sysdeps/ia64/fpu/libm_frexpf.S

   1 .file "libm_frexpf.s"
   2
   3
   4 // Copyright (c) 2000 - 2003, Intel Corporation
   5 // All rights reserved.
   6 //
   7 //
   8 // Redistribution and use in source and binary forms, with or without
   9 // modification, are permitted provided that the following conditions are
  10 // met:
  11 //
  12 // * Redistributions of source code must retain the above copyright
  13 // notice, this list of conditions and the following disclaimer.
  14 //
  15 // * Redistributions in binary form must reproduce the above copyright
  16 // notice, this list of conditions and the following disclaimer in the
  17 // documentation and/or other materials provided with the distribution.
  18 //
  19 // * The name of Intel Corporation may not be used to endorse or promote
  20 // products derived from this software without specific prior written
  21 // permission.
  22
  23 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  24 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  25 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  26 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL OR ITS
  27 // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  29 // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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  31 // OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY OR TORT (INCLUDING
  32 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  33 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  34 //
  35 // Intel Corporation is the author of this code, and requests that all
  36 // problem reports or change requests be submitted to it directly at
  37 // http://www.intel.com/software/products/opensource/libraries/num.htm.
  38 //
  39 // History
  40 //==============================================================
  41 // 02/02/00 Initial version
  42 // 03/20/00 Improved speed
  43 // 06/01/00 Fixed bug when x a double-extended denormal
  44 // 12/08/00 Corrected label on .endp
  45 // 01/23/02 Added handling for int 32 or 64 bits
  46 // 05/20/02 Cleaned up namespace and sf0 syntax
  47 // 02/10/03 Reordered header: .section, .global, .proc, .align
  48 //
  49 // API
  50 //==============================================================
  51 // float __libm_frexpf(float x, int* y, int int_type)
  52 // input  floating point f8, pointer to y (r33), int int_type (r34)
  53 // output floating point f8, returns the fraction of x, 0.5 <= fraction < 1.0
  54 // output int* y, returns the true exponent of x
  55 //
  56 // int_type = 0 if int is 32 bits
  57 // int_type = 1 if int is 64 bits
  58 //
  59 // int* y is returned as a 32 bit integer if int_type = 0
  60 // int* y is returned as a 64 bit integer if int_type = 1
  61 //
  62 // Overview of operation
  63 //==============================================================
  64 // break a floating point x number into fraction and an exponent
  65 // The fraction is returned as a float
  66 // The exponent is returned as an integer pointed to by y
  67 //    This is a true (not a biased exponent) but 0fffe is subtracted
  68 //    as a bias instead of 0xffff. This is because the fraction returned
  69 //    is between 0.5 and 1.0, not the expected IEEE range.
  70 //
  71 // The fraction is 0.5 <= fraction < 1.0
  72 //
  73 // Registers used
  74 //==============================================================
  75 //
  76 // general registers:
  77 // r14  exponent bias for x negative
  78 // r15  exponent bias for x positive
  79 // r16  signexp of x
  80 // r17  exponent mask
  81 // r18  exponent of x
  82 // r19  exponent result
  83 // r20  signexp of 2^64
  84 // r32  on input contains the 32-bit IEEE float that is in f8
  85 // r33  on input pointer to 32-bit or 64-bit integer for exponent
  86 // r34  on input contains 0 if output int is 32 bits, else output int is 64 bits
  87 //
  88 // predicate registers:
  89 // p6   set if x is Nan, zero, or infinity
  90 // p7   set if x negative
  91 // p8   set if x positive
  92 // p9   set if x double-extended denormal
  93 // p10  set if int_type = 0, 32-bit integer
  94 // p11  set if int_type = 1, 64-bit integer
  95 //
  96 // floating-point registers:
  97 // f8  input, output
  98 // f9  normalized x
  99 // f10 signexp for significand result for x positive
 100 // f11 signexp for significand result for x negative
 101 // f12 2^64
 102
 103 .section .text
 104 GLOBAL_LIBM_ENTRY(__libm_frexpf)
 105
 106 // Set signexp for significand result for x>0
 107 // If x is a NaN, zero, or infinity, return it.
 108 // Put 0 in the int pointer.
 109 // x NAN, ZERO, INFINITY?
 110 // Set signexp for significand result for x<0
 111 { .mfi
 112         mov         r15 = 0x0fffe
 113         fclass.m    p6,p7 = f8, 0xe7
 114         mov         r14 = 0x2fffe
 115 }
 116 // Form signexp of 2^64 in case x double-extended denormal
 117 // Save the normalized value of input in f9
 118 // The normalization also sets fault flags and takes faults if necessary
 119 { .mfi
 120         mov         r20 = 0x1003f
 121         fnorm.s0    f9 = f8
 122         nop.i 999 ;;
 123 }
 124
 125 // Move signexp for significand result for x>0 to FP reg
 126 // Form 2^64 in case x double-extended denormal
 127 { .mmi
 128         setf.exp    f10 = r15
 129         setf.exp    f12 = r20
 130         nop.i 999 ;;
 131 }
 132
 133 // Move signexp for significand result for x<0 to FP reg
 134 // p7 if x<0, else p8
 135 // If x=0,nan,inf, set p10 if output int to be 32 bits, or set p11 if 64 bits
 136 { .mfi
 137         setf.exp    f11 = r14
 138 (p7)    fcmp.lt.s0  p7,p8 = f8,f0
 139 (p6)    cmp.eq.unc  p10,p11 = r34, r0 ;;
 140 }
 141
 142 // If x NAN, ZERO, INFINITY, set *y=0 and exit
 143 { .mmb
 144 (p10)   st4         [r33] = r0      // Store *y=0 as 32-bit integer
 145 (p11)   st8         [r33] = r0      // Store *y=0 as 64-bit integer
 146 (p6)    br.ret.spnt b0 ;;
 147 }
 148
 149 // Form exponent mask
 150 // Test for fnorm(x) denormal, means x double-extended denormal
 151 { .mfi
 152         mov         r17 = 0x1ffff
 153         fclass.m    p9,p0 = f9, 0x0b
 154         nop.i 999 ;;
 155 }
 156
 157 // If x double-extended denormal add 64 to exponent bias for scaling
 158 // If x double-extended denormal multiply x * 2^64 which is normal
 159 // Set p10 if output int to be 32 bits, or set p11 if 64 bits
 160 { .mfi
 161 (p9)    add         r15 = 64, r15
 162 (p9)    fmpy.s0     f9 = f9, f12
 163         cmp.eq      p10,p11 = r34, r0 ;;
 164 }
 165
 166 // true exponent stored to int pointer
 167 // the bias is treated as 0xfffe instead of
 168 // normal 0xffff because we want the significand
 169 // to be in the range <=0.5 sig < 1.0
 170 // Store the value of the exponent at the pointer in r33
 171
 172 // If x>0 form significand result
 173 { .mfi
 174         nop.m 999
 175 (p8)    fmerge.se   f8 = f10,f9
 176         nop.i 999  ;;
 177 }
 178
 179 // Get signexp of normalized x
 180 // If x<0 form significand result
 181 { .mfi
 182         getf.exp    r16 = f9
 183 (p7)    fmerge.se   f8 = f11,f9
 184         nop.i 999  ;;
 185 }
 186
 187 // Get exp of normalized x
 188 // Subtract off bias to get true exponent of x
 189 { .mmi
 190         and         r18 = r17,r16 ;;
 191         sub         r19 = r18,r15
 192         nop.i 999  ;;
 193 }
 194
 195 // Store int *y as a 32-bit integer
 196 // Make the value a float
 197 { .mfi
 198 (p10)   st4         [r33] = r19        // Store *y as 32-bit integer
 199         fnorm.s.s0  f8 = f8
 200         nop.i 999
 201 }
 202 { .mfb
 203 (p11)   st8         [r33] = r19        // Store *y as 64-bit integer
 204         nop.f 999
 205         br.ret.sptk b0 ;;
 206 }
 207
 208 GLOBAL_LIBM_END(__libm_frexpf)