mirror of
https://github.com/espressif/esp-idf.git
synced 2025-10-28 12:10:45 +00:00
ecc37c12d7
The `-mtune=esp-base` option is identical to the default tuning profile,
except that `slow_unaligned_access` is set to false.
This reduces the instruction count for built-in `memcpy` and improves
performance, since our chips can handle misaligned access with minimal
penalty (without triggering exceptions).
Example:
void load(uint32_t *r, char* x) {
memcpy(r, x, sizeof(uint32_t));
}
void store(char* x, uint32_t v) {
memcpy(x, &v, sizeof(uint32_t));
}
Previously generated code:
load:
lbu a5,2(a1)
lbu a3,0(a1)
lbu a4,1(a1)
sb a5,2(a0)
sb a3,0(a0)
sb a4,1(a0)
lbu a5,3(a1)
sb a5,3(a0)
ret
store:
srli a3,a1,8
srli a4,a1,16
srli a5,a1,24
addi sp,sp,-16
sb a1,0(a0)
sb a3,1(a0)
sb a4,2(a0)
sb a5,3(a0)
addi sp,sp,16
jr ra
With `-mtune=esp-base`:
load:
lw a5,0(a1)
sw a5,0(a0)
ret
store:
sw a1,0(a0)
ret
Inlining behavior
=================
Without `-mtune=esp-base`:
- `memcpy()` is inlined only when the compile-time size is ≤ 12 bytes.
- Maximum cost: ~25 instructions
With `-mtune=esp-base`:
- `memcpy()` is inlined for all compile-time constant sizes.
- Maximum cost: ~14 instructions
As a result, some applications may see reduced code size, while others
may increase slightly. However, performance always improves because
extra `memcpy` calls are eliminated.
Performance results
===================
esp32p4 (Ethernet iperf):
- No noticeable difference
esp32c61 (Wi-Fi iperf):
- ~2 Mb/s increase for TCP and UDP TX (may be within measurement error)
NOTE
====
Applies only to RISC-V chips that do not have the hardware issue marked
by the SOC_CPU_MISALIGNED_ACCESS_ON_PMP_MISMATCH_ISSUE macro.
24 lines
1.2 KiB
CMake
24 lines
1.2 KiB
CMake
include($ENV{IDF_PATH}/tools/cmake/utilities.cmake)
|
|
|
|
set(CMAKE_SYSTEM_NAME Generic)
|
|
|
|
set(CMAKE_C_COMPILER riscv32-esp-elf-gcc)
|
|
set(CMAKE_CXX_COMPILER riscv32-esp-elf-g++)
|
|
set(CMAKE_ASM_COMPILER riscv32-esp-elf-gcc)
|
|
set(_CMAKE_TOOLCHAIN_PREFIX riscv32-esp-elf-)
|
|
|
|
set(_CMAKE_TOOLCHAIN_COMMON_FLAGS "-march=rv32imac_zicsr_zifencei_zaamo_zalrsc")
|
|
|
|
remove_duplicated_flags("${_CMAKE_TOOLCHAIN_COMMON_FLAGS} -mtune=esp-base ${CMAKE_C_FLAGS}" UNIQ_CMAKE_C_FLAGS)
|
|
set(CMAKE_C_FLAGS "${UNIQ_CMAKE_C_FLAGS}" CACHE STRING "C Compiler Base Flags" FORCE)
|
|
|
|
remove_duplicated_flags("${_CMAKE_TOOLCHAIN_COMMON_FLAGS} -mtune=esp-base ${CMAKE_CXX_FLAGS}" UNIQ_CMAKE_CXX_FLAGS)
|
|
set(CMAKE_CXX_FLAGS "${UNIQ_CMAKE_CXX_FLAGS}" CACHE STRING "C++ Compiler Base Flags" FORCE)
|
|
|
|
remove_duplicated_flags("${_CMAKE_TOOLCHAIN_COMMON_FLAGS} ${CMAKE_ASM_FLAGS}" UNIQ_CMAKE_ASM_FLAGS)
|
|
set(CMAKE_ASM_FLAGS "${UNIQ_CMAKE_ASM_FLAGS}" CACHE STRING "Asm Compiler Base Flags" FORCE)
|
|
|
|
remove_duplicated_flags("-nostartfiles ${_CMAKE_TOOLCHAIN_COMMON_FLAGS} ${CMAKE_EXE_LINKER_FLAGS}"
|
|
UNIQ_CMAKE_SAFE_EXE_LINKER_FLAGS)
|
|
set(CMAKE_EXE_LINKER_FLAGS "${UNIQ_CMAKE_SAFE_EXE_LINKER_FLAGS}" CACHE STRING "Linker Base Flags" FORCE)
|