StackSpace: use std::aligned_alloc() #907
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chfast
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lib/evmone/execution_state.hpp
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| /// The storage allocated for maximum possible number of items. | ||
| /// Items are aligned to 256 bits for better packing in cache lines. | ||
| std::unique_ptr<uint256, Deleter> m_stack_space{allocate()}; |
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I'd put the allocate() call in a constructor.
| /// Returns the pointer to the "bottom", i.e. below the stack space. | ||
| [[nodiscard, clang::no_sanitize("bounds")]] uint256* bottom() noexcept | ||
| { | ||
| return m_stack_space - 1; | ||
| return m_stack_space.get() - 1; |
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Why does it need to go outside the memory bounds?
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It is the convention we use currently: we keep the pointer to the top element on the stack. Therefore its starting position (stack empty) is one element below the allocated memory.
Use `std::aligned_alloc()` (and `_aligned_malloc()` on MSVC) to allocate the memory for EVM stack. This removes unnecessary initialization of the memory to zero (closes #403). The memory alignment is set to 32 bytes (as previously) but allows transitioning to "over-aligned" allocation for additional optimization (see #781).
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| public: | ||
| /// The maximum number of EVM stack items. | ||
| static constexpr auto limit = 1024; | ||
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| StackSpace() noexcept : m_stack_space{allocate()} {} |
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I wonder if
std::unique_ptr<uint256[]>(new (std::align_val_t(sizeof(uint256)) uint256[limit]);achieves the same.
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It looks like, however this specifies the array element alignment, so I wonder what happens if you specify 64 for uint256. I plan to align the allocation to 2048*32.
Use
std::aligned_alloc()(and_aligned_malloc()on MSVC) to allocate the memory for EVM stack.This removes unnecessary initialization of the memory to zero (closes #403).
The memory alignment is set to 32 bytes (as previously) but allows transitioning to "over-aligned" allocation for additional optimization
(see #781).