[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, 11 insertions, 6 deletions

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 233e0accce9..bc587628c95 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -66,12 +66,16 @@ using namespace clang;
 ///         shift-expression '<<' additive-expression
 ///         shift-expression '>>' additive-expression
 ///
-///       relational-expression: [C99 6.5.8]
+///       compare-expression: [C++20 expr.spaceship]
 ///         shift-expression
-///         relational-expression '<' shift-expression
-///         relational-expression '>' shift-expression
-///         relational-expression '<=' shift-expression
-///         relational-expression '>=' shift-expression
+///         compare-expression '<=>' shift-expression
+///
+///       relational-expression: [C99 6.5.8]
+///         compare-expression
+///         relational-expression '<' compare-expression
+///         relational-expression '>' compare-expression
+///         relational-expression '<=' compare-expression
+///         relational-expression '>=' compare-expression
 ///
 ///       equality-expression: [C99 6.5.9]
 ///         relational-expression
@@ -267,7 +271,8 @@ bool Parser::diagnoseUnknownTemplateId(ExprResult LHS, SourceLocation Less) {
 }
 
 bool Parser::isFoldOperator(prec::Level Level) const {
-  return Level > prec::Unknown && Level != prec::Conditional;
+  return Level > prec::Unknown && Level != prec::Conditional &&
+         Level != prec::Spaceship;
 }
 
 bool Parser::isFoldOperator(tok::TokenKind Kind) const {