X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=src%2Fceph%2Fsrc%2Fcommon%2Fcrc32c_ppc_fast_zero_asm.S;fp=src%2Fceph%2Fsrc%2Fcommon%2Fcrc32c_ppc_fast_zero_asm.S;h=a53df1deeadca9014b47150a4f6e33d0a41929ad;hb=812ff6ca9fcd3e629e49d4328905f33eee8ca3f5;hp=0000000000000000000000000000000000000000;hpb=15280273faafb77777eab341909a3f495cf248d9;p=stor4nfv.git diff --git a/src/ceph/src/common/crc32c_ppc_fast_zero_asm.S b/src/ceph/src/common/crc32c_ppc_fast_zero_asm.S new file mode 100644 index 0000000..a53df1d --- /dev/null +++ b/src/ceph/src/common/crc32c_ppc_fast_zero_asm.S @@ -0,0 +1,77 @@ +/* + * Use the fixed point version of Barrett reduction to compute a mod n + * over GF(2) for given n using POWER8 instructions. We use k = 32. + * + * http://en.wikipedia.org/wiki/Barrett_reduction + * + * Copyright (C) 2015 Anton Blanchard , IBM + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of either: + * + * a) the GNU General Public License as published by the Free Software + * Foundation; either version 2 of the License, or (at your option) + * any later version, or + * b) the Apache License, Version 2.0 + */ +#include +#include "common/ppc-opcode.h" + +#undef toc + +#ifndef r1 +#define r1 1 +#endif + +#ifndef r2 +#define r2 2 +#endif + + .section .data +.balign 16 + +.barrett_fz_constants: + /* Barrett constant m - (4^32)/n */ + .octa 0x0000000000000000000000011f91caf6 /* x^64 div p(x) */ + /* Barrett constant n */ + .octa 0x0000000000000000000000011edc6f41 + +.text +/* unsigned int barrett_reduction(unsigned long val) */ +FUNC_START(barrett_reduction) + addis r4,r2,.barrett_fz_constants@toc@ha + addi r4,r4,.barrett_fz_constants@toc@l + + li r5,16 + vxor v1,v1,v1 /* zero v1 */ + + /* Get a into v0 */ + MTVRD(v0, r3) + vsldoi v0,v1,v0,8 /* shift into bottom 64 bits, this is a */ + + /* Load constants */ + lvx v2,0,r4 /* m */ + lvx v3,r5,r4 /* n */ + + /* + * Now for the actual algorithm. The idea is to calculate q, + * the multiple of our polynomial that we need to subtract. By + * doing the computation 2x bits higher (ie 64 bits) and shifting the + * result back down 2x bits, we round down to the nearest multiple. + */ + VPMSUMD(v4,v0,v2) /* ma */ + vsldoi v4,v1,v4,8 /* q = floor(ma/(2^64)) */ + VPMSUMD(v4,v4,v3) /* qn */ + vxor v0,v0,v4 /* a - qn, subtraction is xor in GF(2) */ + + /* + * Get the result into r3. We need to shift it left 8 bytes: + * V0 [ 0 1 2 X ] + * V0 [ 0 X 2 3 ] + */ + vsldoi v0,v0,v1,8 /* shift result into top 64 bits of v0 */ + MFVRD(r3, v0) + + blr +FUNC_END(barrett_reduction) +