1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright 2011 Nexenta Systems, Inc. All rights reserved. 23 */ 24 /* 25 * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 26 * Use is subject to license terms. 27 */ 28 29 .file "ilogbf.s" 30 31 #include "libm.h" 32 LIBM_ANSI_PRAGMA_WEAK(ilogbf,function) 33 #include "libm_synonyms.h" 34 #include "xpg6.h" 35 36 .data 37 .align 8 38 two23: .long 0x4b000000 / 2**23 39 40 ENTRY(ilogbf) 41 movl 4(%esp),%eax / eax <-- x 42 testl $0x7f800000,%eax / is bexp(x) 0? 43 jz .bexp_0 / jump if x is 0 or subnormal 44 / here, biased exponent is non-zero 45 andl $0x7fffffff,%eax / eax <-- abs(x) 46 cmpl $0x7f800000,%eax / is bexp(x) 0xff? 47 jae .bexp_all_1 / jump if x is NaN or Inf 48 shrl $23,%eax / eax <-- zero_xtnd(bexp(x)) 49 subl $127,%eax / unbias exponent by 127 50 ret 51 52 .bexp_all_1: 53 movl $0x7fffffff,%eax / x is NaN or inf, so return 0x7fffffff 54 jmp 0f 55 56 .bexp_0: 57 andl $0x7fffffff,%eax / eax <-- abs(x), and 58 / ZF = 1 iff x = 0.0 59 jnz .ilogb_subnorm 60 movl $0x80000001,%eax / x is +/-0, so return 0x80000001 61 0: 62 PIC_SETUP(0) 63 PIC_G_LOAD(movzwl,__xpg6,ecx) 64 PIC_WRAPUP 65 andl $_C99SUSv3_ilogb_0InfNaN_raises_invalid,%ecx 66 cmpl $0,%ecx 67 je 1f 68 fldz 69 fdivp %st,%st(0) / raise invalid as per SUSv3 70 1: 71 ret 72 73 .ilogb_subnorm: / subnormal input 74 flds 4(%esp) / push x 75 PIC_SETUP(1) 76 fmuls PIC_L(two23) / x*2**23; rebias x by 127+23, 77 / instead of 127 78 PIC_WRAPUP 79 subl $4,%esp / set up storage area 80 fstps (%esp) / store x*2**23 in storage area 81 fwait / (shouldn't raise exception, but 82 / just in case) 83 movl $0x7f800000,%eax / eax <-- single_bexp_mask 84 andl (%esp),%eax / eax[23..30] <-- bexp(x*2**23), 85 / rest_of(eax) <-- 0 86 shrl $23,%eax / eax <-- zero_xtnd(bexp(x*2**23)) 87 subl $150,%eax / unbias rebiased x by 150 (= 127 + 23) 88 addl $4,%esp / restore stack for caller 89 ret 90 .align 4 91 SET_SIZE(ilogbf)