Add a benchmark for aarch64's __init_cpu_features_resolver() (#90)

Author: jroelofs

SingleSource/Benchmarks/Misc/CMakeLists.txt

@@ -1,3 +1,5 @@
+include(CheckSymbolExists)
+
 list(APPEND LDFLAGS -lm )
 list(APPEND CFLAGS -Wno-implicit-int)
 set(FP_TOLERANCE 0.001)
@@ -32,4 +34,11 @@ set(Source
 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)
+  endif()
+endif()
 llvm_singlesource()

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

@@ -0,0 +1,29 @@
+#include <stdio.h>
+
+extern struct {
+  unsigned long long features;
+} __aarch64_cpu_features;
+
+void __init_cpu_features_resolver(void);
+
+int main() {
+    __init_cpu_features_resolver();
+    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();
+
+    if (__aarch64_cpu_features.features != first) {
+        printf("FAILED consistency test: 0x%llx != 0x%llx\n", first,
+               __aarch64_cpu_features.features);
+        return 1;
+    }
+
+    // At 1,000,000 iterations, the reported exec_time doubles as a
+    // per-iteration measurement in microseconds.
+    for (int i = 0; i < 1000000; i++) {
+        __aarch64_cpu_features.features = 0;
+        __init_cpu_features_resolver();
+    }
+}

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

@@ -0,0 +1 @@
+exit 0

SingleSource/UnitTests/AArch64/CMakeLists.txt

@@ -2,9 +2,9 @@ if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
   if(ARCH STREQUAL "AArch64")
     set(Source )
     # TODO: this test is currently only supported on Darwin platforms:
-    if (CMAKE_SYSTEM_NAME MATCHES "Darwin")
+    if (TARGET_OS MATCHES "Darwin")
       list(APPEND Source acle-fmv-features.c)
     endif()
-    llvm_singlesource(PREFIX "aarch64-" Source)
+    llvm_singlesource(PREFIX "aarch64-")
   endif()
 endif()