Emulate MLS on pre-ARMv6T2. Cleaned up thumbee vs. thumb2 confusion.

src/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/cpu.h"
 
 #if V8_LIBC_MSVCRT
 #include <intrin.h>  // __cpuid()
 #endif
 #if V8_OS_POSIX
@@ skipping 241 matching lines @@
              has_sahf_(false),
              has_mmx_(false),
              has_sse_(false),
              has_sse2_(false),
              has_sse3_(false),
              has_ssse3_(false),
              has_sse41_(false),
              has_sse42_(false),
              has_idiva_(false),
              has_neon_(false),
-             has_thumbee_(false),
+             has_thumb2_(false),
              has_vfp_(false),
              has_vfp3_(false),
              has_vfp3_d32_(false) {
   memcpy(vendor_, "Unknown", 8);
 #if V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64
   int cpu_info[4];
 
   // __cpuid with an InfoType argument of 0 returns the number of
   // valid Ids in CPUInfo[0] and the CPU identification string in
   // the other three array elements. The CPU identification string is
@@ skipping 103 matching lines @@
       }
       delete[] processor;
     }
   }
 
   // Try to extract the list of CPU features from ELF hwcaps.
   uint32_t hwcaps = ReadELFHWCaps();
   if (hwcaps != 0) {
     has_idiva_ = (hwcaps & HWCAP_IDIVA) != 0;
     has_neon_ = (hwcaps & HWCAP_NEON) != 0;
-    has_thumbee_ = (hwcaps & HWCAP_THUMBEE) != 0;
     has_vfp_ = (hwcaps & HWCAP_VFP) != 0;
     has_vfp3_ = (hwcaps & (HWCAP_VFPv3 | HWCAP_VFPv3D16 | HWCAP_VFPv4)) != 0;
     has_vfp3_d32_ = (has_vfp3_ && ((hwcaps & HWCAP_VFPv3D16) == 0 ||
                                    (hwcaps & HWCAP_VFPD32) != 0));
   } else {
     // Try to fallback to "Features" CPUInfo field.
     char* features = cpu_info.ExtractField("Features");
     has_idiva_ = HasListItem(features, "idiva");
     has_neon_ = HasListItem(features, "neon");
-    has_thumbee_ = HasListItem(features, "thumbee");
+    has_thumb2_ = HasListItem(features, "thumb2");

[Rodolph Perfetta, 2014/06/13 10:38:23]

thumb2 doesn't get reported as such in cpuinfo:
 * ARMv7 (or higher) => thumb2
 * ARMv6T2 => thumb2
I only know of one ARMv6T2 cpu and it doesn't have an MMU so we could simplify
to ARMv7

[Sven Panne, 2014/06/13 10:49:57]

This was proposed by Benedikt. We can simplify this in another CL if both of you
come to an agreement what the test should look like. :-)

     has_vfp_ = HasListItem(features, "vfp");
     if (HasListItem(features, "vfpv3d16")) {
       has_vfp3_ = true;
     } else if (HasListItem(features, "vfpv3")) {
       has_vfp3_ = true;
       has_vfp3_d32_ = true;
     }
     delete[] features;
   }
 
   // Some old kernels will report vfp not vfpv3. Here we make an attempt
   // to detect vfpv3 by checking for vfp *and* neon, since neon is only
   // available on architectures with vfpv3. Checking neon on its own is
   // not enough as it is possible to have neon without vfp.
   if (has_vfp_ && has_neon_) {
     has_vfp3_ = true;
   }
 
   // VFPv3 implies ARMv7, see ARM DDI 0406B, page A1-6.
   if (architecture_ < 7 && has_vfp3_) {
     architecture_ = 7;
   }
 
-  // ARMv7 implies ThumbEE.
+  // ARMv7 implies Thumb2.
   if (architecture_ >= 7) {
-    has_thumbee_ = true;
+    has_thumb2_ = true;
   }
 
-  // The earliest architecture with ThumbEE is ARMv6T2.
-  if (has_thumbee_ && architecture_ < 6) {
+  // The earliest architecture with Thumb2 is ARMv6T2.
+  if (has_thumb2_ && architecture_ < 6) {
     architecture_ = 6;
   }
 
   // We don't support any FPUs other than VFP.
   has_fpu_ = has_vfp_;
 
 #elif V8_OS_QNX
 
   uint32_t cpu_flags = SYSPAGE_ENTRY(cpuinfo)->flags;
   if (cpu_flags & ARM_CPU_FLAG_V7) {
     architecture_ = 7;
-    has_thumbee_ = true;
+    has_thumb2_ = true;
   } else if (cpu_flags & ARM_CPU_FLAG_V6) {
     architecture_ = 6;
-    // QNX doesn't say if ThumbEE is available.
+    // QNX doesn't say if Thumb2 is available.
     // Assume false for the architectures older than ARMv7.
   }
   ASSERT(architecture_ >= 6);
   has_fpu_ = (cpu_flags & CPU_FLAG_FPU) != 0;
   has_vfp_ = has_fpu_;
   if (cpu_flags & ARM_CPU_FLAG_NEON) {
     has_neon_ = true;
     has_vfp3_ = has_vfp_;
 #ifdef ARM_CPU_FLAG_VFP_D32
     has_vfp3_d32_ = (cpu_flags & ARM_CPU_FLAG_VFP_D32) != 0;
@@ skipping 38 matching lines @@
     if (end == part) {
       part_ = 0;
     }
     delete[] part;
   }
 
 #endif
 }
 
 } }  // namespace v8::internal