use `-i`_ to show
+   inlined frames for a source code location in an inlined function.
 
--  Parses options from the environment variable ``LLVM_ADDR2LINE_OPTS``.
+-  ``llvm-addr2line`` uses `--output-style=GNU`_ by default.
+
+-  ``llvm-addr2line`` parses options from the environment variable
+   ``LLVM_ADDR2LINE_OPTS`` instead of from ``LLVM_SYMBOLIZER_OPTS``.
 
 SEE ALSO
 --------
diff --git a/llvm/test/lit.cfg.py b/llvm/test/lit.cfg.py
--- a/llvm/test/lit.cfg.py
+++ b/llvm/test/lit.cfg.py
@@ -146,10 +146,10 @@
 # FIXME: Why do we have both `lli` and `%lli` that do slightly different things?
 tools.extend([
     'dsymutil', 'lli', 'lli-child-target', 'llvm-ar', 'llvm-as',
-    'llvm-bcanalyzer', 'llvm-config', 'llvm-cov', 'llvm-cxxdump', 'llvm-cvtres',
-    'llvm-diff', 'llvm-dis', 'llvm-dwarfdump', 'llvm-exegesis', 'llvm-extract',
-    'llvm-isel-fuzzer', 'llvm-ifs', 'llvm-install-name-tool',
-    'llvm-jitlink', 'llvm-opt-fuzzer', 'llvm-lib',
+    'llvm-addr2line', 'llvm-bcanalyzer', 'llvm-config', 'llvm-cov',
+    'llvm-cxxdump', 'llvm-cvtres', 'llvm-diff', 'llvm-dis', 'llvm-dwarfdump',
+    'llvm-exegesis', 'llvm-extract', 'llvm-isel-fuzzer', 'llvm-ifs',
+    'llvm-install-name-tool', 'llvm-jitlink', 'llvm-opt-fuzzer', 'llvm-lib',
     'llvm-link', 'llvm-lto', 'llvm-lto2', 'llvm-mc', 'llvm-mca',
     'llvm-modextract', 'llvm-nm', 'llvm-objcopy', 'llvm-objdump',
     'llvm-pdbutil', 'llvm-profdata', 'llvm-ranlib', 'llvm-rc', 'llvm-readelf',
diff --git a/llvm/test/tools/llvm-symbolizer/input-base.test b/llvm/test/tools/llvm-symbolizer/input-base.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/llvm-symbolizer/input-base.test
@@ -0,0 +1,23 @@
+# llvm-symbolizer infers the number base from the form of the address.
+RUN: llvm-symbolizer -e /dev/null -a 0x1234 | FileCheck %s
+RUN: llvm-symbolizer -e /dev/null -a 0X1234 | FileCheck %s
+RUN: llvm-symbolizer -e /dev/null -a 4660 | FileCheck %s
+RUN: llvm-symbolizer -e /dev/null -a 011064 | FileCheck %s
+RUN: llvm-symbolizer -e /dev/null -a 0b1001000110100 | FileCheck %s
+RUN: llvm-symbolizer -e /dev/null -a 0B1001000110100 | FileCheck %s
+RUN: llvm-symbolizer -e /dev/null -a 0o11064 | FileCheck %s
+RUN: llvm-symbolizer -e /dev/null -a 0O11064 | FileCheck %s
+
+# llvm-addr2line always requires hexadecimal, but accepts an optional 0x prefix.
+RUN: llvm-addr2line -e /dev/null -a 0x1234 | FileCheck %s
+RUN: llvm-addr2line -e /dev/null -a 0X1234 | FileCheck %s
+RUN: llvm-addr2line -e /dev/null -a 1234 | FileCheck %s
+RUN: llvm-addr2line -e /dev/null -a 01234 | FileCheck %s
+RUN: llvm-addr2line -e /dev/null -a 0b1010 | FileCheck %s --check-prefix=HEXADECIMAL-NOT-BINARY
+RUN: llvm-addr2line -e /dev/null -a 0B1010 | FileCheck %s --check-prefix=HEXADECIMAL-NOT-BINARY
+RUN: llvm-addr2line -e /dev/null -a 0o1234 | FileCheck %s --check-prefix=INVALID-NOT-OCTAL
+RUN: llvm-addr2line -e /dev/null -a 0O1234 | FileCheck %s --check-prefix=INVALID-NOT-OCTAL
+
+CHECK: 0x1234
+HEXADECIMAL-NOT-BINARY: 0xb1010
+INVALID-NOT-OCTAL: 0o1234
diff --git a/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp b/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp
--- a/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp
+++ b/llvm/tools/llvm-symbolizer/llvm-symbolizer.cpp
@@ -183,7 +183,7 @@
   Frame,
 };
 
-static bool parseCommand(StringRef InputString, Command &Cmd,
+static bool parseCommand(bool IsAddr2Line, StringRef InputString, Command &Cmd,
                          std::string &ModuleName, uint64_t &ModuleOffset) {
   const char kDelimiters[] = " \n\r";
   ModuleName = "";
@@ -197,38 +197,44 @@
     // If no cmd, assume it's CODE.
     Cmd = Command::Code;
   }
-  const char *pos = InputString.data();
+  const char *Pos = InputString.data();
   // Skip delimiters and parse input filename (if needed).
   if (ClBinaryName.empty()) {
-    pos += strspn(pos, kDelimiters);
-    if (*pos == '"' || *pos == '\'') {
-      char quote = *pos;
-      pos++;
-      const char *end = strchr(pos, quote);
-      if (!end)
+    Pos += strspn(Pos, kDelimiters);
+    if (*Pos == '"' || *Pos == '\'') {
+      char Quote = *Pos;
+      Pos++;
+      const char *End = strchr(Pos, Quote);
+      if (!End)
         return false;
-      ModuleName = std::string(pos, end - pos);
-      pos = end + 1;
+      ModuleName = std::string(Pos, End - Pos);
+      Pos = End + 1;
     } else {
-      int name_length = strcspn(pos, kDelimiters);
-      ModuleName = std::string(pos, name_length);
-      pos += name_length;
+      int NameLength = strcspn(Pos, kDelimiters);
+      ModuleName = std::string(Pos, NameLength);
+      Pos += NameLength;
     }
   } else {
     ModuleName = ClBinaryName;
   }
   // Skip delimiters and parse module offset.
-  pos += strspn(pos, kDelimiters);
-  int offset_length = strcspn(pos, kDelimiters);
-  return !StringRef(pos, offset_length).getAsInteger(0, ModuleOffset);
+  Pos += strspn(Pos, kDelimiters);
+  int OffsetLength = strcspn(Pos, kDelimiters);
+  StringRef Offset(Pos, OffsetLength);
+  // GNU addr2line assumes the offset is hexadecimal and allows a redundant
+  // "0x" or "0X" prefix; do the same for compatibility.
+  if (IsAddr2Line)
+    Offset.consume_front("0x") || Offset.consume_front("0X");
+  return !Offset.getAsInteger(IsAddr2Line ? 16 : 0, ModuleOffset);
 }
 
-static void symbolizeInput(StringRef InputString, LLVMSymbolizer &Symbolizer,
-                           DIPrinter &Printer) {
+static void symbolizeInput(bool IsAddr2Line, StringRef InputString,
+                           LLVMSymbolizer &Symbolizer, DIPrinter &Printer) {
   Command Cmd;
   std::string ModuleName;
   uint64_t Offset = 0;
-  if (!parseCommand(StringRef(InputString), Cmd, ModuleName, Offset)) {
+  if (!parseCommand(IsAddr2Line, StringRef(InputString), Cmd, ModuleName,
+                    Offset)) {
     outs() << InputString << "\n";
     return;
   }
@@ -338,12 +344,12 @@
           std::remove_if(StrippedInputString.begin(), StrippedInputString.end(),
                          [](char c) { return c == '\r' || c == '\n'; }),
           StrippedInputString.end());
-      symbolizeInput(StrippedInputString, Symbolizer, Printer);
+      symbolizeInput(IsAddr2Line, StrippedInputString, Symbolizer, Printer);
       outs().flush();
     }
   } else {
     for (StringRef Address : ClInputAddresses)
-      symbolizeInput(Address, Symbolizer, Printer);
+      symbolizeInput(IsAddr2Line, Address, Symbolizer, Printer);
   }
 
   return 0;