Mercurial > mxe-octave
view src/build-msvctools/math/log2f.S @ 3061:f8299bb6c872
Initial support for native MSVC compilation.
* add MSVC support files: compiler wrappers and support libraries
* adapt libiconv to work with MSVC
* adapt gettext to work with MSVC
author | Michael Goffioul <michael.goffioul@gmail.com> |
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date | Mon, 17 Jun 2013 22:43:11 -0400 |
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/* * Written by J.T. Conklin <jtc@netbsd.org>. * Adapted for use as log2 by Ulrich Drepper <drepper@cygnus.com>. * Public domain. * * Changed to use fyl2xp1 for values near 1, <drepper@cygnus.com>. * * Removed header file dependency for use in libmingwex.a by * Danny Smith <dannysmith@users.sourceforge.net> */ .file "log2f.S" .text .align 4 one: .double 1.0 /* It is not important that this constant is precise. It is only a value which is known to be on the safe side for using the fyl2xp1 instruction. */ limit: .double 0.29 .text .align 4 .globl _log2f .def _log2f; .scl 2; .type 32; .endef _log2f: fldl one flds 4(%esp) /* x : 1 */ fxam fnstsw fld %st /* x : x : 1 */ sahf jc 3f /* in case x is NaN or �Inf */ 4: fsub %st(2), %st /* x-1 : x : 1 */ fld %st /* x-1 : x-1 : x : 1 */ fabs /* |x-1| : x-1 : x : 1 */ fcompl limit /* x-1 : x : 1 */ fnstsw /* x-1 : x : 1 */ andb $0x45, %ah jz 2f fstp %st(1) /* x-1 : 1 */ fyl2xp1 /* log(x) */ ret 2: fstp %st(0) /* x : 1 */ fyl2x /* log(x) */ ret 3: jp 4b /* in case x is �Inf */ fstp %st(1) fstp %st(1) ret