Detect OS support for SSE extensions

Signed-off-by: Daryl Maier <maier@ca.ibm.com>

port/common/omrssesupported.cpp

@@ -0,0 +1,190 @@
+/*******************************************************************************
+ *
+ * (c) Copyright IBM Corp. 2017, 2017
+ *
+ *  This program and the accompanying materials are made available
+ *  under the terms of the Eclipse Public License v1.0 and
+ *  Apache License v2.0 which accompanies this distribution.
+ *
+ *      The Eclipse Public License is available at
+ *      http://www.eclipse.org/legal/epl-v10.html
+ *
+ *      The Apache License v2.0 is available at
+ *      http://www.opensource.org/licenses/apache2.0.php
+ *
+ * Contributors:
+ *    Multiple authors (IBM Corp.) - initial API and implementation and/or initial documentation
+ *******************************************************************************/
+
+#include <stdint.h>
+
+#if defined(WIN32)
+#include <intrin.h>
+#include <xmmintrin.h>
+#include <excpt.h>
+#elif defined(LINUX) || defined(OSX)
+#include <xmmintrin.h>
+#include <signal.h>
+#include <setjmp.h>
+#endif
+
+#include "omrcomp.h"
+
+#if defined(LINUX) || defined(OSX)
+
+sigjmp_buf sseEnv;
+
+/**
+ * \fn static void handleSIGILLForSTMXCSR(int signal)
+ *
+ * \brief The Linux signal handler guarding STMXCSR instruction.  If called, the
+ * instruction caused a #UD which indicates that SSE extensions are not supported
+ * on this operating system.
+ *
+ * \param signal The signal for which this handler was invoked
+ *
+ */
+static void
+handleSIGILLForSTMXCSR(int signal) {
+   siglongjmp(sseEnv, 1);
+}
+#endif
+
+
+/**
+ * \fn BOOLEAN targetOSSupportsSSEExtensions(BOOLEAN testFail)
+ *
+ * \brief Determine whether the target OS supports SSE extensions on an x86 processor.
+ * Support for SSE extensions implies support for SSE, SSE2, SSE3, SSSE3, and SSE4.
+ *
+ * An OS that supports SSE extensions must provide support for saving and restoring
+ * SSE state using the FXSAVE and FXRSTOR instructions.  An OS indicates this support
+ * by setting CR4.OSFXSR[bit 9] = 1.  It must also disable x87 emulation by setting
+ * CR0.EM[bit 2] = 0, and the CPUID instruction must report support for at least SSE.
+ *
+ * A user-space process can test for these by executing the STMXCSR instruction
+ * to store the contents of the MXCSR register to a 32-bit memory location.  A
+ * processor will raise a #UD in all modes if any of the above requirements do not
+ * hold.
+ *
+ * Furthermore, an OS is required to provide an exception handler for unmasked SIMD
+ * floating point exceptions.  An OS indicates this support by setting
+ * CR4.OSXMMEXCPT[bit 10] = 1.  However, there is not a straightforward way of
+ * determining this support in user-space other than executing instructions to
+ * generate individual unmasked SIMD exceptions and testing for #UD.
+ *
+ * The code below will only confirm SSE extension support if all SIMD exceptions
+ * are masked.  If any SIMD exceptions are unmasked then SSE extensions will be
+ * considered unsupported.  This restriction should be sufficient for all known
+ * operating systems.
+ *
+ * On Linux and OSX this implementation is NOT thread safe because the sseEnv
+ * sigjmp_buf cannot be shared simultaneously among multiple threads.
+ *
+ * \param testFail When TRUE, force the function to fail by issuing a #UD as the
+ * STMXCSR instruction would if OS support for SSE extensions was not configured.
+ * Useful for testing.
+ *
+ * \return TRUE if the OS supports SSE extensions; FALSE otherwise.
+ *
+ */
+
+BOOLEAN
+targetOSSupportsSSEExtensions(BOOLEAN testFail = FALSE) {
+
+   typedef enum {
+      OS_SSE_Unknown,
+      OS_SSE_Supported,
+      OS_SSE_NotSupported
+   } SSESupportStates;
+
+   SSESupportStates osSupportsSSE = OS_SSE_Unknown;
+
+#if defined(WIN32)
+   __try {
+
+      if (testFail) {
+         /* Force a #UD exception */
+         __ud2();
+      }
+
+      uint32_t mxcsr = _mm_getcsr();
+
+      /*
+       * Check that all SIMD exceptions are masked.  If not, SSE extension
+       * support is considered incomplete by this implementation.
+       */
+      if ((mxcsr & _MM_MASK_MASK) == _MM_MASK_MASK) {
+         osSupportsSSE = OS_SSE_Supported;
+      } else {
+         osSupportsSSE = OS_SSE_NotSupported;
+      }
+   }
+   __except(EXCEPTION_EXECUTE_HANDLER) {
+      osSupportsSSE = OS_SSE_NotSupported;
+   }
+
+#elif defined(LINUX) || defined(OSX)
+
+   /**
+    * Install a SIGILL signal handler to catch any #UD from the STMXCSR instruction.
+    */
+   struct sigaction origAction;
+
+   struct sigaction stmxcsrAction = {{0}};
+   stmxcsrAction.sa_handler = handleSIGILLForSTMXCSR;
+   stmxcsrAction.sa_flags = 0;
+   sigemptyset(&stmxcsrAction.sa_mask);
+
+   sigaction(SIGILL, &stmxcsrAction, &origAction);
+
+   if (sigsetjmp(sseEnv, 1)) {
+      osSupportsSSE = OS_SSE_NotSupported;
+   } else {
+      if (testFail) {
+         /**
+          * Force a #UD exception.  Emit the instruction rather than explicitly
+          * raising a SIGILL to better mimic the behaviour of the STMXCSR if it
+          * fails.
+          */
+         __asm__ volatile ("ud2");
+      }
+
+      uint32_t mxcsr = _mm_getcsr();
+
+      /*
+       * Check that all SIMD exceptions are masked.  If not, SSE extension
+       * support is considered incomplete by this implementation.
+       */
+      if ((mxcsr & _MM_MASK_MASK) == _MM_MASK_MASK) {
+         osSupportsSSE = OS_SSE_Supported;
+      } else {
+         osSupportsSSE = OS_SSE_NotSupported;
+      }
+   }
+
+   sigaction(SIGILL, &origAction, NULL);
+
+#endif
+
+   return (osSupportsSSE == OS_SSE_Supported) ? TRUE : FALSE;
+}
+
+
+#include <stdio.h>
+int
+main() {
+
+  BOOLEAN b;
+
+  for (int i=0; i<1024; i++) {
+     b = targetOSSupportsSSEExtensions();
+     printf("sse=%d\n", b);
+     b = targetOSSupportsSSEExtensions(TRUE);
+     printf("sse=%d\n", b);
+     b = targetOSSupportsSSEExtensions(TRUE);
+     printf("sse=%d\n", b);
+  }
+
+  return 0;
+}