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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/reg_add_sub.c
downloadlinux-stericsson-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/reg_add_sub.c')
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diff --git a/arch/i386/math-emu/reg_add_sub.c b/arch/i386/math-emu/reg_add_sub.c
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+/*---------------------------------------------------------------------------+
+ | reg_add_sub.c |
+ | |
+ | Functions to add or subtract two registers and put the result in a third. |
+ | |
+ | Copyright (C) 1992,1993,1997 |
+ | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ | E-mail billm@suburbia.net |
+ | |
+ | |
+ +---------------------------------------------------------------------------*/
+
+/*---------------------------------------------------------------------------+
+ | For each function, the destination may be any FPU_REG, including one of |
+ | the source FPU_REGs. |
+ | Each function returns 0 if the answer is o.k., otherwise a non-zero |
+ | value is returned, indicating either an exception condition or an |
+ | internal error. |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "reg_constant.h"
+#include "fpu_emu.h"
+#include "control_w.h"
+#include "fpu_system.h"
+
+static
+int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa,
+ FPU_REG const *b, u_char tagb, u_char signb,
+ FPU_REG *dest, int deststnr, int control_w);
+
+/*
+ Operates on st(0) and st(n), or on st(0) and temporary data.
+ The destination must be one of the source st(x).
+ */
+int FPU_add(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
+{
+ FPU_REG *a = &st(0);
+ FPU_REG *dest = &st(deststnr);
+ u_char signb = getsign(b);
+ u_char taga = FPU_gettag0();
+ u_char signa = getsign(a);
+ u_char saved_sign = getsign(dest);
+ int diff, tag, expa, expb;
+
+ if ( !(taga | tagb) )
+ {
+ expa = exponent(a);
+ expb = exponent(b);
+
+ valid_add:
+ /* Both registers are valid */
+ if (!(signa ^ signb))
+ {
+ /* signs are the same */
+ tag = FPU_u_add(a, b, dest, control_w, signa, expa, expb);
+ }
+ else
+ {
+ /* The signs are different, so do a subtraction */
+ diff = expa - expb;
+ if (!diff)
+ {
+ diff = a->sigh - b->sigh; /* This works only if the ms bits
+ are identical. */
+ if (!diff)
+ {
+ diff = a->sigl > b->sigl;
+ if (!diff)
+ diff = -(a->sigl < b->sigl);
+ }
+ }
+
+ if (diff > 0)
+ {
+ tag = FPU_u_sub(a, b, dest, control_w, signa, expa, expb);
+ }
+ else if ( diff < 0 )
+ {
+ tag = FPU_u_sub(b, a, dest, control_w, signb, expb, expa);
+ }
+ else
+ {
+ FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
+ /* sign depends upon rounding mode */
+ setsign(dest, ((control_w & CW_RC) != RC_DOWN)
+ ? SIGN_POS : SIGN_NEG);
+ return TAG_Zero;
+ }
+ }
+
+ if ( tag < 0 )
+ {
+ setsign(dest, saved_sign);
+ return tag;
+ }
+ FPU_settagi(deststnr, tag);
+ return tag;
+ }
+
+ if ( taga == TAG_Special )
+ taga = FPU_Special(a);
+ if ( tagb == TAG_Special )
+ tagb = FPU_Special(b);
+
+ if ( ((taga == TAG_Valid) && (tagb == TW_Denormal))
+ || ((taga == TW_Denormal) && (tagb == TAG_Valid))
+ || ((taga == TW_Denormal) && (tagb == TW_Denormal)) )
+ {
+ FPU_REG x, y;
+
+ if ( denormal_operand() < 0 )
+ return FPU_Exception;
+
+ FPU_to_exp16(a, &x);
+ FPU_to_exp16(b, &y);
+ a = &x;
+ b = &y;
+ expa = exponent16(a);
+ expb = exponent16(b);
+ goto valid_add;
+ }
+
+ if ( (taga == TW_NaN) || (tagb == TW_NaN) )
+ {
+ if ( deststnr == 0 )
+ return real_2op_NaN(b, tagb, deststnr, a);
+ else
+ return real_2op_NaN(a, taga, deststnr, a);
+ }
+
+ return add_sub_specials(a, taga, signa, b, tagb, signb,
+ dest, deststnr, control_w);
+}
+
+
+/* Subtract b from a. (a-b) -> dest */
+int FPU_sub(int flags, int rm, int control_w)
+{
+ FPU_REG const *a, *b;
+ FPU_REG *dest;
+ u_char taga, tagb, signa, signb, saved_sign, sign;
+ int diff, tag = 0, expa, expb, deststnr;
+
+ a = &st(0);
+ taga = FPU_gettag0();
+
+ deststnr = 0;
+ if ( flags & LOADED )
+ {
+ b = (FPU_REG *)rm;
+ tagb = flags & 0x0f;
+ }
+ else
+ {
+ b = &st(rm);
+ tagb = FPU_gettagi(rm);
+
+ if ( flags & DEST_RM )
+ deststnr = rm;
+ }
+
+ signa = getsign(a);
+ signb = getsign(b);
+
+ if ( flags & REV )
+ {
+ signa ^= SIGN_NEG;
+ signb ^= SIGN_NEG;
+ }
+
+ dest = &st(deststnr);
+ saved_sign = getsign(dest);
+
+ if ( !(taga | tagb) )
+ {
+ expa = exponent(a);
+ expb = exponent(b);
+
+ valid_subtract:
+ /* Both registers are valid */
+
+ diff = expa - expb;
+
+ if (!diff)
+ {
+ diff = a->sigh - b->sigh; /* Works only if ms bits are identical */
+ if (!diff)
+ {
+ diff = a->sigl > b->sigl;
+ if (!diff)
+ diff = -(a->sigl < b->sigl);
+ }
+ }
+
+ switch ( (((int)signa)*2 + signb) / SIGN_NEG )
+ {
+ case 0: /* P - P */
+ case 3: /* N - N */
+ if (diff > 0)
+ {
+ /* |a| > |b| */
+ tag = FPU_u_sub(a, b, dest, control_w, signa, expa, expb);
+ }
+ else if ( diff == 0 )
+ {
+ FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
+
+ /* sign depends upon rounding mode */
+ setsign(dest, ((control_w & CW_RC) != RC_DOWN)
+ ? SIGN_POS : SIGN_NEG);
+ return TAG_Zero;
+ }
+ else
+ {
+ sign = signa ^ SIGN_NEG;
+ tag = FPU_u_sub(b, a, dest, control_w, sign, expb, expa);
+ }
+ break;
+ case 1: /* P - N */
+ tag = FPU_u_add(a, b, dest, control_w, SIGN_POS, expa, expb);
+ break;
+ case 2: /* N - P */
+ tag = FPU_u_add(a, b, dest, control_w, SIGN_NEG, expa, expb);
+ break;
+#ifdef PARANOID
+ default:
+ EXCEPTION(EX_INTERNAL|0x111);
+ return -1;
+#endif
+ }
+ if ( tag < 0 )
+ {
+ setsign(dest, saved_sign);
+ return tag;
+ }
+ FPU_settagi(deststnr, tag);
+ return tag;
+ }
+
+ if ( taga == TAG_Special )
+ taga = FPU_Special(a);
+ if ( tagb == TAG_Special )
+ tagb = FPU_Special(b);
+
+ if ( ((taga == TAG_Valid) && (tagb == TW_Denormal))
+ || ((taga == TW_Denormal) && (tagb == TAG_Valid))
+ || ((taga == TW_Denormal) && (tagb == TW_Denormal)) )
+ {
+ FPU_REG x, y;
+
+ if ( denormal_operand() < 0 )
+ return FPU_Exception;
+
+ FPU_to_exp16(a, &x);
+ FPU_to_exp16(b, &y);
+ a = &x;
+ b = &y;
+ expa = exponent16(a);
+ expb = exponent16(b);
+
+ goto valid_subtract;
+ }
+
+ if ( (taga == TW_NaN) || (tagb == TW_NaN) )
+ {
+ FPU_REG const *d1, *d2;
+ if ( flags & REV )
+ {
+ d1 = b;
+ d2 = a;
+ }
+ else
+ {
+ d1 = a;
+ d2 = b;
+ }
+ if ( flags & LOADED )
+ return real_2op_NaN(b, tagb, deststnr, d1);
+ if ( flags & DEST_RM )
+ return real_2op_NaN(a, taga, deststnr, d2);
+ else
+ return real_2op_NaN(b, tagb, deststnr, d2);
+ }
+
+ return add_sub_specials(a, taga, signa, b, tagb, signb ^ SIGN_NEG,
+ dest, deststnr, control_w);
+}
+
+
+static
+int add_sub_specials(FPU_REG const *a, u_char taga, u_char signa,
+ FPU_REG const *b, u_char tagb, u_char signb,
+ FPU_REG *dest, int deststnr, int control_w)
+{
+ if ( ((taga == TW_Denormal) || (tagb == TW_Denormal))
+ && (denormal_operand() < 0) )
+ return FPU_Exception;
+
+ if (taga == TAG_Zero)
+ {
+ if (tagb == TAG_Zero)
+ {
+ /* Both are zero, result will be zero. */
+ u_char different_signs = signa ^ signb;
+
+ FPU_copy_to_regi(a, TAG_Zero, deststnr);
+ if ( different_signs )
+ {
+ /* Signs are different. */
+ /* Sign of answer depends upon rounding mode. */
+ setsign(dest, ((control_w & CW_RC) != RC_DOWN)
+ ? SIGN_POS : SIGN_NEG);
+ }
+ else
+ setsign(dest, signa); /* signa may differ from the sign of a. */
+ return TAG_Zero;
+ }
+ else
+ {
+ reg_copy(b, dest);
+ if ( (tagb == TW_Denormal) && (b->sigh & 0x80000000) )
+ {
+ /* A pseudoDenormal, convert it. */
+ addexponent(dest, 1);
+ tagb = TAG_Valid;
+ }
+ else if ( tagb > TAG_Empty )
+ tagb = TAG_Special;
+ setsign(dest, signb); /* signb may differ from the sign of b. */
+ FPU_settagi(deststnr, tagb);
+ return tagb;
+ }
+ }
+ else if (tagb == TAG_Zero)
+ {
+ reg_copy(a, dest);
+ if ( (taga == TW_Denormal) && (a->sigh & 0x80000000) )
+ {
+ /* A pseudoDenormal */
+ addexponent(dest, 1);
+ taga = TAG_Valid;
+ }
+ else if ( taga > TAG_Empty )
+ taga = TAG_Special;
+ setsign(dest, signa); /* signa may differ from the sign of a. */
+ FPU_settagi(deststnr, taga);
+ return taga;
+ }
+ else if (taga == TW_Infinity)
+ {
+ if ( (tagb != TW_Infinity) || (signa == signb) )
+ {
+ FPU_copy_to_regi(a, TAG_Special, deststnr);
+ setsign(dest, signa); /* signa may differ from the sign of a. */
+ return taga;
+ }
+ /* Infinity-Infinity is undefined. */
+ return arith_invalid(deststnr);
+ }
+ else if (tagb == TW_Infinity)
+ {
+ FPU_copy_to_regi(b, TAG_Special, deststnr);
+ setsign(dest, signb); /* signb may differ from the sign of b. */
+ return tagb;
+ }
+
+#ifdef PARANOID
+ EXCEPTION(EX_INTERNAL|0x101);
+#endif
+
+ return FPU_Exception;
+}
+