[c++20] P0515R3: Parsing support and basic AST construction for operator <=>.

Adding the new enumerator forced a bunch more changes into this patch than I
would have liked. The -Wtautological-compare warning was extended to properly
check the new comparison operator, clang-format needed updating because it uses
precedence levels as weights for determining where to break lines (and several
operators increased their precedence levels with this change), thread-safety
analysis needed changes to build its own IL properly for the new operator.

All "real" semantic checking for this operator has been deferred to a future
patch. For now, we use the relational comparison rules and arbitrarily give
the builtin form of the operator a return type of 'void'.

llvm-svn: 320707

1 files changed, 25 insertions, 12 deletions

diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 45b73f0a2bf..ff0f4d99585 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -127,34 +127,47 @@ void Sema::ActOnForEachDeclStmt(DeclGroupPtrTy dg) {
 /// warning from firing.
 static bool DiagnoseUnusedComparison(Sema &S, const Expr *E) {
   SourceLocation Loc;
-  bool IsNotEqual, CanAssign, IsRelational;
+  bool CanAssign;
+  enum { Equality, Inequality, Relational, ThreeWay } Kind;
 
   if (const BinaryOperator *Op = dyn_cast<BinaryOperator>(E)) {
     if (!Op->isComparisonOp())
       return false;
 
-    IsRelational = Op->isRelationalOp();
+    if (Op->getOpcode() == BO_EQ)
+      Kind = Equality;
+    else if (Op->getOpcode() == BO_NE)
+      Kind = Inequality;
+    else if (Op->getOpcode() == BO_Cmp)
+      Kind = ThreeWay;
+    else {
+      assert(Op->isRelationalOp());
+      Kind = Relational;
+    }
     Loc = Op->getOperatorLoc();
-    IsNotEqual = Op->getOpcode() == BO_NE;
     CanAssign = Op->getLHS()->IgnoreParenImpCasts()->isLValue();
   } else if (const CXXOperatorCallExpr *Op = dyn_cast<CXXOperatorCallExpr>(E)) {
     switch (Op->getOperator()) {
-    default:
-      return false;
     case OO_EqualEqual:
+      Kind = Equality;
+      break;
     case OO_ExclaimEqual:
-      IsRelational = false;
+      Kind = Inequality;
       break;
     case OO_Less:
     case OO_Greater:
     case OO_GreaterEqual:
     case OO_LessEqual:
-      IsRelational = true;
+      Kind = Relational;
       break;
+    case OO_Spaceship:
+      Kind = ThreeWay;
+      break;
+    default:
+      return false;
     }
 
     Loc = Op->getOperatorLoc();
-    IsNotEqual = Op->getOperator() == OO_ExclaimEqual;
     CanAssign = Op->getArg(0)->IgnoreParenImpCasts()->isLValue();
   } else {
     // Not a typo-prone comparison.
@@ -167,15 +180,15 @@ static bool DiagnoseUnusedComparison(Sema &S, const Expr *E) {
     return false;
 
   S.Diag(Loc, diag::warn_unused_comparison)
-    << (unsigned)IsRelational << (unsigned)IsNotEqual << E->getSourceRange();
+    << (unsigned)Kind << E->getSourceRange();
 
   // If the LHS is a plausible entity to assign to, provide a fixit hint to
   // correct common typos.
-  if (!IsRelational && CanAssign) {
-    if (IsNotEqual)
+  if (CanAssign) {
+    if (Kind == Inequality)
       S.Diag(Loc, diag::note_inequality_comparison_to_or_assign)
         << FixItHint::CreateReplacement(Loc, "|=");
-    else
+    else if (Kind == Equality)
       S.Diag(Loc, diag::note_equality_comparison_to_assign)
         << FixItHint::CreateReplacement(Loc, "=");
   }