/* strrchr with SSE4.2 Copyright (C) 2009 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, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ #include #include /* Define multiple versions only for the definition in libc and for the DSO. In static binaries we need strrchr before the initialization happened. */ #if defined SHARED && !defined NOT_IN_libc .text ENTRY(strrchr) .type strrchr, @gnu_indirect_function cmpl $0, __cpu_features+KIND_OFFSET(%rip) jne 1f call __init_cpu_features 1: leaq __strrchr_sse2(%rip), %rax testl $(1<<20), __cpu_features+CPUID_OFFSET+COMMON_CPUID_INDEX_1*CPUID_SIZE+CPUID_ECX_OFFSET(%rip) jz 2f leaq __strrchr_sse42(%rip), %rax 2: ret END(strrchr) /* This implementation uses SSE4 instructions to compare up to 16 bytes at a time looking for the last occurrence of the character c in the string s: char *strrchr (const char *s, int c); We use 0x4a: _SIDD_SBYTE_OPS | _SIDD_CMP_EQUAL_EACH | _SIDD_MOST_SIGNIFICANT on pcmpistri to compare xmm/mem128 0 1 2 3 4 5 6 7 8 9 A B C D E F X X X X X X X X X X X X X X X X against xmm 0 1 2 3 4 5 6 7 8 9 A B C D E F C C C C C C C C C C C C C C C C to find out if the first 16byte data element has a byte C and the last offset. There are 4 cases: 1. The first 16byte data element has EOS and has the byte C at the last offset X. 2. The first 16byte data element is valid and has the byte C at the last offset X. 3. The first 16byte data element has EOS and doesn't have the byte C. 4. The first 16byte data element is valid and doesn't have the byte C. Here is the table of ECX, CFlag, ZFlag and SFlag for 3 cases: case ECX CFlag ZFlag SFlag 1 X 1 1 0 2 X 1 0 0 3 16 0 1 0 4 16 0 0 0 We exit from the loop for cases 1 and 3 with jz which branches when ZFlag is 1. If CFlag == 1, ECX has the offset X for case 1. */ .section .text.sse4.2,"ax",@progbits .align 16 .type __strrchr_sse42, @function __strrchr_sse42: cfi_startproc CALL_MCOUNT testb %sil, %sil je __strend_sse4 xor %eax,%eax /* RAX has the last occurrence of s. */ movd %esi, %xmm1 punpcklbw %xmm1, %xmm1 movl %edi, %esi punpcklbw %xmm1, %xmm1 andl $15, %esi pshufd $0, %xmm1, %xmm1 movq %rdi, %r8 je L(loop) /* Handle unaligned string using psrldq. */ leaq L(psrldq_table)(%rip), %rdx andq $-16, %r8 movslq (%rdx,%rsi,4),%r9 movdqa (%r8), %xmm0 addq %rdx, %r9 jmp *%r9 /* Handle unaligned string with offset 1 using psrldq. */ .p2align 4 L(psrldq_1): psrldq $1, %xmm0 .p2align 4 L(unaligned_pcmpistri): pcmpistri $0x4a, %xmm1, %xmm0 jnc L(unaligned_no_byte) leaq (%rdi,%rcx), %rax L(unaligned_no_byte): /* Find the length of the unaligned string. */ pcmpistri $0x3a, %xmm0, %xmm0 movl $16, %edx subl %esi, %edx cmpl %ecx, %edx /* Return RAX if the unaligned fragment to next 16B already contain the NULL terminator. */ jg L(exit) addq $16, %r8 /* Loop start on aligned string. */ .p2align 4 L(loop): pcmpistri $0x4a, (%r8), %xmm1 jbe L(match_or_eos) addq $16, %r8 jmp L(loop) .p2align 4 L(match_or_eos): je L(had_eos) L(match_no_eos): leaq (%r8,%rcx), %rax addq $16, %r8 jmp L(loop) .p2align 4 L(had_eos): jnc L(exit) leaq (%r8,%rcx), %rax .p2align 4 L(exit): ret /* Handle unaligned string with offset 15 using psrldq. */ .p2align 4 L(psrldq_15): psrldq $15, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 14 using psrldq. */ .p2align 4 L(psrldq_14): psrldq $14, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 13 using psrldq. */ .p2align 4 L(psrldq_13): psrldq $13, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 12 using psrldq. */ .p2align 4 L(psrldq_12): psrldq $12, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 11 using psrldq. */ .p2align 4 L(psrldq_11): psrldq $11, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 10 using psrldq. */ .p2align 4 L(psrldq_10): psrldq $10, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 9 using psrldq. */ .p2align 4 L(psrldq_9): psrldq $9, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 8 using psrldq. */ .p2align 4 L(psrldq_8): psrldq $8, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 7 using psrldq. */ .p2align 4 L(psrldq_7): psrldq $7, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 6 using psrldq. */ .p2align 4 L(psrldq_6): psrldq $6, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 5 using psrldq. */ .p2align 4 L(psrldq_5): psrldq $5, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 4 using psrldq. */ .p2align 4 L(psrldq_4): psrldq $4, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 3 using psrldq. */ .p2align 4 L(psrldq_3): psrldq $3, %xmm0 jmp L(unaligned_pcmpistri) /* Handle unaligned string with offset 2 using psrldq. */ .p2align 4 L(psrldq_2): psrldq $2, %xmm0 jmp L(unaligned_pcmpistri) cfi_endproc .size __strrchr_sse42, .-__strrchr_sse42 .section .rodata.sse4.2,"a",@progbits .p2align 4 L(psrldq_table): .int L(loop) - L(psrldq_table) .int L(psrldq_1) - L(psrldq_table) .int L(psrldq_2) - L(psrldq_table) .int L(psrldq_3) - L(psrldq_table) .int L(psrldq_4) - L(psrldq_table) .int L(psrldq_5) - L(psrldq_table) .int L(psrldq_6) - L(psrldq_table) .int L(psrldq_7) - L(psrldq_table) .int L(psrldq_8) - L(psrldq_table) .int L(psrldq_9) - L(psrldq_table) .int L(psrldq_10) - L(psrldq_table) .int L(psrldq_11) - L(psrldq_table) .int L(psrldq_12) - L(psrldq_table) .int L(psrldq_13) - L(psrldq_table) .int L(psrldq_14) - L(psrldq_table) .int L(psrldq_15) - L(psrldq_table) # undef ENTRY # define ENTRY(name) \ .type __strrchr_sse2, @function; \ .align 16; \ __strrchr_sse2: cfi_startproc; \ CALL_MCOUNT # undef END # define END(name) \ cfi_endproc; .size __strrchr_sse2, .-__strrchr_sse2 # undef libc_hidden_builtin_def /* It doesn't make sense to send libc-internal strrchr calls through a PLT. The speedup we get from using SSE4.2 instruction is likely eaten away by the indirect call in the PLT. */ # define libc_hidden_builtin_def(name) \ .globl __GI_strrchr; __GI_strrchr = __strrchr_sse2 #endif #include "../strrchr.S"