[x86] Disable AVX unless the operating system explicitly claims to support it.

test/unittests/base/cpu-unittest.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/cpu.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace v8 {
 namespace base {
 
 TEST(CPUTest, FeatureImplications) {
   CPU cpu;
 
   // ia32 and x64 features
   EXPECT_TRUE(!cpu.has_sse() || cpu.has_mmx());
   EXPECT_TRUE(!cpu.has_sse2() || cpu.has_sse());
   EXPECT_TRUE(!cpu.has_sse3() || cpu.has_sse2());
   EXPECT_TRUE(!cpu.has_ssse3() || cpu.has_sse3());
   EXPECT_TRUE(!cpu.has_sse41() || cpu.has_sse3());
   EXPECT_TRUE(!cpu.has_sse42() || cpu.has_sse41());
+  EXPECT_TRUE(!cpu.has_avx() || cpu.has_sse2());
+  EXPECT_TRUE(!cpu.has_fma3() || cpu.has_avx());
 
   // arm features
   EXPECT_TRUE(!cpu.has_vfp3_d32() || cpu.has_vfp3());
 }
 
 
 TEST(CPUTest, RequiredFeatures) {
   CPU cpu;
 
 #if V8_HOST_ARCH_ARM
   EXPECT_TRUE(cpu.has_fpu());
 #endif
 
 #if V8_HOST_ARCH_IA32
   EXPECT_TRUE(cpu.has_fpu());
   EXPECT_TRUE(cpu.has_sahf());
 #endif
 
 #if V8_HOST_ARCH_X64
   EXPECT_TRUE(cpu.has_fpu());
   EXPECT_TRUE(cpu.has_cmov());
   EXPECT_TRUE(cpu.has_mmx());
   EXPECT_TRUE(cpu.has_sse());
   EXPECT_TRUE(cpu.has_sse2());
 #endif
 }
 
 }  // namespace base
 }  // namespace v8