HybridCompile: add Option to enable LTO for Arduino part

builder/frameworks/arduino.py

@@ -532,6 +532,7 @@ def safe_remove_sdkconfig_files():
 flag_custom_component_remove = False
 flag_custom_component_add = False
 flag_lib_ignore = False
+flag_lto = False
 
 if mcu == "esp32c2":
     flag_custom_sdkconfig = True
@@ -598,6 +599,9 @@ def has_psram_config():
     if has_unicore_flags():
         build_unflags += " -ustart_app_other_cores"
 
+    if '-fno-lto' in build_unflags:
+        flag_lto = True
+
     new_build_unflags = build_unflags.split()
     env.Replace(BUILD_UNFLAGS=new_build_unflags)
 
@@ -916,6 +920,13 @@ def get_frameworks_in_current_env():
     from component_manager import ComponentManager
     component_manager = ComponentManager(env)
     component_manager.handle_component_settings()
+
+    # Handle LTO flags if flag_lto is set
+    if flag_lto:
+        # First remove existing -fno-lto flags, then add LTO flags
+        component_manager.remove_no_lto_flags()
+        component_manager.add_lto_flags()
+
     silent_action = env.Action(component_manager.restore_pioarduino_build_py)
     # silence scons command output
     silent_action.strfunction = lambda target, source, env: ''

builder/frameworks/component_manager.py

@@ -1271,3 +1271,110 @@ def print_changes_summary(self) -> None:
         session, useful for build reporting and debugging.
         """
         self.logger.print_changes_summary()
+
+    def remove_no_lto_flags(self) -> bool:
+        """
+        Remove all -fno-lto flags from pioarduino-build.py.
+
+        Removes all occurrences of -fno-lto from CCFLAGS, CFLAGS, CXXFLAGS,
+        and LINKFLAGS in the Arduino build script.
+
+        Returns:
+            bool: True if successful, False otherwise
+        """
+        build_py_path = str(Path(self.config.arduino_libs_mcu) / "pioarduino-build.py")
+
+        if not os.path.exists(build_py_path):
+            print(f"Warning: pioarduino-build.py not found at {build_py_path}")
+            return False
+
+        try:
+            with open(build_py_path, 'r', encoding='utf-8') as f:
+                content = f.read()
+
+            # Remove all -fno-lto flags
+            modified_content = re.sub(r'["\']?-fno-lto["\']?,?\s*', '', content)
+
+            # Clean up any resulting empty strings or double commas
+            modified_content = re.sub(r',\s*,', ',', modified_content)
+            modified_content = re.sub(r'\[\s*,', '[', modified_content)
+            modified_content = re.sub(r',\s*\]', ']', modified_content)
+
+            with open(build_py_path, 'w', encoding='utf-8') as f:
+                f.write(modified_content)
+
+            return True
+
+        except (IOError, OSError) as e:
+            print(f"Error removing -fno-lto flags: {e}")
+            return False
+
+    def add_lto_flags(self) -> bool:
+        """
+        Add LTO flags to pioarduino-build.py.
+
+        Adds -flto=auto to CCFLAGS, CFLAGS, CXXFLAGS and -flto to LINKFLAGS
+        in the Arduino build script. Flags are inserted right after the opening bracket.
+
+        Returns:
+            bool: True if successful, False otherwise
+        """
+        build_py_path = str(Path(self.config.arduino_libs_mcu) / "pioarduino-build.py")
+
+        if not os.path.exists(build_py_path):
+            print(f"Warning: pioarduino-build.py not found at {build_py_path}")
+            return False
+
+        try:
+            with open(build_py_path, 'r', encoding='utf-8') as f:
+                content = f.read()
+
+            original_content = content
+            modified = False
+
+            # Add -flto=auto to CCFLAGS right after the opening bracket
+            if 'CCFLAGS=[' in content:
+                ccflags_start = content.find('CCFLAGS=[')
+                ccflags_section_start = ccflags_start + len('CCFLAGS=[')
+                content = (content[:ccflags_section_start] + 
+                          '\n        "-flto=auto",' + 
+                          content[ccflags_section_start:])
+                modified = True
+
+            # Add -flto=auto to CFLAGS right after the opening bracket
+            if 'CFLAGS=[' in content:
+                cflags_start = content.find('CFLAGS=[')
+                cflags_section_start = cflags_start + len('CFLAGS=[')
+                content = (content[:cflags_section_start] + 
+                          '\n        "-flto=auto",' + 
+                          content[cflags_section_start:])
+                modified = True
+
+            # Add -flto=auto to CXXFLAGS right after the opening bracket
+            if 'CXXFLAGS=[' in content:
+                cxxflags_start = content.find('CXXFLAGS=[')
+                cxxflags_section_start = cxxflags_start + len('CXXFLAGS=[')
+                content = (content[:cxxflags_section_start] + 
+                          '\n        "-flto=auto",' + 
+                          content[cxxflags_section_start:])
+                modified = True
+
+            # Add -flto to LINKFLAGS right after the opening bracket
+            if 'LINKFLAGS=[' in content:
+                linkflags_start = content.find('LINKFLAGS=[')
+                linkflags_section_start = linkflags_start + len('LINKFLAGS=[')
+                content = (content[:linkflags_section_start] + 
+                          '\n        "-flto",' + 
+                          content[linkflags_section_start:])
+                modified = True
+
+            if modified:
+                with open(build_py_path, 'w', encoding='utf-8') as f:
+                    f.write(content)
+
+                print("*** Added LTO flags for Arduino compile ***")
+                return True
+
+        except (IOError, OSError) as e:
+            print(f"Error adding LTO flags: {e}")
+            return False