[llvm-branch-commits] [libc] [libc] Application and testing support in baremetal Armv7-M CMake cache file (PR #233497)

[Victor Campos via llvm-branch-commits]

https://github.com/vhscampos updated https://github.com/llvm/llvm-project/pull/233497

>From f0ce5531cc747275009fdebf115b6ef70bb78903 Mon Sep 17 00:00:00 2001
From: Victor Campos <victor.campos at arm.com>
Date: Mon, 19 Oct 2026 17:13:02 +0100
Subject: [PATCH] [libc] Application and testing support in baremetal Armv7-M
 CMake cache file

This patch adds support for linking and running applications, including
tests, targeting baremetal Armv7-M to the corresponding CMake cache
file.

The cache file takes into consideration if compiler-rt is enabled or
not. If it is, then linking applications is possible, and the relevant
CMake variables are set to enable test runs. If not, then only the libc
build is possible and enabled.

Particular libc configuration options, memory mappings, and QEMU options
are based on what Arm Toolchain for Embedded uses in its fully working
downstream testing.
---
 libc/cmake/caches/armv7m-none-eabi.cmake | 48 +++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/libc/cmake/caches/armv7m-none-eabi.cmake b/libc/cmake/caches/armv7m-none-eabi.cmake
index ec7c64d5c839cb..3eaac2b1e0ba4f 100644
--- a/libc/cmake/caches/armv7m-none-eabi.cmake
+++ b/libc/cmake/caches/armv7m-none-eabi.cmake
@@ -1,8 +1,54 @@
 set(CMAKE_SYSTEM_PROCESSOR arm CACHE STRING "")
 set(RUNTIMES_TARGET_TRIPLE "armv7m-none-eabi" CACHE STRING "")
+set(LLVM_LIBC_FULL_BUILD ON CACHE BOOL "")
 
 foreach(lang C;CXX;ASM)
-  set(CMAKE_${lang}_FLAGS "-march=armv7m -mcpu=cortex-m4 -mfloat-abi=soft -Wno-atomic-alignment" CACHE STRING "")
+  set(CMAKE_${lang}_FLAGS "-march=armv7-m -mcpu=cortex-m4 -mfloat-abi=soft -mfpu=none" CACHE STRING "")
 endforeach()
 
+# Offload the errno definition to libc
+set(LIBC_CONF_ERRNO_MODE LIBC_ERRNO_MODE_SHARED CACHE STRING "")
+# Enable floating-point conversions in printf. This became practical with the
+# introduction of float320.
+set(LIBC_CONF_PRINTF_DISABLE_FLOAT OFF CACHE BOOL "")
+set(LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_FLOAT320 ON CACHE BOOL "")
+# Discard unused printf functionality
+set(LIBC_CONF_PRINTF_MODULAR ON CACHE BOOL "")
+
+# Configs for testing and applications are only done if compiler-rt is enabled,
+# as the latter is a dependency for full programs.
+if(compiler-rt IN_LIST LLVM_ENABLE_RUNTIMES)
+  set(LLVM_INCLUDE_TESTS ON CACHE BOOL "")
+  set(LIBC_TEST_BUILTINS_TARGET "clang_rt.builtins-armv7m" CACHE STRING "")
+
+  # Memory mappings
+  set(__boot_flash 0x00000000)
+  set(__boot_flash_size 0x1000)
+  set(__flash 0x21000000)
+  set(__flash_size 0x600000)
+  set(__ram 0x21600000)
+  set(__ram_size 0xA00000)
+  set(__stack_size 0x1000)
+  set(SYMBOLS
+    __boot_flash
+    __boot_flash_size
+    __flash
+    __flash_size
+    __ram
+    __ram_size
+    __stack_size
+  )
+
+  set(DEFSYM_ARGS "")
+  foreach(symbol IN LISTS SYMBOLS)
+    list(APPEND DEFSYM_ARGS "-Wl,--defsym=${symbol}=${${symbol}}")
+  endforeach()
+
+  set(LINKER_SCRIPT "${CMAKE_CURRENT_LIST_DIR}/../../test/UnitTest/llvm-libc-baremetal.ld")
+
+  set(LIBC_TEST_LINK_OPTIONS_DEFAULT "-T;${LINKER_SCRIPT};${DEFSYM_ARGS}" CACHE STRING "")
+
+  set(LIBC_TEST_CMD "qemu-system-arm -M mps2-an386 -cpu cortex-m4 -chardev stdio,mux=on,id=stdio0 -semihosting-config enable=on,chardev=stdio0 -monitor none -serial none -nographic -kernel @BINARY@" CACHE STRING "")
+endif()
+
 include(${CMAKE_CURRENT_LIST_DIR}/baremetal_common.cmake)