build: detect arm32 assembly by default

Author: Raimo33

CMakeLists.txt

@@ -90,25 +90,25 @@ mark_as_advanced(FORCE SECP256K1_TEST_OVERRIDE_WIDE_MULTIPLY)
 set(SECP256K1_ASM "AUTO" CACHE STRING "Assembly to use: \"AUTO\", \"OFF\", \"x86_64\" or \"arm32\" (experimental). [default=AUTO]")
 set_property(CACHE SECP256K1_ASM PROPERTY STRINGS "AUTO" "OFF" "x86_64" "arm32")
 check_string_option_value(SECP256K1_ASM)
-if(SECP256K1_ASM STREQUAL "arm32")
-  enable_language(ASM)
+if(NOT SECP256K1_ASM STREQUAL "OFF")
+  enable_language(ASM OPTIONAL)
+  include(CheckX86_64Assembly)
   include(CheckArm32Assembly)
+  check_x86_64_assembly()
   check_arm32_assembly()
-  if(HAVE_ARM32_ASM)
-    add_compile_definitions(USE_EXTERNAL_ASM=1)
-  else()
+  if(SECP256K1_ASM STREQUAL "x86_64" AND NOT HAVE_X86_64_ASM)
+    message(FATAL_ERROR "x86_64 assembly requested but not available.")
+  elseif(SECP256K1_ASM STREQUAL "arm32" AND NOT HAVE_ARM32_ASM)
     message(FATAL_ERROR "ARM32 assembly requested but not available.")
   endif()
-elseif(SECP256K1_ASM)
-  include(CheckX86_64Assembly)
-  check_x86_64_assembly()
   if(HAVE_X86_64_ASM)
     set(SECP256K1_ASM "x86_64")
     add_compile_definitions(USE_ASM_X86_64=1)
-  elseif(SECP256K1_ASM STREQUAL "AUTO")
-    set(SECP256K1_ASM "OFF")
+  elseif(HAVE_ARM32_ASM)
+    set(SECP256K1_ASM "arm32")
+    add_compile_definitions(USE_EXTERNAL_ASM=1)
   else()
-    message(FATAL_ERROR "x86_64 assembly requested but not available.")
+    set(SECP256K1_ASM "OFF")
   endif()
 endif()