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107 lines
3.5 KiB
ArmAsm
107 lines
3.5 KiB
ArmAsm
/* llround function. PowerPC32 on PowerPC64 version.
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Copyright (C) 2004-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include <math_ldbl_opt.h>
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.section .rodata.cst8,"aM",@progbits,8
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.align 3
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.LC0: .long (52+127)<<23 /* 0x1p+52 */
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.long (-1+127)<<23 /* 0.5 */
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.section ".text"
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/* long [r3] lround (float x [fp1])
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IEEE 1003.1 lround function. IEEE specifies "round to the nearest
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integer value, rounding halfway cases away from zero, regardless of
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the current rounding mode." However PowerPC Architecture defines
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"round to Nearest" as "Choose the best approximation. In case of a
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tie, choose the one that is even (least significant bit o).".
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So we can't use the PowerPC "round to Nearest" mode. Instead we set
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"round toward Zero" mode and round by adding +-0.5 before rounding
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to the integer value.
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It is necessary to detect when x is (+-)0x1.fffffffffffffp-2
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because adding +-0.5 in this case will cause an erroneous shift,
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carry and round. We simply return 0 if 0.5 > x > -0.5. Likewise
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if x is and odd number between +-(2^52 and 2^53-1) a shift and
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carry will erroneously round if biased with +-0.5. Therefore if x
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is greater/less than +-2^52 we don't need to bias the number with
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+-0.5. */
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ENTRY (__llround)
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stwu r1,-16(r1)
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cfi_adjust_cfa_offset (16)
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#ifdef SHARED
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mflr r11
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cfi_register(lr,r11)
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SETUP_GOT_ACCESS(r9,got_label)
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addis r9,r9,.LC0-got_label@ha
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addi r9,r9,.LC0-got_label@l
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mtlr r11
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cfi_same_value (lr)
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lfs fp9,0(r9)
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lfs fp10,4(r9)
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#else
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lis r9,.LC0@ha
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lfs fp9,.LC0@l(r9) /* Load 2^52 into fpr9. */
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lfs fp10,.LC0@l+4(r9) /* Load 0.5 into fpr10. */
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#endif
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fabs fp2,fp1 /* Get the absolute value of x. */
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fsub fp12,fp10,fp10 /* Compute 0.0 into fpr12. */
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fcmpu cr6,fp2,fp10 /* if |x| < 0.5 */
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fcmpu cr7,fp2,fp9 /* if |x| >= 2^52 */
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fcmpu cr1,fp1,fp12 /* x is negative? x < 0.0 */
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blt- cr6,.Lretzero /* 0.5 > x < -0.5 so just return 0. */
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bge- cr7,.Lnobias /* 2^52 > x < -2^52 just convert with no bias. */
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fadd fp3,fp2,fp10 /* |x|+=0.5 bias to prepare to round. */
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bge cr1,.Lconvert /* x is positive so don't negate x. */
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fnabs fp3,fp3 /* -(|x|+=0.5) */
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.Lconvert:
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fctidz fp4,fp3 /* Convert to Integer double word round toward 0. */
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stfd fp4,8(r1)
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nop
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nop
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nop
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lwz r3,8+HIWORD(r1) /* Load return as integer. */
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lwz r4,8+LOWORD(r1)
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.Lout:
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addi r1,r1,16
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blr
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.Lretzero: /* 0.5 > x > -0.5 */
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li r3,0 /* return 0. */
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li r4,0
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b .Lout
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.Lnobias:
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fmr fp3,fp1
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b .Lconvert
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END (__llround)
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weak_alias (__llround, llround)
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strong_alias (__llround, __llroundf)
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weak_alias (__llround, llroundf)
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#ifdef NO_LONG_DOUBLE
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weak_alias (__llround, llroundl)
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strong_alias (__llround, __llroundl)
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#endif
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#if LONG_DOUBLE_COMPAT(libm, GLIBC_2_1)
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compat_symbol (libm, __llround, llroundl, GLIBC_2_1)
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#endif
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