.file "logbl.s"

// Copyright (c) 2000 - 2003, Intel Corporation

// All rights reserved.

//

// Contributed 2000 by the Intel Numerics Group, Intel Corporation

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

// * Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

//

// * Redistributions in binary form must reproduce the above copyright

// notice, this list of conditions and the following disclaimer in the

// documentation and/or other materials provided with the distribution.

//

// * The name of Intel Corporation may not be used to endorse or promote

// products derived from this software without specific prior written

// permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTEL OR ITS

// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY

// OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY OR TORT (INCLUDING

// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

// Intel Corporation is the author of this code, and requests that all

// problem reports or change requests be submitted to it directly at

// http://www.intel.com/software/products/opensource/libraries/num.htm.

//

// History

//==============================================================

// 02/02/00 Initial version

// 02/16/00 Modified to conform to C9X

// 03/16/00 Improved speed

// 04/04/00 Unwind support added

// 05/30/00 Fixed bug when x double-extended denormal

// 08/15/00 Bundle added after call to __libm_error_support to properly

//          set [the previously overwritten] GR_Parameter_RESULT.

// 05/20/02 Cleaned up namespace and sf0 syntax

// 01/20/03 Improved performance

//

// API

//==============================================================

// long double logbl( long double x );

//

// Overview of operation

//==============================================================

// The logbl function extracts the exponent of x as an integer in

// floating-point format.

// logbl computes log2 of x as a long double

//

// logbl is similar to ilogbl but differs in the following ways:

//         +-inf

//            ilogbl: returns INT_MAX

//             logbl: returns +inf

//         Nan  returns FP_LOGBNAN (which is either INT_MAX or INT_MIN)

//            ilogbl: returns INT_MAX (7fffffff)

//             logbl: returns QNAN (quietized SNAN)

//         0    returns FP_ILOGB0 (which is either INT_MIN or -INT_MAX)

//            ilogbl: returns -INT_MAX (80000001)

//             logbl: returns -inf, raises the divide-by-zero exception,

//                   and calls libm_error_support to set domain error

//

// Registers used

//==============================================================

// general registers used:

// r26 -> r38

// r35 -> r38 used as parameters to error path

//

// predicate registers used:

// p6, p7, p8

// floating-point registers used:

// f9, f10, f11

// f8, input

rExpBias            = r26

rExpMask            = r27

rSignexp_x          = r28

rExp_x              = r29

rTrueExp_x          = r30

rExp_2to64          = r31

GR_SAVE_PFS         = r32

GR_SAVE_B0          = r33

GR_SAVE_GP          = r34

GR_Parameter_X      = r35

GR_Parameter_Y      = r36

GR_Parameter_RESULT = r37

GR_Parameter_TAG    = r38

fExp_in_signif      = f9

fNorm_x             = f10

fFloat_Exp          = f10

f2to64              = f11

.section .text

GLOBAL_LIBM_ENTRY(logbl)

// X NORMAL

// TrueExp_x = exp(f8) - 0xffff

// sig = TrueExp_x

// f8 = convert_to_fp (sig))

{ .mfi

      getf.exp        rSignexp_x = f8

      fclass.m        p8,p0 = f8, 0x0b   // Test for x unorm

      mov             rExpBias = 0xffff  // Exponent bias

}

{ .mfi

      nop.m           0

      fnorm.s1        fNorm_x = f8

      mov             rExpMask = 0x1ffff // Exponent mask

}

;;

// Form signexp of 2^64 in case need to scale denormal

{ .mfb

      mov             rExp_2to64 = 0x1003f

      fclass.m        p6,p0 = f8, 0x1e3  // Test x natval, nan, inf

(p8)  br.cond.spnt    LOGB_DENORM        // Branch if x unorm

}

;;

LOGB_COMMON:

// Return here from LOGB_DENORM

{ .mfi

      and             rExp_x = rSignexp_x, rExpMask // Get biased exponent

      fclass.m        p7,p0 = f8, 0x07   // Test x zero

      nop.i           0

}

;;

// X NAN or INFINITY, return f8 * f8

{ .mfb

      sub             rTrueExp_x = rExp_x, rExpBias // Get true exponent

(p6)  fma.s0          f8= f8,f8,f0       // Result if x natval, nan, inf

(p6)  br.ret.spnt     b0                 // Exit if x natval, nan, inf

}

;;

{ .mib

      setf.sig        fExp_in_signif = rTrueExp_x // Exponent as integer in fp

      nop.i 999

(p7)  br.cond.spnt    LOGB_ZERO

}

;;

// Result can be represented in less than 24 bits, so no precision completer

// is needed.

{ .mfb

      nop.m           0

      fcvt.xf         f8 = fExp_in_signif

      br.ret.sptk     b0                 // Exit main path, 0 < |x| < inf

}

;;

LOGB_DENORM:

// Form 2^64 in case need to scale denormal

// Check to see if double-extended denormal

{ .mfi

      setf.exp        f2to64 = rExp_2to64

      fclass.m        p8,p0 = fNorm_x, 0x0b

      nop.i           0

}

;;

{ .mfi

      nop.m           0

      fcmp.eq.s0      p7,p0 = f8, f0           // Dummy op to set denormal flag

      nop.i           0

}

;;

// If double-extended denormal add 64 to exponent bias for scaling

// If double-extended denormal form x * 2^64 which is normal

{ .mfi

(p8)  add             rExpBias = 64, rExpBias

(p8)  fmpy.s1         fNorm_x = fNorm_x, f2to64

      nop.i           0

}

;;

// Logic is the same as normal path but use normalized input

{ .mib

      getf.exp        rSignexp_x = fNorm_x

      nop.i           0

      br.cond.sptk    LOGB_COMMON              // Return to main path

}

;;

LOGB_ZERO:

// Here if x zero

// f10  = -|f8|

// f9  = 1.0/f10 = -1.0/|f8| = -inf

{ .mmf

      alloc           r32=ar.pfs,1,2,4,0

      mov             GR_Parameter_TAG = 150  // Error code

      fmerge.ns       f10 = f0,f8

}

;;

{ .mfb

      nop.m           0

      frcpa.s0        f9,p6 = f1,f10          // Produce -inf, Z flag

      br.cond.sptk    __libm_error_region     // Call error support

}

;;

GLOBAL_LIBM_END(logbl)

libm_alias_ldouble_other (logb, logb)

LOCAL_LIBM_ENTRY(__libm_error_region)

.prologue

{ .mfi

        add   GR_Parameter_Y=-32,sp           // Parameter 2 value

        nop.f 0

.save   ar.pfs,GR_SAVE_PFS

        mov  GR_SAVE_PFS=ar.pfs               // Save ar.pfs

}

{ .mfi

.fframe 64

        add sp=-64,sp                         // Create new stack

        nop.f 0

        mov GR_SAVE_GP=gp                     // Save gp

};;

{ .mmi

        stfe [GR_Parameter_Y] = f0,16         // STORE Parameter 2 on stack

        add GR_Parameter_X    = 16,sp         // Parameter 1 address

.save   b0, GR_SAVE_B0

        mov GR_SAVE_B0=b0                     // Save b0

};;

.body

{ .mib

        stfe [GR_Parameter_X] = f8            // STORE Parameter 1 on stack

        add   GR_Parameter_RESULT = 0,GR_Parameter_Y    // Parameter 3 address

        nop.b 0

}

{ .mib

        stfe [GR_Parameter_Y] = f9            // Store Parameter 3 on stack

        add   GR_Parameter_Y = -16,GR_Parameter_Y

        br.call.sptk b0=__libm_error_support# // Call error handling function

};;

{ .mmi

        add   GR_Parameter_RESULT = 48,sp

        nop.m 0

        nop.i 0

};;

{ .mmi

        ldfe  f8 = [GR_Parameter_RESULT]       // Get return result off stack

.restore sp

        add   sp = 64,sp                       // Restore stack pointer

        mov   b0 = GR_SAVE_B0                  // Restore return address

};;

{ .mib

        mov   gp = GR_SAVE_GP                  // Restore gp

        mov   ar.pfs = GR_SAVE_PFS             // Restore ar.pfs

        br.ret.sptk   b0

};;

LOCAL_LIBM_END(__libm_error_region)

.type   __libm_error_support#,@function

.global __libm_error_support#