Better support a lack of musttail and preserve_none

ConflictSet.cpp

@@ -4700,7 +4700,6 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
 
     interleaved_insert::Result stackResults[100];
 
-#if __has_attribute(preserve_none) && __has_attribute(musttail)
     constexpr int kConcurrent = 16;
     interleaved_insert::Job inProgress[kConcurrent];
     interleaved_insert::Context context;
@@ -4732,8 +4731,6 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     // are done
     inProgress->continuation(inProgress, &context);
 
-#endif
-
     // Phase 2: Perform insertions. Nodes may be upsized during this phase, but
     // old nodes get forwarding pointers installed and are released after
     // phase 2.
@@ -4794,6 +4791,7 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
       }
     }
 
+#if __has_attribute(preserve_none) && __has_attribute(musttail)
     bool allPointWrites = true;
     for (int i = 0; i < count; ++i) {
       if (writes[i].end.len > 0) {
@@ -4801,7 +4799,10 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
         break;
       }
     }
-    if (allPointWrites) {
+#else
+    bool allPointWrites = false;
+#endif
+    if (allPointWrites && count > 1) {
       interleavedPointWrites(writes, count, InternalVersionT(writeVersion));
     } else {
       for (int i = 0; i < count; ++i) {