[CMake][compiler-rt] Make CRT separately buildable

This is useful when building a complete toolchain to ensure that CRT
is built after builtins but before the rest of the compiler-rt.

Differential Revision: https://reviews.llvm.org/D120682

compiler-rt/cmake/Modules/AllSupportedArchDefs.cmake

@@ -27,8 +27,6 @@ set(ALL_SANITIZER_COMMON_SUPPORTED_ARCH ${X86} ${X86_64} ${PPC64} ${RISCV64}
     ${HEXAGON})
 set(ALL_ASAN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64} ${RISCV64}
     ${MIPS32} ${MIPS64} ${PPC64} ${S390X} ${SPARC} ${SPARCV9} ${HEXAGON})
-set(ALL_CRT_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64} ${PPC32}
-    ${PPC64} ${RISCV32} ${RISCV64} ${VE} ${HEXAGON})
 set(ALL_DFSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
 
 if(ANDROID)

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

@@ -238,6 +238,10 @@ function(get_compiler_rt_root_source_dir ROOT_DIR_VAR)
     # Compiler-RT Builtins standalone build.
     # `llvm-project/compiler-rt/lib/builtins`
     set(PATH_TO_COMPILER_RT_SOURCE_ROOT "${CompilerRTBuiltins_SOURCE_DIR}/../../")
+  elseif (DEFINED CompilerRTCRT_SOURCE_DIR)
+    # Compiler-RT CRT standalone build.
+    # `llvm-project/compiler-rt/lib/crt`
+    set(PATH_TO_COMPILER_RT_SOURCE_ROOT "${CompilerRTCRT_SOURCE_DIR}/../../")
   elseif(DEFINED CompilerRT_SOURCE_DIR)
     # Compiler-RT standalone build.
     # `llvm-project/compiler-rt`

compiler-rt/cmake/config-ix.cmake

@@ -611,7 +611,6 @@ if(APPLE)
     SANITIZER_COMMON_SUPPORTED_ARCH)
 
 else()
-  filter_available_targets(CRT_SUPPORTED_ARCH ${ALL_CRT_SUPPORTED_ARCH})
   # Architectures supported by compiler-rt libraries.
   filter_available_targets(SANITIZER_COMMON_SUPPORTED_ARCH
     ${ALL_SANITIZER_COMMON_SUPPORTED_ARCH})
@@ -708,12 +707,6 @@ endif()
 
 # TODO: Add builtins support.
 
-if (CRT_SUPPORTED_ARCH AND OS_NAME MATCHES "Linux" AND NOT LLVM_USE_SANITIZER)
-  set(COMPILER_RT_HAS_CRT TRUE)
-else()
-  set(COMPILER_RT_HAS_CRT FALSE)
-endif()
-
 if (COMPILER_RT_HAS_SANITIZER_COMMON AND DFSAN_SUPPORTED_ARCH AND
     OS_NAME MATCHES "Linux")
   set(COMPILER_RT_HAS_DFSAN TRUE)

compiler-rt/cmake/crt-config-ix.cmake

@@ -0,0 +1,48 @@
+include(BuiltinTests)
+include(CheckCSourceCompiles)
+
+# Make all the tests only check the compiler
+set(TEST_COMPILE_ONLY On)
+
+builtin_check_c_compiler_flag(-fPIC                 COMPILER_RT_HAS_FPIC_FLAG)
+builtin_check_c_compiler_flag(-std=c11              COMPILER_RT_HAS_STD_C11_FLAG)
+builtin_check_c_compiler_flag(-Wno-pedantic         COMPILER_RT_HAS_WNO_PEDANTIC)
+builtin_check_c_compiler_flag(-fno-lto              COMPILER_RT_HAS_FNO_LTO_FLAG)
+builtin_check_c_compiler_flag(-fno-profile-generate COMPILER_RT_HAS_FNO_PROFILE_GENERATE_FLAG)
+builtin_check_c_compiler_flag(-fno-profile-instr-generate COMPILER_RT_HAS_FNO_PROFILE_INSTR_GENERATE_FLAG)
+builtin_check_c_compiler_flag(-fno-profile-instr-use COMPILER_RT_HAS_FNO_PROFILE_INSTR_USE_FLAG)
+
+if(ANDROID)
+  set(OS_NAME "Android")
+else()
+  set(OS_NAME "${CMAKE_SYSTEM_NAME}")
+endif()
+
+set(ARM64 aarch64)
+set(ARM32 arm armhf armv6m armv7m armv7em armv7 armv7s armv7k)
+set(X86 i386)
+set(X86_64 x86_64)
+set(RISCV32 riscv32)
+set(RISCV64 riscv64)
+set(VE ve)
+
+set(ALL_CRT_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64} ${RISCV32} ${RISCV64} ${VE})
+
+include(CompilerRTUtils)
+
+if(NOT APPLE)
+  if(COMPILER_RT_CRT_STANDALONE_BUILD)
+    test_targets()
+  endif()
+  # Architectures supported by compiler-rt crt library.
+  filter_available_targets(CRT_SUPPORTED_ARCH
+    ${ALL_CRT_SUPPORTED_ARCH})
+
+  if (CRT_SUPPORTED_ARCH AND OS_NAME MATCHES "Linux" AND NOT LLVM_USE_SANITIZER)
+    set(COMPILER_RT_HAS_CRT TRUE)
+  else()
+    set(COMPILER_RT_HAS_CRT FALSE)
+  endif()
+endif()
+
+message(STATUS "Supported architectures for crt: ${CRT_SUPPORTED_ARCH}")

compiler-rt/lib/crt/CMakeLists.txt

@@ -1,3 +1,35 @@
+if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+  cmake_minimum_required(VERSION 3.13.4)
+
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+  project(CompilerRTCRT C)
+  set(COMPILER_RT_STANDALONE_BUILD TRUE)
+  set(COMPILER_RT_CRT_STANDALONE_BUILD TRUE)
+
+  set(COMPILER_RT_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../..")
+
+  set(LLVM_COMMON_CMAKE_UTILS "${COMPILER_RT_SOURCE_DIR}/../cmake")
+
+  # Add path for custom modules
+  list(INSERT CMAKE_MODULE_PATH 0
+    "${COMPILER_RT_SOURCE_DIR}/cmake"
+    "${COMPILER_RT_SOURCE_DIR}/cmake/Modules"
+    "${LLVM_COMMON_CMAKE_UTILS}"
+    "${LLVM_COMMON_CMAKE_UTILS}/Modules"
+    )
+
+  include(base-config-ix)
+  include(CompilerRTUtils)
+
+  load_llvm_config()
+  construct_compiler_rt_default_triple()
+
+  include(SetPlatformToolchainTools)
+  include(AddCompilerRT)
+endif()
+
+include(crt-config-ix)
+
 add_compiler_rt_component(crt)
 
 function(check_cxx_section_exists section output)