diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 2f27bf912fa2f..78405f23e4003 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -2163,6 +2163,9 @@ void UnwrappedLineParser::parseIfThenElse() {
     nextToken();
   if (FormatTok->Tok.is(tok::l_paren))
     parseParens();
+  // handle  AttributeMacro  if (x) UNLIKELY
+  if (FormatTok->is(TT_AttributeMacro))
+    nextToken();
   // handle [[likely]] / [[unlikely]]
   if (FormatTok->is(tok::l_square) && tryToParseSimpleAttribute())
     parseSquare();
@@ -2182,6 +2185,9 @@ void UnwrappedLineParser::parseIfThenElse() {
   }
   if (FormatTok->Tok.is(tok::kw_else)) {
     nextToken();
+    // handle  AttributeMacro  else UNLIKELY
+    if (FormatTok->is(TT_AttributeMacro))
+      nextToken();
     // handle [[likely]] / [[unlikely]]
     if (FormatTok->Tok.is(tok::l_square) && tryToParseSimpleAttribute())
       parseSquare();
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 37d08d2d91292..2eb10609646a6 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -22274,6 +22274,42 @@ TEST_F(FormatTest, LikelyUnlikely) {
                "  return 29;\n"
                "}",
                Style);
+
+  verifyFormat("if (argc > 5) [[unlikely]]\n"
+               "  return 29;\n",
+               Style);
+  verifyFormat("if (argc > 5) [[likely]]\n"
+               "  return 29;\n",
+               Style);
+
+  Style.AttributeMacros.push_back("UNLIKELY");
+  Style.AttributeMacros.push_back("LIKELY");
+  verifyFormat("if (argc > 5) UNLIKELY\n"
+               "  return 29;\n",
+               Style);
+
+  verifyFormat("if (argc > 5) UNLIKELY {\n"
+               "  return 29;\n"
+               "}",
+               Style);
+  verifyFormat("if (argc > 5) UNLIKELY {\n"
+               "  return 29;\n"
+               "} else [[likely]] {\n"
+               "  return 42;\n"
+               "}\n",
+               Style);
+  verifyFormat("if (argc > 5) UNLIKELY {\n"
+               "  return 29;\n"
+               "} else LIKELY {\n"
+               "  return 42;\n"
+               "}\n",
+               Style);
+  verifyFormat("if (argc > 5) [[unlikely]] {\n"
+               "  return 29;\n"
+               "} else LIKELY {\n"
+               "  return 42;\n"
+               "}\n",
+               Style);
 }
 
 TEST_F(FormatTest, PenaltyIndentedWhitespace) {