.file "logb.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//==============================================================// double logb( double x );//// Overview of operation//==============================================================// The logb function extracts the exponent of x as an integer in// floating-point format.// logb computes log2 of x as a double//// logb is similar to ilogb but differs in the  following ways://         +-inf//            ilogb: returns INT_MAX//             logb: returns +inf//         Nan  returns FP_LOGBNAN (which is either INT_MAX or INT_MIN)//            ilogb: returns INT_MAX (7fffffff)//             logb: returns QNAN (quietized SNAN)//         0    returns FP_ILOGB0 (which is either INT_MIN or -INT_MAX)//            ilogb: returns -INT_MAX (80000001)//             logb: 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, inputrExpBias            = r26rExpMask            = r27rSignexp_x          = r28rExp_x              = r29rTrueExp_x          = r30rExp_2to64          = r31GR_SAVE_PFS         = r32GR_SAVE_B0          = r33GR_SAVE_GP          = r34GR_Parameter_X      = r35GR_Parameter_Y      = r36GR_Parameter_RESULT = r37GR_Parameter_TAG    = r38fExp_in_signif      = f9fNorm_x             = f10fFloat_Exp          = f10f2to64              = f11.section .textGLOBAL_LIBM_ENTRY(logb)// 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.d.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 = 151  // 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(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        stfd [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        stfd [GR_Parameter_X] = f8            // STORE Parameter 1 on stack        add   GR_Parameter_RESULT = 0,GR_Parameter_Y    // Parameter 3 address        nop.b 0}{ .mib        stfd [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        ldfd  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#