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Hoist span start address calculation out of BitmapPopBatch visitor loop. #702

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Hoist span start address calculation out of BitmapPopBatch visitor loop. #702

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17 changes: 3 additions & 14 deletions tcmalloc/span.h
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Original file line number Diff line number Diff line change
Expand Up @@ -254,10 +254,6 @@ class ABSL_CACHELINE_ALIGNED Span final : public SpanList::Elem {
[[nodiscard]] ObjIdx BitmapPtrToIdx(void* ptr, size_t size,
uint32_t reciprocal) const;
[[nodiscard]] void* BitmapIdxToPtr(ObjIdx idx, size_t size) const;
#ifndef TCMALLOC_INTERNAL_LEGACY_LOCKING
[[nodiscard]] void* BitmapIdxToPtr(ObjIdx idx, size_t size,
uintptr_t start) const;
#endif

#ifdef TCMALLOC_INTERNAL_LEGACY_LOCKING
static constexpr size_t kNonemptyIndexBits = 5;
Expand Down Expand Up @@ -610,15 +606,9 @@ inline Span::ObjIdx Span::OffsetToIdx(uintptr_t offset, uint32_t reciprocal) {
}

#ifndef TCMALLOC_INTERNAL_LEGACY_LOCKING
inline void* Span::BitmapIdxToPtr(ObjIdx idx, size_t size,
uintptr_t start) const {
TC_ASSERT_EQ(start, first_page().start_uintptr());
uintptr_t off = start + idx * size;
return reinterpret_cast<void*>(off);
}

inline void* Span::BitmapIdxToPtr(ObjIdx idx, size_t size) const {
return BitmapIdxToPtr(idx, size, first_page().start_uintptr());
uintptr_t off = first_page().start_uintptr() + idx * size;
return reinterpret_cast<void*>(off);
}
#endif

Expand Down Expand Up @@ -780,10 +770,9 @@ inline size_t Span::BitmapPopBatch(absl::Span<void*> batch,
return count;
#else
void** ptrs = batch.data();
const uintptr_t span_start = first_page().start_uintptr();
size_t popped = bitmap_.PopBatch(
[&](size_t offset) {
*ptrs++ = BitmapIdxToPtr(static_cast<ObjIdx>(offset), size, span_start);
*ptrs++ = BitmapIdxToPtr(static_cast<ObjIdx>(offset), size);
},
batch.size());
allocated_.store(allocated_.load(std::memory_order_relaxed) + popped,
Expand Down
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