Fix the CPU feature detection.

src/cpu.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
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "cpu.h"
+
+#include <algorithm>
+#include <cctype>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+#include "checks.h"
+
+namespace v8 {
+namespace internal {
+
+#if V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64
+
+#if V8_CC_MSVC
+
+#include <intrin.h>  // NOLINT
+
+#elif defined(__i386__) && defined(__pic__)
+
+static V8_INLINE(void __cpuid(int cpu_info[4], int info_type)) {
+  __asm__ volatile (
+    "mov %%ebx, %%edi\n"
+    "cpuid\n"
+    "xchg %%edi, %%ebx\n"
+    : "=a"(cpu_info[0]), "=D"(cpu_info[1]), "=c"(cpu_info[2]), "=d"(cpu_info[3])
+    : "a"(info_type)
+  );
+}
+
+#else  // !V8_CC_MSVC || (!defined(__i386__) && !defined(__pic__))
+
+static void V8_INLINE(__cpuid(int cpu_info[4], int info_type)) {
+  __asm__ volatile (
+    "cpuid \n\t"
+    : "=a"(cpu_info[0]), "=b"(cpu_info[1]), "=c"(cpu_info[2]), "=d"(cpu_info[3])
+    : "a"(info_type)
+  );
+}
+
+#endif
+
+#elif V8_HOST_ARCH_ARM || V8_HOST_ARCH_MIPS
+
+#if V8_HOST_ARCH_ARM
+
+// See <uapi/asm/hwcap.h> kernel header.
+/*
+ * HWCAP flags - for elf_hwcap (in kernel) and AT_HWCAP
+ */
+#define HWCAP_SWP (1 << 0)
+#define HWCAP_HALF  (1 << 1)
+#define HWCAP_THUMB (1 << 2)
+#define HWCAP_26BIT (1 << 3)  /* Play it safe */
+#define HWCAP_FAST_MULT (1 << 4)
+#define HWCAP_FPA (1 << 5)
+#define HWCAP_VFP (1 << 6)
+#define HWCAP_EDSP  (1 << 7)
+#define HWCAP_JAVA  (1 << 8)
+#define HWCAP_IWMMXT  (1 << 9)
+#define HWCAP_CRUNCH  (1 << 10)
+#define HWCAP_THUMBEE (1 << 11)
+#define HWCAP_NEON  (1 << 12)
+#define HWCAP_VFPv3 (1 << 13)
+#define HWCAP_VFPv3D16  (1 << 14) /* also set for VFPv4-D16 */
+#define HWCAP_TLS (1 << 15)
+#define HWCAP_VFPv4 (1 << 16)
+#define HWCAP_IDIVA (1 << 17)
+#define HWCAP_IDIVT (1 << 18)
+#define HWCAP_VFPD32  (1 << 19) /* set if VFP has 32 regs (not 16) */
+#define HWCAP_IDIV  (HWCAP_IDIVA | HWCAP_IDIVT)
+#define HWCAP_LPAE  (1 << 20)
+
+#define AT_HWCAP 16
+
+// Read the ELF HWCAP flags by parsing /proc/self/auxv.
+static uint32_t ReadELFHWCaps() {
+  uint32_t result = 0;
+  FILE* fp = fopen("/proc/self/auxv", "r");
+  if (fp != NULL) {
+    struct { uint32_t tag; uint32_t value; } entry;
+    for (;;) {
+      size_t n = fread(&entry, sizeof(entry), 1, fp);
+      if (n == 0 || (entry.tag == 0 && entry.value == 0)) {
+        break;
+      }
+      if (entry.tag == AT_HWCAP) {
+        result = entry.value;
+        break;
+      }
+    }
+    fclose(fp);
+  }
+  return result;
+}
+
+#endif  // V8_HOST_ARCH_ARM
+
+// Extract the information exposed by the kernel via /proc/cpuinfo.
+class CPUInfo V8_FINAL BASE_EMBEDDED {
+ public:
+  CPUInfo() : datalen_(0) {
+    // Get the size of the cpuinfo file by reading it until the end. This is
+    // required because files under /proc do not always return a valid size
+    // when using fseek(0, SEEK_END) + ftell(). Nor can the be mmap()-ed.
+    static const char PATHNAME[] = "/proc/cpuinfo";
+    FILE* fp = fopen(PATHNAME, "r");
+    if (fp != NULL) {
+      for (;;) {
+        char buffer[256];
+        size_t n = fread(buffer, 1, sizeof(buffer), fp);
+        if (n == 0) {
+          break;
+        }
+        datalen_ += n;
+      }
+      fclose(fp);
+    }
+
+    // Read the contents of the cpuinfo file.
+    data_ = new char[datalen_ + 1];
+    fp = fopen(PATHNAME, "r");
+    if (fp != NULL) {
+      for (size_t offset = 0; offset < datalen_; ) {
+        size_t n = fread(data_ + offset, 1, datalen_ - offset, fp);
+        if (n == 0) {
+          break;
+        }
+        offset += n;
+      }
+      fclose(fp);
+    }
+
+    // Zero-terminate the data.
+    data_[datalen_] = '\0';
+  }
+
+  ~CPUInfo() {
+    delete[] data_;
+  }
+
+  // Extract the content of a the first occurence of a given field in
+  // the content of the cpuinfo file and return it as a heap-allocated
+  // string that must be freed by the caller using delete[].
+  // Return NULL if not found.
+  char* ExtractField(const char* field) const {
+    ASSERT(field != NULL);
+
+    // Look for first field occurence, and ensure it starts the line.
+    size_t fieldlen = strlen(field);
+    char* p = data_;
+    for (;;) {
+      p = strstr(p, field);
+      if (p == NULL) {
+        return NULL;
+      }
+      if (p == data_ || p[-1] == '\n') {
+        break;
+      }
+      p += fieldlen;
+    }
+
+    // Skip to the first colon followed by a space.
+    p = strchr(p + fieldlen, ':');
+    if (p == NULL || !isspace(p[1])) {
+      return NULL;
+    }
+    p += 2;
+
+    // Find the end of the line.
+    char* q = strchr(p, '\n');
+    if (q == NULL) {
+      q = data_ + datalen_;
+    }
+
+    // Copy the line into a heap-allocated buffer.
+    size_t len = q - p;
+    char* result = new char[len + 1];
+    if (result != NULL) {
+      memcpy(result, p, len);
+      result[len] = '\0';
+    }
+    return result;
+  }
+
+ private:
+  char* data_;
+  size_t datalen_;
+};
+
+
+// Checks that a space-separated list of items contains one given 'item'.
+static bool HasListItem(const char* list, const char* item) {
+  ssize_t item_len = strlen(item);
+  const char* p = list;
+  if (p != NULL) {
+    while (*p != '\0') {
+      // Skip whitespace.
+      while (isspace(*p)) ++p;
+
+      // Find end of current list item.
+      const char* q = p;
+      while (*q != '\0' && !isspace(*q)) ++q;
+
+      if (item_len == q - p && memcmp(p, item, item_len) == 0) {
+        return true;
+      }
+
+      // Skip to next item.
+      p = q;
+    }
+  }
+  return false;
+}
+
+#endif  // V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64
+
+CPU::CPU() : stepping_(0),
+             model_(0),
+             ext_model_(0),
+             family_(0),
+             ext_family_(0),
+             type_(0),
+             implementer_(0),
+             architecture_(0),
+             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),
+             has_sse42_(false),
+             has_idiva_(false),
+             has_neon_(false),
+             has_thumbee_(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
+  // 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';
+
+  // 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;
+    has_cmov_ = (cpu_info[3] & 0x00008000) != 0;
+    has_mmx_ = (cpu_info[3] & 0x00800000) != 0;
+    has_sse_ = (cpu_info[3] & 0x02000000) != 0;
+    has_sse2_ = (cpu_info[3] & 0x04000000) != 0;
+    has_sse3_ = (cpu_info[2] & 0x00000001) != 0;
+    has_ssse3_ = (cpu_info[2] & 0x00000200) != 0;
+    has_sse41_ = (cpu_info[2] & 0x00080000) != 0;
+    has_sse42_ = (cpu_info[2] & 0x00100000) != 0;
+  }
+
+  // Query extended IDs.
+  __cpuid(cpu_info, 0x80000000);
+  unsigned num_ext_ids = cpu_info[0];
+
+  // Interpret extended CPU feature information.
+  if (num_ext_ids > 0x80000000) {
+    __cpuid(cpu_info, 0x80000001);
+    // SAHF is always available in compat/legacy mode,
+    // but must be probed in long mode.
+#if V8_HOST_ARCH_IA32
+    has_sahf_ = true;
+#else
+    has_sahf_ = (cpu_info[2] & 0x00000001) != 0;
+#endif
+  }
+#elif V8_HOST_ARCH_ARM
+  CPUInfo cpu_info;
+
+  // Extract implementor from the "CPU implementer" field.
+  char* implementer = cpu_info.ExtractField("CPU implementer");
+  if (implementer != NULL) {
+    char* end ;
+    implementer_ = strtol(implementer, &end, 0);
+    if (end == implementer) {
+      implementer_ = 0;
+    }
+    delete[] implementer;
+  }
+
+  // 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;
+  }
+
+  // Extract architecture from the "CPU Architecture" field.
+  // The list is well-known, unlike the the output of
+  // the 'Processor' field which can vary greatly.
+  // See the definition of the 'proc_arch' array in
+  // $KERNEL/arch/arm/kernel/setup.c and the 'c_show' function in
+  // same file.
+  char* architecture = cpu_info.ExtractField("CPU architecture");
+  if (architecture != NULL) {
+    char* end;
+    architecture_ = strtol(architecture, &end, 10);
+    if (end == architecture) {
+      architecture_ = 0;
+    }
+    delete[] architecture;
+
+    // Unfortunately, it seems that certain ARMv6-based CPUs
+    // report an incorrect architecture number of 7!
+    //
+    // See http://code.google.com/p/android/issues/detail?id=10812
+    //
+    // We try to correct this by looking at the 'elf_format'
+    // field reported by the 'Processor' field, which is of the
+    // form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
+    // an ARMv6-one. For example, the Raspberry Pi is one popular
+    // ARMv6 device that reports architecture 7.
+    if (architecture_ == 7) {
+      char* processor = cpu_info.ExtractField("Processor");
+      if (HasListItem(processor, "(v6l)")) {
+        architecture_ = 6;
+      }
+      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_vfp_ = HasListItem(features, "vfp");
+    if (HasListItem(features, "vfpv3")) {
+      has_vfp3_ = true;
+      has_vfp3_d32_ = true;
+    } else if (HasListItem(features, "vfpv3d16")) {
+      has_vfp3_ = 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.
+  if (architecture_ >= 7) {
+    has_thumbee_ = true;
+  }
+
+  // The earliest architecture with ThumbEE is ARMv6T2.
+  if (has_thumbee_ && architecture_ < 6) {
+    architecture_ = 6;
+  }
+
+  // We don't support any FPUs other than VFP.
+  has_fpu_ = has_vfp_;
+#elif V8_HOST_ARCH_MIPS
+  // 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
+  // facility is universally available on the MIPS architectures,
+  // so it's up to individual OSes to provide such.
+  CPUInfo cpu_info;
+  char* cpu_model = cpu_info.ExtractField("cpu model");
+  has_fpu_ = HasListItem(cpu_model, "FPU");
+  delete[] cpu_model;
+#endif
+}
+
+} }  // namespace v8::internal