[AST] Fix certain consteval assignment and comma operator issues with fixed-point types.

Summary:
Assignment and comma operators for fixed-point types were being constevaled as other
binary operators, but they need special treatment.

Reviewers: rjmccall, leonardchan, bjope

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73189

Author: bevin-hansson

clang/lib/AST/ExprConstant.cpp

@@ -12920,6 +12920,9 @@ bool FixedPointExprEvaluator::VisitCastExpr(const CastExpr *E) {
 }
 
 bool FixedPointExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
+  if (E->isPtrMemOp() || E->isAssignmentOp() || E->getOpcode() == BO_Comma)
+    return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
+
   const Expr *LHS = E->getLHS();
   const Expr *RHS = E->getRHS();
   FixedPointSemantics ResultFXSema =

clang/test/Frontend/fixed_point_crash.c

@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -verify -ffixed-point %s
+
+union a {
+  _Accum x;
+  int i;
+};
+
+int fn1() {
+  union a m;
+  m.x = 5.6k;
+  return m.i;
+}
+
+int fn2() {
+  union a m;
+  m.x = 7, 5.6k; // expected-warning {{expression result unused}}
+  return m.x, m.i; // expected-warning {{expression result unused}}
+}
+
+_Accum acc = (0.5r, 6.9k); // expected-warning {{expression result unused}}