[clang] [Clang] Lower fp atomic compound stmts into atomicrmw (PR #216033)

[Paul Walker via cfe-commits]

================
@@ -4105,14 +4102,21 @@ LValue ScalarExprEmitter::EmitCompoundAssignLValue(
     // the loaded integer to double, performing FP arithmetics, and truncation
     // back as a single atomic operation. Integer promotion is still
     // semantically safe.
-    bool CanEmitAtomicRMW =
+    bool CanEmitIntegerRMW =
         !AtomicValueTy->isBooleanType() && AtomicValueTy->isIntegerType() &&
         ResultTy->isIntegerType() &&
         !(AtomicValueTy->isUnsignedIntegerType() &&
           CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) &&
         CGF.getLangOpts().getSignedOverflowBehavior() !=
             LangOptions::SOB_Trapping;
-    if (CanEmitAtomicRMW) {
+    bool CanEmitFloatingRMW = false;
+    if (!Builder.getIsFPConstrained() && AtomicValueTy->isFloatingType() &&
----------------
paulwalker-arm wrote:

In which case you'll want `CGF.getLangOpts().isFPConstrained()`?

https://github.com/llvm/llvm-project/pull/216033