andrew
6fed133212
Move SIMD operations on potentially-indeterminate Node16::index bytes into file-level assembly, where loading and operating on indeterminate values is well-defined (unlike C++). Restructure scalar fallback loops to iterate [0, numChildren) instead of [0, kMaxNodes). Fix TrivialSpan construction from indeterminate pointers in check::Job::init and insertPointWritesOrSorted to only construct when end.len > 0. Add MSan toolchain to the debug CI build to catch these issues going forward.
25 lines
903 B
C++
25 lines
903 B
C++
#pragma once
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#include <cstdint>
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#if defined(__x86_64__) && !defined(USE_SIMD_FALLBACK)
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// SIMD operations on potentially-indeterminate Node16::index[16] bytes.
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// Implemented in file-level assembly (simd_x86_64.S) because loading and
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// operating on indeterminate values is UB in C++ but well-defined in
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// assembly. The caller must mask the returned bitfield to
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// [0, numChildren) before using it.
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//
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// Each function returns a 16-bit bitmask in the low 16 bits of a uint32_t
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// (upper 16 bits are zero). Bit i is set iff the condition holds at index i.
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extern "C" {
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// Returns bit i set iff idx[i] == key
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uint32_t find_eq_16(const uint8_t idx[16], uint8_t key);
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// Returns bit i set iff idx[i] >= child
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uint32_t find_ge_16(const uint8_t idx[16], uint8_t child);
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// Returns bit i set iff begin <= idx[i] < end
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uint32_t mask_in_range_16(const uint8_t idx[16], uint8_t begin, uint8_t end);
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}
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#endif |