fix auto detect of sve length (#2257)

- apply pertinent compiler flags when trying to compile the detection
code
- improve compiler error message when sve length is not set

CMakeLists.txt

@@ -322,6 +322,18 @@ set(arbor_supported_components)
 # Target microarchitecture for building arbor libraries, tests and examples
 #---------------------------------------------------------------------------
 
+# Set the full set of target flags in ARB_CXX_FLAGS_TARGET_FULL, which
+# will include target-specific -march flags if ARB_ARCH is not "none".
+if(ARB_ARCH STREQUAL "none")
+    set(ARB_CXX_FLAGS_TARGET_FULL ${ARB_CXX_FLAGS_TARGET})
+    set(ARB_CXX_FLAGS_TARGET_FULL_CPU ${ARB_CXX_FLAGS_TARGET})
+else()
+    set_arch_target(ARB_CXXOPT_ARCH_CPU ARB_CXXOPT_ARCH ${ARB_ARCH})
+    set(ARB_CXX_FLAGS_TARGET_FULL ${ARB_CXX_FLAGS_TARGET} ${ARB_CXXOPT_ARCH})
+    set(ARB_CXX_FLAGS_TARGET_FULL_CPU ${ARB_CXX_FLAGS_TARGET} ${ARB_CXXOPT_ARCH_CPU})
+endif()
+
+# Add SVE compiler flags if detected/desired
 set(ARB_SVE_WIDTH "auto" CACHE STRING "Default SVE vector length in bits. Default: auto (detection during configure time).")
 mark_as_advanced(ARB_SVE_WIDTH)
 if (ARB_SVE_WIDTH STREQUAL "auto")
@@ -337,15 +349,8 @@ else()
     set(ARB_SVE_BITS ${ARB_SVE_WIDTH})
     set(ARB_CXX_SVE_FLAGS " -msve-vector-bits=${ARB_SVE_BITS}")
 endif()
-
-# Set the full set of target flags in ARB_CXX_FLAGS_TARGET_FULL, which
-# will include target-specific -march flags if ARB_ARCH is not "none".
-if(ARB_ARCH STREQUAL "none")
-    set(ARB_CXX_FLAGS_TARGET_FULL ${ARB_CXX_FLAGS_TARGET} ${ARB_CXX_SVE_FLAGS})
-else()
-    set_arch_target(ARB_CXXOPT_ARCH ${ARB_ARCH})
-    set(ARB_CXX_FLAGS_TARGET_FULL ${ARB_CXX_FLAGS_TARGET} ${ARB_CXXOPT_ARCH} ${ARB_CXX_SVE_FLAGS})
-endif()
+list(APPEND ARB_CXX_FLAGS_TARGET_FULL
+    "$<$<BUILD_INTERFACE:$<COMPILE_LANGUAGE:CXX>>:${ARB_CXX_SVE_FLAGS}>")
 
 # Compile with `-fvisibility=hidden` to ensure that the symbols of the generated
 # arbor static libraries are hidden from the dynamic symbol tables of any shared

cmake/CompilerOptions.cmake

@@ -95,7 +95,7 @@ set(CXXOPT_WALL
 # Architectures are given by the same names that GCC uses for its
 # -mcpu or -march options.
 
-function(set_arch_target optvar arch)
+function(set_arch_target optvar optvar_cuda_guarded arch)
     if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" OR CMAKE_CXX_COMPILER_ID MATCHES "GNU")
         # Correct compiler option unfortunately depends upon the target architecture family.
         # Extract this information from running the configured compiler with --verbose.
@@ -111,7 +111,7 @@ function(set_arch_target optvar arch)
         string(REGEX REPLACE "-.*" "" target_model "${target}")
 
         # Use -mcpu for all supported targets _except_ for x86 and Apple arm64, where it should be -march.
-        
+
         if (CMAKE_CXX_COMPILER_ID MATCHES "AppleClang" AND CMAKE_CXX_COMPILER_VERSION LESS 15)
             set(arch_opt "")
         else()
@@ -125,6 +125,7 @@ function(set_arch_target optvar arch)
         endif()
     endif()
 
+    set("${optvar}" "${arch_opt}" PARENT_SCOPE)
     get_property(enabled_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
     if ("CUDA" IN_LIST enabled_languages)
         # Prefix architecture options with `-Xcompiler=` when compiling CUDA sources, i.e.
@@ -134,16 +135,19 @@ function(set_arch_target optvar arch)
             list(APPEND arch_opt_cuda_guarded "$<$<COMPILE_LANGUAGE:CUDA>:-Xcompiler=>${opt}")
         endforeach()
 
-        set("${optvar}" "${arch_opt_cuda_guarded}" PARENT_SCOPE)
+        set("${optvar_cuda_guarded}" "${arch_opt_cuda_guarded}" PARENT_SCOPE)
     else()
-        set("${optvar}" "${arch_opt}" PARENT_SCOPE)
+        set("${optvar_cuda_guarded}" "${arch_opt}" PARENT_SCOPE)
     endif()
 
 endfunction()
 
 # Set ${has_sve} and ${sve_length} in parent scope according to auto detection.
 function(get_sve_length has_sve sve_length)
-    try_run(run_var cc_var ${CMAKE_BINARY_DIR} ${PROJECT_SOURCE_DIR}/cmake/sve_length.cpp RUN_OUTPUT_VARIABLE out_var)
+    try_run(run_var cc_var
+        ${CMAKE_BINARY_DIR} ${PROJECT_SOURCE_DIR}/cmake/sve_length.cpp
+        COMPILE_DEFINITIONS ${ARB_CXX_FLAGS_TARGET_FULL_CPU}
+        RUN_OUTPUT_VARIABLE out_var)
 
     if(NOT cc_var)
         message(FATAL_ERROR "compilation of ${PROJECT_SOURCE_DIR}/cmake/sve_length.cpp failed")

cmake/vls_sve_bits.hpp.in

@@ -15,7 +15,7 @@ static constexpr unsigned vls_sve_width = @ARB_SVE_BITS@/64;
 
 // Check required compiler features for VLS_SVE
 #if (!defined(__ARM_FEATURE_SVE_BITS) || __ARM_FEATURE_SVE_BITS != @ARB_SVE_BITS@)
-#error "Vector length specific scalable vector extension (VLS_SVE) not enabled - did you compile with -msve-vector-bits=@ARB_SVE_BITS@?" 
+#error "Vector length specific scalable vector extension (VLS_SVE) not enabled - consider setting ARB_SVE_LENGTH=@ARB_SVE_BITS@"
 #endif
 
 // We currently do not rely on GNU vector extension, __attribute__((vector_size(vls_sve_width)). If defined, we could