Make FlushICache NOP for Nvidia Denver CPU's.

src/base/cpu.cc

 // Copyright 2013 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"
 
 #if V8_LIBC_MSVCRT
 #include <intrin.h>  // __cpuid()
 #endif
 #if V8_OS_LINUX
@@ skipping 282 matching lines @@
 
 CPU::CPU()
     : stepping_(0),
       model_(0),
       ext_model_(0),
       family_(0),
       ext_family_(0),
       type_(0),
       implementer_(0),
       architecture_(0),
+      variant_(-1),

[Benedikt Meurer, 2014/12/15 05:33:36]

Can we default to 0 here instead?

[arajp, 2014/12/18 13:25:05]

Done.

       part_(0),
       has_fpu_(false),
       has_cmov_(false),
       has_sahf_(false),
       has_mmx_(false),
       has_sse_(false),
       has_sse2_(false),
       has_sse3_(false),
       has_ssse3_(false),
       has_sse41_(false),
@@ skipping 20 matching lines @@
   // the other three array elements. The CPU identification string is
   // not in linear order. The code below arranges the information
   // in a human readable form. The human readable order is CPUInfo[1] |
   // CPUInfo[3] | CPUInfo[2]. CPUInfo[2] and CPUInfo[3] are swapped
   // before using memcpy to copy these three array elements to cpu_string.
   __cpuid(cpu_info, 0);
   unsigned num_ids = cpu_info[0];
   std::swap(cpu_info[2], cpu_info[3]);
   memcpy(vendor_, cpu_info + 1, 12);
   vendor_[12] = '\0';
 

[JF, 2014/12/15 16:23:24]

You can call CPUID again with 1 in EAX and get the Model and Extended Model
fields, which are similar to the variant field from cpuinfo.

   // Interpret CPU feature information.
   if (num_ids > 0) {
     __cpuid(cpu_info, 1);
     stepping_ = cpu_info[0] & 0xf;
     model_ = ((cpu_info[0] >> 4) & 0xf) + ((cpu_info[0] >> 12) & 0xf0);
     family_ = (cpu_info[0] >> 8) & 0xf;
     type_ = (cpu_info[0] >> 12) & 0x3;
     ext_model_ = (cpu_info[0] >> 16) & 0xf;
     ext_family_ = (cpu_info[0] >> 20) & 0xff;
     has_fpu_ = (cpu_info[3] & 0x00000001) != 0;
@@ skipping 35 matching lines @@
   char* implementer = cpu_info.ExtractField("CPU implementer");
   if (implementer != NULL) {
     char* end ;
     implementer_ = strtol(implementer, &end, 0);
     if (end == implementer) {
       implementer_ = 0;
     }
     delete[] implementer;
   }
 
+  char* variant = cpu_info.ExtractField("CPU variant");
+  if (variant != NULL) {
+    char* end ;
+    variant_ = strtol(variant, &end, 0);
+    if (end == variant) {
+      variant_ = 0;

[JF, 2014/12/15 16:23:24]

The failure value here is 0, and as Benedikt pointed out above he'd like the
default to be 0.

Won't 0 be the same value as the "Denver" variant? It sounds like /proc/cpuinfo
identifies Denver as variant 0? What do other Tegra devices return as variant?

[arajp, 2014/12/18 13:25:05]

Yes. Denver is identified as 0 in variant.

Recently released Shield Tablet has 0x3 as variant which is a Tegra chip but
doesn't have a Denver CPU.

I changed the failure case to be -1.

+    }
+    delete[] variant;
+  }
+
   // Extract part number from the "CPU part" field.
   char* part = cpu_info.ExtractField("CPU part");
   if (part != NULL) {
     char* end ;
     part_ = strtol(part, &end, 0);
     if (end == part) {
       part_ = 0;
     }
     delete[] part;
   }
@@ skipping 132 matching lines @@
   char* implementer = cpu_info.ExtractField("CPU implementer");
   if (implementer != NULL) {
     char* end ;
     implementer_ = strtol(implementer, &end, 0);
     if (end == implementer) {
       implementer_ = 0;
     }
     delete[] implementer;
   }
 
+  char* variant = cpu_info.ExtractField("CPU variant");
+  if (variant != NULL) {
+    char* end ;
+    variant_ = strtol(variant, &end, 0);
+    if (end == variant) {
+      variant_ = 0;
+    }
+    delete[] variant;
+  }
+
   // Extract part number from the "CPU part" field.
   char* part = cpu_info.ExtractField("CPU part");
   if (part != NULL) {
     char* end ;
     part_ = strtol(part, &end, 0);
     if (end == part) {
       part_ = 0;
     }
     delete[] part;
   }
 
 #endif
 }
 
 } }  // namespace v8::base