From ed4ba238e2cb2f24301c1add238cf7ff062286c3 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Fri, 12 May 2023 10:38:50 +0100
Subject: [PATCH] cmake: Add `check_arm32_assembly` function

---
 CMakeLists.txt                 | 8 +++++++-
 cmake/CheckArm32Assembly.cmake | 6 ++++++
 cmake/source_arm32.s           | 9 +++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 cmake/CheckArm32Assembly.cmake
 create mode 100644 cmake/source_arm32.s

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a1d9eb36e3f77..c764e6423e6c8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -107,7 +107,13 @@ 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)
-  add_compile_definitions(USE_EXTERNAL_ASM=1)
+  include(CheckArm32Assembly)
+  check_arm32_assembly()
+  if(HAVE_ARM32_ASM)
+    add_compile_definitions(USE_EXTERNAL_ASM=1)
+  else()
+    message(FATAL_ERROR "ARM32 assembly optimization requested but not available.")
+  endif()
 elseif(SECP256K1_ASM)
   include(Check64bitAssembly)
   check_64bit_assembly()
diff --git a/cmake/CheckArm32Assembly.cmake b/cmake/CheckArm32Assembly.cmake
new file mode 100644
index 0000000000000..15c44b24b0141
--- /dev/null
+++ b/cmake/CheckArm32Assembly.cmake
@@ -0,0 +1,6 @@
+function(check_arm32_assembly)
+  try_compile(HAVE_ARM32_ASM
+    ${CMAKE_BINARY_DIR}/check_arm32_assembly
+    SOURCES ${CMAKE_SOURCE_DIR}/cmake/source_arm32.s
+  )
+endfunction()
diff --git a/cmake/source_arm32.s b/cmake/source_arm32.s
new file mode 100644
index 0000000000000..d3d9347057a03
--- /dev/null
+++ b/cmake/source_arm32.s
@@ -0,0 +1,9 @@
+.syntax unified
+.eabi_attribute 24, 1
+.eabi_attribute 25, 1
+.text
+.global main
+main:
+	ldr	r0, =0x002A
+	mov	r7, #1
+	swi	0