ARM: Support hardfloat in SCons build and make it a build time setting

src/platform-linux.cc

 // Copyright 2006-2008 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 69 matching lines @@
 
 void OS::Setup() {
   // Seed the random number generator.
   // Convert the current time to a 64-bit integer first, before converting it
   // to an unsigned. Going directly can cause an overflow and the seed to be
   // set to all ones. The seed will be identical for different instances that
   // call this setup code within the same millisecond.
   uint64_t seed = static_cast<uint64_t>(TimeCurrentMillis());
   srandom(static_cast<unsigned int>(seed));
   limit_mutex = CreateMutex();
+
+#ifdef __arm__
+  // When running on ARM hardware check that the EABI used by V8 and
+  // by the C code is the same.
+  bool hard_float = OS::ArmUsingHardFloat();
+  if (hard_float) {
+#if !USE_EABI_HARDFLOAT
+    PrintF("ERROR: Binary compiled with -mfloat-abi=hard but without "
+           "-DUSE_EABI_HARDFLOAT\n");
+    exit(1);
+#endif
+  } else {
+#if USE_EABI_HARDFLOAT
+    PrintF("ERROR: Binary not compiled with -mfloat-abi=hard but with "
+           "-DUSE_EABI_HARDFLOAT\n");
+    exit(1);
+#endif
+  }
+#endif
 }
 
 
 uint64_t OS::CpuFeaturesImpliedByPlatform() {
 #if (defined(__VFP_FP__) && !defined(__SOFTFP__))
   // Here gcc is telling us that we are on an ARM and gcc is assuming
   // that we have VFP3 instructions.  If gcc can assume it then so can
   // we. VFPv3 implies ARMv7, see ARM DDI 0406B, page A1-6.
   return 1u << VFP3 | 1u << ARMv7;
 #elif CAN_USE_ARMV7_INSTRUCTIONS
@@ skipping 35 matching lines @@
         what = search_string;
       }
     }
   }
   fclose(f);
 
   // Did not find string in the proc file.
   return false;
 }
 
+
 bool OS::ArmCpuHasFeature(CpuFeature feature) {
   const char* search_string = NULL;
   // Simple detection of VFP at runtime for Linux.
   // It is based on /proc/cpuinfo, which reveals hardware configuration
   // to user-space applications.  According to ARM (mid 2009), no similar
   // facility is universally available on the ARM architectures,
   // so it's up to individual OSes to provide such.
   switch (feature) {
     case VFP3:
       search_string = "vfpv3";
@@ skipping 15 matching lines @@
     // available on architectures with vfpv3.
     // Checking neon on its own is not enough as it is possible to have neon
     // without vfp.
     if (CPUInfoContainsString("vfp") && CPUInfoContainsString("neon")) {
       return true;
     }
   }
 
   return false;
 }
+
+
+// Simple helper function to detect whether the C code is compiled with
+// option -mfloat-abi=hard. The register d0 is loaded with 1.0 and the register
+// pair r0, r1 is loaded with 0.0. If -mfloat-abi=hard is pased to GCC then
+// calling this will return 1.0 and otherwise 0.0.
+static void ArmUsingHardFloatHelper() {
+  asm("mov r0, #0");
+  asm("mov r1, #0");
+  asm("movt r1, #16368");
+  asm("vmov d0, r0, r1");
+  asm("mov r0, #0");
+  asm("mov r1, #0");
+}
+
+
+bool OS::ArmUsingHardFloat() {
+  // Cast helper function from returning void to returning double.
+  typedef double (*F)();
+  F f = FUNCTION_CAST<F>(FUNCTION_ADDR(ArmUsingHardFloatHelper));
+  return f() == 1.0;
+}
 #endif  // def __arm__
 
 
 #ifdef __mips__
 bool OS::MipsCpuHasFeature(CpuFeature feature) {
   const char* search_string = NULL;
   const char* file_name = "/proc/cpuinfo";
   // Simple detection of FPU at runtime for Linux.
   // It is based on /proc/cpuinfo, which reveals hardware configuration
   // to user-space applications.  According to MIPS (early 2010), no similar
@@ skipping 893 matching lines @@
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SignalSender::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal