Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release:

MFC r309142 (by emaste):

Add WITH_LLD_AS_LD build knob

If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation

MFC r310840:

Reapply 310775, now it also builds correctly if lldb is disabled:

Move llvm-objdump from CLANG_EXTRAS to installed by default

We currently install three tools from binutils 2.17.50: as, ld, and
objdump. Work is underway to migrate to a permissively-licensed
tool-chain, with one goal being the retirement of binutils 2.17.50.

LLVM's llvm-objdump is intended to be compatible with GNU objdump
although it is currently missing some options and may have formatting
differences. Enable it by default for testing and further investigation.
It may later be changed to install as /usr/bin/objdump, it becomes a
fully viable replacement.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D8879

MFC r312855 (by emaste):

Rename LLD_AS_LD to LLD_IS_LD, for consistency with CLANG_IS_CC

Reported by:	Dan McGregor <dan.mcgregor usask.ca>

MFC r313559 | glebius | 2017-02-10 18:34:48 +0100 (Fri, 10 Feb 2017) | 5 lines

Don't check struct rtentry on FreeBSD, it is an internal kernel structure.
On other systems it may be API structure for SIOCADDRT/SIOCDELRT.

Reviewed by:	emaste, dim

MFC r314152 (by jkim):

Remove an assembler flag, which is redundant since r309124.  The upstream
took care of it by introducing a macro NO_EXEC_STACK_DIRECTIVE.

http://llvm.org/viewvc/llvm-project?rev=273500&view=rev

Reviewed by:	dim

MFC r314564:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
4.0.0 (branches/release_40 296509).  The release will follow soon.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Also note that as of 4.0.0, lld should be able to link the base system
on amd64 and aarch64.  See the WITH_LLD_IS_LLD setting in src.conf(5).
Though please be aware that this is work in progress.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/4.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Jan Beich, Antoine Brodin and Eric Fiselier for
their help.

Relnotes:	yes
Exp-run:	antoine
PR:		215969, 216008

MFC r314708:

For now, revert r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

This commit is the cause of excessive compile times on skein_block.c
(and possibly other files) during kernel builds on amd64.

We never saw the problematic behavior described in this upstream commit,
so for now it is better to revert it.  An upstream bug has been filed
here: https://bugs.llvm.org/show_bug.cgi?id=32142

Reported by:	mjg

MFC r314795:

Reapply r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

Pull in r296992 from upstream llvm trunk (by Sanjoy Das):

  [SCEV] Decrease the recursion threshold for CompareValueComplexity

  Fixes PR32142.

  r287232 accidentally increased the recursion threshold for
  CompareValueComplexity from 2 to 32.  This change reverses that
  change by introducing a separate flag for CompareValueComplexity's
  threshold.

The latter revision fixes the excessive compile times for skein_block.c.

MFC r314907 | mmel | 2017-03-08 12:40:27 +0100 (Wed, 08 Mar 2017) | 7 lines

Unbreak ARMv6 world.

The new compiler_rt library imported with clang 4.0.0 have several fatal
issues (non-functional __udivsi3 for example) with ARM specific instrict
functions. As temporary workaround, until upstream solve these problems,
disable all thumb[1][2] related feature.

MFC r315016:

Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release.
We were already very close to the last release candidate, so this is a
pretty minor update.

Relnotes:	yes

MFC r316005:

Revert r314907, and pull in r298713 from upstream compiler-rt trunk (by
Weiming Zhao):

  builtins: Select correct code fragments when compiling for Thumb1/Thum2/ARM ISA.

  Summary:
  Value of __ARM_ARCH_ISA_THUMB isn't based on the actual compilation
  mode (-mthumb, -marm), it reflect's capability of given CPU.

  Due to this:
   - use  __tbumb__ and __thumb2__ insteand of __ARM_ARCH_ISA_THUMB
   - use '.thumb' directive consistently  in all affected files
   - decorate all thumb functions using
     DEFINE_COMPILERRT_THUMB_FUNCTION()

  ---------
  Note: This patch doesn't fix broken Thumb1 variant of __udivsi3 !

  Reviewers: weimingz, rengolin, compnerd

  Subscribers: aemerson, dim

  Differential Revision: https://reviews.llvm.org/D30938

Discussed with:	mmel

1 files changed, 521 insertions, 0 deletions

diff --git a/contrib/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h b/contrib/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h
new file mode 100644
index 0000000..035d92b
--- /dev/null
+++ b/contrib/compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h
@@ -0,0 +1,521 @@
+//===-- sanitizer_allocator_primary64.h -------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Part of the Sanitizer Allocator.
+//
+//===----------------------------------------------------------------------===//
+#ifndef SANITIZER_ALLOCATOR_H
+#error This file must be included inside sanitizer_allocator.h
+#endif
+
+template<class SizeClassAllocator> struct SizeClassAllocator64LocalCache;
+
+// SizeClassAllocator64 -- allocator for 64-bit address space.
+// The template parameter Params is a class containing the actual parameters.
+//
+// Space: a portion of address space of kSpaceSize bytes starting at SpaceBeg.
+// If kSpaceBeg is ~0 then SpaceBeg is chosen dynamically my mmap.
+// Otherwise SpaceBeg=kSpaceBeg (fixed address).
+// kSpaceSize is a power of two.
+// At the beginning the entire space is mprotect-ed, then small parts of it
+// are mapped on demand.
+//
+// Region: a part of Space dedicated to a single size class.
+// There are kNumClasses Regions of equal size.
+//
+// UserChunk: a piece of memory returned to user.
+// MetaChunk: kMetadataSize bytes of metadata associated with a UserChunk.
+
+// FreeArray is an array free-d chunks (stored as 4-byte offsets)
+//
+// A Region looks like this:
+// UserChunk1 ... UserChunkN <gap> MetaChunkN ... MetaChunk1 FreeArray
+
+struct SizeClassAllocator64FlagMasks {  //  Bit masks.
+  enum {
+    kRandomShuffleChunks = 1,
+  };
+};
+
+template <class Params>
+class SizeClassAllocator64 {
+ public:
+  static const uptr kSpaceBeg = Params::kSpaceBeg;
+  static const uptr kSpaceSize = Params::kSpaceSize;
+  static const uptr kMetadataSize = Params::kMetadataSize;
+  typedef typename Params::SizeClassMap SizeClassMap;
+  typedef typename Params::MapUnmapCallback MapUnmapCallback;
+
+  static const bool kRandomShuffleChunks =
+      Params::kFlags & SizeClassAllocator64FlagMasks::kRandomShuffleChunks;
+
+  typedef SizeClassAllocator64<Params> ThisT;
+  typedef SizeClassAllocator64LocalCache<ThisT> AllocatorCache;
+
+  // When we know the size class (the region base) we can represent a pointer
+  // as a 4-byte integer (offset from the region start shifted right by 4).
+  typedef u32 CompactPtrT;
+  static const uptr kCompactPtrScale = 4;
+  CompactPtrT PointerToCompactPtr(uptr base, uptr ptr) {
+    return static_cast<CompactPtrT>((ptr - base) >> kCompactPtrScale);
+  }
+  uptr CompactPtrToPointer(uptr base, CompactPtrT ptr32) {
+    return base + (static_cast<uptr>(ptr32) << kCompactPtrScale);
+  }
+
+  void Init(s32 release_to_os_interval_ms) {
+    uptr TotalSpaceSize = kSpaceSize + AdditionalSize();
+    if (kUsingConstantSpaceBeg) {
+      CHECK_EQ(kSpaceBeg, reinterpret_cast<uptr>(
+                              MmapFixedNoAccess(kSpaceBeg, TotalSpaceSize)));
+    } else {
+      NonConstSpaceBeg =
+          reinterpret_cast<uptr>(MmapNoAccess(TotalSpaceSize));
+      CHECK_NE(NonConstSpaceBeg, ~(uptr)0);
+    }
+    SetReleaseToOSIntervalMs(release_to_os_interval_ms);
+    MapWithCallback(SpaceEnd(), AdditionalSize());
+  }
+
+  s32 ReleaseToOSIntervalMs() const {
+    return atomic_load(&release_to_os_interval_ms_, memory_order_relaxed);
+  }
+
+  void SetReleaseToOSIntervalMs(s32 release_to_os_interval_ms) {
+    atomic_store(&release_to_os_interval_ms_, release_to_os_interval_ms,
+                 memory_order_relaxed);
+  }
+
+  void MapWithCallback(uptr beg, uptr size) {
+    CHECK_EQ(beg, reinterpret_cast<uptr>(MmapFixedOrDie(beg, size)));
+    MapUnmapCallback().OnMap(beg, size);
+  }
+
+  void UnmapWithCallback(uptr beg, uptr size) {
+    MapUnmapCallback().OnUnmap(beg, size);
+    UnmapOrDie(reinterpret_cast<void *>(beg), size);
+  }
+
+  static bool CanAllocate(uptr size, uptr alignment) {
+    return size <= SizeClassMap::kMaxSize &&
+      alignment <= SizeClassMap::kMaxSize;
+  }
+
+  NOINLINE void ReturnToAllocator(AllocatorStats *stat, uptr class_id,
+                                  const CompactPtrT *chunks, uptr n_chunks) {
+    RegionInfo *region = GetRegionInfo(class_id);
+    uptr region_beg = GetRegionBeginBySizeClass(class_id);
+    CompactPtrT *free_array = GetFreeArray(region_beg);
+
+    BlockingMutexLock l(&region->mutex);
+    uptr old_num_chunks = region->num_freed_chunks;
+    uptr new_num_freed_chunks = old_num_chunks + n_chunks;
+    EnsureFreeArraySpace(region, region_beg, new_num_freed_chunks);
+    for (uptr i = 0; i < n_chunks; i++)
+      free_array[old_num_chunks + i] = chunks[i];
+    region->num_freed_chunks = new_num_freed_chunks;
+    region->n_freed += n_chunks;
+
+    MaybeReleaseToOS(class_id);
+  }
+
+  NOINLINE void GetFromAllocator(AllocatorStats *stat, uptr class_id,
+                                 CompactPtrT *chunks, uptr n_chunks) {
+    RegionInfo *region = GetRegionInfo(class_id);
+    uptr region_beg = GetRegionBeginBySizeClass(class_id);
+    CompactPtrT *free_array = GetFreeArray(region_beg);
+
+    BlockingMutexLock l(&region->mutex);
+    if (UNLIKELY(region->num_freed_chunks < n_chunks)) {
+      PopulateFreeArray(stat, class_id, region,
+                        n_chunks - region->num_freed_chunks);
+      CHECK_GE(region->num_freed_chunks, n_chunks);
+    }
+    region->num_freed_chunks -= n_chunks;
+    uptr base_idx = region->num_freed_chunks;
+    for (uptr i = 0; i < n_chunks; i++)
+      chunks[i] = free_array[base_idx + i];
+    region->n_allocated += n_chunks;
+  }
+
+
+  bool PointerIsMine(const void *p) {
+    uptr P = reinterpret_cast<uptr>(p);
+    if (kUsingConstantSpaceBeg && (kSpaceBeg % kSpaceSize) == 0)
+      return P / kSpaceSize == kSpaceBeg / kSpaceSize;
+    return P >= SpaceBeg() && P < SpaceEnd();
+  }
+
+  uptr GetRegionBegin(const void *p) {
+    if (kUsingConstantSpaceBeg)
+      return reinterpret_cast<uptr>(p) & ~(kRegionSize - 1);
+    uptr space_beg = SpaceBeg();
+    return ((reinterpret_cast<uptr>(p)  - space_beg) & ~(kRegionSize - 1)) +
+        space_beg;
+  }
+
+  uptr GetRegionBeginBySizeClass(uptr class_id) {
+    return SpaceBeg() + kRegionSize * class_id;
+  }
+
+  uptr GetSizeClass(const void *p) {
+    if (kUsingConstantSpaceBeg && (kSpaceBeg % kSpaceSize) == 0)
+      return ((reinterpret_cast<uptr>(p)) / kRegionSize) % kNumClassesRounded;
+    return ((reinterpret_cast<uptr>(p) - SpaceBeg()) / kRegionSize) %
+           kNumClassesRounded;
+  }
+
+  void *GetBlockBegin(const void *p) {
+    uptr class_id = GetSizeClass(p);
+    uptr size = ClassIdToSize(class_id);
+    if (!size) return nullptr;
+    uptr chunk_idx = GetChunkIdx((uptr)p, size);
+    uptr reg_beg = GetRegionBegin(p);
+    uptr beg = chunk_idx * size;
+    uptr next_beg = beg + size;
+    if (class_id >= kNumClasses) return nullptr;
+    RegionInfo *region = GetRegionInfo(class_id);
+    if (region->mapped_user >= next_beg)
+      return reinterpret_cast<void*>(reg_beg + beg);
+    return nullptr;
+  }
+
+  uptr GetActuallyAllocatedSize(void *p) {
+    CHECK(PointerIsMine(p));
+    return ClassIdToSize(GetSizeClass(p));
+  }
+
+  uptr ClassID(uptr size) { return SizeClassMap::ClassID(size); }
+
+  void *GetMetaData(const void *p) {
+    uptr class_id = GetSizeClass(p);
+    uptr size = ClassIdToSize(class_id);
+    uptr chunk_idx = GetChunkIdx(reinterpret_cast<uptr>(p), size);
+    uptr region_beg = GetRegionBeginBySizeClass(class_id);
+    return reinterpret_cast<void *>(GetMetadataEnd(region_beg) -
+                                    (1 + chunk_idx) * kMetadataSize);
+  }
+
+  uptr TotalMemoryUsed() {
+    uptr res = 0;
+    for (uptr i = 0; i < kNumClasses; i++)
+      res += GetRegionInfo(i)->allocated_user;
+    return res;
+  }
+
+  // Test-only.
+  void TestOnlyUnmap() {
+    UnmapWithCallback(SpaceBeg(), kSpaceSize + AdditionalSize());
+  }
+
+  static void FillMemoryProfile(uptr start, uptr rss, bool file, uptr *stats,
+                           uptr stats_size) {
+    for (uptr class_id = 0; class_id < stats_size; class_id++)
+      if (stats[class_id] == start)
+        stats[class_id] = rss;
+  }
+
+  void PrintStats(uptr class_id, uptr rss) {
+    RegionInfo *region = GetRegionInfo(class_id);
+    if (region->mapped_user == 0) return;
+    uptr in_use = region->n_allocated - region->n_freed;
+    uptr avail_chunks = region->allocated_user / ClassIdToSize(class_id);
+    Printf(
+        "  %02zd (%6zd): mapped: %6zdK allocs: %7zd frees: %7zd inuse: %6zd "
+        "num_freed_chunks %7zd avail: %6zd rss: %6zdK releases: %6zd\n",
+        class_id, ClassIdToSize(class_id), region->mapped_user >> 10,
+        region->n_allocated, region->n_freed, in_use,
+        region->num_freed_chunks, avail_chunks, rss >> 10,
+        region->rtoi.num_releases);
+  }
+
+  void PrintStats() {
+    uptr total_mapped = 0;
+    uptr n_allocated = 0;
+    uptr n_freed = 0;
+    for (uptr class_id = 1; class_id < kNumClasses; class_id++) {
+      RegionInfo *region = GetRegionInfo(class_id);
+      total_mapped += region->mapped_user;
+      n_allocated += region->n_allocated;
+      n_freed += region->n_freed;
+    }
+    Printf("Stats: SizeClassAllocator64: %zdM mapped in %zd allocations; "
+           "remains %zd\n",
+           total_mapped >> 20, n_allocated, n_allocated - n_freed);
+    uptr rss_stats[kNumClasses];
+    for (uptr class_id = 0; class_id < kNumClasses; class_id++)
+      rss_stats[class_id] = SpaceBeg() + kRegionSize * class_id;
+    GetMemoryProfile(FillMemoryProfile, rss_stats, kNumClasses);
+    for (uptr class_id = 1; class_id < kNumClasses; class_id++)
+      PrintStats(class_id, rss_stats[class_id]);
+  }
+
+  // ForceLock() and ForceUnlock() are needed to implement Darwin malloc zone
+  // introspection API.
+  void ForceLock() {
+    for (uptr i = 0; i < kNumClasses; i++) {
+      GetRegionInfo(i)->mutex.Lock();
+    }
+  }
+
+  void ForceUnlock() {
+    for (int i = (int)kNumClasses - 1; i >= 0; i--) {
+      GetRegionInfo(i)->mutex.Unlock();
+    }
+  }
+
+  // Iterate over all existing chunks.
+  // The allocator must be locked when calling this function.
+  void ForEachChunk(ForEachChunkCallback callback, void *arg) {
+    for (uptr class_id = 1; class_id < kNumClasses; class_id++) {
+      RegionInfo *region = GetRegionInfo(class_id);
+      uptr chunk_size = ClassIdToSize(class_id);
+      uptr region_beg = SpaceBeg() + class_id * kRegionSize;
+      for (uptr chunk = region_beg;
+           chunk < region_beg + region->allocated_user;
+           chunk += chunk_size) {
+        // Too slow: CHECK_EQ((void *)chunk, GetBlockBegin((void *)chunk));
+        callback(chunk, arg);
+      }
+    }
+  }
+
+  static uptr ClassIdToSize(uptr class_id) {
+    return SizeClassMap::Size(class_id);
+  }
+
+  static uptr AdditionalSize() {
+    return RoundUpTo(sizeof(RegionInfo) * kNumClassesRounded,
+                     GetPageSizeCached());
+  }
+
+  typedef SizeClassMap SizeClassMapT;
+  static const uptr kNumClasses = SizeClassMap::kNumClasses;
+  static const uptr kNumClassesRounded = SizeClassMap::kNumClassesRounded;
+
+ private:
+  static const uptr kRegionSize = kSpaceSize / kNumClassesRounded;
+  // FreeArray is the array of free-d chunks (stored as 4-byte offsets).
+  // In the worst case it may reguire kRegionSize/SizeClassMap::kMinSize
+  // elements, but in reality this will not happen. For simplicity we
+  // dedicate 1/8 of the region's virtual space to FreeArray.
+  static const uptr kFreeArraySize = kRegionSize / 8;
+
+  static const bool kUsingConstantSpaceBeg = kSpaceBeg != ~(uptr)0;
+  uptr NonConstSpaceBeg;
+  uptr SpaceBeg() const {
+    return kUsingConstantSpaceBeg ? kSpaceBeg : NonConstSpaceBeg;
+  }
+  uptr SpaceEnd() const { return  SpaceBeg() + kSpaceSize; }
+  // kRegionSize must be >= 2^32.
+  COMPILER_CHECK((kRegionSize) >= (1ULL << (SANITIZER_WORDSIZE / 2)));
+  // kRegionSize must be <= 2^36, see CompactPtrT.
+  COMPILER_CHECK((kRegionSize) <= (1ULL << (SANITIZER_WORDSIZE / 2 + 4)));
+  // Call mmap for user memory with at least this size.
+  static const uptr kUserMapSize = 1 << 16;
+  // Call mmap for metadata memory with at least this size.
+  static const uptr kMetaMapSize = 1 << 16;
+  // Call mmap for free array memory with at least this size.
+  static const uptr kFreeArrayMapSize = 1 << 16;
+
+  atomic_sint32_t release_to_os_interval_ms_;
+
+  struct ReleaseToOsInfo {
+    uptr n_freed_at_last_release;
+    uptr num_releases;
+    u64 last_release_at_ns;
+  };
+
+  struct RegionInfo {
+    BlockingMutex mutex;
+    uptr num_freed_chunks;  // Number of elements in the freearray.
+    uptr mapped_free_array;  // Bytes mapped for freearray.
+    uptr allocated_user;  // Bytes allocated for user memory.
+    uptr allocated_meta;  // Bytes allocated for metadata.
+    uptr mapped_user;  // Bytes mapped for user memory.
+    uptr mapped_meta;  // Bytes mapped for metadata.
+    u32 rand_state; // Seed for random shuffle, used if kRandomShuffleChunks.
+    uptr n_allocated, n_freed;  // Just stats.
+    ReleaseToOsInfo rtoi;
+  };
+  COMPILER_CHECK(sizeof(RegionInfo) >= kCacheLineSize);
+
+  u32 Rand(u32 *state) {  // ANSI C linear congruential PRNG.
+    return (*state = *state * 1103515245 + 12345) >> 16;
+  }
+
+  u32 RandN(u32 *state, u32 n) { return Rand(state) % n; }  // [0, n)
+
+  void RandomShuffle(u32 *a, u32 n, u32 *rand_state) {
+    if (n <= 1) return;
+    for (u32 i = n - 1; i > 0; i--)
+      Swap(a[i], a[RandN(rand_state, i + 1)]);
+  }
+
+  RegionInfo *GetRegionInfo(uptr class_id) {
+    CHECK_LT(class_id, kNumClasses);
+    RegionInfo *regions =
+        reinterpret_cast<RegionInfo *>(SpaceBeg() + kSpaceSize);
+    return &regions[class_id];
+  }
+
+  uptr GetMetadataEnd(uptr region_beg) {
+    return region_beg + kRegionSize - kFreeArraySize;
+  }
+
+  uptr GetChunkIdx(uptr chunk, uptr size) {
+    if (!kUsingConstantSpaceBeg)
+      chunk -= SpaceBeg();
+
+    uptr offset = chunk % kRegionSize;
+    // Here we divide by a non-constant. This is costly.
+    // size always fits into 32-bits. If the offset fits too, use 32-bit div.
+    if (offset >> (SANITIZER_WORDSIZE / 2))
+      return offset / size;
+    return (u32)offset / (u32)size;
+  }
+
+  CompactPtrT *GetFreeArray(uptr region_beg) {
+    return reinterpret_cast<CompactPtrT *>(region_beg + kRegionSize -
+                                           kFreeArraySize);
+  }
+
+  void EnsureFreeArraySpace(RegionInfo *region, uptr region_beg,
+                            uptr num_freed_chunks) {
+    uptr needed_space = num_freed_chunks * sizeof(CompactPtrT);
+    if (region->mapped_free_array < needed_space) {
+      CHECK_LE(needed_space, kFreeArraySize);
+      uptr new_mapped_free_array = RoundUpTo(needed_space, kFreeArrayMapSize);
+      uptr current_map_end = reinterpret_cast<uptr>(GetFreeArray(region_beg)) +
+                             region->mapped_free_array;
+      uptr new_map_size = new_mapped_free_array - region->mapped_free_array;
+      MapWithCallback(current_map_end, new_map_size);
+      region->mapped_free_array = new_mapped_free_array;
+    }
+  }
+
+
+  NOINLINE void PopulateFreeArray(AllocatorStats *stat, uptr class_id,
+                                  RegionInfo *region, uptr requested_count) {
+    // region->mutex is held.
+    uptr size = ClassIdToSize(class_id);
+    uptr beg_idx = region->allocated_user;
+    uptr end_idx = beg_idx + requested_count * size;
+    uptr region_beg = GetRegionBeginBySizeClass(class_id);
+    if (end_idx > region->mapped_user) {
+      if (!kUsingConstantSpaceBeg && region->mapped_user == 0)
+        region->rand_state = static_cast<u32>(region_beg >> 12);  // From ASLR.
+      // Do the mmap for the user memory.
+      uptr map_size = kUserMapSize;
+      while (end_idx > region->mapped_user + map_size)
+        map_size += kUserMapSize;
+      CHECK_GE(region->mapped_user + map_size, end_idx);
+      MapWithCallback(region_beg + region->mapped_user, map_size);
+      stat->Add(AllocatorStatMapped, map_size);
+      region->mapped_user += map_size;
+    }
+    CompactPtrT *free_array = GetFreeArray(region_beg);
+    uptr total_count = (region->mapped_user - beg_idx) / size;
+    uptr num_freed_chunks = region->num_freed_chunks;
+    EnsureFreeArraySpace(region, region_beg, num_freed_chunks + total_count);
+    for (uptr i = 0; i < total_count; i++) {
+      uptr chunk = beg_idx + i * size;
+      free_array[num_freed_chunks + total_count - 1 - i] =
+          PointerToCompactPtr(0, chunk);
+    }
+    if (kRandomShuffleChunks)
+      RandomShuffle(&free_array[num_freed_chunks], total_count,
+                    &region->rand_state);
+    region->num_freed_chunks += total_count;
+    region->allocated_user += total_count * size;
+    CHECK_LE(region->allocated_user, region->mapped_user);
+
+    region->allocated_meta += total_count * kMetadataSize;
+    if (region->allocated_meta > region->mapped_meta) {
+      uptr map_size = kMetaMapSize;
+      while (region->allocated_meta > region->mapped_meta + map_size)
+        map_size += kMetaMapSize;
+      // Do the mmap for the metadata.
+      CHECK_GE(region->mapped_meta + map_size, region->allocated_meta);
+      MapWithCallback(GetMetadataEnd(region_beg) -
+                      region->mapped_meta - map_size, map_size);
+      region->mapped_meta += map_size;
+    }
+    CHECK_LE(region->allocated_meta, region->mapped_meta);
+    if (region->mapped_user + region->mapped_meta >
+        kRegionSize - kFreeArraySize) {
+      Printf("%s: Out of memory. Dying. ", SanitizerToolName);
+      Printf("The process has exhausted %zuMB for size class %zu.\n",
+          kRegionSize / 1024 / 1024, size);
+      Die();
+    }
+  }
+
+  void MaybeReleaseChunkRange(uptr region_beg, uptr chunk_size,
+                              CompactPtrT first, CompactPtrT last) {
+    uptr beg_ptr = CompactPtrToPointer(region_beg, first);
+    uptr end_ptr = CompactPtrToPointer(region_beg, last) + chunk_size;
+    ReleaseMemoryPagesToOS(beg_ptr, end_ptr);
+  }
+
+  // Attempts to release some RAM back to OS. The region is expected to be
+  // locked.
+  // Algorithm:
+  // * Sort the chunks.
+  // * Find ranges fully covered by free-d chunks
+  // * Release them to OS with madvise.
+  void MaybeReleaseToOS(uptr class_id) {
+    RegionInfo *region = GetRegionInfo(class_id);
+    const uptr chunk_size = ClassIdToSize(class_id);
+    const uptr page_size = GetPageSizeCached();
+
+    uptr n = region->num_freed_chunks;
+    if (n * chunk_size < page_size)
+      return;  // No chance to release anything.
+    if ((region->n_freed - region->rtoi.n_freed_at_last_release) * chunk_size <
+        page_size) {
+      return;  // Nothing new to release.
+    }
+
+    s32 interval_ms = ReleaseToOSIntervalMs();
+    if (interval_ms < 0)
+      return;
+
+    u64 now_ns = NanoTime();
+    if (region->rtoi.last_release_at_ns + interval_ms * 1000000ULL > now_ns)
+      return;  // Memory was returned recently.
+    region->rtoi.last_release_at_ns = now_ns;
+
+    uptr region_beg = GetRegionBeginBySizeClass(class_id);
+    CompactPtrT *free_array = GetFreeArray(region_beg);
+    SortArray(free_array, n);
+
+    const uptr scaled_chunk_size = chunk_size >> kCompactPtrScale;
+    const uptr kScaledGranularity = page_size >> kCompactPtrScale;
+
+    uptr range_beg = free_array[0];
+    uptr prev = free_array[0];
+    for (uptr i = 1; i < n; i++) {
+      uptr chunk = free_array[i];
+      CHECK_GT(chunk, prev);
+      if (chunk - prev != scaled_chunk_size) {
+        CHECK_GT(chunk - prev, scaled_chunk_size);
+        if (prev + scaled_chunk_size - range_beg >= kScaledGranularity) {
+          MaybeReleaseChunkRange(region_beg, chunk_size, range_beg, prev);
+          region->rtoi.n_freed_at_last_release = region->n_freed;
+          region->rtoi.num_releases++;
+        }
+        range_beg = chunk;
+      }
+      prev = chunk;
+    }
+  }
+};
+
+