[libc] Add hooks for extra options in running hermetic tests (#147931)

Part of #145349. These hooks are required downstream in order to run
hermetic tests. See arm/arm-toolchain#420 for
more context on how this PR will be used.

Author: saturn691

libc/CMakeLists.txt

@@ -76,6 +76,13 @@ add_compile_definitions(LIBC_NAMESPACE=${LIBC_NAMESPACE})
 set(LIBC_COMPILE_OPTIONS_DEFAULT "" CACHE STRING "Architecture to tell clang to optimize for (e.g. -march=... or -mcpu=...)")
 set(LIBC_TEST_COMPILE_OPTIONS_DEFAULT "" CACHE STRING "Common compile options for all the tests.")
 
+set(LIBC_LINK_OPTIONS_DEFAULT "" CACHE STRING "Arguments used when linking.")
+set(LIBC_TEST_LINK_OPTIONS_DEFAULT "" CACHE STRING "Common link options for all the tests.")
+
+set(LIBC_TEST_CMD "" CACHE STRING
+  "The full test command in the form <command> binary=@BINARY@, if using another program to test (e.g. QEMU)")
+set(LIBC_TEST_HERMETIC_ONLY "" OFF CACHE BOOL "Only enable hermetic tests.")
+
 list(APPEND LIBC_COMPILE_OPTIONS_DEFAULT ${LIBC_COMMON_TUNE_OPTIONS})
 
 # Check --print-resource-dir to find the compiler resource dir if this flag

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -233,7 +233,11 @@ function(create_libc_unittest fq_target_name)
   _get_common_test_compile_options(compile_options "${LIBC_UNITTEST_C_TEST}"
                                    "${LIBC_UNITTEST_FLAGS}")
   # TODO: Ideally we would have a separate function for link options.
-  set(link_options ${compile_options})
+  set(link_options
+    ${compile_options}
+    ${LIBC_LINK_OPTIONS_DEFAULT}
+    ${LIBC_TEST_LINK_OPTIONS_DEFAULT}
+  )
   list(APPEND compile_options ${LIBC_UNITTEST_COMPILE_OPTIONS})
 
   if(SHOW_INTERMEDIATE_OBJECTS)
@@ -580,12 +584,26 @@ function(add_integration_test test_name)
       -march=${LIBC_GPU_TARGET_ARCHITECTURE} -nostdlib -static
       "--cuda-path=${LIBC_CUDA_ROOT}")
   elseif(LIBC_CC_SUPPORTS_NOSTDLIBPP)
-    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib++ -static)
+    set(link_options
+      -nolibc
+      -nostartfiles
+      -nostdlib++
+      -static
+      ${LIBC_LINK_OPTIONS_DEFAULT}
+      ${LIBC_TEST_LINK_OPTIONS_DEFAULT}
+    )
+    target_link_options(${fq_build_target_name} PRIVATE ${link_options})
   else()
     # Older version of gcc does not support `nostdlib++` flag.  We use
     # `nostdlib` and link against libgcc_s, which cannot be linked statically.
-    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib)
-    list(APPEND link_libraries ${LIBGCC_S_LOCATION})
+    set(link_options
+      -nolibc
+      -nostartfiles
+      -static
+      ${LIBC_LINK_OPTIONS_DEFAULT}
+      ${LIBC_TEST_LINK_OPTIONS_DEFAULT}
+    )
+    target_link_options(${fq_build_target_name} PRIVATE ${link_options})
   endif()
   target_link_libraries(
     ${fq_build_target_name}
@@ -774,11 +792,26 @@ function(add_libc_hermetic test_name)
       -march=${LIBC_GPU_TARGET_ARCHITECTURE} -nostdlib -static
       "--cuda-path=${LIBC_CUDA_ROOT}")
   elseif(LIBC_CC_SUPPORTS_NOSTDLIBPP)
-    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib++ -static)
+    set(link_options
+      -nolibc
+      -nostartfiles
+      -nostdlib++
+      -static
+      ${LIBC_LINK_OPTIONS_DEFAULT}
+      ${LIBC_TEST_LINK_OPTIONS_DEFAULT}
+    )
+    target_link_options(${fq_build_target_name} PRIVATE ${link_options})
   else()
     # Older version of gcc does not support `nostdlib++` flag.  We use
     # `nostdlib` and link against libgcc_s, which cannot be linked statically.
-    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib)
+    set(link_options
+      -nolibc
+      -nostartfiles
+      -static
+      ${LIBC_LINK_OPTIONS_DEFAULT}
+      ${LIBC_TEST_LINK_OPTIONS_DEFAULT}
+    )
+    target_link_options(${fq_build_target_name} PRIVATE ${link_options})
     list(APPEND link_libraries ${LIBGCC_S_LOCATION})
   endif()
   target_link_libraries(
@@ -809,9 +842,16 @@ function(add_libc_hermetic test_name)
   endif()
 
   if(NOT HERMETIC_TEST_NO_RUN_POSTBUILD)
-    set(test_cmd ${HERMETIC_TEST_ENV}
+    if (LIBC_TEST_CMD)
+      # In the form of "<command> binary=@BINARY@", e.g. "qemu-system-arm -loader$<COMMA>file=@BINARY@"
+      string(REPLACE "@BINARY@" "$<TARGET_FILE:${fq_build_target_name}>" test_cmd_parsed ${LIBC_TEST_CMD})
+      string(REPLACE " " ";" test_cmd "${test_cmd_parsed}")
+    else()
+      set(test_cmd ${HERMETIC_TEST_ENV}
         $<$<BOOL:${LIBC_TARGET_OS_IS_GPU}>:${gpu_loader_exe}> ${CMAKE_CROSSCOMPILING_EMULATOR} ${HERMETIC_TEST_LOADER_ARGS}
         $<TARGET_FILE:${fq_build_target_name}> ${HERMETIC_TEST_ARGS})
+    endif()
+
     add_custom_target(
       ${fq_target_name}
       DEPENDS ${fq_target_name}.__cmd__
@@ -863,7 +903,9 @@ function(add_libc_test test_name)
       # Tests like the file tests perform file operations on disk file. If we
       # don't chain up the unit test and hermetic test, then those tests will
       # step on each other's files.
-      add_dependencies(${fq_test_name}.__hermetic__ ${fq_test_name}.__unit__)
+      if(NOT LIBC_TEST_HERMETIC_ONLY)
+        add_dependencies(${fq_test_name}.__hermetic__ ${fq_test_name}.__unit__)
+      endif()
     endif()
   endif()
 endfunction(add_libc_test)