[sanitizer] Size class map & local cache improvements

Summary:
- Reland rL324263, this time allowing for a compile-time decision as to whether
  or not use the 32-bit division. A single test is using a class map covering
  a maximum size greater than 4GB, this can be checked via the template
  parameters, and allows SizeClassAllocator64PopulateFreeListOOM to pass;
- `MaxCachedHint` is always called on a class id for which we have already
  computed the size, but we still recompute `Size(class_id)`. Change the
  prototype of the function to work on sizes instead of class ids. This also
  allows us to get rid of the `kBatchClassID` special case. Update the callers
  accordingly;
- `InitCache` and `Drain` will start iterating at index 1: index 0 contents are
  unused and can safely be left to be 0. Plus we do not pay the cost of going
  through an `UNLIKELY` in `MaxCachedHint`, and touching memory that is
  otherwise not used;
- `const` some variables in the areas modified;
- Remove an spurious extra line at the end of a file.

Reviewers: alekseyshl, tl0gic, dberris

Reviewed By: alekseyshl, dberris

Subscribers: dberris, kubamracek, delcypher, llvm-commits, #sanitizers

Differential Revision: https://reviews.llvm.org/D43088

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@324906 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 15 deletions

diff --git a/lib/sanitizer_common/sanitizer_allocator_primary32.h b/lib/sanitizer_common/sanitizer_allocator_primary32.h
index 6c682aff6..4e87bd7fe 100644
--- a/lib/sanitizer_common/sanitizer_allocator_primary32.h
+++ b/lib/sanitizer_common/sanitizer_allocator_primary32.h
@@ -84,8 +84,8 @@ class SizeClassAllocator32 {
     static uptr AllocationSizeRequiredForNElements(uptr n) {
       return sizeof(uptr) * 2 + sizeof(void *) * n;
     }
-    static uptr MaxCached(uptr class_id) {
-      return Min(kMaxNumCached, SizeClassMap::MaxCachedHint(class_id));
+    static uptr MaxCached(uptr size) {
+      return Min(kMaxNumCached, SizeClassMap::MaxCachedHint(size));
     }
 
     TransferBatch *next;
@@ -156,10 +156,11 @@ class SizeClassAllocator32 {
     CHECK_LT(class_id, kNumClasses);
     SizeClassInfo *sci = GetSizeClassInfo(class_id);
     SpinMutexLock l(&sci->mutex);
-    if (sci->free_list.empty() &&
-        UNLIKELY(!PopulateFreeList(stat, c, sci, class_id)))
-      return nullptr;
-    CHECK(!sci->free_list.empty());
+    if (sci->free_list.empty()) {
+      if (UNLIKELY(!PopulateFreeList(stat, c, sci, class_id)))
+        return nullptr;
+      DCHECK(!sci->free_list.empty());
+    }
     TransferBatch *b = sci->free_list.front();
     sci->free_list.pop_front();
     return b;
@@ -275,7 +276,7 @@ class SizeClassAllocator32 {
   COMPILER_CHECK(sizeof(SizeClassInfo) == kCacheLineSize);
 
   uptr ComputeRegionId(uptr mem) {
-    uptr res = mem >> kRegionSizeLog;
+    const uptr res = mem >> kRegionSizeLog;
     CHECK_LT(res, kNumPossibleRegions);
     return res;
   }
@@ -329,22 +330,22 @@ class SizeClassAllocator32 {
 
   bool PopulateFreeList(AllocatorStats *stat, AllocatorCache *c,
                         SizeClassInfo *sci, uptr class_id) {
-    uptr size = ClassIdToSize(class_id);
-    uptr reg = AllocateRegion(stat, class_id);
-    if (UNLIKELY(!reg))
+    const uptr region = AllocateRegion(stat, class_id);
+    if (UNLIKELY(!region))
       return false;
     if (kRandomShuffleChunks)
       if (UNLIKELY(sci->rand_state == 0))
         // The random state is initialized from ASLR (PIE) and time.
         sci->rand_state = reinterpret_cast<uptr>(sci) ^ NanoTime();
-    uptr n_chunks = kRegionSize / (size + kMetadataSize);
-    uptr max_count = TransferBatch::MaxCached(class_id);
-    CHECK_GT(max_count, 0);
+    const uptr size = ClassIdToSize(class_id);
+    const uptr n_chunks = kRegionSize / (size + kMetadataSize);
+    const uptr max_count = TransferBatch::MaxCached(size);
+    DCHECK_GT(max_count, 0);
     TransferBatch *b = nullptr;
-    const uptr kShuffleArraySize = 48;
+    constexpr uptr kShuffleArraySize = 48;
     uptr shuffle_array[kShuffleArraySize];
     uptr count = 0;
-    for (uptr i = reg; i < reg + n_chunks * size; i += size) {
+    for (uptr i = region; i < region + n_chunks * size; i += size) {
       shuffle_array[count++] = i;
       if (count == kShuffleArraySize) {
         if (UNLIKELY(!PopulateBatches(c, sci, class_id, &b, max_count,