/* memset/bzero with unaligned store and rep stosb Copyright (C) 2016-2017 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 . */ /* memset is implemented as: 1. Use overlapping store to avoid branch. 2. If size is less than VEC, use integer register stores. 3. If size is from VEC_SIZE to 2 * VEC_SIZE, use 2 VEC stores. 4. If size is from 2 * VEC_SIZE to 4 * VEC_SIZE, use 4 VEC stores. 5. If size is more to 4 * VEC_SIZE, align to 4 * VEC_SIZE with 4 VEC stores and store 4 * VEC at a time until done. */ #include #ifndef MEMSET_CHK_SYMBOL # define MEMSET_CHK_SYMBOL(p,s) MEMSET_SYMBOL(p, s) #endif #ifndef WMEMSET_CHK_SYMBOL # define WMEMSET_CHK_SYMBOL(p,s) WMEMSET_SYMBOL(p, s) #endif #ifndef VZEROUPPER # if VEC_SIZE > 16 # define VZEROUPPER vzeroupper # else # define VZEROUPPER # endif #endif #ifndef VZEROUPPER_SHORT_RETURN # if VEC_SIZE > 16 # define VZEROUPPER_SHORT_RETURN vzeroupper # else # define VZEROUPPER_SHORT_RETURN rep # endif #endif #ifndef MOVQ # if VEC_SIZE > 16 # define MOVQ vmovq # else # define MOVQ movq # endif #endif /* Threshold to use Enhanced REP STOSB. Since there is overhead to set up REP STOSB operation, REP STOSB isn't faster on short data. The memset micro benchmark in glibc shows that 2KB is the approximate value above which REP STOSB becomes faster on processors with Enhanced REP STOSB. Since the stored value is fixed, larger register size has minimal impact on threshold. */ #ifndef REP_STOSB_THRESHOLD # define REP_STOSB_THRESHOLD 2048 #endif #ifndef SECTION # error SECTION is not defined! #endif .section SECTION(.text),"ax",@progbits #if VEC_SIZE == 16 && IS_IN (libc) ENTRY (__bzero) movq %rdi, %rax /* Set return value. */ movq %rsi, %rdx /* Set n. */ pxor %xmm0, %xmm0 jmp L(entry_from_bzero) END (__bzero) weak_alias (__bzero, bzero) #endif #if IS_IN (libc) # if defined SHARED ENTRY_CHK (WMEMSET_CHK_SYMBOL (__wmemset_chk, unaligned)) cmpq %rdx, %rcx jb HIDDEN_JUMPTARGET (__chk_fail) END_CHK (WMEMSET_CHK_SYMBOL (__wmemset_chk, unaligned)) # endif ENTRY (WMEMSET_SYMBOL (__wmemset, unaligned)) shlq $2, %rdx WMEMSET_VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi) jmp L(entry_from_bzero) END (WMEMSET_SYMBOL (__wmemset, unaligned)) #endif #if defined SHARED && IS_IN (libc) ENTRY_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned)) cmpq %rdx, %rcx jb HIDDEN_JUMPTARGET (__chk_fail) END_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned)) #endif ENTRY (MEMSET_SYMBOL (__memset, unaligned)) MEMSET_VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi) L(entry_from_bzero): cmpq $VEC_SIZE, %rdx jb L(less_vec) cmpq $(VEC_SIZE * 2), %rdx ja L(more_2x_vec) /* From VEC and to 2 * VEC. No branch when size == VEC_SIZE. */ VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx) VMOVU %VEC(0), (%rdi) VZEROUPPER ret #if defined USE_MULTIARCH && IS_IN (libc) END (MEMSET_SYMBOL (__memset, unaligned)) # if VEC_SIZE == 16 ENTRY (__memset_chk_erms) cmpq %rdx, %rcx jb HIDDEN_JUMPTARGET (__chk_fail) END (__memset_chk_erms) /* Only used to measure performance of REP STOSB. */ ENTRY (__memset_erms) # else /* Provide a symbol to debugger. */ ENTRY (MEMSET_SYMBOL (__memset, erms)) # endif L(stosb): /* Issue vzeroupper before rep stosb. */ VZEROUPPER movq %rdx, %rcx movzbl %sil, %eax movq %rdi, %rdx rep stosb movq %rdx, %rax ret # if VEC_SIZE == 16 END (__memset_erms) # else END (MEMSET_SYMBOL (__memset, erms)) # endif # if defined SHARED && IS_IN (libc) ENTRY_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned_erms)) cmpq %rdx, %rcx jb HIDDEN_JUMPTARGET (__chk_fail) END_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned_erms)) # endif ENTRY (MEMSET_SYMBOL (__memset, unaligned_erms)) MEMSET_VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi) cmpq $VEC_SIZE, %rdx jb L(less_vec) cmpq $(VEC_SIZE * 2), %rdx ja L(stosb_more_2x_vec) /* From VEC and to 2 * VEC. No branch when size == VEC_SIZE. */ VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx) VMOVU %VEC(0), (%rdi) VZEROUPPER ret L(stosb_more_2x_vec): cmpq $REP_STOSB_THRESHOLD, %rdx ja L(stosb) #endif L(more_2x_vec): cmpq $(VEC_SIZE * 4), %rdx ja L(loop_start) VMOVU %VEC(0), (%rdi) VMOVU %VEC(0), VEC_SIZE(%rdi) VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx) VMOVU %VEC(0), -(VEC_SIZE * 2)(%rdi,%rdx) L(return): VZEROUPPER ret L(loop_start): leaq (VEC_SIZE * 4)(%rdi), %rcx VMOVU %VEC(0), (%rdi) andq $-(VEC_SIZE * 4), %rcx VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx) VMOVU %VEC(0), VEC_SIZE(%rdi) VMOVU %VEC(0), -(VEC_SIZE * 2)(%rdi,%rdx) VMOVU %VEC(0), (VEC_SIZE * 2)(%rdi) VMOVU %VEC(0), -(VEC_SIZE * 3)(%rdi,%rdx) VMOVU %VEC(0), (VEC_SIZE * 3)(%rdi) VMOVU %VEC(0), -(VEC_SIZE * 4)(%rdi,%rdx) addq %rdi, %rdx andq $-(VEC_SIZE * 4), %rdx cmpq %rdx, %rcx je L(return) L(loop): VMOVA %VEC(0), (%rcx) VMOVA %VEC(0), VEC_SIZE(%rcx) VMOVA %VEC(0), (VEC_SIZE * 2)(%rcx) VMOVA %VEC(0), (VEC_SIZE * 3)(%rcx) addq $(VEC_SIZE * 4), %rcx cmpq %rcx, %rdx jne L(loop) VZEROUPPER_SHORT_RETURN ret L(less_vec): /* Less than 1 VEC. */ # if VEC_SIZE != 16 && VEC_SIZE != 32 && VEC_SIZE != 64 # error Unsupported VEC_SIZE! # endif # if VEC_SIZE > 32 cmpb $32, %dl jae L(between_32_63) # endif # if VEC_SIZE > 16 cmpb $16, %dl jae L(between_16_31) # endif MOVQ %xmm0, %rcx cmpb $8, %dl jae L(between_8_15) cmpb $4, %dl jae L(between_4_7) cmpb $1, %dl ja L(between_2_3) jb 1f movb %cl, (%rdi) 1: VZEROUPPER ret # if VEC_SIZE > 32 /* From 32 to 63. No branch when size == 32. */ L(between_32_63): vmovdqu %ymm0, -32(%rdi,%rdx) vmovdqu %ymm0, (%rdi) VZEROUPPER ret # endif # if VEC_SIZE > 16 /* From 16 to 31. No branch when size == 16. */ L(between_16_31): vmovdqu %xmm0, -16(%rdi,%rdx) vmovdqu %xmm0, (%rdi) VZEROUPPER ret # endif /* From 8 to 15. No branch when size == 8. */ L(between_8_15): movq %rcx, -8(%rdi,%rdx) movq %rcx, (%rdi) VZEROUPPER ret L(between_4_7): /* From 4 to 7. No branch when size == 4. */ movl %ecx, -4(%rdi,%rdx) movl %ecx, (%rdi) VZEROUPPER ret L(between_2_3): /* From 2 to 3. No branch when size == 2. */ movw %cx, -2(%rdi,%rdx) movw %cx, (%rdi) VZEROUPPER ret END (MEMSET_SYMBOL (__memset, unaligned_erms))