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Cold part of make_space() code moved to reallocate member function. (#4130) 

Change makes make_space() code much friendlier for the compiler to inline which makes significant (measurable) performance improvements.
This commit is contained in:
Mateusz Pusz 2017-01-09 19:10:11 +01:00 committed by Wouter van Oortmerssen
parent 2c4dce5ba7
commit ab7949dc16
1 changed files with 15 additions and 11 deletions
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26
include/flatbuffers/flatbuffers.h
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@ -539,17 +539,7 @@ class vector_downward {
uint8_t *make_space(size_t len) { uint8_t *make_space(size_t len) {
if (len > static_cast<size_t>(cur_ - buf_)) { if (len > static_cast<size_t>(cur_ - buf_)) {
auto old_size = size(); reallocate(len);
auto largest_align = AlignOf<largest_scalar_t>();
reserved_ += (std::max)(len, growth_policy(reserved_));
// Round up to avoid undefined behavior from unaligned loads and stores.
reserved_ = (reserved_ + (largest_align - 1)) & ~(largest_align - 1);
auto new_buf = allocator_.allocate(reserved_);
auto new_cur = new_buf + reserved_ - old_size;
memcpy(new_cur, cur_, old_size);
cur_ = new_cur;
allocator_.deallocate(buf_);
buf_ = new_buf;
} }
cur_ -= len; cur_ -= len;
// Beyond this, signed offsets may not have enough range: // Beyond this, signed offsets may not have enough range:
@ -593,6 +583,20 @@ class vector_downward {
uint8_t *buf_; uint8_t *buf_;
uint8_t *cur_; // Points at location between empty (below) and used (above). uint8_t *cur_; // Points at location between empty (below) and used (above).
const simple_allocator &allocator_; const simple_allocator &allocator_;
void reallocate(size_t len) {
auto old_size = size();
auto largest_align = AlignOf<largest_scalar_t>();
reserved_ += (std::max)(len, growth_policy(reserved_));
// Round up to avoid undefined behavior from unaligned loads and stores.
reserved_ = (reserved_ + (largest_align - 1)) & ~(largest_align - 1);
auto new_buf = allocator_.allocate(reserved_);
auto new_cur = new_buf + reserved_ - old_size;
memcpy(new_cur, cur_, old_size);
cur_ = new_cur;
allocator_.deallocate(buf_);
buf_ = new_buf;
}
}; };
// Converts a Field ID to a virtual table offset. // Converts a Field ID to a virtual table offset.