1.file "libm_frexp.s" 2 3 4// Copyright (c) 2000 - 2003, Intel Corporation 5// All rights reserved. 6// 7// 8// Redistribution and use in source and binary forms, with or without 9// modification, are permitted provided that the following conditions are 10// met: 11// 12// * Redistributions of source code must retain the above copyright 13// notice, this list of conditions and the following disclaimer. 14// 15// * Redistributions in binary form must reproduce the above copyright 16// notice, this list of conditions and the following disclaimer in the 17// documentation and/or other materials provided with the distribution. 18// 19// * The name of Intel Corporation may not be used to endorse or promote 20// products derived from this software without specific prior written 21// permission. 22 23// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 24// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 25// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 26// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL OR ITS 27// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 28// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 29// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 30// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 31// OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY OR TORT (INCLUDING 32// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 33// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34// 35// Intel Corporation is the author of this code, and requests that all 36// problem reports or change requests be submitted to it directly at 37// http://www.intel.com/software/products/opensource/libraries/num.htm. 38// 39// History 40//============================================================== 41// 02/02/00 Initial version 42// 03/20/00 Improved speed 43// 06/01/00 Fixed bug when x a double-extended denormal 44// 12/08/00 Corrected label on .endp 45// 01/23/02 Added handling for int 32 or 64 bits 46// 05/20/02 Cleaned up namespace and sf0 syntax 47// 02/10/03 Reordered header: .section, .global, .proc, .align 48// 49// API 50//============================================================== 51// double __libm_frexp(double x, int* y, int int_type) 52// input floating point f8, pointer to y (r33), int int_type (r34) 53// output floating point f8, returns the fraction of x, 0.5 <= fraction < 1.0 54// output int* y, returns the true exponent of x 55// 56// int_type = 0 if int is 32 bits 57// int_type = 1 if int is 64 bits 58// 59// int* y is returned as a 32 bit integer if int_type = 0 60// int* y is returned as a 64 bit integer if int_type = 1 61// 62// Overview of operation 63//============================================================== 64// break a floating point x number into fraction and an exponent 65// The fraction is returned as a double 66// The exponent is returned as an integer pointed to by y 67// This is a true (not a biased exponent) but 0fffe is subtracted 68// as a bias instead of 0xffff. This is because the fraction returned 69// is between 0.5 and 1.0, not the expected IEEE range. 70// 71// The fraction is 0.5 <= fraction < 1.0 72// 73// Registers used 74//============================================================== 75// 76// general registers: 77// r14 exponent bias for x negative 78// r15 exponent bias for x positive 79// r16 signexp of x 80// r17 exponent mask 81// r18 exponent of x 82// r19 exponent result 83// r20 signexp of 2^64 84// r32 on input contains the 64-bit IEEE double that is in f8 85// r33 on input pointer to 32-bit or 64-bit integer for exponent 86// r34 on input contains 0 if output int is 32 bits, else output int is 64 bits 87// 88// predicate registers: 89// p6 set if x is Nan, zero, or infinity 90// p7 set if x negative 91// p8 set if x positive 92// p9 set if x double-extended denormal 93// p10 set if int_type = 0, 32-bit integer 94// p11 set if int_type = 1, 64-bit integer 95// 96// floating-point registers: 97// f8 input, output 98// f9 normalized x 99// f10 signexp for significand result for x positive 100// f11 signexp for significand result for x negative 101// f12 2^64 102 103.section .text 104GLOBAL_LIBM_ENTRY(__libm_frexp) 105 106// Set signexp for significand result for x>0 107// If x is a NaN, zero, or infinity, return it. 108// Put 0 in the int pointer. 109// x NAN, ZERO, INFINITY? 110// Set signexp for significand result for x<0 111{ .mfi 112 mov r15 = 0x0fffe 113 fclass.m p6,p7 = f8, 0xe7 114 mov r14 = 0x2fffe 115} 116// Form signexp of 2^64 in case x double-extended denormal 117// Save the normalized value of input in f9 118// The normalization also sets fault flags and takes faults if necessary 119{ .mfi 120 mov r20 = 0x1003f 121 fnorm.s0 f9 = f8 122 nop.i 999 ;; 123} 124 125// Move signexp for significand result for x>0 to FP reg 126// Form 2^64 in case x double-extended denormal 127{ .mmi 128 setf.exp f10 = r15 129 setf.exp f12 = r20 130 nop.i 999 ;; 131} 132 133// Move signexp for significand result for x<0 to FP reg 134// p7 if x<0, else p8 135// If x=0,nan,inf, set p10 if output int to be 32 bits, or set p11 if 64 bits 136{ .mfi 137 setf.exp f11 = r14 138(p7) fcmp.lt.s0 p7,p8 = f8,f0 139(p6) cmp.eq.unc p10,p11 = r34, r0 ;; 140} 141 142// If x NAN, ZERO, INFINITY, set *y=0 and exit 143{ .mmb 144(p10) st4 [r33] = r0 // Store *y=0 as 32-bit integer 145(p11) st8 [r33] = r0 // Store *y=0 as 64-bit integer 146(p6) br.ret.spnt b0 ;; 147} 148 149// Form exponent mask 150// Test for fnorm(x) denormal, means x double-extended denormal 151{ .mfi 152 mov r17 = 0x1ffff 153 fclass.m p9,p0 = f9, 0x0b 154 nop.i 999 ;; 155} 156 157// If x double-extended denormal add 64 to exponent bias for scaling 158// If x double-extended denormal multiply x * 2^64 which is normal 159// Set p10 if output int to be 32 bits, or set p11 if 64 bits 160{ .mfi 161(p9) add r15 = 64, r15 162(p9) fmpy.s0 f9 = f9, f12 163 cmp.eq p10,p11 = r34, r0 ;; 164} 165 166// true exponent stored to int pointer 167// the bias is treated as 0xfffe instead of 168// normal 0xffff because we want the significand 169// to be in the range <=0.5 sig < 1.0 170// Store the value of the exponent at the pointer in r33 171 172// If x>0 form significand result 173{ .mfi 174 nop.m 999 175(p8) fmerge.se f8 = f10,f9 176 nop.i 999 ;; 177} 178 179// Get signexp of normalized x 180// If x<0 form significand result 181{ .mfi 182 getf.exp r16 = f9 183(p7) fmerge.se f8 = f11,f9 184 nop.i 999 ;; 185} 186 187// Get exp of normalized x 188// Subtract off bias to get true exponent of x 189{ .mmi 190 and r18 = r17,r16 ;; 191 sub r19 = r18,r15 192 nop.i 999 ;; 193} 194 195// Store int *y as a 32-bit integer 196// Make the value a double 197{ .mfi 198(p10) st4 [r33] = r19 // Store *y as 32-bit integer 199 fnorm.d.s0 f8 = f8 200 nop.i 999 201} 202{ .mfb 203(p11) st8 [r33] = r19 // Store *y as 64-bit integer 204 nop.f 999 205 br.ret.sptk b0 ;; 206} 207 208GLOBAL_LIBM_END(__libm_frexp) 209