diff --git a/libc/src/string/memory_utils/memcmp_implementations.h b/libc/src/string/memory_utils/memcmp_implementations.h --- a/libc/src/string/memory_utils/memcmp_implementations.h +++ b/libc/src/string/memory_utils/memcmp_implementations.h @@ -26,21 +26,86 @@ namespace __llvm_libc { [[maybe_unused]] LIBC_INLINE MemcmpReturnType -inline_memcmp_embedded_tiny(CPtr p1, CPtr p2, size_t count) { +inline_memcmp_byte_per_byte(CPtr p1, CPtr p2, size_t offset, size_t count) { LIBC_LOOP_NOUNROLL - for (size_t offset = 0; offset < count; ++offset) + for (; offset < count; ++offset) if (auto value = generic::Memcmp<1>::block(p1 + offset, p2 + offset)) return value; return MemcmpReturnType::ZERO(); } +[[maybe_unused]] LIBC_INLINE MemcmpReturnType +inline_memcmp_aligned_access_64bit(CPtr p1, CPtr p2, size_t count) { + constexpr size_t kAlign = sizeof(uint64_t); + if (count <= 2 * kAlign) + return inline_memcmp_byte_per_byte(p1, p2, 0, count); + size_t bytes_to_p1_align = distance_to_align_up(p1); + if (auto value = inline_memcmp_byte_per_byte(p1, p2, 0, bytes_to_p1_align)) + return value; + size_t offset = bytes_to_p1_align; + size_t p2_alignment = distance_to_align_down(p2 + offset); + for (; offset < count - kAlign; offset += kAlign) { + uint64_t b; + if (p2_alignment == 0) + b = load64_aligned(p2, offset); + else if (p2_alignment == 4) + b = load64_aligned(p2, offset); + else if (p2_alignment == 2) + b = load64_aligned(p2, offset); + else + b = load64_aligned( + p2, offset); + uint64_t a = load64_aligned(p1, offset); + if (a != b) { + // TODO use cmp_neq_uint64_t from D148717 once it's submitted. + return Endian::to_big_endian(a) < Endian::to_big_endian(b) ? -1 : 1; + } + } + return inline_memcmp_byte_per_byte(p1, p2, offset, count); +} + +[[maybe_unused]] LIBC_INLINE MemcmpReturnType +inline_memcmp_aligned_access_32bit(CPtr p1, CPtr p2, size_t count) { + constexpr size_t kAlign = sizeof(uint32_t); + if (count <= 2 * kAlign) + return inline_memcmp_byte_per_byte(p1, p2, 0, count); + size_t bytes_to_p1_align = distance_to_align_up(p1); + if (auto value = inline_memcmp_byte_per_byte(p1, p2, 0, bytes_to_p1_align)) + return value; + size_t offset = bytes_to_p1_align; + size_t p2_alignment = distance_to_align_down(p2 + offset); + for (; offset < count - kAlign; offset += kAlign) { + uint32_t b; + if (p2_alignment == 0) + b = load32_aligned(p2, offset); + else if (p2_alignment == 2) + b = load32_aligned(p2, offset); + else + b = load32_aligned(p2, offset); + uint32_t a = load32_aligned(p1, offset); + if (a != b) { + // TODO use cmp_uint32_t from D148717 once it's submitted. + // We perform the difference as an uint64_t. + const int64_t diff = static_cast(Endian::to_big_endian(a)) - + static_cast(Endian::to_big_endian(b)); + // And reduce the uint64_t into an uint32_t. + return static_cast((diff >> 1) | (diff & 0xFFFF)); + } + } + return inline_memcmp_byte_per_byte(p1, p2, offset, count); +} + LIBC_INLINE MemcmpReturnType inline_memcmp(CPtr p1, CPtr p2, size_t count) { #if defined(LIBC_TARGET_ARCH_IS_X86) return inline_memcmp_x86(p1, p2, count); #elif defined(LIBC_TARGET_ARCH_IS_AARCH64) return inline_memcmp_aarch64(p1, p2, count); +#elif defined(LIBC_TARGET_ARCH_IS_RISCV64) + return inline_memcmp_aligned_access_64bit(p1, p2, count); +#elif defined(LIBC_TARGET_ARCH_IS_RISCV32) + return inline_memcmp_aligned_access_32bit(p1, p2, count); #else - return inline_memcmp_embedded_tiny(p1, p2, count); + return inline_memcmp_byte_per_byte(p1, p2, 0, count); #endif }