From 0151c0ce4d4c549d5ce096cb21b7a96688018df2 Mon Sep 17 00:00:00 2001 From: Roland Conybeare Date: Tue, 6 Jan 2026 00:11:29 -0500 Subject: [PATCH] xo-arena: annex AllocHeaderConfig.hpp from xo-alloc2 --- include/xo/alloc2/AllocHeaderConfig.hpp | 168 ------------------------ 1 file changed, 168 deletions(-) delete mode 100644 include/xo/alloc2/AllocHeaderConfig.hpp diff --git a/include/xo/alloc2/AllocHeaderConfig.hpp b/include/xo/alloc2/AllocHeaderConfig.hpp deleted file mode 100644 index ab56088..0000000 --- a/include/xo/alloc2/AllocHeaderConfig.hpp +++ /dev/null @@ -1,168 +0,0 @@ -/** @file AllocHeaderConfig.hpp -* - * @author Roland Conybeare, Dec 2025 - **/ - -#pragma once - -#include "AllocHeader.hpp" -#include "padding.hpp" -#include - -namespace xo { - namespace mm { - /* - * Each allocation is preceded by a 64-bit header. - * Header is split into 3 configurable-width bit fields, - * labelled (from hi to lo bit order) {tseq, age, size}. - * - * 1. tseq. seq# identifying object types; needed for gc. - * 2. gen. age cohort; increases when alloc survives gc. - * 3. size. alloc size. - * - * Arena allocator only uses size. - * X1 collector uses {tseq, gen, size} - * - * alloc header - * - * TTTTTTTTTTTTGGGGGZZZZZZZZZZZZ - * < tseq >< size > - * - * masking - * - * ..432107654321076543210 bit - * - * > < .gen_bits - * 0..............01111111 gen_mask_unshifted - * 0..011111110..........0 gen_mask_shifted - * > < gen_shift - */ - struct AllocHeaderConfig { - using repr_type = AllocHeader; - using span_type = std::pair; - - AllocHeaderConfig() = default; - AllocHeaderConfig(std::uint32_t gz, - std::uint8_t guard_byte, - std::uint8_t t, - std::uint8_t a, - std::uint8_t z) noexcept : guard_z_{gz}, - guard_byte_{guard_byte}, - tseq_bits_{t}, - age_bits_{a}, - size_bits_{z} {} - - /** create header tuple (@p t, @p a, @p z) - * with typeseq @p t, age @p a, size @p z - **/ - std::uint64_t mkheader(std::uint64_t t, - std::uint64_t a, - std::uint64_t z) const noexcept { - uint64_t tseq_bits = (t << (age_bits_ + size_bits_)) & tseq_mask(); - uint64_t age_bits = (a << size_bits_) & age_mask(); - uint64_t size_bits = z & size_mask();; - - return (tseq_bits | age_bits | size_bits); - } - - std::uint64_t tseq_mask() const noexcept { - // e.g. - // FF FF FF 00 00 00 00 00 - // with tseq_bits=24, age_bits=8, size_bits=32 - // - return ((1ul << tseq_bits_) - 1) << (age_bits_ + size_bits_); - } - - std::uint64_t age_mask() const noexcept { - // e.g. - // 00 00 00 FF 00 00 00 00 - // with age_bits=8, size_bits=32 - // - return ((1ul << age_bits_) - 1) << size_bits_; - } - - std::uint64_t size_mask() const noexcept { - // e.g. - // 00 00 00 00 FF FF FF FF - // with size_bits=32 - // - return ((1ul << size_bits_) - 1); - } - - /** extract type id from alloc header @p hdr **/ - std::uint32_t tseq(repr_type hdr) const noexcept { - // e.g. - // 0x302010 - // for header - // 30 20 10 -- -- -- -- -- - // with tseq_bits_ = 24, age_bits_ + size_bits_ = 40 - // - return (hdr.repr_ & tseq_mask()) >> (age_bits_ + size_bits_); - } - - /** extract age from alloc header @p hdr **/ - std::uint32_t age(repr_type hdr) const noexcept { - // e.g. - // 0xa0 - // for header - // -- -- -- a0 -- -- -- -- - // with age_bits_ = 8, size_bits_ = 32 - // - return (hdr.repr_ & age_mask()) >> size_bits_; - } - - /** extract size from alloc header @p hdr **/ - std::size_t size(repr_type hdr) const noexcept { - // e.g. - // 0x01020300 - // for header - // -- -- -- -- 01 02 03 00 - // with size_bits_ = 32 - // - return (hdr.repr_ & size_mask()); - } - - /** extract padded size from alloc header @p hdr **/ - std::size_t size_with_padding(repr_type hdr) const noexcept { - return padding::with_padding(this->size(hdr)); - } - - /** true iff sentinel tseq, flagging a forwarding pointer **/ - bool is_forwarding_tseq(repr_type hdr) const noexcept { - // e.g. - // 0xFFFFFF - // i.e. header - // FF FF FF -- -- -- -- -- - // with tseq_bits_ = 24, age_bits + size_bits_ = 40 - // - return (hdr.repr_ & tseq_mask()) == tseq_mask(); - } - - bool is_size_enabled() const noexcept { return size_bits_ > 0; } - - /** construct alloc header for a forwarding object **/ - AllocHeader mark_forwarding_tseq(AllocHeader hdr) const noexcept { - return AllocHeader((hdr.repr_ & ~tseq_mask()) | tseq_mask()); - } - - /** if non-zero, allocate extra space between allocs, and fill - * with fixed test-pattern contents. Allows for simple - * runtime arena sanitizing checks. - * Will be rounded up to multiple of @ref padding::c_alloc_alignment - **/ - std::uint32_t guard_z_ = 0; - /** if guard_z_ > 0, write at least that many copies - * of this guard byte following each complete allocation - **/ - std::uint8_t guard_byte_ = 0xfd; - /** number of bits for tseq **/ - std::uint8_t tseq_bits_ = 24; - /** number of bits for age **/ - std::uint8_t age_bits_ = 8; - /** number of bits for size **/ - std::uint8_t size_bits_ = 32; - }; - } /*namespace mm*/ -} /*namespace xo*/ - -/* end AllocHeaderConfig.hpp */