arch/arm: Add LLVM configuration to CMake

Added LLVM-specific configuration variables to ARM architecture CMake files:
- LLVM_ARCHTYPE for architecture variant (thumbv6m, thumbv7a, etc)
- LLVM_CPUTYPE for CPU target (cortex-m0, cortex-a5, etc)
- LLVM_ABITYPE for ABI (eabi/eabihf)

These changes enable LLVM/Clang toolchain support while maintaining
compatibility with existing GCC configurations. The LLVM variables
are set based on the same architecture/CPU/FPU configurations used
for GCC flags.

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

Author: no1wudi

arch/arm/src/cmake/armv6-m.cmake

@@ -21,3 +21,8 @@
 # ##############################################################################
 
 add_compile_options(-mcpu=cortex-m0 -mthumb -mfloat-abi=soft)
+
+# LLVM Configuration
+set(LLVM_ARCHTYPE thumbv6m)
+set(LLVM_ABITYPE eabi)
+set(LLVM_CPUTYPE cortex-m0)

arch/arm/src/cmake/armv7-a.cmake

@@ -24,12 +24,28 @@ set(PLATFORM_FLAGS)
 
 if(CONFIG_ARCH_CORTEXA5)
   list(APPEND PLATFORM_FLAGS -mcpu=cortex-a5)
+  set(LLVM_CPUTYPE cortex-a5)
 elseif(CONFIG_ARCH_CORTEXA7)
   list(APPEND PLATFORM_FLAGS -mcpu=cortex-a7)
+  set(LLVM_CPUTYPE cortex-a7)
 elseif(CONFIG_ARCH_CORTEXA8)
   list(APPEND PLATFORM_FLAGS -mcpu=cortex-a8)
+  set(LLVM_CPUTYPE cortex-a8)
 elseif(CONFIG_ARCH_CORTEXA9)
   list(APPEND PLATFORM_FLAGS -mcpu=cortex-a9)
+  set(LLVM_CPUTYPE cortex-a9)
+endif()
+
+if(CONFIG_ARM_THUMB)
+  set(LLVM_ARCHTYPE thumbv7a)
+else()
+  set(LLVM_ARCHTYPE armv7-a)
+endif()
+
+if(CONFIG_ARCH_FPU)
+  set(LLVM_ABITYPE eabihf)
+else()
+  set(LLVM_ABITYPE eabi)
 endif()
 
 if(NOT CONFIG_ARM_DPFPU32)

arch/arm/src/cmake/armv7-m.cmake

@@ -38,4 +38,23 @@ else() # gcc
   set(TOOLCHAIN_ARCH_FILE armv7-m_gcc)
 endif()
 
+# LLVM Configuration
+if(CONFIG_ARCH_CORTEXM3)
+  set(LLVM_ARCHTYPE thumbv7m)
+  set(LLVM_CPUTYPE cortex-m3)
+else()
+  set(LLVM_ARCHTYPE thumbv7em)
+  if(CONFIG_ARCH_CORTEXM4)
+    set(LLVM_CPUTYPE cortex-m4)
+  elseif(CONFIG_ARCH_CORTEXM7)
+    set(LLVM_CPUTYPE cortex-m7)
+  endif()
+endif()
+
+if(CONFIG_ARCH_FPU)
+  set(LLVM_ABITYPE eabihf)
+else()
+  set(LLVM_ABITYPE eabi)
+endif()
+
 include(${TOOLCHAIN_ARCH_FILE})

arch/arm/src/cmake/armv8-m.cmake

@@ -22,6 +22,31 @@
 
 set(PLATFORM_FLAGS)
 
+# LLVM Configuration
+if(CONFIG_ARCH_CORTEXM23)
+  set(LLVM_ARCHTYPE thumbv8m.base)
+  set(LLVM_CPUTYPE cortex-m23)
+elseif(CONFIG_ARCH_CORTEXM33)
+  set(LLVM_ARCHTYPE thumbv8m.main)
+  set(LLVM_CPUTYPE cortex-m33)
+elseif(CONFIG_ARCH_CORTEXM35P)
+  set(LLVM_ARCHTYPE thumbv8m.main)
+  set(LLVM_CPUTYPE cortex-m35p)
+elseif(CONFIG_ARCH_CORTEXM55)
+  set(LLVM_ARCHTYPE thumbv8.1m.main)
+  set(LLVM_CPUTYPE cortex-m55)
+elseif(CONFIG_ARCH_CORTEXM85)
+  set(LLVM_ARCHTYPE thumbv8.1m.main)
+  set(LLVM_CPUTYPE cortex-m85)
+endif()
+
+# Set ABI type based on FPU configuration
+if(CONFIG_ARCH_FPU)
+  set(LLVM_ABITYPE eabihf)
+else()
+  set(LLVM_ABITYPE eabi)
+endif()
+
 if(CONFIG_ARM_DSP)
   set(EXTCPUFLAGS +dsp)
 endif()