[PATCH] D80144: [clang-format] @lefticus just taught the world how to use [[unlikely]] but we forgot to teach clang-format

[MyDeveloperDay via Phabricator via cfe-commits]

MyDeveloperDay created this revision.
MyDeveloperDay added reviewers: krasimir, mitchell-stellar, JakeMerdichAMD, curdeius, lefticus.
MyDeveloperDay added projects: clang, clang-format.

https://twitter.com/lefticus/status/1262392152950288384?s=20

Jason Turner's (@lefticus) most recent C++ weekly explains the usage of [[likely]] and [[unlikely]] in an 'if/else' context in C++ 20

clang-format leaves the code a little messy afterwards..

  if (argc > 5)
    [[unlikely]] {
      // ...
    }
  else if (argc < 0)
    [[likely]] {
      // ...
    }
  else
    [[likely]] {
      // ...
    }

try to improve the situation

  if (argc > 5) [[unlikely]] {
    // ...
  } else if (argc < 0) [[likely]] {
    // ...
  } else [[likely]] {
    // ...
  }




Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80144

Files:
  clang/lib/Format/UnwrappedLineParser.cpp
  clang/unittests/Format/FormatTest.cpp


Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -15849,6 +15849,36 @@
   verifyFormat("operator&&(int(&&)(), class Foo);", Style);
 }
 
+TEST_F(FormatTest, LikelyUnlikely) {
+  FormatStyle Style = getLLVMStyle();
+
+  verifyFormat("if (argc > 5) [[unlikely]] {\n"
+               "  return 29;\n"
+               "}",
+               Style);
+
+  verifyFormat("if (argc > 5) [[likely]] {\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 if (argc > 10) [[likely]] {\n"
+               "  return 99;\n"
+               "} else {\n"
+               "  return 42;\n"
+               "}\n",
+               Style);
+}
+
 } // namespace
 } // namespace format
 } // namespace clang
Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -1954,6 +1954,9 @@
     nextToken();
   if (FormatTok->Tok.is(tok::l_paren))
     parseParens();
+  // handle [[likely]] / [[unlikely]]
+  if (FormatTok->is(tok::l_square))
+    parseSquare();
   bool NeedsUnwrappedLine = false;
   if (FormatTok->Tok.is(tok::l_brace)) {
     CompoundStatementIndenter Indenter(this, Style, Line->Level);
@@ -1970,6 +1973,9 @@
   }
   if (FormatTok->Tok.is(tok::kw_else)) {
     nextToken();
+    // handle [[likely]] / [[unlikely]]
+    if (FormatTok->is(tok::l_square))
+      parseSquare();
     if (FormatTok->Tok.is(tok::l_brace)) {
       CompoundStatementIndenter Indenter(this, Style, Line->Level);
       parseBlock(/*MustBeDeclaration=*/false);


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