Index: clang/lib/Driver/Driver.cpp
===================================================================
--- clang/lib/Driver/Driver.cpp
+++ clang/lib/Driver/Driver.cpp
@@ -1231,11 +1231,20 @@
     StringRef PassedFlags = A->getValue();
     std::vector<std::string> SuggestedCompletions;
 
+    unsigned short DisableFlags = options::NoDriverOption | options::Unsupported | options::Ignored;
+    // We want to show cc1-only options only when clang is invoked as "clang -cc1".
+    // When clang is invoked as "clang -cc1", we add "#" to ther beginning of an --autocomplete
+    // option so that the clang driver can distinguish whether it is requested to show cc1-only options or not.
+    if (PassedFlags[0] == '#') {
+      DisableFlags &= ~options::NoDriverOption;
+      PassedFlags = PassedFlags.substr(1);
+    }
+
     if (PassedFlags.find(',') == StringRef::npos) {
       // If the flag is in the form of "--autocomplete=-foo",
       // we were requested to print out all option names that start with "-foo".
       // For example, "--autocomplete=-fsyn" is expanded to "-fsyntax-only".
-      SuggestedCompletions = Opts->findByPrefix(PassedFlags);
+      SuggestedCompletions = Opts->findByPrefix(PassedFlags, DisableFlags);
     } else {
       // If the flag is in the form of "--autocomplete=foo,bar", we were
       // requested to print out all option values for "-foo" that start with
Index: clang/test/Driver/autocomplete.c
===================================================================
--- clang/test/Driver/autocomplete.c
+++ clang/test/Driver/autocomplete.c
@@ -36,3 +36,7 @@
 // MTHREADMODELALL: posix single
 // RUN: %clang --autocomplete=-mrelocation-model, | FileCheck %s -check-prefix=MRELOCMODELALL
 // MRELOCMODELALL: dynamic-no-pic pic ropi ropi-rwpi rwpi static
+// RUN: %clang --autocomplete=-mrelocation-mode | FileCheck %s -check-prefix=MRELOCMODEL_CLANG
+// MRELOCMODEL_CLANG-NOT: -mrelocation-model
+// RUN: %clang --autocomplete=#-mrelocation-mode | FileCheck %s -check-prefix=MRELOCMODEL_CC1
+// MRELOCMODEL_CC1: -mrelocation-model
Index: clang/utils/bash-autocomplete.sh
===================================================================
--- clang/utils/bash-autocomplete.sh
+++ clang/utils/bash-autocomplete.sh
@@ -10,18 +10,23 @@
   # So, we need to partially undo bash tokenization here for integrity.
   local w1="${COMP_WORDS[$cword - 1]}"
   local w2="${COMP_WORDS[$cword - 2]}"
+  # Clang want to know if -cc1 option is specified or not, because we don't want to show
+  # cc1 options otherwise.
+  if [[ "${COMP_WORDS[1]}" == "-cc1" || "$w1" == "-Xclang" ]]; then
+    arg="#"
+  fi
   if [[ "$cur" == -* ]]; then
     # -foo<tab>
-    arg="$cur"
+    arg="$arg$cur"
   elif [[ "$w1" == -*  && "$cur" == '=' ]]; then
     # -foo=<tab>
-    arg="$w1=,"
+    arg="$arg$w1=,"
   elif [[ "$w1" == -* ]]; then
     # -foo <tab> or -foo bar<tab>
-    arg="$w1,$cur"
+    arg="$arg$w1,$cur"
   elif [[ "$w2" == -* && "$w1" == '=' ]]; then
     # -foo=bar<tab>
-    arg="$w2=,$cur"
+    arg="$arg$w2=,$cur"
   fi
 
   flags=$( "${COMP_WORDS[0]}" --autocomplete="$arg" 2>/dev/null )
Index: llvm/include/llvm/Option/OptTable.h
===================================================================
--- llvm/include/llvm/Option/OptTable.h
+++ llvm/include/llvm/Option/OptTable.h
@@ -140,7 +140,8 @@
   //  to start with.
   ///
   /// \return The vector of flags which start with Cur.
-  std::vector<std::string> findByPrefix(StringRef Cur) const;
+  std::vector<std::string> findByPrefix(StringRef Cur,
+                                        unsigned short DisableFlags) const;
 
   /// \brief Parse a single argument; returning the new argument and
   /// updating Index.
Index: llvm/lib/Option/OptTable.cpp
===================================================================
--- llvm/lib/Option/OptTable.cpp
+++ llvm/lib/Option/OptTable.cpp
@@ -225,11 +225,15 @@
   return {};
 }
 
-std::vector<std::string> OptTable::findByPrefix(StringRef Cur) const {
+std::vector<std::string>
+OptTable::findByPrefix(StringRef Cur, unsigned short DisableFlags) const {
   std::vector<std::string> Ret;
   for (const Info &In : OptionInfos.slice(FirstSearchableIndex)) {
     if (!In.Prefixes)
       continue;
+    if (In.Flags & DisableFlags)
+      continue;
+
     for (int I = 0; In.Prefixes[I]; I++) {
       std::string S = std::string(In.Prefixes[I]) + std::string(In.Name);
       if (StringRef(S).startswith(Cur))