From 118f1592ff5d04cdcb35d779c3e93575cfad71ae Mon Sep 17 00:00:00 2001
From: Radoslaw Koppel <radoslaw.koppel@nordicsemi.no>
Date: Tue, 27 Feb 2024 13:17:37 +0100
Subject: [PATCH] buildsystem: Enable LTO also for the application
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It turns out that currently LTO is enabled only for the kernel.
This commit updates it to enable it for the whole application
and adds additional LTO exclusions required for the standard
C libraries to build and link properly.

Signed-off-by: Radosław Koppel <radoslaw.koppel@nordicsemi.no>
---
 CMakeLists.txt                   | 2 +-
 lib/libc/newlib/CMakeLists.txt   | 3 +++
 lib/libc/picolibc/CMakeLists.txt | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f1fb89660f9..a229c06413e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -214,7 +214,7 @@ endif()
 zephyr_compile_options(${OPTIMIZATION_FLAG})
 
 if(CONFIG_LTO)
-  add_compile_options($<TARGET_PROPERTY:compiler,optimization_lto>)
+  zephyr_compile_options($<TARGET_PROPERTY:compiler,optimization_lto>)
   add_link_options($<TARGET_PROPERTY:linker,lto_arguments>)
 endif()
 
diff --git a/lib/libc/newlib/CMakeLists.txt b/lib/libc/newlib/CMakeLists.txt
index 6556a3e814c..35c6a9b6337 100644
--- a/lib/libc/newlib/CMakeLists.txt
+++ b/lib/libc/newlib/CMakeLists.txt
@@ -3,6 +3,9 @@
 zephyr_library()
 zephyr_library_sources(libc-hooks.c)
 
+# Do not allow LTO when compiling libc-hooks.c file
+set_source_files_properties(libc-hooks.c PROPERTIES COMPILE_OPTIONS $<TARGET_PROPERTY:compiler,prohibit_lto>)
+
 # Zephyr normally uses -ffreestanding, which with current GNU toolchains
 # means that the flag macros used by newlib 3.x <inttypes.h> to signal
 # support for PRI.64 macros are not present.  To make them available we
diff --git a/lib/libc/picolibc/CMakeLists.txt b/lib/libc/picolibc/CMakeLists.txt
index 23e84231e2a..87fb0d9d8ec 100644
--- a/lib/libc/picolibc/CMakeLists.txt
+++ b/lib/libc/picolibc/CMakeLists.txt
@@ -3,6 +3,9 @@
 zephyr_library()
 zephyr_library_sources(libc-hooks.c)
 
+# Do not allow LTO when compiling libc-hooks.c file
+set_source_files_properties(libc-hooks.c PROPERTIES COMPILE_OPTIONS $<TARGET_PROPERTY:compiler,prohibit_lto>)
+
 # define __LINUX_ERRNO_EXTENSIONS__ so we get errno defines like -ESHUTDOWN
 # used by the network stack
 zephyr_compile_definitions(__LINUX_ERRNO_EXTENSIONS__)