Adapt "cross compile?" check for Apple Silicon

[yln]

Summary

This piece of code tries to implement the semantics "cross compile?" to
determine CFLAGS used for test binary compilation.

if(ANDROID OR ${arch} MATCHES "arm|aarch64|riscv32|riscv64")

Since Apple Silicon, macOS runs on arm64e, so we take the wrong branch
when compiling and running tests locally "on the host" on an AS machine.

Furthermore, for Apple code, we use the separate
get_test_cflags_for_apple_platform function to determine these test
compiliation flags and get_test_cc_for_arch is only ever used in the
"compile & run on host" case, so we can short-curcuit the "cross
compile?" check here.

rdar://91446703

[yln]

@thetruestblue please verify that this fixes the problem you saw on your AS machine.

[arichardson]

compiler-rt/cmake/config-ix.cmake

247

Could this use if(CMAKE_CROSSCOMPILING) instead?

[yln]

compiler-rt/cmake/config-ix.cmake

247

That certainly looks like a promising option. Note that we are determining the build flags for compiling tests in compiler-rt here and multiple targets are usually generated.

It seems to work for Darwin (CMAKE_CROSSCOMPILING always being false there), but I am hesitant to change this without being able to test it for other platforms.

Should we do something like this to issue warnings for a while before switching over?

+  if(ANDROID OR (NOT APPLE AND ${arch} MATCHES "arm|aarch64|riscv32|riscv64"))
+    if(NOT CMAKE_CROSSCOMPILING)
+      set(cc_mismatch TRUE)
+    endif()
+  else()
+    if(CMAKE_CROSSCOMPILING)
+      set(cc_mismatch TRUE)
+    endif()
+  endif()
+  if (cc_mismatch)
+    message(WARNING "compiler-rt test CFLAGS cross-compilation detection does not match CMAKE_CROSSCOMPILING.  "
+                    "Please go to https://reviews.llvm.org/D123633 and let us know when this happens.")
+  endif()

[thetruestblue]

In D123633#3446709, @yln wrote:

@thetruestblue please verify that this fixes the problem you saw on your AS machine.

This fixes tsan tests on AS.

compiler-rt/cmake/config-ix.cmake

else()
     endif()
   endif()
 endfunction()
 
 # Returns a compiler and CFLAGS that should be used to run tests for the
 # specific architecture.  When cross-compiling, this is controled via
 # COMPILER_RT_TEST_COMPILER and COMPILER_RT_TEST_COMPILER_CFLAGS.
 macro(get_test_cc_for_arch arch cc_out cflags_out)
-  if(ANDROID OR ${arch} MATCHES "arm|aarch64|riscv32|riscv64")
+  if(ANDROID OR (NOT APPLE AND ${arch} MATCHES "arm|aarch64|riscv32|riscv64"))
     # This is only true if we are cross-compiling.
     # Build all tests with host compiler and use host tools.
     set(${cc_out} ${COMPILER_RT_TEST_COMPILER})
     set(${cflags_out} ${COMPILER_RT_TEST_COMPILER_CFLAGS})
   else()
     get_target_flags_for_arch(${arch} ${cflags_out})
     if(APPLE)
       list(APPEND ${cflags_out} ${DARWIN_osx_CFLAGS})