diff options
Diffstat (limited to 'sysdeps/powerpc/powerpc64/power8/strlen.S')
| -rw-r--r-- | sysdeps/powerpc/powerpc64/power8/strlen.S | 297 |
1 files changed, 297 insertions, 0 deletions
diff --git a/sysdeps/powerpc/powerpc64/power8/strlen.S b/sysdeps/powerpc/powerpc64/power8/strlen.S new file mode 100644 index 0000000000..0142747e71 --- /dev/null +++ b/sysdeps/powerpc/powerpc64/power8/strlen.S @@ -0,0 +1,297 @@ +/* Optimized strlen implementation for PowerPC64/POWER8 using a vectorized + loop. + Copyright (C) 2016 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 + <http://www.gnu.org/licenses/>. */ + +#include <sysdep.h> + +/* TODO: change these to the actual instructions when the minimum required + binutils allows it. */ +#define MFVRD(r,v) .long (0x7c000067 | ((v)<<(32-11)) | ((r)<<(32-16))) +#define VBPERMQ(t,a,b) .long (0x1000054c \ + | ((t)<<(32-11)) \ + | ((a)<<(32-16)) \ + | ((b)<<(32-21)) ) + +/* int [r3] strlen (char *s [r3]) */ + +/* TODO: change this to .machine power8 when the minimum required binutils + allows it. */ + .machine power7 +EALIGN (strlen, 4, 0) + CALL_MCOUNT 1 + dcbt 0,r3 + clrrdi r4,r3,3 /* Align the address to doubleword boundary. */ + rlwinm r6,r3,3,26,28 /* Calculate padding. */ + li r0,0 /* Doubleword with null chars to use + with cmpb. */ + li r5,-1 /* MASK = 0xffffffffffffffff. */ + ld r12,0(r4) /* Load doubleword from memory. */ +#ifdef __LITTLE_ENDIAN__ + sld r5,r5,r6 +#else + srd r5,r5,r6 /* MASK = MASK >> padding. */ +#endif + orc r9,r12,r5 /* Mask bits that are not part of the string. */ + cmpb r10,r9,r0 /* Check for null bytes in DWORD1. */ + cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */ + bne cr7,L(done) + + /* For shorter strings (< 64 bytes), we will not use vector registers, + as the overhead isn't worth it. So, let's use GPRs instead. This + will be done the same way as we do in the POWER7 implementation. + Let's see if we are aligned to a quadword boundary. If so, we can + jump to the first (non-vectorized) loop. Otherwise, we have to + handle the next DWORD first. */ + mtcrf 0x01,r4 + mr r9,r4 + addi r9,r9,8 + bt 28,L(align64) + + /* Handle the next 8 bytes so we are aligned to a quadword + boundary. */ + ldu r5,8(r4) + cmpb r10,r5,r0 + cmpdi cr7,r10,0 + addi r9,r9,8 + bne cr7,L(done) + +L(align64): + /* Proceed to the old (POWER7) implementation, checking two doublewords + per iteraction. For the first 56 bytes, we will just check for null + characters. After that, we will also check if we are 64-byte aligned + so we can jump to the vectorized implementation. We will unroll + these loops to avoid excessive branching. */ + ld r6,8(r4) + ldu r5,16(r4) + cmpb r10,r6,r0 + cmpb r11,r5,r0 + or r5,r10,r11 + cmpdi cr7,r5,0 + addi r9,r9,16 + bne cr7,L(dword_zero) + + ld r6,8(r4) + ldu r5,16(r4) + cmpb r10,r6,r0 + cmpb r11,r5,r0 + or r5,r10,r11 + cmpdi cr7,r5,0 + addi r9,r9,16 + bne cr7,L(dword_zero) + + ld r6,8(r4) + ldu r5,16(r4) + cmpb r10,r6,r0 + cmpb r11,r5,r0 + or r5,r10,r11 + cmpdi cr7,r5,0 + addi r9,r9,16 + bne cr7,L(dword_zero) + + /* Are we 64-byte aligned? If so, jump to the vectorized loop. + Note: aligning to 64-byte will necessarily slow down performance for + strings around 64 bytes in length due to the extra comparisons + required to check alignment for the vectorized loop. This is a + necessary tradeoff we are willing to take in order to speed up the + calculation for larger strings. */ + andi. r10,r9,63 + beq cr0,L(preloop) + ld r6,8(r4) + ldu r5,16(r4) + cmpb r10,r6,r0 + cmpb r11,r5,r0 + or r5,r10,r11 + cmpdi cr7,r5,0 + addi r9,r9,16 + bne cr7,L(dword_zero) + + andi. r10,r9,63 + beq cr0,L(preloop) + ld r6,8(r4) + ldu r5,16(r4) + cmpb r10,r6,r0 + cmpb r11,r5,r0 + or r5,r10,r11 + cmpdi cr7,r5,0 + addi r9,r9,16 + bne cr7,L(dword_zero) + + andi. r10,r9,63 + beq cr0,L(preloop) + ld r6,8(r4) + ldu r5,16(r4) + cmpb r10,r6,r0 + cmpb r11,r5,r0 + or r5,r10,r11 + cmpdi cr7,r5,0 + addi r9,r9,16 + bne cr7,L(dword_zero) + + andi. r10,r9,63 + beq cr0,L(preloop) + ld r6,8(r4) + ldu r5,16(r4) + cmpb r10,r6,r0 + cmpb r11,r5,r0 + or r5,r10,r11 + cmpdi cr7,r5,0 + addi r9,r9,16 + + /* At this point, we are necessarily 64-byte aligned. If no zeroes were + found, jump to the vectorized loop. */ + beq cr7,L(preloop) + +L(dword_zero): + /* OK, one (or both) of the doublewords contains a null byte. Check + the first doubleword and decrement the address in case the first + doubleword really contains a null byte. */ + + cmpdi cr6,r10,0 + addi r4,r4,-8 + bne cr6,L(done) + + /* The null byte must be in the second doubleword. Adjust the address + again and move the result of cmpb to r10 so we can calculate the + length. */ + + mr r10,r11 + addi r4,r4,8 + + /* If the null byte was found in the non-vectorized code, compute the + final length. r10 has the output of the cmpb instruction, that is, + it contains 0xff in the same position as the null byte in the + original doubleword from the string. Use that to calculate the + length. */ +L(done): +#ifdef __LITTLE_ENDIAN__ + addi r9, r10,-1 /* Form a mask from trailing zeros. */ + andc r9, r9,r10 + popcntd r0, r9 /* Count the bits in the mask. */ +#else + cntlzd r0,r10 /* Count leading zeros before the match. */ +#endif + subf r5,r3,r4 + srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */ + add r3,r5,r0 /* Compute final length. */ + blr + + /* Vectorized implementation starts here. */ + .p2align 4 +L(preloop): + /* Set up for the loop. */ + mr r4,r9 + li r7, 16 /* Load required offsets. */ + li r8, 32 + li r9, 48 + li r12, 8 + vxor v0,v0,v0 /* VR with null chars to use with + vcmpequb. */ + + /* Main loop to look for the end of the string. We will read in + 64-byte chunks. Align it to 32 bytes and unroll it 3 times to + leverage the icache performance. */ + .p2align 5 +L(loop): + lvx v1,r4,r0 /* Load 4 quadwords. */ + lvx v2,r4,r7 + lvx v3,r4,r8 + lvx v4,r4,r9 + vminub v5,v1,v2 /* Compare and merge into one VR for speed. */ + vminub v6,v3,v4 + vminub v7,v5,v6 + vcmpequb. v7,v7,v0 /* Check for NULLs. */ + addi r4,r4,64 /* Adjust address for the next iteration. */ + bne cr6,L(vmx_zero) + + lvx v1,r4,r0 /* Load 4 quadwords. */ + lvx v2,r4,r7 + lvx v3,r4,r8 + lvx v4,r4,r9 + vminub v5,v1,v2 /* Compare and merge into one VR for speed. */ + vminub v6,v3,v4 + vminub v7,v5,v6 + vcmpequb. v7,v7,v0 /* Check for NULLs. */ + addi r4,r4,64 /* Adjust address for the next iteration. */ + bne cr6,L(vmx_zero) + + lvx v1,r4,r0 /* Load 4 quadwords. */ + lvx v2,r4,r7 + lvx v3,r4,r8 + lvx v4,r4,r9 + vminub v5,v1,v2 /* Compare and merge into one VR for speed. */ + vminub v6,v3,v4 + vminub v7,v5,v6 + vcmpequb. v7,v7,v0 /* Check for NULLs. */ + addi r4,r4,64 /* Adjust address for the next iteration. */ + beq cr6,L(loop) + +L(vmx_zero): + /* OK, we found a null byte. Let's look for it in the current 64-byte + block and mark it in its corresponding VR. */ + vcmpequb v1,v1,v0 + vcmpequb v2,v2,v0 + vcmpequb v3,v3,v0 + vcmpequb v4,v4,v0 + + /* We will now 'compress' the result into a single doubleword, so it + can be moved to a GPR for the final calculation. First, we + generate an appropriate mask for vbpermq, so we can permute bits into + the first halfword. */ + vspltisb v10,3 + lvsl v11,r0,r0 + vslb v10,v11,v10 + + /* Permute the first bit of each byte into bits 48-63. */ + VBPERMQ(v1,v1,v10) + VBPERMQ(v2,v2,v10) + VBPERMQ(v3,v3,v10) + VBPERMQ(v4,v4,v10) + + /* Shift each component into its correct position for merging. */ +#ifdef __LITTLE_ENDIAN__ + vsldoi v2,v2,v2,2 + vsldoi v3,v3,v3,4 + vsldoi v4,v4,v4,6 +#else + vsldoi v1,v1,v1,6 + vsldoi v2,v2,v2,4 + vsldoi v3,v3,v3,2 +#endif + + /* Merge the results and move to a GPR. */ + vor v1,v2,v1 + vor v2,v3,v4 + vor v4,v1,v2 + MFVRD(r10,v4) + + /* Adjust address to the begninning of the current 64-byte block. */ + addi r4,r4,-64 + +#ifdef __LITTLE_ENDIAN__ + addi r9, r10,-1 /* Form a mask from trailing zeros. */ + andc r9, r9,r10 + popcntd r0, r9 /* Count the bits in the mask. */ +#else + cntlzd r0,r10 /* Count leading zeros before the match. */ +#endif + subf r5,r3,r4 + add r3,r5,r0 /* Compute final length. */ + blr + +END (strlen) +libc_hidden_builtin_def (strlen) |