improvement: replace likely macro with C++20 attribute (SFTtech#1517)

Replace likely macro with C++20 attribute

copying.md

@@ -143,6 +143,7 @@ _the openage authors_ are:
 | Matthias Geiger             | CountOmega                  | matthias dawt geiger1024 à outlook dawt com       |
 | Yuvraj Tetarwal             | YuviTz1                     | yuvi56789 à gmail dawt com                        |
 | Tarun Samanta               | TS                          | [email protected]                          |
+| Derek Frogget               | FoggyLight                  | [email protected]                                 |
 
 If you're a first-time committer, add yourself to the above list. This is not
 just for legal reasons, but also to keep an overview of all those nicknames.

libopenage/curve/keyframe_container.h

@@ -1,4 +1,4 @@
-// Copyright 2017-2019 the openage authors. See copying.md for legal info.
+// Copyright 2017-2023 the openage authors. See copying.md for legal info.
 
 #pragma once
 
@@ -411,7 +411,7 @@ KeyframeContainer<T>::erase_group(const time_t &time,
 	// erase elements until all element with that time are purged
 	while (at != std::end(this->container) and at->time == time) {
 		at = this->container.erase(at);
-		if (likely(at != std::begin(this->container))) {
+		if (at != std::begin(this->container)) [[likely]] {
 			--at;
 		}
 	}

libopenage/datastructure/pairing_heap.h

@@ -256,6 +256,7 @@ class PairingHeap final {
 		// 1. link root children pairwise, last node may be alone
 		element_t first_pair = nullptr;
 		element_t previous_pair = nullptr;
+
 		while (current_sibling != nullptr) [[unlikely]] {
 			element_t link0 = current_sibling;
 			element_t link1 = current_sibling->next_sibling;
@@ -377,7 +378,7 @@ class PairingHeap final {
 	 * O(1)
 	 */
 	void decrease(const element_t &node) {
-		if (likely(node != this->root_node)) {
+		if (node != this->root_node) [[likely]] {
 			// cut out the node and its subtree
 			node->loosen();
 			this->root_node = node->link_with(this->root_node);
@@ -394,7 +395,7 @@ class PairingHeap final {
 	 * O(1) (but slower than decrease), and O(pop) when node is the root.
 	 */
 	void update(const element_t &node) {
-		if (likely(node != this->root_node)) {
+		if (node != this->root_node) [[likely]] {
 			this->unlink_node(node);
 			this->push_node(node);
 		}

libopenage/error/error.cpp

@@ -22,6 +22,7 @@ Error::Error(const log::message &msg, bool generate_backtrace, bool store_cause)
 	:
 	std::runtime_error{runtime_error_message},
 	msg(msg) {
+
 	if (enable_break_on_create) [[unlikely]] {
 		BREAKPOINT;
 	}
@@ -42,7 +43,7 @@ void Error::store_cause() {
 	// we could simply do this->cause = std::current_exception(),
 	// but we need to trim the cause Error's backtrace.
 
-	if (likely(!std::current_exception())) {
+	if (!std::current_exception()) [[likely]] {
 		return;
 	}
 

libopenage/pyinterface/exctranslate.cpp

@@ -55,6 +55,7 @@ void translate_exc_cpp_to_py() {
 		throw;
 
 	} catch (PyException &exc) {
+
 		if (raise_cpp_pyexception == nullptr) [[unlikely]] {
 			throw Error(MSG(err) <<
 				"raise_pyexception_in_py is uninitialized; "
@@ -66,6 +67,7 @@ void translate_exc_cpp_to_py() {
 		raise_cpp_pyexception(&exc);
 
 	} catch (Error &exc) {
+
 		if (raise_cpp_error == nullptr) [[unlikely]] {
 			throw Error(MSG(err) <<
 				"raise_error_in_py is uninitialized; "
@@ -95,7 +97,7 @@ void translate_exc_py_to_cpp() {
 			"can't check for and translate Python exception to C++ exception.");
 	}
 
-	if (likely(not check_for_py_exception())) {
+	if (not check_for_py_exception()) [[likely]] {
 		// no exception has occurred.
 		return;
 	}

libopenage/util/compiler.h

@@ -41,18 +41,6 @@
 	#endif // HAVE_SSIZE_T
 #endif // _MSC_VER
 
-/*
- * Branch prediction tuning.
- * the expression is expected to be true (=likely) or false (=unlikely).
- *
- * btw, this implementation was taken from the Linux kernel.
- */
-#if defined(__GNUC__)
-#define likely(x)    __builtin_expect(!!(x), 1)
-#else
-#define likely(x)   (x)
-#endif
-
 
 /**
  * Software breakpoint if you're too lazy

libopenage/util/compress/lzxd.cpp

@@ -243,7 +243,7 @@ int HuffmanTable<maxsymbols_p, tablebits_p, allow_empty>::read_sym() {
 	unsigned i = 1 << (sizeof(lzx->bits.bit_buffer) * 8 - tablebits);
 	while (sym >= maxsymbols) {
 		// huff_traverse
-		if (((i >>= 1) == 0)) [[unlikely]] {
+		if ((i >>= 1) == 0) [[unlikely]] {
 			throw Error(MSG(err) << "huff_error in huff_traverse");
 		}
 		sym = table[(sym << 1) | ((lzx->bits.bit_buffer & i) ? 1 : 0)];

libopenage/util/csv.cpp

@@ -1,4 +1,4 @@
-// Copyright 2013-2017 the openage authors. See copying.md for legal info.
+// Copyright 2013-2023 the openage authors. See copying.md for legal info.
 
 #include "csv.h"
 
@@ -48,7 +48,7 @@ CSVCollection::CSVCollection(const Path &entryfile_path) {
 				continue;
 			}
 
-			if (likely(current_file.size() > 0)) {
+			if (current_file.size() > 0) [[likely]] {
 				// add line to the current file linelist
 				this->data.at(current_file).push_back(line);
 			}

libopenage/util/path.cpp

@@ -1,4 +1,4 @@
-// Copyright 2015-2019 the openage authors. See copying.md for legal info.
+// Copyright 2015-2023 the openage authors. See copying.md for legal info.
 
 #include "path.h"
 
@@ -28,7 +28,7 @@ void path_normalizer(Path::parts_t &output, const Path::parts_t &input) {
 			continue;
 		}
 		else if (part == "..") {
-			if (likely(output.size() > 0)) {
+			if (output.size() > 0) [[likely]] {
 				output.pop_back();
 			}
 		}
@@ -294,7 +294,7 @@ std::string Path::get_stem() const {
 Path Path::joinpath(const parts_t &subpaths) const {
 	parts_t new_parts = this->parts;
 	for (auto &part : subpaths) {
-		if (likely(part.size() > 0)) {
+		if (part.size() > 0) [[likely]] {
 			new_parts.push_back(part);
 		}
 	}

libopenage/util/strings.cpp

@@ -144,7 +144,7 @@ std::vector<std::string> split_escape(const std::string &txt, char delim, size_t
 
 	// output vector
 	std::vector<std::string> items;
-	if (likely(size_hint)) {
+	if (size_hint) [[likely]] {
 		items.reserve(size_hint);
 	}