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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/i386/math-emu/poly_2xm1.c
downloadconfigs-2.6.12-rc2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/i386/math-emu/poly_2xm1.c')
-rw-r--r--arch/i386/math-emu/poly_2xm1.c156
1 files changed, 156 insertions, 0 deletions
diff --git a/arch/i386/math-emu/poly_2xm1.c b/arch/i386/math-emu/poly_2xm1.c
new file mode 100644
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+++ b/arch/i386/math-emu/poly_2xm1.c
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+/*---------------------------------------------------------------------------+
+ | poly_2xm1.c |
+ | |
+ | Function to compute 2^x-1 by a polynomial approximation. |
+ | |
+ | Copyright (C) 1992,1993,1994,1997 |
+ | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ | E-mail billm@suburbia.net |
+ | |
+ | |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "reg_constant.h"
+#include "fpu_emu.h"
+#include "fpu_system.h"
+#include "control_w.h"
+#include "poly.h"
+
+
+#define HIPOWER 11
+static const unsigned long long lterms[HIPOWER] =
+{
+ 0x0000000000000000LL, /* This term done separately as 12 bytes */
+ 0xf5fdeffc162c7543LL,
+ 0x1c6b08d704a0bfa6LL,
+ 0x0276556df749cc21LL,
+ 0x002bb0ffcf14f6b8LL,
+ 0x0002861225ef751cLL,
+ 0x00001ffcbfcd5422LL,
+ 0x00000162c005d5f1LL,
+ 0x0000000da96ccb1bLL,
+ 0x0000000078d1b897LL,
+ 0x000000000422b029LL
+};
+
+static const Xsig hiterm = MK_XSIG(0xb17217f7, 0xd1cf79ab, 0xc8a39194);
+
+/* Four slices: 0.0 : 0.25 : 0.50 : 0.75 : 1.0,
+ These numbers are 2^(1/4), 2^(1/2), and 2^(3/4)
+ */
+static const Xsig shiftterm0 = MK_XSIG(0, 0, 0);
+static const Xsig shiftterm1 = MK_XSIG(0x9837f051, 0x8db8a96f, 0x46ad2318);
+static const Xsig shiftterm2 = MK_XSIG(0xb504f333, 0xf9de6484, 0x597d89b3);
+static const Xsig shiftterm3 = MK_XSIG(0xd744fcca, 0xd69d6af4, 0x39a68bb9);
+
+static const Xsig *shiftterm[] = { &shiftterm0, &shiftterm1,
+ &shiftterm2, &shiftterm3 };
+
+
+/*--- poly_2xm1() -----------------------------------------------------------+
+ | Requires st(0) which is TAG_Valid and < 1. |
+ +---------------------------------------------------------------------------*/
+int poly_2xm1(u_char sign, FPU_REG *arg, FPU_REG *result)
+{
+ long int exponent, shift;
+ unsigned long long Xll;
+ Xsig accumulator, Denom, argSignif;
+ u_char tag;
+
+ exponent = exponent16(arg);
+
+#ifdef PARANOID
+ if ( exponent >= 0 ) /* Don't want a |number| >= 1.0 */
+ {
+ /* Number negative, too large, or not Valid. */
+ EXCEPTION(EX_INTERNAL|0x127);
+ return 1;
+ }
+#endif /* PARANOID */
+
+ argSignif.lsw = 0;
+ XSIG_LL(argSignif) = Xll = significand(arg);
+
+ if ( exponent == -1 )
+ {
+ shift = (argSignif.msw & 0x40000000) ? 3 : 2;
+ /* subtract 0.5 or 0.75 */
+ exponent -= 2;
+ XSIG_LL(argSignif) <<= 2;
+ Xll <<= 2;
+ }
+ else if ( exponent == -2 )
+ {
+ shift = 1;
+ /* subtract 0.25 */
+ exponent--;
+ XSIG_LL(argSignif) <<= 1;
+ Xll <<= 1;
+ }
+ else
+ shift = 0;
+
+ if ( exponent < -2 )
+ {
+ /* Shift the argument right by the required places. */
+ if ( FPU_shrx(&Xll, -2-exponent) >= 0x80000000U )
+ Xll++; /* round up */
+ }
+
+ accumulator.lsw = accumulator.midw = accumulator.msw = 0;
+ polynomial_Xsig(&accumulator, &Xll, lterms, HIPOWER-1);
+ mul_Xsig_Xsig(&accumulator, &argSignif);
+ shr_Xsig(&accumulator, 3);
+
+ mul_Xsig_Xsig(&argSignif, &hiterm); /* The leading term */
+ add_two_Xsig(&accumulator, &argSignif, &exponent);
+
+ if ( shift )
+ {
+ /* The argument is large, use the identity:
+ f(x+a) = f(a) * (f(x) + 1) - 1;
+ */
+ shr_Xsig(&accumulator, - exponent);
+ accumulator.msw |= 0x80000000; /* add 1.0 */
+ mul_Xsig_Xsig(&accumulator, shiftterm[shift]);
+ accumulator.msw &= 0x3fffffff; /* subtract 1.0 */
+ exponent = 1;
+ }
+
+ if ( sign != SIGN_POS )
+ {
+ /* The argument is negative, use the identity:
+ f(-x) = -f(x) / (1 + f(x))
+ */
+ Denom.lsw = accumulator.lsw;
+ XSIG_LL(Denom) = XSIG_LL(accumulator);
+ if ( exponent < 0 )
+ shr_Xsig(&Denom, - exponent);
+ else if ( exponent > 0 )
+ {
+ /* exponent must be 1 here */
+ XSIG_LL(Denom) <<= 1;
+ if ( Denom.lsw & 0x80000000 )
+ XSIG_LL(Denom) |= 1;
+ (Denom.lsw) <<= 1;
+ }
+ Denom.msw |= 0x80000000; /* add 1.0 */
+ div_Xsig(&accumulator, &Denom, &accumulator);
+ }
+
+ /* Convert to 64 bit signed-compatible */
+ exponent += round_Xsig(&accumulator);
+
+ result = &st(0);
+ significand(result) = XSIG_LL(accumulator);
+ setexponent16(result, exponent);
+
+ tag = FPU_round(result, 1, 0, FULL_PRECISION, sign);
+
+ setsign(result, sign);
+ FPU_settag0(tag);
+
+ return 0;
+
+}