{"id":818176,"url":"http://patchwork.ozlabs.org/api/patches/818176/?format=json","web_url":"http://patchwork.ozlabs.org/project/glibc/patch/59C8E292.6030505@arm.com/","project":{"id":41,"url":"http://patchwork.ozlabs.org/api/projects/41/?format=json","name":"GNU C Library","link_name":"glibc","list_id":"libc-alpha.sourceware.org","list_email":"libc-alpha@sourceware.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<59C8E292.6030505@arm.com>","list_archive_url":null,"date":"2017-09-25T11:03:46","name":"[3/7,v2] New generic log2f","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"483be109f5ddb98d71c4d8f99415a51e2fe0c6c4","submitter":{"id":65667,"url":"http://patchwork.ozlabs.org/api/people/65667/?format=json","name":"Szabolcs Nagy","email":"szabolcs.nagy@arm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/glibc/patch/59C8E292.6030505@arm.com/mbox/","series":[{"id":4935,"url":"http://patchwork.ozlabs.org/api/series/4935/?format=json","web_url":"http://patchwork.ozlabs.org/project/glibc/list/?series=4935","date":"2017-09-25T10:57:58","name":"Optimized expf, exp2f, logf, log2f and powf","version":1,"mbox":"http://patchwork.ozlabs.org/series/4935/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/818176/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/818176/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":["patchwork-incoming@bilbo.ozlabs.org","mailing list libc-alpha@sourceware.org"],"Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=sourceware.org\n\t(client-ip=209.132.180.131; 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Linux x86_64;\n\trv:31.0) Gecko/20100101 Thunderbird/31.8.0","MIME-Version":"1.0","To":"GNU C Library ","CC":"nd@arm.com","Subject":"[PATCH 3/7 v2] New generic log2f","References":"<59C8E136.6070606@arm.com>","In-Reply-To":"<59C8E136.6070606@arm.com>","Content-Type":"multipart/mixed;\n\tboundary=\"------------040701050608030008020806\"","X-ClientProxiedBy":"VI1PR0401CA0017.eurprd04.prod.outlook.com\n\t(2603:10a6:800:4a::27) To AM5PR0802MB2481.eurprd08.prod.outlook.com\n\t(2603:10a6:203:97::23)","X-MS-PublicTrafficType":"Email","X-MS-Office365-Filtering-Correlation-Id":"edfe472d-48e2-43fe-e793-08d504051a44","X-MS-Office365-Filtering-HT":"Tenant","X-Microsoft-Antispam":"UriScan:; BCL:0; PCL:0;\n\tRULEID:(22001)(2017030254152)(48565401081)(2017052603199)(49563074)(201703131423075)(201703031133081)(201702281549075);\n\tSRVR:AM5PR0802MB2481; ","X-Microsoft-Exchange-Diagnostics":["1; AM5PR0802MB2481;\n\t3:79xpHh9BS/7xGvqbp8F5/RoKKxiVWKeXR3lXDvlMvVxe5wJMlCnZ94ZT7tNm6KuENrKfW0KDQqNMgGql/gl3E1nd89gWRrLPVMaGNvLXKbZJIURgLSQkEcFD9z+1gXAAqIWKAX6PWCisYjzUAb9gvL9QSAeg+J68GD9mjNLHNX8X6C7IaU6dDhdYtmeW65BBGcRl/CWozUn29ZMInuEZD9/60i8f/5hwizexp/C7abyrLVq7E8rrQ49y8EuRupoV;\n\t25:9gD9LOdOcBL95pTLC3LQitZDnlrtZ9XgJtKjk2YtPjB+1PXRXyAyl49HMJdlOj8p6aZM237zLTsENT8opNh3e4LcXdIHd/DPTAOue/ERcUQ9+ynilsLEQDZh2pwTYl2bXgM0ZMtRW9fRDxF5oDM7xd6vGfHrwxQmpKMd7pgKXB6f7dy/Qp/WDztbTkaXy6q9yMecotJKkj8oTA18KjGRFcof1lNJ7fMtrM+E1xYSym71XboDnUQwIawE0gRB+v8mHVlJ+SEiNzyAxDzz5puY1jNV1adC9CNNP2RZHLuwLtS7tD16fqYxyJf3dkoCx6IS0+9BZY8Lx2WvB3n2cIGpjw==;\n\t31:1xOsYvRrN1X/TKH2zwodFhvyYexmZNVWWJ0aFkFgOzmcPXow2KLN6BWyEBGVnjZ+rki+M31g5kO9eDG3qXVWF/OmbL0u+oh3FOP18So6SmO+1EELudHc9RIkBaMe8wjIVa3+JCwyBymIWSrG6bzhz2Q6SOQebG8oCnXbzrZsP1yJzA5RVG3USWTQH/C+DVWZ2kuW/38rhQpGKzTCNVEqj1V35A73Hrqx06KzKHJ/t2E=","1; 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SFP:1101; SCL:1; SRVR:AM5PR0802MB2481;\n\tH:[10.2.206.69]; FPR:; SPF:None; PTR:InfoNoRecords; A:1; MX:1;\n\tLANG:en; ","Received-SPF":"None (protection.outlook.com: arm.com does not designate\n\tpermitted sender hosts)","SpamDiagnosticOutput":"1:99","SpamDiagnosticMetadata":"NSPM","X-OriginatorOrg":"arm.com","X-MS-Exchange-CrossTenant-OriginalArrivalTime":"25 Sep 2017 11:03:49.8926\n\t(UTC)","X-MS-Exchange-CrossTenant-FromEntityHeader":"Hosted","X-MS-Exchange-CrossTenant-Id":"f34e5979-57d9-4aaa-ad4d-b122a662184d","X-MS-Exchange-Transport-CrossTenantHeadersStamped":"AM5PR0802MB2481"},"content":"v2:\n- __log2f_data is attribute_hidden","diff":"From e931f4585585e39ccb5f1f3a29debe670eb53629 Mon Sep 17 00:00:00 2001\nFrom: Szabolcs Nagy \nDate: Mon, 4 Sep 2017 17:53:47 +0100\nSubject: [PATCH 3/7] New generic log2f\n\nSimilar to the new logf: double precision arithmetics and a small\nlookup table is used. The argument reduction step is the same as in\nthe new logf.\n\nwithout wrapper on aarch64:\nlog2f reciprocal-throughput: 2.3x faster\nlog2f latency: 2.1x faster\nold worst case error: 1.72 ulp\nnew worst case error: 0.75 ulp\naarch64 .text size: -252 bytes\naarch64 .rodata size: +244 bytes\n\n2017-09-19 Szabolcs Nagy \n\n\t* math/Makefile (type-float-routines): Add e_log2f_data.\n\t* sysdeps/ieee754/flt-32/e_log2f.c: New implementation.\n\t* sysdeps/ieee754/flt-32/e_log2f_data.c: New file.\n\t* sysdeps/ieee754/flt-32/math_config.h (__log2f_data): Define.\n\t(LOG2F_TABLE_BITS, LOG2F_POLY_ORDER): Define.\n\t* sysdeps/i386/fpu/e_log2f_data.c: New file.\n\t* sysdeps/ia64/fpu/e_log2f_data.c: New file.\n\t* sysdeps/m68k/m680x0/fpu/e_log2f_data.c: New file.\n---\n math/Makefile | 3 +-\n sysdeps/i386/fpu/e_log2f_data.c | 1 +\n sysdeps/ia64/fpu/e_log2f_data.c | 1 +\n sysdeps/ieee754/flt-32/e_log2f.c | 148 +++++++++++++++++----------------\n sysdeps/ieee754/flt-32/e_log2f_data.c | 44 ++++++++++\n sysdeps/ieee754/flt-32/math_config.h | 11 +++\n sysdeps/m68k/m680x0/fpu/e_log2f_data.c | 1 +\n 7 files changed, 135 insertions(+), 74 deletions(-)\n create mode 100644 sysdeps/i386/fpu/e_log2f_data.c\n create mode 100644 sysdeps/ia64/fpu/e_log2f_data.c\n create mode 100644 sysdeps/ieee754/flt-32/e_log2f_data.c\n create mode 100644 sysdeps/m68k/m680x0/fpu/e_log2f_data.c\n\ndiff --git a/math/Makefile b/math/Makefile\nindex 919fec13ef..b4b3101592 100644\n--- a/math/Makefile\n+++ b/math/Makefile\n@@ -115,7 +115,8 @@ type-double-routines := branred doasin dosincos halfulp mpa mpatan2\t\\\n \n # float support\n type-float-suffix := f\n-type-float-routines := k_rem_pio2f math_errf e_exp2f_data e_logf_data\n+type-float-routines := k_rem_pio2f math_errf e_exp2f_data e_logf_data\t\\\n+\t\t e_log2f_data\n \n # _Float128 support\n type-float128-suffix := f128\ndiff --git a/sysdeps/i386/fpu/e_log2f_data.c b/sysdeps/i386/fpu/e_log2f_data.c\nnew file mode 100644\nindex 0000000000..1cc8931700\n--- /dev/null\n+++ b/sysdeps/i386/fpu/e_log2f_data.c\n@@ -0,0 +1 @@\n+/* Not needed. */\ndiff --git a/sysdeps/ia64/fpu/e_log2f_data.c b/sysdeps/ia64/fpu/e_log2f_data.c\nnew file mode 100644\nindex 0000000000..1cc8931700\n--- /dev/null\n+++ b/sysdeps/ia64/fpu/e_log2f_data.c\n@@ -0,0 +1 @@\n+/* Not needed. */\ndiff --git a/sysdeps/ieee754/flt-32/e_log2f.c b/sysdeps/ieee754/flt-32/e_log2f.c\nindex 782d901094..6c42f27843 100644\n--- a/sysdeps/ieee754/flt-32/e_log2f.c\n+++ b/sysdeps/ieee754/flt-32/e_log2f.c\n@@ -1,86 +1,88 @@\n-/* e_logf.c -- float version of e_log.c.\n- * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.\n- * adapted for log2 by Ulrich Drepper \n- */\n+/* Single-precision log2 function.\n+ Copyright (C) 2017 Free Software Foundation, Inc.\n+ This file is part of the GNU C Library.\n \n-/*\n- * ====================================================\n- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\n- *\n- * Developed at SunPro, a Sun Microsystems, Inc. business.\n- * Permission to use, copy, modify, and distribute this\n- * software is freely granted, provided that this notice\n- * is preserved.\n- * ====================================================\n- */\n+ The GNU C Library is free software; you can redistribute it and/or\n+ modify it under the terms of the GNU Lesser General Public\n+ License as published by the Free Software Foundation; either\n+ version 2.1 of the License, or (at your option) any later version.\n+\n+ The GNU C Library is distributed in the hope that it will be useful,\n+ but WITHOUT ANY WARRANTY; without even the implied warranty of\n+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU\n+ Lesser General Public License for more details.\n \n+ You should have received a copy of the GNU Lesser General Public\n+ License along with the GNU C Library; if not, see\n+ . */\n \n #include \n-#include \n-#include \n+#include \n+#include \"math_config.h\"\n+\n+/*\n+LOG2F_TABLE_BITS = 4\n+LOG2F_POLY_ORDER = 4\n \n-static const float\n-ln2 = 0.69314718055994530942,\n-two25 = 3.355443200e+07,\t/* 0x4c000000 */\n-Lg1 = 6.6666668653e-01,\t/* 3F2AAAAB */\n-Lg2 = 4.0000000596e-01,\t/* 3ECCCCCD */\n-Lg3 = 2.8571429849e-01, /* 3E924925 */\n-Lg4 = 2.2222198546e-01, /* 3E638E29 */\n-Lg5 = 1.8183572590e-01, /* 3E3A3325 */\n-Lg6 = 1.5313838422e-01, /* 3E1CD04F */\n-Lg7 = 1.4798198640e-01; /* 3E178897 */\n+ULP error: 0.752 (nearest rounding.)\n+Relative error: 1.9 * 2^-26 (before rounding.)\n+*/\n \n-static const float zero = 0.0;\n+#define N (1 << LOG2F_TABLE_BITS)\n+#define T __log2f_data.tab\n+#define A __log2f_data.poly\n+#define OFF 0x3f330000\n \n float\n-__ieee754_log2f(float x)\n+__ieee754_log2f (float x)\n {\n-\tfloat hfsq,f,s,z,R,w,t1,t2,dk;\n-\tint32_t k,ix,i,j;\n+ /* double_t for better performance on targets with FLT_EVAL_METHOD==2. */\n+ double_t z, r, r2, p, y, y0, invc, logc;\n+ uint32_t ix, iz, top, tmp;\n+ int k, i;\n+\n+ ix = asuint (x);\n+#if WANT_ROUNDING\n+ /* Fix sign of zero with downward rounding when x==1. */\n+ if (__glibc_unlikely (ix == 0x3f800000))\n+ return 0;\n+#endif\n+ if (__glibc_unlikely (ix - 0x00800000 >= 0x7f800000 - 0x00800000))\n+ {\n+ /* x < 0x1p-126 or inf or nan. */\n+ if (ix * 2 == 0)\n+\treturn __math_divzerof (1);\n+ if (ix == 0x7f800000) /* log2(inf) == inf. */\n+\treturn x;\n+ if ((ix & 0x80000000) || ix * 2 >= 0xff000000)\n+\treturn __math_invalidf (x);\n+ /* x is subnormal, normalize it. */\n+ ix = asuint (x * 0x1p23f);\n+ ix -= 23 << 23;\n+ }\n+\n+ /* x = 2^k z; where z is in range [OFF,2*OFF] and exact.\n+ The range is split into N subintervals.\n+ The ith subinterval contains z and c is near its center. */\n+ tmp = ix - OFF;\n+ i = (tmp >> (23 - LOG2F_TABLE_BITS)) % N;\n+ top = tmp & 0xff800000;\n+ iz = ix - top;\n+ k = (int32_t) tmp >> 23; /* arithmetic shift */\n+ invc = T[i].invc;\n+ logc = T[i].logc;\n+ z = (double_t) asfloat (iz);\n \n-\tGET_FLOAT_WORD(ix,x);\n+ /* log2(x) = log1p(z/c-1)/ln2 + log2(c) + k */\n+ r = z * invc - 1;\n+ y0 = logc + (double_t) k;\n \n-\tk=0;\n-\tif (ix < 0x00800000) {\t\t\t/* x < 2**-126 */\n-\t if (__builtin_expect((ix&0x7fffffff)==0, 0))\n-\t\treturn -two25/__fabsf (x);\t/* log(+-0)=-inf */\n-\t if (__builtin_expect(ix<0, 0))\n-\t\treturn (x-x)/(x-x);\t/* log(-#) = NaN */\n-\t k -= 25; x *= two25; /* subnormal number, scale up x */\n-\t GET_FLOAT_WORD(ix,x);\n-\t}\n-\tif (__builtin_expect(ix >= 0x7f800000, 0)) return x+x;\n-\tk += (ix>>23)-127;\n-\tix &= 0x007fffff;\n-\ti = (ix+(0x95f64<<3))&0x800000;\n-\tSET_FLOAT_WORD(x,ix|(i^0x3f800000));\t/* normalize x or x/2 */\n-\tk += (i>>23);\n-\tdk = (float)k;\n-\tf = x-(float)1.0;\n-\tif((0x007fffff&(15+ix))<16) {\t/* |f| < 2**-20 */\n-\t if(f==zero)\n-\t {\n-\t\tif (FIX_INT_FP_CONVERT_ZERO && dk == 0.0f)\n-\t\t dk = 0.0f;\n-\t\treturn dk;\n-\t }\n-\t R = f*f*((float)0.5-(float)0.33333333333333333*f);\n-\t return dk-(R-f)/ln2;\n-\t}\n-\ts = f/((float)2.0+f);\n-\tz = s*s;\n-\ti = ix-(0x6147a<<3);\n-\tw = z*z;\n-\tj = (0x6b851<<3)-ix;\n-\tt1= w*(Lg2+w*(Lg4+w*Lg6));\n-\tt2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));\n-\ti |= j;\n-\tR = t2+t1;\n-\tif(i>0) {\n-\t hfsq=(float)0.5*f*f;\n-\t return dk-((hfsq-(s*(hfsq+R)))-f)/ln2;\n-\t} else {\n-\t return dk-((s*(f-R))-f)/ln2;\n-\t}\n+ /* Pipelined polynomial evaluation to approximate log1p(r)/ln2. */\n+ r2 = r * r;\n+ y = A[1] * r + A[2];\n+ y = A[0] * r2 + y;\n+ p = A[3] * r + y0;\n+ y = y * r2 + p;\n+ return (float) y;\n }\n strong_alias (__ieee754_log2f, __log2f_finite)\ndiff --git a/sysdeps/ieee754/flt-32/e_log2f_data.c b/sysdeps/ieee754/flt-32/e_log2f_data.c\nnew file mode 100644\nindex 0000000000..e39de3ba56\n--- /dev/null\n+++ b/sysdeps/ieee754/flt-32/e_log2f_data.c\n@@ -0,0 +1,44 @@\n+/* Data definition for log2f.\n+ Copyright (C) 2017 Free Software Foundation, Inc.\n+ This file is part of the GNU C Library.\n+\n+ The GNU C Library is free software; you can redistribute it and/or\n+ modify it under the terms of the GNU Lesser General Public\n+ License as published by the Free Software Foundation; either\n+ version 2.1 of the License, or (at your option) any later version.\n+\n+ The GNU C Library is distributed in the hope that it will be useful,\n+ but WITHOUT ANY WARRANTY; without even the implied warranty of\n+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU\n+ Lesser General Public License for more details.\n+\n+ You should have received a copy of the GNU Lesser General Public\n+ License along with the GNU C Library; if not, see\n+ . */\n+\n+#include \"math_config.h\"\n+\n+const struct log2f_data __log2f_data = {\n+ .tab = {\n+ { 0x1.661ec79f8f3bep+0, -0x1.efec65b963019p-2 },\n+ { 0x1.571ed4aaf883dp+0, -0x1.b0b6832d4fca4p-2 },\n+ { 0x1.49539f0f010bp+0, -0x1.7418b0a1fb77bp-2 },\n+ { 0x1.3c995b0b80385p+0, -0x1.39de91a6dcf7bp-2 },\n+ { 0x1.30d190c8864a5p+0, -0x1.01d9bf3f2b631p-2 },\n+ { 0x1.25e227b0b8eap+0, -0x1.97c1d1b3b7afp-3 },\n+ { 0x1.1bb4a4a1a343fp+0, -0x1.2f9e393af3c9fp-3 },\n+ { 0x1.12358f08ae5bap+0, -0x1.960cbbf788d5cp-4 },\n+ { 0x1.0953f419900a7p+0, -0x1.a6f9db6475fcep-5 },\n+ { 0x1p+0, 0x0p+0 },\n+ { 0x1.e608cfd9a47acp-1, 0x1.338ca9f24f53dp-4 },\n+ { 0x1.ca4b31f026aap-1, 0x1.476a9543891bap-3 },\n+ { 0x1.b2036576afce6p-1, 0x1.e840b4ac4e4d2p-3 },\n+ { 0x1.9c2d163a1aa2dp-1, 0x1.40645f0c6651cp-2 },\n+ { 0x1.886e6037841edp-1, 0x1.88e9c2c1b9ff8p-2 },\n+ { 0x1.767dcf5534862p-1, 0x1.ce0a44eb17bccp-2 },\n+ },\n+ .poly = {\n+ -0x1.712b6f70a7e4dp-2, 0x1.ecabf496832ep-2, -0x1.715479ffae3dep-1,\n+ 0x1.715475f35c8b8p0,\n+ }\n+};\ndiff --git a/sysdeps/ieee754/flt-32/math_config.h b/sysdeps/ieee754/flt-32/math_config.h\nindex 9dde0f98eb..cca0b53d36 100644\n--- a/sysdeps/ieee754/flt-32/math_config.h\n+++ b/sysdeps/ieee754/flt-32/math_config.h\n@@ -123,4 +123,15 @@ extern const struct logf_data\n double poly[LOGF_POLY_ORDER];\n } __logf_data attribute_hidden;\n \n+#define LOG2F_TABLE_BITS 4\n+#define LOG2F_POLY_ORDER 4\n+extern const struct log2f_data\n+{\n+ struct\n+ {\n+ double invc, logc;\n+ } tab[1 << LOG2F_TABLE_BITS];\n+ double poly[LOG2F_POLY_ORDER];\n+} __log2f_data attribute_hidden;\n+\n #endif\ndiff --git a/sysdeps/m68k/m680x0/fpu/e_log2f_data.c b/sysdeps/m68k/m680x0/fpu/e_log2f_data.c\nnew file mode 100644\nindex 0000000000..1cc8931700\n--- /dev/null\n+++ b/sysdeps/m68k/m680x0/fpu/e_log2f_data.c\n@@ -0,0 +1 @@\n+/* Not needed. */\n-- \n2.11.0\n\n","prefixes":["3/7","v2"]}