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Diffstat (limited to 'sysdeps/powerpc/powerpc64/fpu/s_roundl.S')
| -rw-r--r-- | sysdeps/powerpc/powerpc64/fpu/s_roundl.S | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/sysdeps/powerpc/powerpc64/fpu/s_roundl.S b/sysdeps/powerpc/powerpc64/fpu/s_roundl.S new file mode 100644 index 0000000000..20da828a82 --- /dev/null +++ b/sysdeps/powerpc/powerpc64/fpu/s_roundl.S @@ -0,0 +1,133 @@ +/* long double round function. + IBM extended format long double version. + Copyright (C) 2004, 2006 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 <sysdep.h> +#include <math_ldbl_opt.h> + + .section ".toc","aw" +.LC0: /* 2**52 */ + .tc FD_43300000_0[TC],0x4330000000000000 +.LC1: /* 0.5 */ + .tc FD_3fe00000_0[TC],0x3fe0000000000000 + .section ".text" + +/* long double [fp1,fp2] roundl (long double x [fp1,fp2]) + IEEE 1003.1 round function. IEEE specifies "round to the nearest + integer value, rounding halfway cases away from zero, regardless of + the current rounding mode." However PowerPC Architecture defines + "Round to Nearest" as "Choose the best approximation. In case of a + tie, choose the one that is even (least significant bit o).". + So we can't use the PowerPC "Round to Nearest" mode. Instead we set + "Round toward Zero" mode and round by adding +-0.5 before rounding + to the integer value. */ + +ENTRY (__roundl) + mffs fp11 /* Save current FPU rounding mode. */ + lfd fp13,.LC0@toc(2) + fabs fp0,fp1 + fabs fp9,fp2 + fsub fp12,fp13,fp13 /* generate 0.0 */ + fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */ + fcmpu cr6,fp1,fp12 /* if (x > 0.0) */ + bnl- cr7,.L2 + mtfsfi 7,1 /* Set rounding mode toward 0. */ + lfd fp10,.LC1@toc(2) + ble- cr6,.L1 + fneg fp2,fp12 + fadd fp1,fp1,fp10 /* x+= 0.5; */ + fadd fp1,fp1,fp13 /* x+= TWO52; */ + fsub fp1,fp1,fp13 /* x-= TWO52; */ + fabs fp1,fp1 /* if (x == 0.0) x = 0.0; */ +.L0: + mtfsf 0x01,fp11 /* restore previous rounding mode. */ + blr +.L1: + fsub fp9,fp1,fp10 /* x-= 0.5; */ + fneg fp2,fp12 + bge- cr6,.L0 /* if (x < 0.0) */ + fsub fp1,fp9,fp13 /* x-= TWO52; */ + fadd fp1,fp1,fp13 /* x+= TWO52; */ + fnabs fp1,fp1 /* if (x == 0.0) x = -0.0; */ + mtfsf 0x01,fp11 /* restore previous rounding mode. */ + blr + +/* The high double is > TWO52 so we need to round the low double and + perhaps the high double. In this case we have to round the low + double and handle any adjustment to the high double that may be + caused by rounding (up). This is complicated by the fact that the + high double may already be rounded and the low double may have the + opposite sign to compensate.This gets a bit tricky so we use the + following algorithm: + + tau = floor(x_high/TWO52); + x0 = x_high - tau; + x1 = x_low + tau; + r1 = rint(x1); + y_high = x0 + r1; + y_low = x0 - y_high + r1; + return y; */ +.L2: + fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */ + fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */ + fcmpu cr5,fp2,fp12 /* if (x_low > 0.0) */ + lfd fp10,.LC1@toc(2) + bgelr- cr7 /* return x; */ + beqlr- cr0 + mtfsfi 7,1 /* Set rounding mode toward 0. */ + fdiv fp8,fp1,fp13 /* x_high/TWO52 */ + + bng- cr6,.L6 /* if (x > 0.0) */ + fctidz fp0,fp8 + fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */ + bng cr5,.L4 /* if (x_low > 0.0) */ + fmr fp3,fp1 + fmr fp4,fp2 + b .L5 +.L4: /* if (x_low < 0.0) */ + fsub fp3,fp1,fp8 /* x0 = x_high - tau; */ + fadd fp4,fp2,fp8 /* x1 = x_low + tau; */ +.L5: + fadd fp5,fp4,fp10 /* r1 = x1 + 0.5; */ + fadd fp5,fp5,fp13 /* r1 = r1 + TWO52; */ + fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */ + b .L9 +.L6: /* if (x < 0.0) */ + fctidz fp0,fp8 + fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */ + bnl cr5,.L7 /* if (x_low < 0.0) */ + fmr fp3,fp1 + fmr fp4,fp2 + b .L8 +.L7: /* if (x_low > 0.0) */ + fsub fp3,fp1,fp8 /* x0 = x_high - tau; */ + fadd fp4,fp2,fp8 /* x1 = x_low + tau; */ +.L8: + fsub fp5,fp4,fp10 /* r1 = x1 - 0.5; */ + fsub fp5,fp5,fp13 /* r1-= TWO52; */ + fadd fp5,fp5,fp13 /* r1+= TWO52; */ +.L9: + mtfsf 0x01,fp11 /* restore previous rounding mode. */ + fadd fp1,fp3,fp5 /* y_high = x0 + r1; */ + fsub fp2,fp3,fp1 /* y_low = x0 - y_high + r1; */ + fadd fp2,fp2,fp5 + blr +END (__roundl) + +long_double_symbol (libm, __roundl, roundl) |