ircd: Apply branch expectation attributes to various case labels.

ircd/allocator.cc

@@ -56,12 +56,15 @@ ircd::allocator::allocate(const size_t alignment,
 	void *ret;
 	switch(int errc(::posix_memalign(&ret, alignment, size)); errc)
 	{
+		[[likely]]
 		case 0:
 			break;
 
+		[[unlikely]]
 		case int(std::errc::not_enough_memory):
 			throw std::bad_alloc{};
 
+		[[unlikely]]
 		default:
 			throw_system_error();
 			__builtin_unreachable();
@@ -249,9 +252,11 @@ ircd::allocator::advise(const const_buffer &buf,
 	assert(aligned(data(buf), info::page_size));
 	switch(const auto r(::madvise(mutable_cast(data(buf)), size(buf), advice)); r)
 	{
+		[[likely]]
 		case 0:
 			return size(buf);          // success
 
+		[[unlikely]]
 		default:
 			throw_system_error(r);     // error
 	}

ircd/db.cc

@@ -4398,6 +4398,7 @@ ircd::db::throw_on_error::throw_on_error(const rocksdb::Status &status)
 
 	switch(status.code())
 	{
+		[[likely]]
 		case Status::kOk:
 			return;
 
@@ -4412,6 +4413,7 @@ ircd::db::throw_on_error::throw_on_error(const rocksdb::Status &status)
 			[[fallthrough]];
 		#endif
 
+		[[unlikely]]
 		default:
 			throw error
 			{
@@ -4444,6 +4446,7 @@ ircd::db::error_to_status::error_to_status(const std::error_code &e)
 
 	switch(e.value())
 	{
+		[[likely]]
 		case 0:
 			return Status::OK();
 
@@ -4529,6 +4532,7 @@ ircd::db::append(rocksdb::WriteBatch &batch,
 	const auto v(slice(std::get<2>(delta)));
 	switch(std::get<0>(delta))
 	{
+		[[unlikely]]
 		case op::GET:            assert(0);                    break;
 		case op::SET:            batch.Put(c, k, v);           break;
 		case op::MERGE:          batch.Merge(c, k, v);         break;
@@ -5120,11 +5124,13 @@ ircd::db::valid(const rocksdb::Iterator &it)
 	{
 		using rocksdb::Status;
 
+		[[likely]]
 		case Status::kOk:
 		case Status::kNotFound:
 		case Status::kIncomplete:
 			return it.Valid();
 
+		[[unlikely]]
 		default:
 			throw_on_error
 			{
@@ -5142,13 +5148,16 @@ ircd::db::valid(const rocksdb::Status &s)
 	{
 		using rocksdb::Status;
 
+		[[likely]]
 		case Status::kOk:
 			return true;
 
+		[[likely]]
 		case Status::kNotFound:
 		case Status::kIncomplete:
 			return false;
 
+		[[unlikely]]
 		default:
 			throw_on_error{s};
 			__builtin_unreachable();

ircd/db_database.cc

@@ -523,7 +523,7 @@ ircd::db::loglevel(const database &d)
 
 	switch(level)
 	{
-		default:
+		[[unlikely]]
 		case rocksdb::NUM_INFO_LOG_LEVELS:
 			assert(0);
 
@@ -534,6 +534,9 @@ ircd::db::loglevel(const database &d)
 		case rocksdb::INFO_LEVEL:      return log::level::INFO;
 		case rocksdb::DEBUG_LEVEL:     return log::level::DEBUG;
 	}
+
+	assert(0);
+	__builtin_unreachable();
 }
 
 ircd::db::options

ircd/fs.cc

@@ -2332,8 +2332,13 @@ ircd::fs::advise(const fd &fd,
 		cnt = std::min(opts.offset + count - off, max_count);
 		switch(const auto r(::posix_fadvise(fd, off, cnt, advice)); r)
 		{
-			case 0:   break;
-			default:  throw_system_error(r);
+			[[likely]]
+			case 0:
+				break;
+
+			[[unlikely]]
+			default:
+				throw_system_error(r);
 		}
 	}
 	while(off + cnt < opts.offset + count);

ircd/net.cc

@@ -1671,6 +1671,7 @@ try
 		};
 		break;
 
+		[[unlikely]]
 		default:
 			throw ircd::not_implemented{};
 	}
@@ -1760,7 +1761,9 @@ try
 			return;
 		}
 
-		default: throw ircd::not_implemented{};
+		[[unlikely]]
+		default:
+			throw ircd::not_implemented{};
 	}
 }
 catch(const boost::system::system_error &e)
@@ -2188,6 +2191,7 @@ noexcept try
 		}
 
 		// A cancelation means there was no timeout.
+		[[likely]]
 		case int(std::errc::operation_canceled):
 		{
 			assert(ec.category() == std::system_category());
@@ -2196,6 +2200,7 @@ noexcept try
 		}
 
 		// All other errors are unexpected, logged and ignored here.
+		[[unlikely]]
 		default: throw panic
 		{
 			"socket(%p): unexpected :%s",
@@ -2520,6 +2525,7 @@ noexcept try
 
 	if(!valid) switch(err)
 	{
+		[[unlikely]]
 		case X509_V_OK:
 			assert(0);
 

ircd/net_dns_resolver.cc

@@ -172,6 +172,7 @@ ircd::net::dns::resolver::make_query(const mutable_buffer &buf,
 	string_view hoststr;
 	switch(tag.opts.qtype)
 	{
+		[[unlikely]]
 		case 0: throw error
 		{
 			"Query type is required to form a question."
@@ -803,6 +804,7 @@ ircd::net::dns::resolver::handle_error(const header &header,
 {
 	switch(header.rcode)
 	{
+		[[likely]]
 		case 0: // NoError; continue
 			return true;
 

ircd/resource.cc

@@ -1117,6 +1117,7 @@ try
 			return;
 		}
 
+		[[unlikely]]
 		default: throw http::error
 		{
 			"Cannot send json::%s as response content",

ircd/server.cc

@@ -1236,6 +1236,7 @@ ircd::server::peer::handle_error(link &link,
 
 	if(system_category(ec)) switch(ec.value())
 	{
+		[[unlikely]]
 		case 0:
 			assert(0);
 			break;
@@ -2414,6 +2415,7 @@ noexcept try
 
 	if(system_category(ec)) switch(ec.value())
 	{
+		[[likely]]
 		case 0:
 			handle_writable_success();
 			return;
@@ -2601,6 +2603,7 @@ noexcept try
 
 	if(system_category(ec)) switch(ec.value())
 	{
+		[[likely]]
 		case 0:
 			handle_readable_success();
 			return;