Set LTO option only if it's supported and the build is not a debug build

CMakeLists.txt

@@ -70,6 +70,21 @@ else()
     add_compile_options($<$<NOT:$<CONFIG:Debug>>:-O3>)
 endif()
 
+find_package(OpenMP REQUIRED)
+
+# Check for LTO support (which in CMake is lumped in with IPO).
+include(CheckIPOSupported)
+check_ipo_supported(RESULT HAVE_IPO)
+
+# Helper function for setting LTO flag (but only if the config is not debug).
+function(enable_lto target_name)
+    if(HAVE_IPO)
+        set_property(TARGET ${target_name} PROPERTY
+            INTERPROCEDURAL_OPTIMIZATION $<NOT:$<CONFIG:Debug>>
+        )
+    endif()
+endfunction()
+
 # Always build the basic part.
 add_subdirectory(pybind_interface/basic)
 add_subdirectory(pybind_interface/decide)

Makefile

@@ -48,18 +48,10 @@ HIPCCFLAGS := $(BASE_HIPCCFLAGS) $(HIPCCFLAGS)
 
 LTO_FLAGS := -flto=auto
 USING_CLANG := $(shell $(CXX) --version | grep -isq clang && echo "true")
-ifeq ($(USING_CLANG),"true")
+ifeq ($(USING_CLANG),true)
     LTO_FLAGS := -flto
 endif
 
-# Test if OpenMP header files are available and we can link with the library.
-OMP_CHECK_CMD := echo "int main() { return 0; }" | \
-    $(CXX) -fopenmp -x c++ - -o /dev/null 2>/dev/null
-HAVE_OPENMP := $(shell $(OMP_CHECK_CMD) && echo "true")
-ifeq ($(HAVE_OPENMP),true)
-    OPENMP_FLAGS := -fopenmp
-endif
-
 ifdef DEBUG
     DEBUG_FLAGS := -g -O0
     CXXFLAGS += $(DEBUG_FLAGS)

pybind_interface/avx2/CMakeLists.txt

@@ -17,8 +17,11 @@ project(qsim)
 
 if(MSVC)
     add_compile_options(/arch:AVX2 /openmp)
+    # Add /O2 to any configuration that is NOT Debug.
+    # This prevents a conflict with /RTC1 in DEBUG builds.
+    add_compile_options($<$<NOT:$<CONFIG:Debug>>:/O2>)
 else()
-    add_compile_options(-mavx2 -mfma -flto=auto)
+    add_compile_options(-mavx2 -mfma -O3)
     execute_process(
         COMMAND bash --noprofile -c "grep -qs bmi2 /proc/cpuinfo"
         RESULT_VARIABLE _EXIT_CODE
@@ -46,4 +49,6 @@ endif()
 include(../GetPybind11.cmake)
 pybind11_add_module(qsim_avx2 pybind_main_avx2.cpp)
 
-target_link_libraries(qsim_avx2 PRIVATE qsim_openmp_config)
+target_link_libraries(qsim_avx2 PUBLIC OpenMP::OpenMP_CXX)
+
+enable_lto(qsim_avx2)

pybind_interface/avx512/CMakeLists.txt

@@ -18,7 +18,7 @@ project(qsim)
 if(MSVC)
     add_compile_options(/arch:AVX512 /openmp)
 else()
-    add_compile_options(-mavx512f -mbmi2 -flto=auto)
+    add_compile_options(-mavx512f -mbmi2 -O3)
 endif()
 
 if(APPLE)
@@ -39,4 +39,6 @@ endif()
 include(../GetPybind11.cmake)
 pybind11_add_module(qsim_avx512 pybind_main_avx512.cpp)
 
-target_link_libraries(qsim_avx512 PRIVATE qsim_openmp_config)
+target_link_libraries(qsim_avx512 PUBLIC OpenMP::OpenMP_CXX)
+
+enable_lto(qsim_avx512)

pybind_interface/basic/CMakeLists.txt

@@ -18,7 +18,7 @@ project(qsim)
 if(MSVC)
     add_compile_options(/openmp)
 else()
-    add_compile_options(-flto=auto)
+    add_compile_options(-O3)
 endif()
 
 if(APPLE)
@@ -39,4 +39,6 @@ endif()
 include(../GetPybind11.cmake)
 pybind11_add_module(qsim_basic pybind_main_basic.cpp)
 
-target_link_libraries(qsim_basic PRIVATE qsim_openmp_config)
+target_link_libraries(qsim_basic PUBLIC OpenMP::OpenMP_CXX)
+
+enable_lto(qsim_basic)

pybind_interface/sse/CMakeLists.txt

@@ -18,7 +18,7 @@ project(qsim)
 if(MSVC)
     add_compile_options(/openmp)
 else()
-    add_compile_options(-msse4 -flto=auto)
+    add_compile_options(-msse4 -O3)
 endif()
 
 if(APPLE)
@@ -39,4 +39,6 @@ endif()
 include(../GetPybind11.cmake)
 pybind11_add_module(qsim_sse pybind_main_sse.cpp)
 
-target_link_libraries(qsim_sse PRIVATE qsim_openmp_config)
+target_link_libraries(qsim_sse PUBLIC OpenMP::OpenMP_CXX)
+
+enable_lto(qsim_sse)