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Ref. #926. Fixes for LTO build. #928

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Ref. #926. Fixes for LTO build. #928

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7a9ffa9
Ref. #926. Fixes for LTO build.
Nov 8, 2022
1c93116
function signature fix for heap_newlib.cpp
ser-plu Nov 8, 2022
a096405
'used' attribute for vectorsRom
Nov 10, 2022
c5ea8ee
'used' attribute for vectorsRam and Undefined_Handler
Nov 10, 2022
0be5e03
spaces fix
Nov 10, 2022
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4 changes: 2 additions & 2 deletions src/modm/platform/clock/stm32/rcc.cpp.in
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Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,8 @@ modm_weak void SystemCoreClockUpdate() { /* Nothing to update */ }

namespace modm::platform
{
constinit uint16_t modm_fastdata delay_fcpu_MHz(computeDelayMhz(Rcc::BootFrequency));
constinit uint16_t modm_fastdata delay_ns_per_loop(computeDelayNsPerLoop(Rcc::BootFrequency));
constinit uint16_t modm_fastdata modm_used delay_fcpu_MHz(computeDelayMhz(Rcc::BootFrequency));
constinit uint16_t modm_fastdata modm_used delay_ns_per_loop(computeDelayNsPerLoop(Rcc::BootFrequency));

// ----------------------------------------------------------------------------
%% if target.family == "f0"
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7 changes: 4 additions & 3 deletions src/modm/platform/core/cortex/vectors.c.in
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Expand Up @@ -33,7 +33,7 @@ typedef void (* const FunctionPointer)(void);
extern uint32_t __main_stack_top[];

// Define the vector table
modm_section(".vector_rom")
modm_section(".vector_rom") modm_used
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probably also necessary for vectorsRam just below.

Basically everything that's implicitly linked needs to be marked as used? Seems like a lot of work…

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@salkinium salkinium Nov 10, 2022 •
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Can you perhaps extract the symbols of the resulting ELF files with/without LTO and diff them? That would perhaps give you a more definitive list of lost symbols.
It's scons symbols but we seem to not have it for CMake.
Otherwise try: arm-none-eabi-nm -S -C --size-sort -td file.elf

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I don't see much difference any more. vectorsRam indeed is required to be used, I just use the ROM-mapped vector table in my project.

One more symbol missing is modm_abandon, but I think it is just optimised out as an empty function.

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Maybe, Undefined_Handler also requires the attribute. But I am not 100% sure

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I'll have a look myself tomorrow to check if we can enable LTO by default at least for the release build.

FunctionPointer vectorsRom[] =
{
(FunctionPointer)__main_stack_top, // -16: stack pointer
Expand All @@ -50,7 +50,7 @@ FunctionPointer vectorsRom[] =
};
%% if vector_table_location == "ram"
// reserve space for the remapped vector table in RAM
modm_section(".vector_ram")
modm_section(".vector_ram") modm_used
FunctionPointer vectorsRam[sizeof(vectorsRom) / sizeof(FunctionPointer)];
%% endif

Expand All @@ -65,7 +65,8 @@ FunctionPointer vectorsRam[sizeof(vectorsRom) / sizeof(FunctionPointer)];
#include <modm/architecture/interface/assert.h>
%% endif

void Undefined_Handler(void)
modm_used void
Undefined_Handler(void)
{
%% if with_assert
const int32_t irqn = ((int32_t)__get_IPSR()) - 16;
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2 changes: 1 addition & 1 deletion src/modm/platform/heap/cortex/heap_newlib.cpp
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Expand Up @@ -40,7 +40,7 @@ void __modm_initialize_memory(void)
* Note: This implementation is not thread safe (despite taking a
* _reent structure as a parameter).
*/
void *
modm_used void *
_sbrk_r(struct _reent *, ptrdiff_t size)
{
const uint8_t *const heap = heap_top;
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2 changes: 1 addition & 1 deletion src/modm/platform/heap/cortex/no_heap.c.in
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Expand Up @@ -19,7 +19,7 @@ void __modm_initialize_memory(void)
}

// ----------------------------------------------------------------------------
modm_weak modm_section("{{ no_heap_section }}")
modm_weak modm_used modm_section("{{ no_heap_section }}")
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Wouldn't that always trigger the warning of the heap module not being included even if heap is not used in the application code?

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When heap is used, no_heap.cpp is excluded from build, isn't it?

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Yeah, but if heap is not used, then this weak _sbrk_r acts as a "canary function" that the linker tries to link if someone tries to use malloc (which internally calls _sbrk_r via Newlib.
This function is normally garbage collected by the linker because nobody calls it, but is then DISCARDed in the linkerscript, thus the linker will fail with an error message.

void* _sbrk_r(struct _reent *r, ptrdiff_t size)
{
(void) r;
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5 changes: 5 additions & 0 deletions tools/build_script_generator/cmake/resources/ci_CMakeLists.txt.in
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Expand Up @@ -41,6 +41,11 @@ set(CMAKE_OBJDUMP ${TOOLCHAIN_PREFIX}-objdump)
set(CMAKE_AR ${TOOLCHAIN_PREFIX}-gcc-ar)
set(CMAKE_NM ${TOOLCHAIN_PREFIX}-gcc-nm)

SET(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> qcs <TARGET> <LINK_FLAGS> <OBJECTS>")
SET(CMAKE_C_ARCHIVE_FINISH ":")
SET(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> qcs <TARGET> <LINK_FLAGS> <OBJECTS>")
SET(CMAKE_CXX_ARCHIVE_FINISH ":")

project({{ project_name }} CXX C)

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
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