--- /dev/null
+/* Optimized strncmp implementation for PowerPC64/POWER10.
+ Copyright (C) 2025 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/>. */
+
+#include <sysdep.h>
+
+/* Implements the function
+
+ int [r3] strncmp (const char *s1 [r3], const char *s2 [r4], size_t [r5] n)
+
+ The implementation uses unaligned doubleword access to avoid specialized
+ code paths depending of data alignment for first 32 bytes and uses
+ vectorised loops after that. */
+
+#ifndef STRNCMP
+# define STRNCMP strncmp
+#endif
+
+#define COMPARE_16(vreg1,vreg2,offset) \
+ lxv vreg1+32,offset(r3); \
+ lxv vreg2+32,offset(r4); \
+ vcmpnezb. v7,vreg1,vreg2; \
+ bne cr6,L(different); \
+ cmpldi cr7,r5,16; \
+ ble cr7,L(ret0); \
+ addi r5,r5,-16;
+
+#define COMPARE_32(vreg1,vreg2,offset,label1,label2) \
+ lxvp vreg1+32,offset(r3); \
+ lxvp vreg2+32,offset(r4); \
+ vcmpnezb. v7,vreg1+1,vreg2+1; \
+ bne cr6,L(label1); \
+ vcmpnezb. v7,vreg1,vreg2; \
+ bne cr6,L(label2); \
+ cmpldi cr7,r5,32; \
+ ble cr7,L(ret0); \
+ addi r5,r5,-32;
+
+#define TAIL_FIRST_16B(vreg1,vreg2) \
+ vctzlsbb r6,v7; \
+ cmpld cr7,r5,r6; \
+ ble cr7,L(ret0); \
+ vextubrx r5,r6,vreg1; \
+ vextubrx r4,r6,vreg2; \
+ subf r3,r4,r5; \
+ blr;
+
+#define TAIL_SECOND_16B(vreg1,vreg2) \
+ vctzlsbb r6,v7; \
+ addi r0,r6,16; \
+ cmpld cr7,r5,r0; \
+ ble cr7,L(ret0); \
+ vextubrx r5,r6,vreg1; \
+ vextubrx r4,r6,vreg2; \
+ subf r3,r4,r5; \
+ blr;
+
+#define CHECK_N_BYTES(reg1,reg2,len_reg) \
+ sldi r6,len_reg,56; \
+ lxvl 32+v4,reg1,r6; \
+ lxvl 32+v5,reg2,r6; \
+ add reg1,reg1,len_reg; \
+ add reg2,reg2,len_reg; \
+ vcmpnezb v7,v4,v5; \
+ vctzlsbb r6,v7; \
+ cmpld cr7,r6,len_reg; \
+ blt cr7,L(different); \
+ cmpld cr7,r5,len_reg; \
+ ble cr7,L(ret0); \
+ sub r5,r5,len_reg; \
+
+ .machine power10
+ENTRY_TOCLESS (STRNCMP, 4)
+ /* Check if size is 0. */
+ cmpdi cr0,r5,0
+ beq cr0,L(ret0)
+ andi. r7,r3,4095
+ andi. r8,r4,4095
+ cmpldi cr0,r7,4096-16
+ cmpldi cr1,r8,4096-16
+ bgt cr0,L(crosses)
+ bgt cr1,L(crosses)
+ COMPARE_16(v4,v5,0)
+ addi r3,r3,16
+ addi r4,r4,16
+
+L(crosses):
+ andi. r7,r3,15
+ subfic r7,r7,16 /* r7(nalign1) = 16 - (str1 & 15). */
+ andi. r9,r4,15
+ subfic r8,r9,16 /* r8(nalign2) = 16 - (str2 & 15). */
+ cmpld cr7,r7,r8
+ beq cr7,L(same_aligned)
+ blt cr7,L(nalign1_min)
+
+ /* nalign2 is minimum and s2 pointer is aligned. */
+ CHECK_N_BYTES(r3,r4,r8)
+ /* Are we on the 64B hunk which crosses a page? */
+ andi. r10,r3,63 /* Determine offset into 64B hunk. */
+ andi. r8,r3,15 /* The offset into the 16B hunk. */
+ neg r7,r3
+ andi. r9,r7,15 /* Number of bytes after a 16B cross. */
+ rlwinm. r7,r7,26,0x3F /* ((r4-4096))>>6&63. */
+ beq L(compare_64_pagecross)
+ mtctr r7
+ b L(compare_64B_unaligned)
+
+ /* nalign1 is minimum and s1 pointer is aligned. */
+L(nalign1_min):
+ CHECK_N_BYTES(r3,r4,r7)
+ /* Are we on the 64B hunk which crosses a page? */
+ andi. r10,r4,63 /* Determine offset into 64B hunk. */
+ andi. r8,r4,15 /* The offset into the 16B hunk. */
+ neg r7,r4
+ andi. r9,r7,15 /* Number of bytes after a 16B cross. */
+ rlwinm. r7,r7,26,0x3F /* ((r4-4096))>>6&63. */
+ beq L(compare_64_pagecross)
+ mtctr r7
+
+ .p2align 5
+L(compare_64B_unaligned):
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ COMPARE_16(v4,v5,32)
+ COMPARE_16(v4,v5,48)
+ addi r3,r3,64
+ addi r4,r4,64
+ bdnz L(compare_64B_unaligned)
+
+ /* Cross the page boundary of s2, carefully. Only for first
+ iteration we have to get the count of 64B blocks to be checked.
+ From second iteration and beyond, loop counter is always 63. */
+L(compare_64_pagecross):
+ li r11, 63
+ mtctr r11
+ cmpldi r10,16
+ ble L(cross_4)
+ cmpldi r10,32
+ ble L(cross_3)
+ cmpldi r10,48
+ ble L(cross_2)
+L(cross_1):
+ CHECK_N_BYTES(r3,r4,r9)
+ CHECK_N_BYTES(r3,r4,r8)
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ COMPARE_16(v4,v5,32)
+ addi r3,r3,48
+ addi r4,r4,48
+ b L(compare_64B_unaligned)
+L(cross_2):
+ COMPARE_16(v4,v5,0)
+ addi r3,r3,16
+ addi r4,r4,16
+ CHECK_N_BYTES(r3,r4,r9)
+ CHECK_N_BYTES(r3,r4,r8)
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ addi r3,r3,32
+ addi r4,r4,32
+ b L(compare_64B_unaligned)
+L(cross_3):
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ addi r3,r3,32
+ addi r4,r4,32
+ CHECK_N_BYTES(r3,r4,r9)
+ CHECK_N_BYTES(r3,r4,r8)
+ COMPARE_16(v4,v5,0)
+ addi r3,r3,16
+ addi r4,r4,16
+ b L(compare_64B_unaligned)
+L(cross_4):
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ COMPARE_16(v4,v5,32)
+ addi r3,r3,48
+ addi r4,r4,48
+ CHECK_N_BYTES(r3,r4,r9)
+ CHECK_N_BYTES(r3,r4,r8)
+ b L(compare_64B_unaligned)
+
+L(same_aligned):
+ CHECK_N_BYTES(r3,r4,r7)
+ /* Align s1 to 32B and adjust s2 address.
+ Use lxvp only if both s1 and s2 are 32B aligned. */
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ COMPARE_16(v4,v5,32)
+ COMPARE_16(v4,v5,48)
+ addi r3,r3,64
+ addi r4,r4,64
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ addi r5,r5,32
+
+ clrldi r6,r3,59
+ subfic r7,r6,32
+ add r3,r3,r7
+ add r4,r4,r7
+ subf r5,r7,r5
+ andi. r7,r4,0x1F
+ beq cr0,L(32B_aligned_loop)
+
+ .p2align 5
+L(16B_aligned_loop):
+ COMPARE_16(v4,v5,0)
+ COMPARE_16(v4,v5,16)
+ COMPARE_16(v4,v5,32)
+ COMPARE_16(v4,v5,48)
+ addi r3,r3,64
+ addi r4,r4,64
+ b L(16B_aligned_loop)
+
+ /* Calculate and return the difference. */
+L(different):
+ TAIL_FIRST_16B(v4,v5)
+
+ .p2align 5
+L(32B_aligned_loop):
+ COMPARE_32(v14,v16,0,tail1,tail2)
+ COMPARE_32(v14,v16,32,tail1,tail2)
+ COMPARE_32(v14,v16,64,tail1,tail2)
+ COMPARE_32(v14,v16,96,tail1,tail2)
+ addi r3,r3,128
+ addi r4,r4,128
+ b L(32B_aligned_loop)
+
+L(tail1): TAIL_FIRST_16B(v15,v17)
+L(tail2): TAIL_SECOND_16B(v14,v16)
+
+ .p2align 5
+L(ret0):
+ li r3,0
+ blr
+
+END(STRNCMP)
+libc_hidden_builtin_def(strncmp)
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