Enabling optimization flags in a CMakeLists.txt file

This is the first time I'm asking a question here...

Prelimineris

I've written some code to compare Filters (such as Bloom filter and more). The code is available here.

While performing various benchmarking, I notice that switching between the flags

SET(CMAKE_CXX_FLAGS "-O0 -mavx2 -mbmi2")

or

SET(CMAKE_CXX_FLAGS "-O3 -mavx2 -mbmi2")

Changes the benchmarking drastically (1000 times faster for some tests).

I tried to determine which specific flag (or flags) caused this speed up.

Problem Statement

I tried adding flags manually, for example by writing:

SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -finline-functions -funswitch-loops -fpredictive-commoning -fgcse-after-reload -ftree-vectorize -fipa-cp-clone")

Although I added all of the flags mentioned here, it did not cause such speedup.

Am I enabling optimization flags correctly?

thanks for reading, any help is welcome.

Full CMakeLists.txt file:

cmake_minimum_required(VERSION 3.14)
project(Filters)

set(CMAKE_CXX_STANDARD 14)
#SET(CMAKE_CXX_FLAGS "-O0 -mavx2 -mbmi2")
#SET(CMAKE_CXX_FLAGS "-O1 -mavx2 -mbmi2")
#SET(CMAKE_CXX_FLAGS "-O2 -mavx2 -mbmi2")
#SET(CMAKE_CXX_FLAGS "-O3 -mavx2 -mbmi2")
SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mavx2 -mbmi2  -fauto-inc-dec -fcompare-elim -fcprop-registers -fdce -fdefer-pop -fdelayed-branch -fdse -fguess-branch-probability -fif-conversion2 -fif-conversion -fipa-pure-const -fipa-profile -fipa-reference -fmerge-constants -fsplit-wide-types -ftree-bit-ccp -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -ftree-phiprop -ftree-sra -ftree-pta -ftree-ter -funit-at-a-time -DNDEBUG -fthread-jumps -falign-functions  -falign-jumps -falign-loops  -falign-labels -fcaller-saves -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks -fdelete-null-pointer-checks -fdevirtualize -fexpensive-optimizations -fgcse  -fgcse-lm -finline-small-functions -findirect-inlining -fipa-sra -foptimize-sibling-calls -fpartial-inlining -fpeephole2 -fregmove -freorder-blocks  -freorder-functions -frerun-cse-after-loop -fsched-interblock  -fsched-spec -fschedule-insns  -fschedule-insns2 -fstrict-aliasing -fstrict-overflow -ftree-switch-conversion -ftree-pre -ftree-vrp")

#include_directories(.)
include_directories(Bloom_Filter)
include_directories(PD_Filter)
include_directories(Tests)
include_directories(morton)
include_directories(xorfilter)
include_directories(cuckoofilter)

find_package(OpenSSL REQUIRED)

add_executable(
        Filters
        hashutil.h
        Tests/wrappers.hpp
        Tests/tests.hpp Tests/tests.cpp
        Tests/new_tests.hpp Tests/new_tests.cpp
        Tests/printutil.cpp Tests/printutil.hpp
        Bloom_Filter/counting_bloom.h
        Bloom_Filter/simd-block.h
        Bloom_Filter/simd-block-fixed-fpp.h

        PD_Filter/PD.cpp
        PD_Filter/hashutil.hpp PD_Filter/hashutil.cpp
        PD_Filter/hash_table.hpp PD_Filter/hash_table.cpp
        PD_Filter/dict.hpp
        PD_Filter/macros.h

        #        main.cpp
        #        morton/hash_util.h
        #        morton/block.h
        #        morton/bf.h
        #        morton/block.h
        #        morton/compressed_cuckoo_config.h
        #        morton/compressed_cuckoo_filter.h
        #        morton/fixed_point.h
        #        morton/morton_filter.h
        #        morton/morton_sample_configs.h
        #        morton/morton_util.h
        #        morton/test_util.h
        #        morton/util.h
        #        morton/vector_types.h
        Tests/high_load.cpp Tests/high_load.hpp)

target_link_libraries(Filters OpenSSL::SSL)

Edit

now using add_compile_options:

cmake_minimum_required(VERSION 3.14)
project(Filters)

set(CMAKE_CXX_STANDARD 14)
#SET(CMAKE_CXX_FLAGS "-O0 -mavx2 -mbmi2")
#SET(CMAKE_CXX_FLAGS "-O1 -mavx2 -mbmi2")
#SET(CMAKE_CXX_FLAGS "-O2 -mavx2 -mbmi2")
#SET(CMAKE_CXX_FLAGS "-O3 -mavx2 -mbmi2")

#include_directories(.)
include_directories(Bloom_Filter)
include_directories(PD_Filter)
include_directories(Tests)
include_directories(morton)
include_directories(xorfilter)
include_directories(cuckoofilter)

find_package(OpenSSL REQUIRED)
SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mavx2 -mbmi2 -DNDEBUG")

add_compile_options(-fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments -fcompare-elim -fcprop-registers -fdce -fdefer-pop -fdelayed-branch -fdse -fforward-propagate -fguess-branch-probability -fif-conversion -fif-conversion2 -finline-functions-called-once -fipa-profile -fipa-pure-const -fipa-reference -fmerge-constants -fmove-loop-invariants -fomit-frame-pointer -freorder-blocks -fshrink-wrap -fshrink-wrap-separate -fsplit-wide-types -fssa-backprop -fssa-phiopt -ftree-bit-ccp -ftree-ccp -ftree-ch -ftree-coalesce-vars -ftree-copy-prop -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -ftree-phiprop -ftree-pta -ftree-scev-cprop -ftree-sink -ftree-slsr -ftree-sra -ftree-ter -funit-at-a-time -falign-functions  -falign-jumps -falign-labels  -falign-loops -fcaller-saves -fcode-hoisting -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks -fdelete-null-pointer-checks -fdevirtualize  -fdevirtualize-speculatively -fexpensive-optimizations -fsplit-loops -fgcse  -fgcse-lm -fhoist-adjacent-loads -finline-functions -finline-small-functions -findirect-inlining -fipa-bit-cp  -fipa-cp  -fipa-icf -fipa-ra  -fipa-sra  -fipa-vrp -fisolate-erroneous-paths-dereference -flra-remat -foptimize-sibling-calls -foptimize-strlen -fpartial-inlining -fpeephole2 -freorder-blocks-algorithm=stc -freorder-blocks-and-partition  -freorder-functions -frerun-cse-after-loop -fschedule-insns  -fschedule-insns2 -fsched-interblock  -fsched-spec -fstore-merging -fstrict-aliasing -fthread-jumps -ftree-builtin-call-dce -ftree-pre -ftree-switch-conversion  -ftree-tail-merge -ftree-vrp -fgcse-after-reload -fipa-cp-clone -floop-interchange -floop-unroll-and-jam -fpeel-loops -fpredictive-commoning -fsplit-loops -fsplit-paths -ftree-loop-distribution -ftree-loop-vectorize -ftree-partial-pre -ftree-slp-vectorize -funswitch-loops -fvect-cost-model -fvect-cost-model=dynamic)
add_executable(
        Filters
        hashutil.h
        Tests/wrappers.hpp
        Tests/tests.hpp Tests/tests.cpp
        Tests/new_tests.hpp Tests/new_tests.cpp
        Tests/printutil.cpp Tests/printutil.hpp
        Bloom_Filter/counting_bloom.h
        Bloom_Filter/simd-block.h
        Bloom_Filter/simd-block-fixed-fpp.h

        PD_Filter/PD.cpp
        PD_Filter/hashutil.hpp PD_Filter/hashutil.cpp
        PD_Filter/hash_table.hpp PD_Filter/hash_table.cpp
        PD_Filter/dict.hpp
        PD_Filter/macros.h

        #        main.cpp
        #        morton/hash_util.h
        #        morton/block.h
        #        morton/bf.h
        #        morton/block.h
        #        morton/compressed_cuckoo_config.h
        #        morton/compressed_cuckoo_filter.h
        #        morton/fixed_point.h
        #        morton/morton_filter.h
        #        morton/morton_sample_configs.h
        #        morton/morton_util.h
        #        morton/test_util.h
        #        morton/util.h
        #        morton/vector_types.h
        Tests/high_load.cpp Tests/high_load.hpp)



target_link_libraries(Filters OpenSSL::SSL)