--- /dev/null
+/* memcmp/wmemcmp optimized with 256-bit EVEX instructions.
+ Copyright (C) 2021 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#if IS_IN (libc)
+
+/* memcmp/wmemcmp is implemented as:
+ 1. For size from 2 to 7 bytes, load as big endian with movbe and bswap
+ to avoid branches.
+ 2. Use overlapping compare to avoid branch.
+ 3. Use vector compare when size >= 4 bytes for memcmp or size >= 8
+ bytes for wmemcmp.
+ 4. If size is 8 * VEC_SIZE or less, unroll the loop.
+ 5. Compare 4 * VEC_SIZE at a time with the aligned first memory
+ area.
+ 6. Use 2 vector compares when size is 2 * VEC_SIZE or less.
+ 7. Use 4 vector compares when size is 4 * VEC_SIZE or less.
+ 8. Use 8 vector compares when size is 8 * VEC_SIZE or less. */
+
+# include <sysdep.h>
+
+# ifndef MEMCMP
+# define MEMCMP __memcmp_evex_movbe
+# endif
+
+# define VMOVU vmovdqu64
+
+# ifdef USE_AS_WMEMCMP
+# define VPCMPEQ vpcmpeqd
+# else
+# define VPCMPEQ vpcmpeqb
+# endif
+
+# define XMM1 xmm17
+# define XMM2 xmm18
+# define YMM1 ymm17
+# define YMM2 ymm18
+# define YMM3 ymm19
+# define YMM4 ymm20
+# define YMM5 ymm21
+# define YMM6 ymm22
+
+# define VEC_SIZE 32
+# ifdef USE_AS_WMEMCMP
+# define VEC_MASK 0xff
+# define XMM_MASK 0xf
+# else
+# define VEC_MASK 0xffffffff
+# define XMM_MASK 0xffff
+# endif
+
+/* Warning!
+ wmemcmp has to use SIGNED comparison for elements.
+ memcmp has to use UNSIGNED comparison for elemnts.
+*/
+
+ .section .text.evex,"ax",@progbits
+ENTRY (MEMCMP)
+# ifdef USE_AS_WMEMCMP
+ shl $2, %RDX_LP
+# elif defined __ILP32__
+ /* Clear the upper 32 bits. */
+ movl %edx, %edx
+# endif
+ cmp $VEC_SIZE, %RDX_LP
+ jb L(less_vec)
+
+ /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k1
+ kmovd %k1, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+
+ cmpq $(VEC_SIZE * 2), %rdx
+ jbe L(last_vec)
+
+ /* More than 2 * VEC. */
+ cmpq $(VEC_SIZE * 8), %rdx
+ ja L(more_8x_vec)
+ cmpq $(VEC_SIZE * 4), %rdx
+ jb L(last_4x_vec)
+
+ /* From 4 * VEC to 8 * VEC, inclusively. */
+ VMOVU (%rsi), %YMM1
+ VPCMPEQ (%rdi), %YMM1, %k1
+
+ VMOVU VEC_SIZE(%rsi), %YMM2
+ VPCMPEQ VEC_SIZE(%rdi), %YMM2, %k2
+
+ VMOVU (VEC_SIZE * 2)(%rsi), %YMM3
+ VPCMPEQ (VEC_SIZE * 2)(%rdi), %YMM3, %k3
+
+ VMOVU (VEC_SIZE * 3)(%rsi), %YMM4
+ VPCMPEQ (VEC_SIZE * 3)(%rdi), %YMM4, %k4
+
+ kandd %k1, %k2, %k5
+ kandd %k3, %k4, %k6
+ kandd %k5, %k6, %k6
+
+ kmovd %k6, %eax
+ cmpl $VEC_MASK, %eax
+ jne L(4x_vec_end)
+
+ leaq -(4 * VEC_SIZE)(%rdi, %rdx), %rdi
+ leaq -(4 * VEC_SIZE)(%rsi, %rdx), %rsi
+ VMOVU (%rsi), %YMM1
+ VPCMPEQ (%rdi), %YMM1, %k1
+
+ VMOVU VEC_SIZE(%rsi), %YMM2
+ VPCMPEQ VEC_SIZE(%rdi), %YMM2, %k2
+ kandd %k1, %k2, %k5
+
+ VMOVU (VEC_SIZE * 2)(%rsi), %YMM3
+ VPCMPEQ (VEC_SIZE * 2)(%rdi), %YMM3, %k3
+ kandd %k3, %k5, %k5
+
+ VMOVU (VEC_SIZE * 3)(%rsi), %YMM4
+ VPCMPEQ (VEC_SIZE * 3)(%rdi), %YMM4, %k4
+ kandd %k4, %k5, %k5
+
+ kmovd %k5, %eax
+ cmpl $VEC_MASK, %eax
+ jne L(4x_vec_end)
+ xorl %eax, %eax
+ ret
+
+ .p2align 4
+L(last_2x_vec):
+ /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k2
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+
+L(last_vec):
+ /* Use overlapping loads to avoid branches. */
+ leaq -VEC_SIZE(%rdi, %rdx), %rdi
+ leaq -VEC_SIZE(%rsi, %rdx), %rsi
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k2
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+ ret
+
+ .p2align 4
+L(first_vec):
+ /* A byte or int32 is different within 16 or 32 bytes. */
+ tzcntl %eax, %ecx
+# ifdef USE_AS_WMEMCMP
+ xorl %eax, %eax
+ movl (%rdi, %rcx, 4), %edx
+ cmpl (%rsi, %rcx, 4), %edx
+L(wmemcmp_return):
+ setl %al
+ negl %eax
+ orl $1, %eax
+# else
+ movzbl (%rdi, %rcx), %eax
+ movzbl (%rsi, %rcx), %edx
+ sub %edx, %eax
+# endif
+ ret
+
+# ifdef USE_AS_WMEMCMP
+ .p2align 4
+L(4):
+ xorl %eax, %eax
+ movl (%rdi), %edx
+ cmpl (%rsi), %edx
+ jne L(wmemcmp_return)
+ ret
+# else
+ .p2align 4
+L(between_4_7):
+ /* Load as big endian with overlapping movbe to avoid branches. */
+ movbe (%rdi), %eax
+ movbe (%rsi), %ecx
+ shlq $32, %rax
+ shlq $32, %rcx
+ movbe -4(%rdi, %rdx), %edi
+ movbe -4(%rsi, %rdx), %esi
+ orq %rdi, %rax
+ orq %rsi, %rcx
+ subq %rcx, %rax
+ je L(exit)
+ sbbl %eax, %eax
+ orl $1, %eax
+ ret
+
+ .p2align 4
+L(exit):
+ ret
+
+ .p2align 4
+L(between_2_3):
+ /* Load as big endian to avoid branches. */
+ movzwl (%rdi), %eax
+ movzwl (%rsi), %ecx
+ shll $8, %eax
+ shll $8, %ecx
+ bswap %eax
+ bswap %ecx
+ movb -1(%rdi, %rdx), %al
+ movb -1(%rsi, %rdx), %cl
+ /* Subtraction is okay because the upper 8 bits are zero. */
+ subl %ecx, %eax
+ ret
+
+ .p2align 4
+L(1):
+ movzbl (%rdi), %eax
+ movzbl (%rsi), %ecx
+ subl %ecx, %eax
+ ret
+# endif
+
+ .p2align 4
+L(zero):
+ xorl %eax, %eax
+ ret
+
+ .p2align 4
+L(less_vec):
+# ifdef USE_AS_WMEMCMP
+ /* It can only be 0, 4, 8, 12, 16, 20, 24, 28 bytes. */
+ cmpb $4, %dl
+ je L(4)
+ jb L(zero)
+# else
+ cmpb $1, %dl
+ je L(1)
+ jb L(zero)
+ cmpb $4, %dl
+ jb L(between_2_3)
+ cmpb $8, %dl
+ jb L(between_4_7)
+# endif
+ cmpb $16, %dl
+ jae L(between_16_31)
+ /* It is between 8 and 15 bytes. */
+ vmovq (%rdi), %XMM1
+ vmovq (%rsi), %XMM2
+ VPCMPEQ %XMM1, %XMM2, %k2
+ kmovw %k2, %eax
+ subl $XMM_MASK, %eax
+ jnz L(first_vec)
+ /* Use overlapping loads to avoid branches. */
+ leaq -8(%rdi, %rdx), %rdi
+ leaq -8(%rsi, %rdx), %rsi
+ vmovq (%rdi), %XMM1
+ vmovq (%rsi), %XMM2
+ VPCMPEQ %XMM1, %XMM2, %k2
+ kmovw %k2, %eax
+ subl $XMM_MASK, %eax
+ jnz L(first_vec)
+ ret
+
+ .p2align 4
+L(between_16_31):
+ /* From 16 to 31 bytes. No branch when size == 16. */
+ VMOVU (%rsi), %XMM2
+ VPCMPEQ (%rdi), %XMM2, %k2
+ kmovw %k2, %eax
+ subl $XMM_MASK, %eax
+ jnz L(first_vec)
+
+ /* Use overlapping loads to avoid branches. */
+ leaq -16(%rdi, %rdx), %rdi
+ leaq -16(%rsi, %rdx), %rsi
+ VMOVU (%rsi), %XMM2
+ VPCMPEQ (%rdi), %XMM2, %k2
+ kmovw %k2, %eax
+ subl $XMM_MASK, %eax
+ jnz L(first_vec)
+ ret
+
+ .p2align 4
+L(more_8x_vec):
+ /* More than 8 * VEC. Check the first VEC. */
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k2
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+
+ /* Align the first memory area for aligned loads in the loop.
+ Compute how much the first memory area is misaligned. */
+ movq %rdi, %rcx
+ andl $(VEC_SIZE - 1), %ecx
+ /* Get the negative of offset for alignment. */
+ subq $VEC_SIZE, %rcx
+ /* Adjust the second memory area. */
+ subq %rcx, %rsi
+ /* Adjust the first memory area which should be aligned now. */
+ subq %rcx, %rdi
+ /* Adjust length. */
+ addq %rcx, %rdx
+
+L(loop_4x_vec):
+ /* Compare 4 * VEC at a time forward. */
+ VMOVU (%rsi), %YMM1
+ VPCMPEQ (%rdi), %YMM1, %k1
+
+ VMOVU VEC_SIZE(%rsi), %YMM2
+ VPCMPEQ VEC_SIZE(%rdi), %YMM2, %k2
+ kandd %k2, %k1, %k5
+
+ VMOVU (VEC_SIZE * 2)(%rsi), %YMM3
+ VPCMPEQ (VEC_SIZE * 2)(%rdi), %YMM3, %k3
+ kandd %k3, %k5, %k5
+
+ VMOVU (VEC_SIZE * 3)(%rsi), %YMM4
+ VPCMPEQ (VEC_SIZE * 3)(%rdi), %YMM4, %k4
+ kandd %k4, %k5, %k5
+
+ kmovd %k5, %eax
+ cmpl $VEC_MASK, %eax
+ jne L(4x_vec_end)
+
+ addq $(VEC_SIZE * 4), %rdi
+ addq $(VEC_SIZE * 4), %rsi
+
+ subq $(VEC_SIZE * 4), %rdx
+ cmpq $(VEC_SIZE * 4), %rdx
+ jae L(loop_4x_vec)
+
+ /* Less than 4 * VEC. */
+ cmpq $VEC_SIZE, %rdx
+ jbe L(last_vec)
+ cmpq $(VEC_SIZE * 2), %rdx
+ jbe L(last_2x_vec)
+
+L(last_4x_vec):
+ /* From 2 * VEC to 4 * VEC. */
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k2
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+
+ addq $VEC_SIZE, %rdi
+ addq $VEC_SIZE, %rsi
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k2
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+
+ /* Use overlapping loads to avoid branches. */
+ leaq -(3 * VEC_SIZE)(%rdi, %rdx), %rdi
+ leaq -(3 * VEC_SIZE)(%rsi, %rdx), %rsi
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k2
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+
+ addq $VEC_SIZE, %rdi
+ addq $VEC_SIZE, %rsi
+ VMOVU (%rsi), %YMM2
+ VPCMPEQ (%rdi), %YMM2, %k2
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+ ret
+
+ .p2align 4
+L(4x_vec_end):
+ kmovd %k1, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec)
+ kmovd %k2, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec_x1)
+ kmovd %k3, %eax
+ subl $VEC_MASK, %eax
+ jnz L(first_vec_x2)
+ kmovd %k4, %eax
+ subl $VEC_MASK, %eax
+ tzcntl %eax, %ecx
+# ifdef USE_AS_WMEMCMP
+ xorl %eax, %eax
+ movl (VEC_SIZE * 3)(%rdi, %rcx, 4), %edx
+ cmpl (VEC_SIZE * 3)(%rsi, %rcx, 4), %edx
+ jmp L(wmemcmp_return)
+# else
+ movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax
+ movzbl (VEC_SIZE * 3)(%rsi, %rcx), %edx
+ sub %edx, %eax
+# endif
+ ret
+
+ .p2align 4
+L(first_vec_x1):
+ tzcntl %eax, %ecx
+# ifdef USE_AS_WMEMCMP
+ xorl %eax, %eax
+ movl VEC_SIZE(%rdi, %rcx, 4), %edx
+ cmpl VEC_SIZE(%rsi, %rcx, 4), %edx
+ jmp L(wmemcmp_return)
+# else
+ movzbl VEC_SIZE(%rdi, %rcx), %eax
+ movzbl VEC_SIZE(%rsi, %rcx), %edx
+ sub %edx, %eax
+# endif
+ ret
+
+ .p2align 4
+L(first_vec_x2):
+ tzcntl %eax, %ecx
+# ifdef USE_AS_WMEMCMP
+ xorl %eax, %eax
+ movl (VEC_SIZE * 2)(%rdi, %rcx, 4), %edx
+ cmpl (VEC_SIZE * 2)(%rsi, %rcx, 4), %edx
+ jmp L(wmemcmp_return)
+# else
+ movzbl (VEC_SIZE * 2)(%rdi, %rcx), %eax
+ movzbl (VEC_SIZE * 2)(%rsi, %rcx), %edx
+ sub %edx, %eax
+# endif
+ ret
+END (MEMCMP)
+#endif
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