src/third_party/mozjs-45/js/src/jit/arm64/vixl/Cpu-vixl.cpp

// Copyright 2015, ARM Limited
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are met:
//
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//     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
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//     used to endorse or promote products derived from this software without
//     specific prior written permission.
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#include "jit/arm64/vixl/Cpu-vixl.h"
#include "jit/arm64/vixl/Utils-vixl.h"

namespace vixl {

// Initialise to smallest possible cache size.
unsigned CPU::dcache_line_size_ = 1;
unsigned CPU::icache_line_size_ = 1;


// Currently computes I and D cache line size.
void CPU::SetUp() {
  uint32_t cache_type_register = GetCacheType();

  // The cache type register holds information about the caches, including I
  // D caches line size.
  static const int kDCacheLineSizeShift = 16;
  static const int kICacheLineSizeShift = 0;
  static const uint32_t kDCacheLineSizeMask = 0xf << kDCacheLineSizeShift;
  static const uint32_t kICacheLineSizeMask = 0xf << kICacheLineSizeShift;

  // The cache type register holds the size of the I and D caches in words as
  // a power of two.
  uint32_t dcache_line_size_power_of_two =
      (cache_type_register & kDCacheLineSizeMask) >> kDCacheLineSizeShift;
  uint32_t icache_line_size_power_of_two =
      (cache_type_register & kICacheLineSizeMask) >> kICacheLineSizeShift;

  dcache_line_size_ = 4 << dcache_line_size_power_of_two;
  icache_line_size_ = 4 << icache_line_size_power_of_two;
}


uint32_t CPU::GetCacheType() {
#ifdef __aarch64__
  uint64_t cache_type_register;
  // Copy the content of the cache type register to a core register.
  __asm__ __volatile__ ("mrs %[ctr], ctr_el0"  // NOLINT
                        : [ctr] "=r" (cache_type_register));
  VIXL_ASSERT(is_uint32(cache_type_register));
  return cache_type_register;
#else
  // This will lead to a cache with 1 byte long lines, which is fine since
  // neither EnsureIAndDCacheCoherency nor the simulator will need this
  // information.
  return 0;
#endif
}


void CPU::EnsureIAndDCacheCoherency(void *address, size_t length) {
#ifdef __aarch64__
  // Implement the cache synchronisation for all targets where AArch64 is the
  // host, even if we're building the simulator for an AAarch64 host. This
  // allows for cases where the user wants to simulate code as well as run it
  // natively.

  if (length == 0) {
    return;
  }

  // The code below assumes user space cache operations are allowed.

  // Work out the line sizes for each cache, and use them to determine the
  // start addresses.
  uintptr_t start = reinterpret_cast<uintptr_t>(address);
  uintptr_t dsize = static_cast<uintptr_t>(dcache_line_size_);
  uintptr_t isize = static_cast<uintptr_t>(icache_line_size_);
  uintptr_t dline = start & ~(dsize - 1);
  uintptr_t iline = start & ~(isize - 1);

  // Cache line sizes are always a power of 2.
  VIXL_ASSERT(IsPowerOf2(dsize));
  VIXL_ASSERT(IsPowerOf2(isize));
  uintptr_t end = start + length;

  do {
    __asm__ __volatile__ (
      // Clean each line of the D cache containing the target data.
      //
      // dc       : Data Cache maintenance
      //     c    : Clean
      //      va  : by (Virtual) Address
      //        u : to the point of Unification
      // The point of unification for a processor is the point by which the
      // instruction and data caches are guaranteed to see the same copy of a
      // memory location. See ARM DDI 0406B page B2-12 for more information.
      "   dc    cvau, %[dline]\n"
      :
      : [dline] "r" (dline)
      // This code does not write to memory, but the "memory" dependency
      // prevents GCC from reordering the code.
      : "memory");
    dline += dsize;
  } while (dline < end);

  __asm__ __volatile__ (
    // Make sure that the data cache operations (above) complete before the
    // instruction cache operations (below).
    //
    // dsb      : Data Synchronisation Barrier
    //      ish : Inner SHareable domain
    //
    // The point of unification for an Inner Shareable shareability domain is
    // the point by which the instruction and data caches of all the processors
    // in that Inner Shareable shareability domain are guaranteed to see the
    // same copy of a memory location.  See ARM DDI 0406B page B2-12 for more
    // information.
    "   dsb   ish\n"
    : : : "memory");

  do {
    __asm__ __volatile__ (
      // Invalidate each line of the I cache containing the target data.
      //
      // ic      : Instruction Cache maintenance
      //    i    : Invalidate
      //     va  : by Address
      //       u : to the point of Unification
      "   ic   ivau, %[iline]\n"
      :
      : [iline] "r" (iline)
      : "memory");
    iline += isize;
  } while (iline < end);

  __asm__ __volatile__ (
    // Make sure that the instruction cache operations (above) take effect
    // before the isb (below).
    "   dsb  ish\n"

    // Ensure that any instructions already in the pipeline are discarded and
    // reloaded from the new data.
    // isb : Instruction Synchronisation Barrier
    "   isb\n"
    : : : "memory");
#else
  // If the host isn't AArch64, we must be using the simulator, so this function
  // doesn't have to do anything.
  USE(address, length);
#endif
}

}  // namespace vixl