patch-2.1.73 linux/arch/i386/math-emu/reg_divide.c

• Lines: 207
• Date: Tue Dec 9 17:57:09 1997
• Orig file: v2.1.72/linux/arch/i386/math-emu/reg_divide.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.72/linux/arch/i386/math-emu/reg_divide.c linux/arch/i386/math-emu/reg_divide.c
@@ -0,0 +1,206 @@
+/*---------------------------------------------------------------------------+
+ |  reg_divide.c                                                             |
+ |                                                                           |
+ | Divide one FPU_REG by another and put the result in a destination FPU_REG.|
+ |                                                                           |
+ | Copyright (C) 1996                                                        |
+ |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ |                  E-mail   billm@jacobi.maths.monash.edu.au                |
+ |                                                                           |
+ |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
+ |    one was raised, or -1 on internal error.                               |
+ |                                                                           |
+ +---------------------------------------------------------------------------*/
+
+/*---------------------------------------------------------------------------+
+ | The destination may be any FPU_REG, including one of the source FPU_REGs. |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "reg_constant.h"
+#include "fpu_emu.h"
+#include "fpu_system.h"
+
+/*
+  Divide one register by another and put the result into a third register.
+  */
+int FPU_div(int flags, int rm, int control_w)
+{
+  FPU_REG x, y;
+  FPU_REG const *a, *b, *st0_ptr, *st_ptr;
+  FPU_REG *dest;
+  u_char taga, tagb, signa, signb, sign, saved_sign;
+  int tag, deststnr;
+
+  if ( flags & DEST_RM )
+    deststnr = rm;
+  else
+    deststnr = 0;
+
+  if ( flags & REV )
+    {
+      b = &st(0);
+      st0_ptr = b;
+      tagb = FPU_gettag0();
+      if ( flags & LOADED )
+	{
+	  a = (FPU_REG *)rm;
+	  taga = flags & 0x0f;
+	}
+      else
+	{
+	  a = &st(rm);
+	  st_ptr = a;
+	  taga = FPU_gettagi(rm);
+	}
+    }
+  else
+    {
+      a = &st(0);
+      st0_ptr = a;
+      taga = FPU_gettag0();
+      if ( flags & LOADED )
+	{
+	  b = (FPU_REG *)rm;
+	  tagb = flags & 0x0f;
+	}
+      else
+	{
+	  b = &st(rm);
+	  st_ptr = b;
+	  tagb = FPU_gettagi(rm);
+	}
+    }
+
+  signa = getsign(a);
+  signb = getsign(b);
+
+  sign = signa ^ signb;
+
+  dest = &st(deststnr);
+  saved_sign = getsign(dest);
+
+  if ( !(taga | tagb) )
+    {
+      /* Both regs Valid, this should be the most common case. */
+      reg_copy(a, &x);
+      reg_copy(b, &y);
+      setpositive(&x);
+      setpositive(&y);
+      tag = FPU_u_div(&x, &y, dest, control_w, sign);
+
+      if ( tag < 0 )
+	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)) )
+    {
+      if ( denormal_operand() < 0 )
+	return FPU_Exception;
+
+      FPU_to_exp16(a, &x);
+      FPU_to_exp16(b, &y);
+      tag = FPU_u_div(&x, &y, dest, control_w, sign);
+      if ( tag < 0 )
+	return tag;
+
+      FPU_settagi(deststnr, tag);
+      return tag;
+    }
+  else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) )
+    {
+      if ( tagb != TAG_Zero )
+	{
+	  /* Want to find Zero/Valid */
+	  if ( tagb == TW_Denormal )
+	    {
+	      if ( denormal_operand() < 0 )
+		return FPU_Exception;
+	    }
+
+	  /* The result is zero. */
+	  FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
+	  setsign(dest, sign);
+	  return TAG_Zero;
+	}
+      /* We have an exception condition, either 0/0 or Valid/Zero. */
+      if ( taga == TAG_Zero )
+	{
+	  /* 0/0 */
+	  return arith_invalid(deststnr);
+	}
+      /* Valid/Zero */
+      return FPU_divide_by_zero(deststnr, sign);
+    }
+  /* Must have infinities, NaNs, etc */
+  else if ( (taga == TW_NaN) || (tagb == TW_NaN) )
+    {
+      if ( flags & LOADED )
+	return real_2op_NaN((FPU_REG *)rm, flags & 0x0f, 0, st0_ptr);
+
+      if ( flags & DEST_RM )
+	{
+	  int tag;
+	  tag = FPU_gettag0();
+	  if ( tag == TAG_Special )
+	    tag = FPU_Special(st0_ptr);
+	  return real_2op_NaN(st0_ptr, tag, rm, (flags & REV) ? st0_ptr : &st(rm));
+	}
+      else
+	{
+	  int tag;
+	  tag = FPU_gettagi(rm);
+	  if ( tag == TAG_Special )
+	    tag = FPU_Special(&st(rm));
+	  return real_2op_NaN(&st(rm), tag, 0, (flags & REV) ? st0_ptr : &st(rm));
+	}
+    }
+  else if (taga == TW_Infinity)
+    {
+      if (tagb == TW_Infinity)
+	{
+	  /* infinity/infinity */
+	  return arith_invalid(deststnr);
+	}
+      else
+	{
+	  /* tagb must be Valid or Zero */
+	  if ( (tagb == TW_Denormal) && (denormal_operand() < 0) )
+	    return FPU_Exception;
+	  
+	  /* Infinity divided by Zero or Valid does
+	     not raise and exception, but returns Infinity */
+	  FPU_copy_to_regi(a, TAG_Special, deststnr);
+	  setsign(dest, sign);
+	  return taga;
+	}
+    }
+  else if (tagb == TW_Infinity)
+    {
+      if ( (taga == TW_Denormal) && (denormal_operand() < 0) )
+	return FPU_Exception;
+
+      /* The result is zero. */
+      FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
+      setsign(dest, sign);
+      return TAG_Zero;
+    }
+#ifdef PARANOID
+  else
+    {
+      EXCEPTION(EX_INTERNAL|0x102);
+      return FPU_Exception;
+    }
+#endif PARANOID
+
+}