Blame sysdeps/powerpc/powerpc64/fpu/s_roundf.S

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/* roundf  function.  PowerPC64 version.
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   Copyright (C) 2004-2018 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 <libm-alias-float.h>
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	.section	".toc","aw"
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	.p2align 3
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.LC0:	/* 2**23 */
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	.long 0x4b000000
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.LC1:	/* 0.5 */
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	.long 0x3f000000
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	.section	".text"
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/* float [fp1] roundf  (float x [fp1])
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   IEEE 1003.1 round 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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ENTRY (__roundf, 4)
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	CALL_MCOUNT 0
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	lfs	fp13,.LC0@toc(2)
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	fabs	fp0,fp1
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	fsubs	fp12,fp13,fp13	/* generate 0.0  */
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	fcmpu	cr7,fp0,fp13	/* if (fabs(x) > TWO23)  */
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	mffs	fp11		/* Save current FPU rounding mode and
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				   "inexact" state.  */
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	fcmpu	cr6,fp1,fp12	/* if (x > 0.0)  */
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	bnl-	cr7,.L10
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	mtfsfi	7,1		/* Set rounding mode toward 0.  */
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	lfs	fp10,.LC1@toc(2)
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	ble-	cr6,.L4
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	fadds	fp1,fp1,fp10	/* x+= 0.5;  */
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	fadds	fp1,fp1,fp13	/* x+= TWO23;  */
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	fsubs	fp1,fp1,fp13	/* x-= TWO23;  */
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	fabs	fp1,fp1		/* if (x == 0.0)  */
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				/* x = 0.0; */
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	mtfsf	0xff,fp11	/* Restore previous rounding mode and
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				   "inexact" state.  */
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	blr
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.L4:
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	fsubs	fp9,fp1,fp10	/* x+= 0.5;  */
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	bge-	cr6,.L9		/* if (x < 0.0)  */
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	fsubs	fp1,fp9,fp13	/* x-= TWO23;  */
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	fadds	fp1,fp1,fp13	/* x+= TWO23;  */
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	fnabs	fp1,fp1		/* if (x == 0.0)  */
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				/* x = -0.0; */
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.L9:
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	mtfsf	0xff,fp11	/* Restore previous rounding mode and
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				   "inexact" state.  */
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	blr
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.L10:
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	/* Ensure sNaN input is converted to qNaN.  */
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	fcmpu	cr7,fp1,fp1
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	beqlr	cr7
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	fadds	fp1,fp1,fp1
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	blr
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	END (__roundf)
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libm_alias_float (__round, round)
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