[arm][arm64] Remove COHERENT_CACHE support

src/arm64/assembler-arm64.cc

 // Copyright 2013 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
@@ skipping 33 matching lines @@
 // -----------------------------------------------------------------------------
 // CpuFeatures implementation.
 
 void CpuFeatures::ProbeImpl(bool cross_compile) {
   // AArch64 has no configuration options, no further probing is required.
   supported_ = 0;
 
   // Only use statically determined features for cross compile (snapshot).
   if (cross_compile) return;
 
-  // Probe for runtime features
-  base::CPU cpu;
-  if (cpu.implementer() == base::CPU::NVIDIA &&
-      cpu.variant() == base::CPU::NVIDIA_DENVER &&
-      cpu.part() <= base::CPU::NVIDIA_DENVER_V10) {
-    // TODO(jkummerow): This is turned off as an experiment to see if it
-    // affects crash rates. Keep an eye on crash reports and either remove
-    // coherent cache support permanently, or re-enable it!
-    // supported_ |= 1u << COHERENT_CACHE;
-  }
+  // We used to probe for coherent cache support, but on older CPUs it
+  // causes crashes (crbug.com/524337), and newer CPUs don't even have
+  // the feature any more.
 }
 
-
 void CpuFeatures::PrintTarget() { }
-
-
-void CpuFeatures::PrintFeatures() {
-  printf("COHERENT_CACHE=%d\n", CpuFeatures::IsSupported(COHERENT_CACHE));
-}
-
+void CpuFeatures::PrintFeatures() {}
 
 // -----------------------------------------------------------------------------
 // CPURegList utilities.
 
 CPURegister CPURegList::PopLowestIndex() {
   DCHECK(IsValid());
   if (IsEmpty()) {
     return NoCPUReg;
   }
   int index = CountTrailingZeros(list_, kRegListSizeInBits);
@@ skipping 3091 matching lines @@
   movk(scratch, (target_offset >> 32) & 0xFFFF, 32);
   DCHECK((target_offset >> 48) == 0);
   add(rd, rd, scratch);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64