Merge pull request #28974 from jdduke/cherrypicks_L1BTW

Cherry-pick for fixes for dotprod detection on iOS

tensorflow/lite/experimental/ruy/detect_dotprod.cc

@@ -13,7 +13,19 @@ See the License for the specific language governing permissions and
 limitations under the License.
 ==============================================================================*/
 
-#ifdef __aarch64__
+// b/132973173: this signal-handling code does not work as intended on iOS,
+// resulting in 'EXC_BAD_INSTRUCTION' signals killing the process.
+// Is it because this code uses a signal handler for SIGILL, and Apple's
+// EXC_BAD_INSTRUCTION is actually a different signal?
+// Anyway, we don't need this code on Apple devices at the moment, as none of
+// them supports dot-product instructions at the moment.
+// In fact, for the moment, we only care about Linux, so restricting to it
+// limits our risk.
+#if defined __aarch64__ && defined __linux__
+#define RUY_IMPLEMENT_DETECT_DOTPROD
+#endif
+
+#ifdef RUY_IMPLEMENT_DETECT_DOTPROD
 
 #include <setjmp.h>
 #include <signal.h>
@@ -28,7 +40,7 @@ limitations under the License.
 
 namespace ruy {
 
-#ifdef __aarch64__
+#ifdef RUY_IMPLEMENT_DETECT_DOTPROD
 
 namespace {
 

tensorflow/lite/experimental/ruy/path.h

@@ -98,9 +98,14 @@ inline Path GetMostSignificantPath(Path path_mask) {
 // ruy::kAllPaths represents all Path's that make sense to on a given
 // base architecture.
 #ifdef __aarch64__
+#ifdef __linux__
 constexpr Path kAllPaths =
     Path::kReference | Path::kStandardCpp | Path::kNeon | Path::kNeonDotprod;
 #else
+// We don't know how to do runtime dotprod detection outside of linux for now.
+constexpr Path kAllPaths = Path::kReference | Path::kStandardCpp | Path::kNeon;
+#endif
+#else
 constexpr Path kAllPaths = Path::kReference | Path::kStandardCpp;
 #endif