Index: lib/sanitizer_common/sanitizer_allocator_primary32.h
===================================================================
--- lib/sanitizer_common/sanitizer_allocator_primary32.h
+++ lib/sanitizer_common/sanitizer_allocator_primary32.h
@@ -118,7 +118,6 @@
   }
 
   void *MapWithCallback(uptr size) {
-    size = RoundUpTo(size, GetPageSizeCached());
     void *res = MmapOrDie(size, "SizeClassAllocator32");
     MapUnmapCallback().OnMap((uptr)res, size);
     return res;
@@ -285,7 +284,7 @@
       return 0;
     MapUnmapCallback().OnMap(res, kRegionSize);
     stat->Add(AllocatorStatMapped, kRegionSize);
-    CHECK_EQ(0U, (res & (kRegionSize - 1)));
+    CHECK(IsAligned(res, kRegionSize));
     possible_regions.set(ComputeRegionId(res), static_cast<u8>(class_id));
     return res;
   }
@@ -303,17 +302,17 @@
       return false;
     uptr n_chunks = kRegionSize / (size + kMetadataSize);
     uptr max_count = TransferBatch::MaxCached(class_id);
+    CHECK_GT(max_count, 0);
     TransferBatch *b = nullptr;
     for (uptr i = reg; i < reg + n_chunks * size; i += size) {
       if (!b) {
         b = c->CreateBatch(class_id, this, (TransferBatch*)i);
-        if (!b)
+        if (UNLIKELY(!b))
           return false;
         b->Clear();
       }
       b->Add((void*)i);
       if (b->Count() == max_count) {
-        CHECK_GT(b->Count(), 0);
         sci->free_list.push_back(b);
         b = nullptr;
       }
Index: lib/sanitizer_common/sanitizer_allocator_primary64.h
===================================================================
--- lib/sanitizer_common/sanitizer_allocator_primary64.h
+++ lib/sanitizer_common/sanitizer_allocator_primary64.h
@@ -389,7 +389,7 @@
 
   bool MapWithCallback(uptr beg, uptr size) {
     uptr mapped = reinterpret_cast<uptr>(MmapFixedOrDieOnFatalError(beg, size));
-    if (!mapped)
+    if (UNLIKELY(!mapped))
       return false;
     CHECK_EQ(beg, mapped);
     MapUnmapCallback().OnMap(beg, size);
Index: lib/sanitizer_common/sanitizer_posix.cc
===================================================================
--- lib/sanitizer_common/sanitizer_posix.cc
+++ lib/sanitizer_common/sanitizer_posix.cc
@@ -129,7 +129,7 @@
                            PROT_READ | PROT_WRITE,
                            MAP_PRIVATE | MAP_ANON, -1, 0);
   int reserrno;
-  if (internal_iserror(res, &reserrno))
+  if (UNLIKELY(internal_iserror(res, &reserrno)))
     ReportMmapFailureAndDie(size, mem_type, "allocate", reserrno, raw_report);
   IncreaseTotalMmap(size);
   return (void *)res;
@@ -138,7 +138,7 @@
 void UnmapOrDie(void *addr, uptr size) {
   if (!addr || !size) return;
   uptr res = internal_munmap(addr, size);
-  if (internal_iserror(res)) {
+  if (UNLIKELY(internal_iserror(res))) {
     Report("ERROR: %s failed to deallocate 0x%zx (%zd) bytes at address %p\n",
            SanitizerToolName, size, size, addr);
     CHECK("unable to unmap" && 0);
@@ -152,7 +152,7 @@
                            PROT_READ | PROT_WRITE,
                            MAP_PRIVATE | MAP_ANON, -1, 0);
   int reserrno;
-  if (internal_iserror(res, &reserrno)) {
+  if (UNLIKELY(internal_iserror(res, &reserrno))) {
     if (reserrno == ENOMEM)
       return nullptr;
     ReportMmapFailureAndDie(size, mem_type, "allocate", reserrno);
@@ -170,15 +170,15 @@
   CHECK(IsPowerOfTwo(alignment));
   uptr map_size = size + alignment;
   uptr map_res = (uptr)MmapOrDieOnFatalError(map_size, mem_type);
-  if (!map_res)
+  if (UNLIKELY(!map_res))
     return nullptr;
   uptr map_end = map_res + map_size;
   uptr res = map_res;
-  if (res & (alignment - 1))  // Not aligned.
-    res = (map_res + alignment) & ~(alignment - 1);
-  uptr end = res + size;
-  if (res != map_res)
+  if (!IsAligned(res, alignment)) {
+    res = (map_res + alignment - 1) & ~(alignment - 1);
     UnmapOrDie((void*)map_res, res - map_res);
+  }
+  uptr end = res + size;
   if (end != map_end)
     UnmapOrDie((void*)end, map_end - end);
   return (void*)res;
@@ -192,7 +192,7 @@
                          MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
                          -1, 0);
   int reserrno;
-  if (internal_iserror(p, &reserrno))
+  if (UNLIKELY(internal_iserror(p, &reserrno)))
     ReportMmapFailureAndDie(size, mem_type, "allocate noreserve", reserrno);
   IncreaseTotalMmap(size);
   return (void *)p;
@@ -206,10 +206,10 @@
       MAP_PRIVATE | MAP_ANON | MAP_FIXED,
       -1, 0);
   int reserrno;
-  if (internal_iserror(p, &reserrno)) {
+  if (UNLIKELY(internal_iserror(p, &reserrno))) {
     if (tolerate_enomem && reserrno == ENOMEM)
       return nullptr;
-    char mem_type[30];
+    char mem_type[40];
     internal_snprintf(mem_type, sizeof(mem_type), "memory at address 0x%zx",
                       fixed_addr);
     ReportMmapFailureAndDie(size, mem_type, "allocate", reserrno);