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[kutil] Calculate block-size order with clz

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Previously we were using a less efficient loop method of finding the
appropriate block size order, now we use __builtin_clz, which should use
the CPU's clz instruction if it's available.
This commit is contained in:
Justin C. Miller
2020-07-30 19:54:25 -07:00
parent 73221dfe34
commit 94c1f0d3fc
1 changed files with 3 additions and 2 deletions
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5
src/libraries/kutil/heap_allocator.cpp
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@@ -74,9 +74,10 @@ heap_allocator::allocate(size_t length)
{ {
size_t total = length + sizeof(mem_header); size_t total = length + sizeof(mem_header);
unsigned order = min_order; if (length == 0)
while (total > (1 << order)) order++; return nullptr;
unsigned order = 64 - __builtin_clz(length);
kassert(order <= max_order, "Tried to allocate a block bigger than max_order"); kassert(order <= max_order, "Tried to allocate a block bigger than max_order");
if (order > max_order) if (order > max_order)
return nullptr; return nullptr;