ARM: Changed the handling of compiletime CPU feature detection

src/arm/assembler-arm.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 33 matching lines @@
 namespace v8 {
 namespace internal {
 
 #ifdef DEBUG
 bool CpuFeatures::initialized_ = false;
 #endif
 unsigned CpuFeatures::supported_ = 0;
 unsigned CpuFeatures::found_by_runtime_probing_ = 0;
 
 
-#ifdef __arm__
+// Get the CPU features enabled by the build. For cross compilation the
+// preprocessor symbols CAN_USE_ARMV7_INSTRUCTIONS and CAN_USE_VFP_INSTRUCTIONS
+// can be defined to enable ARMv7 and VFPv3 instructions when building the
+// snapshot.
 static uint64_t CpuFeaturesImpliedByCompiler() {
   uint64_t answer = 0;
 #ifdef CAN_USE_ARMV7_INSTRUCTIONS
   answer |= 1u << ARMv7;
 #endif  // def CAN_USE_ARMV7_INSTRUCTIONS
+#ifdef CAN_USE_VFP_INSTRUCTIONS
+  answer |= 1u << VFP3 | 1u << ARMv7;
+#endif  // def CAN_USE_VFP_INSTRUCTIONS
+
+#ifdef __arm__
   // If the compiler is allowed to use VFP then we can use VFP too in our code
   // generation even when generating snapshots.  This won't work for cross
   // compilation. VFPv3 implies ARMv7, see ARM DDI 0406B, page A1-6.
 #if defined(__VFP_FP__) && !defined(__SOFTFP__)
   answer |= 1u << VFP3 | 1u << ARMv7;
 #endif  // defined(__VFP_FP__) && !defined(__SOFTFP__)
-#ifdef CAN_USE_VFP_INSTRUCTIONS
-  answer |= 1u << VFP3 | 1u << ARMv7;
-#endif  // def CAN_USE_VFP_INSTRUCTIONS
+#endif  // def __arm__
+
   return answer;
 }
-#endif  // def __arm__
 
 
 void CpuFeatures::Probe() {
   ASSERT(!initialized_);
 #ifdef DEBUG
   initialized_ = true;
 #endif
+
+  // Get the features implied by the OS and the compiler settings. This is the
+  // minimal set of features which is also alowed for generated code in the
+  // snapshot.
+  supported_ |= OS::CpuFeaturesImpliedByPlatform();
+  supported_ |= CpuFeaturesImpliedByCompiler();
+
+  if (Serializer::enabled()) {
+    // No probing for features if we might serialize (generate snapshot).
+    return;
+  }
+
 #ifndef __arm__
   // For the simulator=arm build, use VFP when FLAG_enable_vfp3 is
   // enabled. VFPv3 implies ARMv7, see ARM DDI 0406B, page A1-6.
   if (FLAG_enable_vfp3) {
     supported_ |= 1u << VFP3 | 1u << ARMv7;
   }
   // For the simulator=arm build, use ARMv7 when FLAG_enable_armv7 is enabled
   if (FLAG_enable_armv7) {
     supported_ |= 1u << ARMv7;
   }
 #else  // def __arm__
-  if (Serializer::enabled()) {
-    supported_ |= OS::CpuFeaturesImpliedByPlatform();
-    supported_ |= CpuFeaturesImpliedByCompiler();
-    return;  // No features if we might serialize.
-  }
-
-  if (OS::ArmCpuHasFeature(VFP3)) {
+  // Probe for additional features not already known to be available.
+  if (!IsSupported(VFP3) && OS::ArmCpuHasFeature(VFP3)) {
     // This implementation also sets the VFP flags if runtime
     // detection of VFP returns true. VFPv3 implies ARMv7, see ARM DDI
     // 0406B, page A1-6.
     supported_ |= 1u << VFP3 | 1u << ARMv7;
     found_by_runtime_probing_ |= 1u << VFP3 | 1u << ARMv7;
   }
 
-  if (OS::ArmCpuHasFeature(ARMv7)) {
+  if (!IsSupported(ARMv7) && OS::ArmCpuHasFeature(ARMv7)) {
     supported_ |= 1u << ARMv7;
     found_by_runtime_probing_ |= 1u << ARMv7;
   }
 #endif
 }
 
 
 // -----------------------------------------------------------------------------
 // Implementation of RelocInfo
 
@@ skipping 2724 matching lines @@
 
   // Since a constant pool was just emitted, move the check offset forward by
   // the standard interval.
   next_buffer_check_ = pc_offset() + kCheckConstInterval;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM