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Promote 16-bit allocated counts to unsigned before absl::bit_width in CentralFreeList. #722

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Promote 16-bit allocated counts to unsigned before absl::bit_width in CentralFreeList. #722

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20 changes: 19 additions & 1 deletion tcmalloc/central_freelist.h
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Original file line number Diff line number Diff line change
Expand Up @@ -467,7 +467,12 @@ inline Span* CentralFreeList<Forwarder>::ReleaseToSpans(

const uint8_t prev_index = span->nonempty_index();
const uint16_t prev_allocated = span->Allocated();
#ifndef TCMALLOC_INTERNAL_LEGACY_LOCKING
const uint8_t prev_bitwidth =
absl::bit_width(static_cast<unsigned>(prev_allocated));
#else
const uint8_t prev_bitwidth = absl::bit_width(prev_allocated);
#endif
if (ABSL_PREDICT_FALSE(
!span->FreelistPushBatch(batch, object_size, size_reciprocal))) {
// Update the histogram as the span is full and will be removed from the
Expand All @@ -483,7 +488,12 @@ inline Span* CentralFreeList<Forwarder>::ReleaseToSpans(
// utilization to the histogram after we release objects to the span.
uint16_t cur_allocated = prev_allocated - batch.size();
TC_ASSERT_EQ(cur_allocated, span->Allocated());
#ifndef TCMALLOC_INTERNAL_LEGACY_LOCKING
const uint8_t cur_bitwidth =
absl::bit_width(static_cast<unsigned>(cur_allocated));
#else
const uint8_t cur_bitwidth = absl::bit_width(cur_allocated);
#endif
if (cur_bitwidth != prev_bitwidth) {
RecordSpanUtil(prev_bitwidth, /*increase=*/false);
RecordSpanUtil(cur_bitwidth, /*increase=*/true);
Expand Down Expand Up @@ -714,8 +724,11 @@ inline int CentralFreeList<Forwarder>::RemoveRange(absl::Span<void*> batch) {
const uint16_t prev_allocated = span->Allocated();
#ifndef TCMALLOC_INTERNAL_LEGACY_LOCKING
ASSUME(prev_allocated > 0);
#endif
const uint8_t prev_bitwidth =
absl::bit_width(static_cast<unsigned>(prev_allocated));
#else
const uint8_t prev_bitwidth = absl::bit_width(prev_allocated);
#endif
TC_ASSERT_EQ(prev_index, span->nonempty_index());
#ifdef TCMALLOC_INTERNAL_LEGACY_LOCKING
// Clobber prev_index to trigger reload, restoring previous behavior.
Expand All @@ -737,7 +750,12 @@ inline int CentralFreeList<Forwarder>::RemoveRange(absl::Span<void*> batch) {
// add it again once we pop the objects.
const uint16_t cur_allocated = prev_allocated + here;
TC_ASSERT_EQ(cur_allocated, span->Allocated());
#ifndef TCMALLOC_INTERNAL_LEGACY_LOCKING
const uint8_t cur_bitwidth =
absl::bit_width(static_cast<unsigned>(cur_allocated));
#else
const uint8_t cur_bitwidth = absl::bit_width(cur_allocated);
#endif
if (cur_bitwidth != prev_bitwidth) {
RecordSpanUtil(prev_bitwidth, /*increase=*/false);
RecordSpanUtil(cur_bitwidth, /*increase=*/true);
Expand Down
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