[FMV][AArch64] Run the aarch64-init-cpu-features test on Linux. (#172)

Currently we are only running this test on Darwin platforms. I had to adjust
the runtime initialization routine because on Linux the dynamic loader will
pass a HWCAP parameter to the ifunc resolver function, whereas on Darwin no
arguments are passed.

SingleSource/Benchmarks/Misc/CMakeLists.txt

@@ -35,10 +35,20 @@ if(NOT ARCH STREQUAL "PowerPC" OR NOT TARGET_OS STREQUAL "Darwin")
   list(APPEND Source dt.c)
 endif()
 if(ARCH STREQUAL "AArch64")
-  file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/CheckHaveAArch64FMV.h "void __init_cpu_features_resolver(void);")
-  check_symbol_exists(__init_cpu_features_resolver ${CMAKE_CURRENT_BINARY_DIR}/CheckHaveAArch64FMV.h HAVE_AARCH64_FMV)
-  if(HAVE_AARCH64_FMV AND TARGET_OS STREQUAL "Darwin")
-    list(APPEND Source aarch64-init-cpu-features.c)
+  if(TARGET_OS STREQUAL "Darwin")
+    file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/CheckHasAArch64FMV.h "void __init_cpu_features_resolver(void);")
+    check_symbol_exists(__init_cpu_features_resolver ${CMAKE_CURRENT_BINARY_DIR}/CheckHasAArch64FMV.h HAS_AARCH64_FMV)
+    if(HAS_AARCH64_FMV)
+      list(APPEND CFLAGS -DHAS_DARWIN_FMV)
+      list(APPEND Source aarch64-init-cpu-features.c)
+    endif()
+  elseif(TARGET_OS STREQUAL "Linux")
+    file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/CheckHasAArch64FMV.h "void __init_cpu_features(void);")
+    check_symbol_exists(__init_cpu_features ${CMAKE_CURRENT_BINARY_DIR}/CheckHasAArch64FMV.h HAS_AARCH64_FMV)
+    if(HAS_AARCH64_FMV)
+      list(APPEND CFLAGS -DHAS_LINUX_FMV)
+      list(APPEND Source aarch64-init-cpu-features.c)
+    endif()
   endif()
 endif()
 llvm_singlesource()

SingleSource/Benchmarks/Misc/aarch64-init-cpu-features.c

@@ -4,15 +4,21 @@ extern struct {
   unsigned long long features;
 } __aarch64_cpu_features;
 
-void __init_cpu_features_resolver(void);
+#if HAS_DARWIN_FMV
+# define RUNTIME_INIT __init_cpu_features_resolver
+#elif HAS_LINUX_FMV
+# define RUNTIME_INIT __init_cpu_features
+#endif
+
+void RUNTIME_INIT(void);
 
 int main() {
-    __init_cpu_features_resolver();
+    RUNTIME_INIT();
     const unsigned long long first = __aarch64_cpu_features.features;
 
     // Manually reset it, so we can check that the result is consistent.
     __aarch64_cpu_features.features = 0;
-    __init_cpu_features_resolver();
+    RUNTIME_INIT();
 
     if (__aarch64_cpu_features.features != first) {
         printf("FAILED consistency test: 0x%llx != 0x%llx\n", first,
@@ -24,6 +30,6 @@ int main() {
     // per-iteration measurement in microseconds.
     for (int i = 0; i < 1000000; i++) {
         __aarch64_cpu_features.features = 0;
-        __init_cpu_features_resolver();
+        RUNTIME_INIT();
     }
 }